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This study aimed to evaluate seminal and sperm production, growth, health, and lipid metabolism of male silver catfish (Rhamdia quelen) fed diets containing l -carnitine and varying lipid sources. Herein, males and females (167.33 ± 9.24 g) were both fed across 223 d with eight (08) isoproteic (282 g of digestible protein kg of ration −1) and isoenergetic (13.34 MJ of digestible energy kg of ration −1) diets, containing 0.00, 0.15, 0.45, and 0.75 g l -carnitine kg −1 of feed, soybean, and marine fish oils. Feeding males with diets containing l -carnitine and different oils resulted in an interactive effect (p < 0.05) that improved sperm production. Furthermore, males fed soybean oil and 0.45 g l -carnitine kg −1 had the highest seminal pH and sperm velocities. Fish fed fish oil and 0.75 g l -carnitine kg−1 had the highest gonadosomatic indexes, sperm production, and superoxide dismutase activities recorded in the testes. The testes of these fish also showed increases in docosahexaenoic acid (DHA), polyunsaturated fatty acids (PUFAs), n-3 fatty acids, and higher n-3: n-6 ratios. The individual effect of oils produced viscera with more (p < 0.05) fat, in addition to having higher (p < 0.05) blood levels of albumin, total cholesterol, triglycerides, alongside the lowest level of aspartate aminotransferase in fish fed marine fish oil. The individual effect of l -carnitine also produced muscles with less (p < 0.05) fat, in addition to the highest (p < 0.05) amount of total cholesterol with the lowest amount of high-density lipoprotein (HDL) cholesterol in the blood of fish fed with 0.75 g l -carnitine kg−1. l -carnitine and oils in the diets promoted hepatic and testicular protection whilst regulating lipid metabolism and fatty acid profile in the liver and testes of silver catfish (Rhamdia quelen) males. These benefits led to greater sperm production when fish oil and 0.75 g kg −1 were used, and faster spermatozoa with soybean oil and 0.45 g kg −1. • Diets with 0.75 g kg−1 l -carnitine and fish oil improved the Rhamdia sperm production. • Rations with l -carnitine and fish oil increased PUFAs deposition in Rhamdia testes. • Dietary l -carnitine and fish oil improved the antioxidant status of Rhamdia testes. • Lipid metabolism of Rhamdia male were regulated by dietary l -carnitine and oil source. [ABSTRACT FROM AUTHOR]

The nutrient removal, biomass production and nutritional value of the halophyte Salicornia ramosissima were evaluated in the context of an Integrated Multi-Trophic Aquaculture (IMTA) system. The experiment consisted of an indoor fish RAS whose effluent was used to feed two different halophyte hydroponic systems: a Nutrient Film Technique (NFT) system or a Deep Water Culture (DWC) system. The highest yield of S. ramosissima was observed in the DWC (320 g m−2 day−1), this system showed significantly higher yields compared to the NFT. Both hydroponic systems were effective in removing nutrients from the fish RAS wastewater, contributing to the wastes valorization process. Maximal nutrient uptake efficiencies were: 82.8% and 68.6% NO 3 − in the DWC and the NFT, respectively; 72.6% PO 4 3− in the DWC and 82.9% in the NFT; 63.6% NO 2 − in the DWC vs 56.4% in the NFT; and 89.2% NH 4 + in the DWC vs 94.1% in the NFT. The lipid profile of the halophytes in the DWC was analysed. The total lipid content ranged from 2.99% to 3.83%. The fatty acids (FA) profile in the leaves was dominated by polyunsaturated fatty acids (about 66%), which were represented by α-linolenic acid (41%) and linoleic acid (24%), followed by saturated fatty acids (28%) with palmitic acid (22%) as the major component. A small component of monounsaturated fatty acids accounts for about 12% of total FA. Regarding lipid classes, pigments were the most abundant compounds followed by glycolipids, phospholipids, flavonoids and sterols. The study supports the potential of S. ramosissima to valorise aquaculture wastes and its high nutritional interest. The experimental systems minimized waste and maximized resources utilization. Such integrated approaches can contribute to the sustainability and resilience of aquaculture systems while providing additional economic opportunities through the production of high value halophyte products. • Salicornia ramosissima was hydroponically cultivated in a NFT system and in a DWC system with fish RAS effluents. • The DWC system provided the best yield (320 g m−2 day−1). • Both systems removed >75% of DIN and 80% of DIP present in the effluent. • The lipid profile of S. ramosissima is affected by nutritional stress and cultivation conditions. [ABSTRACT FROM AUTHOR]

Thraustochytrids are a group of unicellular marine protists that are noted for their ability to produce high amounts of lipids, especially docosahexaenoic acid (DHA), making them a valuable source for replacing fish oil in aquafeeds. Varying levels of Aurantiochrytrium acetophilum meal (TM) were evaluated as replacement of fish oil in extruded diets for juvenile Atlantic salmon on growth, nutrient apparent digestibility, fatty acid composition in muscle and liver and expression of genes associated with lipid metabolism. Four experimental diets were tested: a control diet without the inclusion of A. acetophilum meal and three experimental diets derived from the control diet, in which fish oil was progressively replaced by the addition of A. acetophilum meal at 2.5% (TM 2.5), 6.5% (TM 6.5) and 12% (TM 12) respectively. After 12 weeks of feeding, the growth, feed conversion, condition factor and survival of the fish were not affected by the inclusion of A. acetophilum in the diet. However, the 12% inclusion significantly decreased the viscerosomatic index of the fish and the digestibility of protein, lipids, ash and energy compared to the other experimental diets. The lipid content and fatty acid profile of the liver and muscle were significantly affected by diet composition. In both tissues, fish fed the TM 12 diet retained the highest levels of DHA. However, it was also observed that EPA concentrations lessened with increasing dietary content of A. acetophilum meal. Finally, the decrease in the expression of Δ5fad in the fish fed with the TM 6.5 and TM 12 diets showed that fish do not require a higher expression of this desaturase for DHA production, due to the high content of this fatty acid in A. acetophilum meal. • A. acetophilum meal can be used as lipids source in Atlantic salmon diets. • Higher dietary inclusions of A. acetophilum meal modify visceral fat reserves in Atlantic salmon. • Substitution of fish oil with 12% A. acetophilum meal affects nutrient digestibility in Atlantic salmon juvenile. • DHA retention in liver and muscle of Atlantic salmon increased with the dietary concentration of A. acetophilum meal. • Diets with high levels of DHA from A. acetophilum meal depressed expression of the Δ5fad. [ABSTRACT FROM AUTHOR]

Parental nutrition plays important roles in reproductive performance and offspring health of broodstock yellow catfish. However, there is a lack of relevant knowledge concerning the broodstocks of many fish species. This study investigated the influence of dietary lipid levels on growth, spawning performance, tissue fatty acid profiles, sex hormone secretion, and offspring health status of yellow catfish (Pelteobagrus fulvidraco). Five experimental diets were designed containing a 7:3 ratio of fish oil and corn oil blends with graded lipid levels (6.3%, 8.2%, 10.8%, 12.2%, and 14.4% by dry weight) and were fed to female broodstock yellow catfish for 8 weeks. The results showed that weight gain, egg diameter, fertilization ratio, and hatching ratio increased initially and then decreased with increasing dietary lipid levels, reaching optimal peaks in the L10.8 group. Broodstock fed a diet with 10.8% lipid obtained the highest 17-β estradiol concentration. The deposition of highly unsaturated fatty acids in tissues increased initially and then decreased with the increase in dietary lipids, reaching a peak in the 10.8% group. Plasma superoxide dismutase activity and total glutathione content were lowest in fish fed a diet with a 6.3% lipid level, while the contents of malondialdehyde and cortisol in larvae 3 days post-hatching showed an opposite trend, indicating that a low-fat diet reduced the antioxidant capacity of broodstock and induced a stress response that had negative effects on offspring health. Broodstock fed a diet with an appropriate lipid level could increase the expression of antioxidant enzymes by activating the nrf2 signaling pathway. Based on the regression of dietary lipid level and weight gain, reproductive performance, and egg quality of fish, the optimal dietary lipid level was 10.1–11.7% for broodstock yellow catfish. • The optimal dietary lipid requirement of broodstock P. fulvidraco is 10% -11.1%. • Optimal lipid diet could improve reproductive performance and egg quality of P. fulvidraco. • Appropriate dietary lipid intake promotes HUFA deposition in the ovary. • Insufficient lipid diet reduced the antioxidant capacity of broodstock. • Insufficient lipid diet induced stress responses in offspring larvae. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effects of dietary inclusion of black soldier fly (Hermetia illucens) larvae oil (HIO) on fillet fatty acid (FA) profiles and other nutritional traits of gilthead seabream (Sparus aurata). Four experimental diets were formulated with 45% crude protein and 18% lipids (circa 50:50 of fish oil and vegetable oil (VO) blend: 20% rapeseed, 30% palm, and 50% linseed oil) and HIO was used to replace VO blend at 42%, 84%, and 100%, corresponding to a dietary inclusion level of 4%, 7.9%, and 9.5%, respectively. After a feeding trial of 10 weeks, several fillet quality traits were analyzed, including morphometric and somatometric indexes, physical and chemical characteristics, FA profile, and lipid peroxidation products. No differences were found in the morphometric and somatometric parameters, or skin and fillet color. The fillets FA profile was significantly modulated by the experimental diets, showing an increase in saturated fatty acids (SFA), particularly lauric acid, and a decrease in monosaturated FA and n-3 and n-6 polyunsaturated fatty acids (PUFA) with the increase of HIO inclusion, while eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents were not affected. Fillets FA quality indexes (PUFA/SFA, n-3/n-6 PUFA ratio, hypocholesterolemic/hypercholesterolemic ratio, thrombogenicity, and atherogenicity indexes) were also modulated by dietary HIO inclusion. Fillets pH was reduced and water holding capacity increased with dietary HIO inclusion. Fillet lipid peroxidation level (measured as TBARS) was significantly decreased with dietary HIO inclusion despite an increase in conjugated dienes. Overall, results showed that HIO can efficiently replace VO in gilthead seabream diets, without major negative effects on fillet characteristics and quality traits while decreasing fillet lipid oxidation. • Dietary replacement of vegetable oils with Hermetia illucens larvae oil (HIO) impacted the fillet's fatty acid (FA) profile. • Although saturated FA content increased with HIO inclusion, EPA and DHA levels were maintained in the fillet. • Lipid quality indexes were within the recommended levels for a healthy human diet. [ABSTRACT FROM AUTHOR]

Diets with high-lipid levels may reduce fish growth, feed intake and increase fat deposition, jeopardizing fillet quality and shelf-life, which may be of major concern for the final consumer. To mitigate these potentially harmful effects, several nutritional strategies have been applied, including the use of functional ingredients. In this study, European sea bass (initial body weight 21.4 g) were fed six isonitrogenous (45% crude protein) diets with 16% and 22% lipid levels and supplemented with oleic acid (OA) at 0, 1, and 2% as a functional ingredient. Increasing dietary lipid levels did not affect fish growth performance, feed intake, and feed utilization. Independently of lipid level, dietary OA supplementation decreased feed intake and increased feed efficiency and Nitrogen (N) retention (% N Intake). Whole-body composition, hepatosomatic and visceral somatic indexes were not affected by dietary composition. The liver and muscle lipid contents were also not affected by dietary composition. The liver fatty acid profile was not affected by dietary lipid level, but monounsaturated fatty acid (MUFA) content decreased while polyunsaturated fatty acid (PUFA) content decreased with dietary OA supplementation. In the muscle, PUFA content decreased with dietary lipid levels, particularly C18:2n-6 (LA) and C20:2n-6. Dietary OA supplementation increased muscle MUFA, particularly OA (C18:1n-9), and reduced PUFA content. Compared to fish fed with 1OA diets, fish fed with 2OA diets presented a decreased area covered by lipids in the liver. Dietary OA supplementation increased hepatic glucose-6-phosphate dehydrogenase (G6PDH) activity and decreased malic enzyme (ME) activity, while no differences were observed in the activity of fatty acid synthase (FAS) and enzymes related to β-oxidation. Moreover, dietary OA supplementation decreased mechanistic target of rapamycin (mTOR) protein levels, while protein kinase B (Akt) and the phosphorylated state levels of both Akt and mTOR were not affected by dietary composition. Overall, dietary OA supplementation decreased feed intake and improved feed efficiency, without affecting growth performance, contributing to mitigate the potentially harmful effects of high-lipid diets in European sea bass. • Growth performance and feed utilization were not affected by dietary lipid levels. • OA supplementation decreases FI and improves FE and NR (% NI). • Dietary OA supplementation increased MUFA but decrease PUFA content in the liver. • Dietary OA supplementation decreased mTOR protein levels. [ABSTRACT FROM AUTHOR]

In oviparous species, physico-chemical characteristics of eggs are an indicator of maternal physiological traits and environmental conditions of the site where the females develop. In this study, we aim to (a) determine the physico-chemical characteristics of eggs from wild Caiman latirostris populations; (b) evaluate if fertile and infertile eggs differ in physico-chemical characteristics associated with suchest reproductive success; and (c) compare the present results with findings in other crocodilian species to identify characteristics that would be associated with reproductive biology and adaptations to their environments. Eggs were collected and identified, and different morphometric variables (percentage of components, and protein, total lipids and fatty acid composition) were determined. Fertile and infertile eggs did not differ in weight or component (eggshell, yolk and albumen) percentages of total egg weight. Fatty acid profiles of yolk differed between fertile and infertile eggs in C14:0, C16:1 and C17:1. However, the comparison of profiles among clutches showed differences in 12 fatty acids. We also observed differences in percentage of egg components respect to other crocodilian species, particularly of albumen, which had a lower proportion in C. latirostris . Our results suggest that egg infertility may not be related to maternal lipid investment. We propose using yolk of infertile eggs (which is similar to that of fertile eggs) as a non-invasive method to identify and evaluate the difference in FA composition of eggs for breedings female of varyns diets. [ABSTRACT FROM AUTHOR]

It was evaluated the effect of DHA (extract from Aurantiochytrium sp.) inclusion in diets formulated with poultry by-product meal (PBM) using beef tallow (TALLOW) to fulfill the lipid demand in substitution of fish oil (FO) in juvenile totoaba (9.5 ± 0.1 g). With this purpose four diets were formulated to contain PBM with FO (PBM + FO positive control) or TALLOW (PBM + TALLOW negative control) and two diets containing different levels of DHA; one supplemented with 50% (PBM + TALLOW+50%DHA) and 100% DHA (PBM + TALLOW+100%DHA), based on DHA requirements for marine carnivore fish. After nine weeks, no signs of fatty acid (FA) deficiency were noticed; survival was above 92% across dietary treatments, and production performance was also similar, with exception of feed conversion ratio and viscerosomatic index. Tissues proximate composition was affected by dietary treatments. Tallow-based diets increased hepatic lipid content. However, 100% DHA supplementation adjusted this effect. Overall blood parameters were not influenced by tallow inclusion, except for triglycerides. Fish fed the PBM + TALLOW diet exhibited significant higher levels of triglycerides compared to those fed the PBM + FO diets. However, the DHA supplementation in both levels amended this effect. The FA profile in the liver and muscle tissues were affected and reflected the dietary fatty acid composition to some extent. Tallow-based diets exhibited significantly higher levels of MUFAs (e.g., 18:1n-9) and reduced levels of SFAs than those fed the PBM + FO control diet. Muscle tissue of fish fed the PBM + TALLOW diet exhibited significantly lower levels of DHA and EPA than that fed PBM + FO diet. However, DHA supplementation partially corrected this effect by enhancing DHA content in muscle. The magnitude of LC-PUFA “sparing effect” in the present study was limited due to the elevated levels of dietary 18:2n-6 from the PBM that accumulated in the muscle tissue in the extent of the LC-PUFAs. In summary, the current results provide valuable insights regarding dietary DHA in juvenile totoaba towards formulating fish oil-free diets. Dietary PBM and beef tallow successfully replaced FO in the context of production performance and overall blood parameters. DHA supplementation was beneficial for enhancing the levels of this human health-promoting fatty acid in the muscle tissue. Also, it might increase fish performance reducing the need of using fish oil in aquafeeds. We suggest that towards fish oil-free aquafeed formulations it is essential to balance the dietary fatty acids. Concomitant to this fact, it will be necessary to reduce the lipid content in PBM to facilitate feed formulation. [ABSTRACT FROM AUTHOR]

During European eel assisted reproduction, timely administration of hormones that induce oocyte maturation and ovulation is a major factor influencing subsequent egg quality. This treatment commonly comprises one injection of fish pituitary extract (PE) as a primer followed by a 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) injection. In this context, the present study aimed at optimizing timing of the dual hormone administration by applying a lipid droplet-based oocyte maturation scale, previously developed for Japanese eel to determine the maturational status of each female. Using wild-caught female eels, the potential effect of female size, egg fatty acid composition and dry weight on egg quality was also analyzed. Larval survival at 3 days post hatch was used to differentiate High- and Low-quality egg batches. Results showed that lipid droplet diameter was significantly smaller in High-quality eggs than in Low-quality egg batches, indicating that females producing High-quality eggs received the PE primer and DHP generally at an earlier developmental stage than those producing Low-quality batches. These results confirm that oocyte lipid droplet diameter is a useful indicator of female maturational status for optimization of induction of oocyte maturation and ovulation in European eel. Additional parameters, including female size, egg fatty acid composition and dry weight, were similar between high and low quality egg batches. This insight regarding the fatty acid composition of eggs obtained from wild-caught female eels may help advancing the development of tailored diets for increased reproductive success of farmed broodstock. [ABSTRACT FROM AUTHOR]

Diet-to-tissue transfer of long-chain polyunsaturated fatty acids (LC-PUFAs) is more efficient when diets contain saturated fatty acid (SFA) or monounsaturated fatty acid (MUFA)-rich alternative lipids. This mechanism, the omega-3 or LC-PUFA “sparing effect”, encourages more efficient metabolism of the limited LC-PUFAs available in terms of their important physiological functions and tissue retention, and the likelihood of successful fish oil sparing (i.e. complete fish oil replacement maintaining growth and tissue fatty acid profile). However, it is still unclear whether dietary SFAs and MUFAs are equivalent or interact synergistically or antagonistically in this context. Accordingly, we compared production performance and tissue fatty acid composition of California Yellowtail fed diets containing fish oil (rich in LC-PUFAs) or soybean oil (rich in C 18 PUFAs), partially hydrogenated soybean oil (rich in MUFAs), fully hydrogenated soybean oil (rich in SFAs), or blends of these soybean oils. After 10 weeks, production performance was not affected by dietary lipid source or fatty acid composition, and tissue fatty acid profiles generally mimicked dietary fatty acid composition. However, tissues of fish fed SFA-rich lipids exhibited the greatest similarity to those fed fish oil, and fillets of fish fed fully hydrogenated soybean oil had significantly higher levels of LC-PUFAs (43.9 g LC-PUFA /100 g fatty acid methyl esters; FAMEs) than those fed any of the other diets (22.5–36.9 g LC-PUFA /100 g FAMEs), including the LC-PUFA-rich fish oil-based feed (39.8 g LC-PUFA /100 g FAMEs). Power regression analyses demonstrated a stronger positive relationship between dietary SFAs with fillet LC-PUFA deposition ( r 2  = 0.73) than dietary MUFAs ( r 2  = 0.09), whereas dietary C 18 PUFAs were observed to have a negative relationship with fillet LC-PUFA content ( r 2  = 0.85). These trends were also observed in liver and eye tissues, and to a lesser extent in brain tissue. Multiple linear regression analyses demonstrated a stronger relationship between dietary levels of PUFAs and SFAs and tissue fatty acid profile composition, including LC-PUFA content, than dietary levels of PUFAs and MUFAs. Fillet lipid content varied significantly, with the FISH and C 18 PUFA SOY diets displaying the highest levels. The same pattern was observed for liver lipid content, but not significantly. Our findings suggest that SFAs are the primary drivers of LC-PUFA sparing, whereas MUFAs exert a weaker independent sparing effect and appear to diminish the sparing effect of dietary SFAs when MUFAs were also present. [ABSTRACT FROM AUTHOR]

To determine differences between commercial size wild and farmed blackspot seabream, some parameters affecting quality were evaluated during shelf life, namely the fatty acid profiles, pH, muscle colour and Quality Index Method (QIM). In addition, a histological study of the lipids' distribution in the myotome (slow or fast twitch) in different dorsal areas was performed. In farmed fish, three diets were tested. One of them was a commercial diet formulated with a high proportion of lipids, mostly from fish oil. The other two diets were formulated with reduced lipid levels by 60%. In one (low lipid diet, LL) the proportions of protein sources were maintained and in the other (low lipid diet + fish meal, LL +) most of the protein was provided as fish meal. Lipid depots were not found to be different in the myocytes of the fast-twitch fibers. However, regional differences were identified in the slow-twitch fibers depending on the area and the diet, whether in the cranial, medial or caudal portion of the dorsal myotome. The worst scores of the QIM were recorded for the Control diet and the wild fish group. In addition, QIM showed a positive correlation with total n -3 and a negative with other lipid fractions. The a* values in skin and the chroma in muscle of the wild fish were superior to those measured in farmed fish. Fish fed the LL + diet had higher fillet protein content than that of the wild counterpart. As for nutritional value, farmed fish were able to deposit more DHA than was offered in all experimental diets used, especially with the LL + diet which yielded threefold more DHA. [ABSTRACT FROM AUTHOR]

Diet at start feeding can affect fish development, pigmentation and growth, and live feed can provide all the dietary requirements of larvae. Enriched rotifers and Artemia are normally used as live feed in the first stages of commercial larval production, however, wild zooplankton or copepods provide better results. The goal of this study was to evaluate whether supplementing enriched rotifers and Artemia (RA) with fish protein hydrolysate (RA-PH) or a small amount of wild zooplankton (RA-Zoo; 5–10% of total prey items) would improve the nutritional quality of larval cod ( Gadus morhua ), and how it correlated with larval growth rates. Wild zooplankton had significantly higher proportions of the polyunsaturated fatty acids 22:6ω3 (DHA, 23%) and 20:5ω3 (EPA, 11%). Larvae fed wild zooplankton also had higher proportions of essential omega-3 fatty acids (43% RA-Zoo; ≈ 39–40% RA/RA-PH) and much higher EPA/ARA ratios compared to those only fed with enriched rotifers and Artemia or these prey items plus protein hydrolysate (≈ 4 RA-Zoo; ≈ 1.3–3 RA/RA-PH). Further, these fatty acid proportions correlated significantly with larval growth rates and improved fish development. Based on these results, we recommend the inclusion of small amounts of wild zooplankton or commercially produced copepods with high proportions of DHA and EPA, and low proportions of ARA, in the initial diet of Atlantic cod larvae. [ABSTRACT FROM AUTHOR]

The accumulation and mobilization of lipids and fatty acids are known to vary greatly between the ovary and hepatopancreas of crab broodstock during ovarian development. However, the underlying mechanism is not completely understood. In the present study, we analyzed and compared the biochemical compositions and expression profiles of lipid metabolism-related genes during each maturation stage in Scylla paramamosain. The results revealed that ovaries deposited large amounts of total lipid contents with a predominance of neutral lipids, mainly triacylglycerol (TAG), rich in high levels of saturated fatty acids throughout ovarian development. Microsomal triglyceride transfer protein (MTP), surfeit locus protein 4 (SURF4) and apolipocrustacein (ApoCr) transcription levels were significantly increased in the hepatopancreas as did transcription levels of the vitellogenin receptor (VTGR) in the ovary during ovarian development (P < 0.05). We speculated the possible mechanism by which MTP transported TAG to ApoCr, then SURF4 conveyed ApoCr from the hepatopancreas to the hemolymph during ovarian development, and finally, ApoCr was absorbed by the VTGR of oocytes, leading to a higher gonadosomatic index (GSI) and lipid deposition regulated by lipogenesis and lipolysis genes. These results are considered to provide fundamental information for further reproductive biology research on female mud crabs. • The ovary of Scylla paramamosain deposited large amounts of neutral lipids, mainly triacylglycerol (TAG), rich in saturated fatty acids throughout ovarian development. • The possible mechanism underlying the accumulation and mobilization of lipids between the hepatopancreas and ovary of female Scylla paramamosain during ovarian development. • The results of this study may provide insight into the formulation of artificial diets that more effectively promote the vitellogenesis of broodstock in crabs. [ABSTRACT FROM AUTHOR]

Recent studies have found that feeding high levels of long chain polyunsaturated fatty acids (LC-PUFA) influenced the steroid biosynthesis pathway of Atlantic salmon on a transcriptomic level, although research observed on a metabolic level is lacking. Dietary lipid and chronic stress have also been suggested to play a role in steroidogenesis. A study was performed on Atlantic salmon post-smolts (184 g) fed with diets of high and low levels of lipid with and without high levels of LC-PUFA under hypoxic (stressed) or normoxic (unstressed) conditions. Liver, head kidney and blood samples were collected after 35 and 116 days to determine short- and long-term effects. On day 35, dissolved oxygen affected the levels of the steroid hormones 11-deoxycortisol, cortisone and testosterone as well as the relative expression of cyp11a involved in steroidogenesis and ud2a2 involved in sex steroid metabolism. On day 116, an interaction between lipid x LC-PUFA x oxygen was found for cyp11a , hsd3b (steroidogenesis) and ud2a2 genes, whereas LC-PUFA and/or oxygen affected the steroid levels of 11-dehydrocorticosterone, corticosterone, cortisol, dehydroepiandrosterone, pregnenolone and testosterone. The observation that both LC-PUFA and oxygen affected cyp11a expression and the levels of pregnenolone, provides evidence for the influence of both parameters on the rate-limiting point of steroid production, which can take >35 days to establish. The 3-way interaction between lipid, LC-PUFA and dissolved oxygen on the expression of steroid genes suggests that the chronic stressor of hypoxia may be over-riding dietary influences of the lipid and LC-PUFA, though the relative proportion of LC-PUFA within the lipid may play a role as well. In terms of fatty acid composition, low dietary lipid and high LC-PUFA increased the levels of total n-6 and n-3 PUFA in the liver, particularly EPA and DHA, and the head kidney to a lesser extent. In terms of immune pathways, hypoxia influenced cytokine gene expression (tgfb, il10), cellular repair gene expression (gr, hsp70 and hsp90) and eicosanoid levels (PGE2 and LTB5) in the head kidney, while dietary lipid and LC-PUFA influenced cytokines (ifnγ and il1β) and eicosanoids (PGE2 and LTB5). These findings demonstrate that feeding different levels of LC-PUFA significantly alters steroidogenesis and innate immune response in Atlantic salmon post-smolts with additional interactions from dietary lipid and hypoxia stress. These results will significantly impact the aquaculture industry since it demonstrates salmon fed high levels of LC-PUFA are likely more resilient to cope with chronic stressors (e.g. prolonged hypoxia) due to lower corticosteroid levels and upregulated immune response. • Effect of dietary lipid, LC-PUFA and oxygen on steroid and immune responses of Atlantic salmon. • Hypoxic stress upregulated expression and levels of steroids and immune factors. • High dietary LC-PUFA downregulated expression and levels of steroids after 116 days. • High dietary lipid and LC-PUFA upregulated cytokine expression and levels of eicosanoids. • Salmon fed higher LC-PUFA are likely more resilient to cope with hypoxic stress. [ABSTRACT FROM AUTHOR]

Feed intake is subjected to a complex regulation involving a plethora of signals, among which nutrients stand as one of the most important. In mammals, the gastrointestinal tract is able to sense nutrients in the lumen, and respond with the release of signaling molecules that ultimately modulate brain circuits governing appetite, resulting in decreased/increased feeding. Whether equivalent mechanisms operate in fish remains unknown. In a recent study, we described that the gastrointestinal tract of rainbow trout contains several sensors for free fatty acids (FAs), and that the luminal presence of FAs of different length and degree of unsaturation modulates the levels of key gastrointestinal hormones involved in feed intake regulation. In this study, our aim was to characterize the impact of such a luminal presence of FAs on brain appetite-regulatory centers, as well as its effects on rainbow trout feed intake. Major results from this study demonstrated that: (i) FAs of different length and degree of unsaturation [medium-chain (MCFAs, octanoate), long-chain (LCFAs, oleate), long-chain polyunsaturated (PUFA, α-linolenate), and short-chain (SCFA, butyrate) FAs] differentially modulate feed intake levels when administered intragastrically, (ii) intragastrically-administered FAs modulate the phosphorylation status of appetite-related transcription factors, as well as mRNA levels of key appetite-regulating neuropeptides, in the hypothalamus and/or telencephalon, (iii) luminal presence of FAs results in changes in the central abundance of mRNAs encoding gastrointestinal hormone receptors, and (vi) luminal FA-derived central changes in neuropeptide mRNAs are not observed (or are lessened) in vagotomized fish. Together, these results provide comprehensive evidence in favor of a gut-brain axis in fish. In addition, we observed different responses in terms of feed intake regulation depending on the type of fatty acid administered into the lumen, which is very relevant for aquaculture considering differences in fatty acid composition in aquafeeds. • Food intake in rainbow trout is differentially modulated by fatty acids of varied length and degree of unsaturation • The luminal presence of fatty acids alters central circuits governing food intake • Vagal transmission mediates (at least in part) afferent nutrient sensing-derived signaling from the gut to the brain [ABSTRACT FROM AUTHOR]

Senegalese sole ( Solea senegalensis ) is a highly-valuable flatfish species with interest for diversification of aquaculture in Mediterranean countries. Unlike other fish species known to have a high dietary DHA requirement during the larval stage, several studies have suggested dietary DHA could play a minor role for Senegalese sole during the early developmental stages. This suggestion was recently supported by studies that indicated an ability of Senegalese sole to biosynthesise DHA from its precursors during the larval period. However, it is still uncertain if Senegalese sole post-larvae can effectively grow on low dietary DHA levels during weaning. Moreover, recent studies focusing on the juvenile phase of Senegalese sole have suggested a possible impairment of this species to efficiently digest or absorb high dietary lipid levels. Yet, if a reduction of dietary lipid levels would affect a normal development of Senegalese sole during the early stages remains to be established. Therefore, this study aimed at determining if a reduction of dietary DHA and lipid levels would affect Senegalese sole performance and lipid metabolism during weaning and post-larval period. In this study, Senegalese sole post-larvae were reared according to four dietary treatments: low lipid levels (treatments LFAT and LFAT_DHA) and moderate lipid levels (MODFAT and MODFAT_DHA). DHA levels in LFAT_DHA and MODFAT_DHA diets were higher than in LFAT and MODFAT diets, respectively. Subsequently, effects of experimental diets on Senegalese sole post-larval growth, survival, fatty acid composition and histopathological condition of intestinal and liver tissues were evaluated. Results showed that feeding on diets with low DHA and lipid levels significantly reduced the growth performance of Senegalese sole post-larvae. However, at the end of the experimental period, no significant differences were observed for post-larval survival in response to dietary treatments. In overall, this study disadvises that weaning diets for Senegalese sole post-larvae should contain low DHA and lipid levels, as a reduction of these levels may compromise post-larval growth performance. Statement of relevance Determining essential fatty acid requirements in marine fish larvae is of utmost importance for the aquaculture industry, contributing to fulfil the growth potential of farmed species. In the case of Senegalese sole, a highly valued species farmed in Mediterranean countries, it may have the capacity to biosynthesise DHA from its precursors during the larval stage. However, the inclusion of DHA-rich oils in weaning diets is costly, considerable savings could be achieved by replacing DHA-rich oils by common fish oils in weaning diets for this species. Furthermore, Senegalese sole has also been shown a poor ability to deal with high dietary lipid levels during the juvenile stage. However, no studies have addressed this capacity in Senegalese sole larvae. This study comprises an evaluation on the effects of reducing dietary DHA and lipid levels during Senegalese sole weaning by integrating an assessment of these effects on post-larval growth, survival, fatty acid composition and histopathological condition. [ABSTRACT FROM AUTHOR]

Flesh quality, including beneficial fatty acid composition and physicochemical qualities, is the most important factor for many consumers. The actions and mechanisms of promotion of polyunsaturated fatty acid (PUFA) contents, muscle hardness, and related signalling pathways by lipids were investigated in sub-adult grass carp. In this experiment, 450 healthy grass carp (initial body weight 756.57 ± 1.28 g) were selected and randomly divided into 6 treatments, and fish in each group were fed diets with different lipid levels (0.79, 1.58, 2.72, 4.06, 5.16, and 6.33%) for 60 days. The results showed that compared with the control group (0.79% lipid diet), the optimal lipid levels in the diet increased the percentage of weight gain (PWG), feed intake (FI) and flesh rate (P < 0.05), indicating that lipids improved the growth performance of sub-adult grass carp. The optimal levels of lipids also increased muscle PUFA content, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (P < 0.05), which demonstrated that lipids improved beneficial fatty acid composition in the muscle. Meanwhile, optimal lipid levels increased muscle shear force, collagen content and myofibre density (P < 0.05), which indicated that lipids improved muscle physicochemical qualities. We further explored the mechanism of lipid-increased muscle PUFA content and muscle hardness in fish. We observed that the increase in muscle PUFA content by optimal lipid levels may be related to the promotion of LC-PUFA biosynthesis and catabolism signalling pathways (LXRα/SREBP-1, Sp1, and PPARα) in fish. Meanwhile, the enhancement of muscle hardness by optimal levels of lipids may be associated with the increase in collagen content as well as the improvement of the muscle histological characteristics (diameter and density) in fish. The increase in the muscle collagen content may be related to lipids motivating collagen synthesis pathways including the TGF-β1/Smads pathway at the transcriptional level and the PI3K/Akt/LARP6 signalling pathway at the initial stage of translation. In addition, the increase in muscle fibre density may be attributed to lipid-upregulated MRFs (MyoD, MyoG and Myf5) mRNA levels and decreased myostatin (MSTN1 and MSTN2) mRNA levels (P < 0.05), which were involved in myofibre development. Collectively, lipid-improved flesh quality, including beneficial muscle fatty acid composition and physicochemical qualities, is connected with the activation of related signalling pathways and regulatory factors. Moreover, based on PWG and muscle shear force, the dietary lipid requirements for sub-adult grass carp (756–1459 g) were 4.01% and 3.65% of the diet, respectively. • Lipid enhanced the growth performance, lipid metabolism and transport of fish. • Lipid improved muscle beneficial fatty acids composition of fish. • Lipid-increased LC-PUFA contents were affected by biosynthesis and catabolism. • Lipid improved muscle physicochemical qualities of fish. • Lipid-enhanced muscle hardness may be related to collagen and muscle fibre. [ABSTRACT FROM AUTHOR]

Low temperature is an important stress factor for warm-water marine mollusks. It is well known that lipids play an important role in the resistance of low temperature stress in mollusks. The noble scallop Chlamys nobilis is an important economic warm-water bivalve. It has been cultured in the waters of southern China since the 1980s. However, C. nobilis often experiences regional mass mortality in winter. In the present study, the variation of lipids and fatty acids in C. nobilis were studied in differentiated temperatures (water temperature was gradually decreased from 27 °C to 15, 13 and 11 °C). The results demonstrated that lipid peroxidation increased at low temperatures, gills were damaged at 13 and 11 °C, and the condition index decreased only at 11 °C. Moreover, the level of triglycerides and total cholesterol in digestive glands increased significantly at 15 and 13 °C, and the triglycerides in adductor muscles also increased significantly at low temperatures. Furthermore, the level of ∑n-6 PUFA in digestive glands and adductor muscles increased significantly, the level of ∑n-3 PUFA and EPA + DHA in adductor muscles increased significantly, whereas the level of ∑n-3 PUFA and EPA + DHA in digestive glands decreased significantly at 13 and 11 °C. This is the first report on the variations of lipids and fatty acids in mollusks under chronic low temperature stress. The present results also showed that both lipids and PUFA played important roles in animal resistance to low temperature stress, which can provide guidance for improving low temperature tolerance of bivalves. • Low temperature induce gill damage and lipids peroxidation in noble scallop. • Triglycerides and cholesterol of digestive gland increased at low temperature. • Triglycerides and cholesterol decreased at near lethal low temperature (11 °C). • Low temperature stress increase the EPA + DHA in adductor muscle. • Low temperature stress decrease the EPA + DHA in digestive gland. [ABSTRACT FROM AUTHOR]

An eight-week feeding trial was conducted to evaluate the influence of an alternating linseed oil (LO) and fish oil (FO) feeding strategy in black seabream A. schlegelii (initial weight, 8.49 ± 0.01 g). Two isonitrogenous and isolipidic feeds were formulated to contain FO or LO, and used to enable three feeding strategy treatments termed FO (feeding the FO diet for 8 weeks), LO (feeding the LO diet for 8 weeks) and FO re-feeding (feeding LO for 4 weeks then FO for 4 weeks). Fish in the FO re-feeding and FO groups had significantly higher final body weights (FBW), weight gains (WG), specific growth rates (SGR) but lower muscle lipid content than fish in the LO group. In muscle, the FO re-feeding strategy restored eicosapentaenoic and docosahexaenoic acid contents to 82.67% and 83.84%, respectively, of those in fish fed the FO treatment. In addition, the FO re-feeding strategy significantly down-regulated the expression levels of genes related to long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis and lipogenesis, including fatty acyl desaturase (fads2), elongase of very long-chain fatty acids 4a (elovl4a) and sterol regulatory element-binding protein-1 (srebp-1) compared to fish fed the LO treatment. Similarly, the hepatic Srebp-1c concentration in fish in the FO re-feeding group was markedly lower than in fish in the LO treatment group. Expression of the lipid catabolism gene adipose triglyceride lipase (atgl) was up-regulated in fish in the FO re-feeding group compared with fish in the LO group. Overall, the present study indicated that a strategy of re-feeding FO following feeding LO for four-week promoted growth, mitigated lipid accumulation in muscle, and effectively restored muscle n-3 LC-PUFA levels in A. schlegelii. • Dietary LO had an adverse effect on growth in A. schlegelii. • Growth and feed utilization were recovered by FO re-feeding in A. schlegelii. • FO re-feeding could effectively restore DHA and EPA contents in muscle. • After FO re-feeding, DHA and EPA were better retained in muscle than in liver. • FO-refeeding reduced lipid accumulation by regulating gene expression. [ABSTRACT FROM AUTHOR]

Abstract: Stock enhancement, through the release of cultured juveniles, has been suggested as a possible recovery tool for depleted red (Paralithodes camtschaticus) and blue (Paralithodes platypus) king crab populations in Alaska, USA. Considerable progress has been made in the past decade in red king crab culture technology, but similar technologies are less developed for blue king crabs. We examined changes in organic content, lipid classes, and fatty acids (FAs) during the larval (zoeae), post-larval (glaucothoe), and first juvenile stages to understand energetics, nutritional requirements, and potential dietary deficiencies of this new aquaculture species. Total lipids increased throughout the larval stages and then showed a decrease in both total lipids and neutral storage lipids (triacylglycerols) during the non-feeding glaucothoe phase. The proportions of C18 polyunsaturated FAs (PUFAs) dramatically increased from the first zoeal (Z1) to the second zoeal stage (Z2), reflecting the uptake of enriched Artemia FAs. Both the selective retention of C20 & 22 PUFAs relative to their diet and the proportional increase in these PUFAs during the non-feeding glaucothoe stage suggest that they are essential for early growth and survival. Analytical measures of total lipids were highly correlated with a hatchery-based visual assessment of maximum lipid droplet size, an index of relative nutritional health. Formulated hatchery larval diets containing high levels of C20 & 22 PUFAs may optimize nutrition in early ontogeny for blue king crabs, but future research should refine specific ratios and absolute amounts. [Copyright &y& Elsevier]

Abstract: High-quality live food is essential for reducing the frequent high mortality of newly hatched fat snook (Centropomus parallelus) larvae in hatcheries. Copepods, a rich nutrition source, cultivated with the microalgae Chaetoceros muelleri and Isochrysis galbana, were evaluated as food for 0–14-day-old larvae. Two experiments were performed using nine 50-L tanks stocked with 2500 embryonated fat snook eggs. Three different dietary (treatments) were tested in triplicate: Experiment 1, Treatment 1 (Control), using rotifers Brachionus rotundiformis (20mL−1); Treatment 2 (Copepod), larvae were fed with Acartia tonsa (nauplii and copepodits, 0.1mL−1); and Treatment 3 (Mixed), larvae were fed with A. tonsa (0.05mL−1) and rotifers (10mL−1). In Experiment 2 to increase the density of live food, food organisms and the phytoplankton were introduced into the experimental tanks with the embryonated eggs and were stocked: Treatment 1, 20rotifersmL−1; Treatment 2, 0.5copepodsmL−1; and Treatment 3, 10rotifersmL−1 and 0.25copepodsmL−1. In Experiment 1, the Mixed Treatment increased significantly the survival rate (16.0%±7.5%) and mean larval weight (0.84±0.05mg) in relation to the other treatments. In Experiment 2, we observed significant improvements in larval notochord flexion in the Copepod and Mixed Treatment. The essential fatty acid profile of fat snook eggs had a DHA:EPA:ARA ratio of 11.4:2.4:1.0 while larvae in the Mixed and Copepods Treatments had ratios of 2.5:1.9:1.0 and 5.5:1.9:1.0, respectively. We conclude that the survival, development and the relationship between the major fatty acids were improved in treatments with copepods. [Copyright &y& Elsevier]

Abstract: Salmon aquaculture is currently reliant on fish oil as the major source of the very long chain (VLc) n−3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This report details the first study of an alternative source of EPA from the yeast Yarrowia lipolytica in feed for fish. Atlantic salmon was fed three dietary levels, 10% (Y10), 20% (Y20) and 30% (Y30) of a heat killed dried yeast biomass containing 6% EPA and 20% oil by weight for 95days. The yeast biomass was replacing fish meal, rapeseed oil and wheat meal in the diets. The increase in fish weight from 180 to 400g on the diets containing yeast, was comparable to groups fed control diets with either rapeseed oil (RO) or a mix of rapeseed and fish oil. The apparent digestibility coefficient for energy, protein and lipids, including n−3 fatty acids, decreased with increased inclusion of yeast biomass. Feed conversion ratio was higher, and energy retention lower, in the Y30 group than in the others. Protein retention was the lowest in the Y30 and FO groups followed by Y20. Fillet fatty acid composition reflected the higher ratio of EPA to DHA in the feeds added yeast. However, lower whole body retention of EPA, and higher retention of DPA (docosapentaenoic acid) and DHA, compared to average fatty acid retention, suggest that there had been some conversion of the EPA provided by the yeast into DPA (docosapentaenoic acid) and DHA in fish. [Copyright &y& Elsevier]

Abstract: A 30-day trial was performed to evaluate the reproductive performance of wild and 2nd generation domesticated Farfantepenaeus duorarum broodstock. Changes in biochemical composition and fatty acids (FA) profile in the 1st and 4th spawn order females were used as indicators of nutritional condition. Wild population of F. duorarum presented significantly better reproductive outcomes as compared to domesticated ones. Wild spawners achieved significantly higher number of eggs per spawn, number of egg per spawn per g of spawner''s body weight and number of nauplii per spawn (P<0.05). Latency period was significantly shorter (P<0.05) for wild than for domesticated females (11 vs 17days). Wild spawners also presented less mortality (6 vs 12%), higher number of total spawns (51 vs 33), spawns per ablated and per spawning females as well as higher total eggs and nauplii production. On the other hand, domesticated females presented higher number of females that spawned at least once (89 vs 76%). The higher spawning activity was reflected in lower levels of acylglycerides (AG) and cholesterol content in wild hepatopancreas (HP) and ovary (OV) (P<0.05). FA profile, mainly represented by ARA, EPA and sum of n−3 were higher in hepatopancreas and ovary of wild females, however lower levels were detected in eggs as a result of a high spawning activity. Multivariate analysis performed to detected simultaneous variation in biochemical variables indicated AG as variation pattern''s responsive. [Copyright &y& Elsevier]

Abstract: The tropical spiny lobster, Panulirus ornatus, is a commercially important Palinurid marine lobster species of high market value with wild populations distributed throughout the tropical and sub-tropical Indo-Pacific region. As wild populations of P. ornatus has been over-exploited, so there is interest in the development of this lobster aquaculture to meet current and rising market demand for supply. However, a major challenge for closed-life cycle production of Palinurid lobsters is the development of a commercially viable hatchery technology. There is minimum knowledge of larval nutrition, and in particular, the lipid requirements. The current study focused on investigations into the growth pattern and ontogenetic changes of lipid composition for early–mid stage P. ornatus (stages I–VI) under controlled laboratory conditions. Body wet weight (WW), dry weight (DW) and total body length (TBL) increased exponentially with the number of stages. There were large increases in WW, DW and TBL between stages I and VI, with increases of 4092%, 3864% and 504%, respectively. The greatest increase in DW and WW was noted between stages III to IV while the greatest specific growth rate (SGR) was noted during stages I to II. The lipid class profile of phyllosoma was dominated by phospholipids (PL) for all early stages (I–V) despite the high triacylglyceride (TG) content of Artemia; which was the primary food source. The newly hatched phyllosoma contained higher percentages of total saturated fatty acids (SFA), 20:5n3 (EPA), 22:6n3 (DHA) and total highly unsaturated fatty acids (HUFA) compared to that found in all other stages. From stages II to V, the total lipid, lipid class and fatty acid profile of phyllosoma resembled those of their diet with the exception of 20:4n6 (ARA). The increase in ARA concentration during phyllosoma development (stages II–V) suggested that mid-stage phyllosoma (IV and V) had a higher requirement compared to that noted in early-stage (II and III) phyllosoma. It was noted that early-stage (II and III) phyllosoma preferentially sequestered and accumulated a higher proportion of EPA and DHA compared to that present in their diets. These data indicate that early–mid stage P. ornatus phyllosoma have an ability to preferentially sequester, store or modify their dietary lipid composition to support normal growth and development. These results provide important morphometric date useful in the evaluation of larval feed and culture conditions as well as, providing baseline larval lipid nutrition data required for the development of artificial diets for P. ornatus phyllosoma. [Copyright &y& Elsevier]

Abstract: Gilthead sea bream (Sparus aurata) were fed in triplicate groups with a commercial standard diet from the juvenile stage to male–female sex reversal under natural day-length and temperature conditions. Every 3–4months during the two-year production cycle, 9 fish were randomly selected and sampled for flesh composition analyses of total lipid levels and fatty acid (FA) composition. Curvilinear regressions fitting total lipid levels and % FAs in total lipids were made to underline the differential distribution of a given fillet FA within neutral and polar lipid fractions. This dataset along with published results on market-size fish were combined for multilinear regression approaches, with the aim of describing strong relationships (P<0.0001) between fillet FA composition and two independent variables: dietary FA composition and fillet lipid level. For saturated (14:0, 16:0, 18:0) and monounsaturated (16:1n-7, 18:1n-7, 18:1n-9, 20:1n-9) FAs, the overall variance in fillet FA composition is primarily explained by dietary FA composition and secondly by fillet lipid level. This second independent variable also contributes to explain the variations observed in arachidonic acid (20:4n-6) and docosahexaenoic acid (22:6n-3), but a statistically significant contribution is not found for linoleic acid (18:2n-6), linolenic acid (18:3n-3), eicosapentaenoic acid (20:5n-3) and docosapentaenoic acid (22:5n-3). The consistency of these predictive equations in our particular rearing conditions was proved by means of a test validation trial, using fish fed an experimental diet based on plant proteins and fish oil. [Copyright &y& Elsevier]

Abstract: Recently, we reported that growth of Atlantic salmon was reduced as dietary fishmeal (FM) was lowered from 25% to 5% in dual-substituted feeds compared to a control diet, formulated to represent the current upper levels of substitution of FM and fish oil. In the present study, the effects of different alternative protein blends and binders on growth of salmon fed dual-substituted feeds containing only 11% FM, and with 60% of dietary fish oil replaced by rapeseed oil were investigated. Salmon of initial weight 1.3kg were grown to market size (>3kg) over a period of 19weeks. Salmon fed the diets with reduced FM showed lower final weight, SGR and TGC, associated with reduced feed intake. There was a tendency for increased FCR in fish fed the diets containing reduced FM although this was not significant, and there was no effect on PER. There were no significant effects on digestibility of protein or fat but the two parameters varied reciprocally and there were clear trends of increased protein and lower fat digestibilities in fish fed diets with reduced FM. Although lipid and fatty acid compositions did not vary greatly between diets there were significant effects on fish tissue compositions. Thus, liver lipid was generally reduced in fish fed diets with lower FM, significantly so in two of the four treatments. The proportions of monoenes were significantly lower and those of polyunsaturated fatty acids (PUFA) significantly higher in flesh and liver of fish fed diets with reduced levels of FM. The increased proportions of PUFA were due to increased percentages of 20:4n−6, 20:5n−3, 22:5n−3 and, although not consistently significant, 22:6n−3. The mechanisms for these unexpected effects of diet on tissue lipids and fatty acids are discussed. [Copyright &y& Elsevier]

Abstract: Although the use of fish meal (FM) and fish oil (FO) has been extensive in Atlantic salmon culture, there is a growing need for less reliance on these commodities. Moreover, it is crucial for the aquafeed industry to optimise the use of dietary protein and to improve the protein utilisation in salmon diets. The interactive effects of the dietary protein/lipid level and rapeseed oil (RO) inclusion on growth, feed utilisation, nutrient and fatty acid (FA) digestibility and whole body chemical composition of large Atlantic salmon (Salmo salar L.), reared at summer water temperatures (11.6°C), were investigated in a ten week feeding trial. The fish (initial weight 2053g) were fed six isoenergetic diets in a factorial design containing 350g kg−1/350g, kg−1, 330g kg−1/360g kg−1, 290g kg−1/380g kg−1 of protein/lipid for high protein (HP), medium protein (MP) and low protein (LP) diets, respectively. At all protein/lipid levels the oil source was either FO or RO (60% of the added oil). At the end of the trial the final weights ranged from 3340–3664g and the FCR from 0.99–1.10. The protein level did not affect significantly any of the growth parameters but the oil source had a significant effect on final weight, specific growth rate (SGR) and thermal growth coefficient (TGC), showing improved growth with RO inclusion. This could be explained by the significantly higher lipid digestibility of the fish fed the diets containing RO (86.1 vs. 92.2%) which was probably affected by the diet FA composition; the apparent digestibility coefficient (ADC) of saturated FA, and to a lesser extent of unsaturated FA and especially monoenes, was improved by RO inclusion. The protein ADC was significantly affected by the protein level indicating a higher ADC for the HP diets compared to the LP (80.1 vs. 77.7%, respectively). Regarding the whole body composition, moisture was significantly affected by both factors, the fat content was significantly affected only by the oil source, while significant interactions were shown for the protein content. In conclusion, the results of this study suggest that low protein/high lipid diets can be used with no negative effects on the growth, FCR and chemical composition of Atlantic salmon reared at high water temperatures. Moreover, the replacement of FO with RO can enhance the growth of the fish as well as the nutrient and FA digestibility of the diets. [Copyright &y& Elsevier]

Abstract: The fatty acid reserves of broodstocks profoundly affect the fecundity of spawners as well as the quality of the newly hatched larvae. Investigation of the lipid and fatty acid changes in wild-caught broodstocks during the reproductive season should elucidate the most effective strategy with which to enrich broodstocks in artificial breeding programs. This paper investigated the lipid and fatty acid compositions of wild broodstocks of silver pomfret, Pampus argenteus, caught at the Zhoushan fishery ground during the reproductive season. The results indicated that there were significant differences in lipid content among gonad, muscle and liver; mean lipid levels in ovary, testis, liver and muscle were 41.85%, 18.54%, 27.80% and 32.31%, respectively. The lipid content in gonads at developmental stages III–V was relatively more stable than that in muscle or liver, although the lipid level increased in ovary and decreased in muscle as the female broodstocks developed from phase III to phase V. There were significant differences in fatty acid levels among broodstock ovary, testis, muscle and liver. The dominant fatty acids in ovary were as follows: 18:1n−9 (16.91%)>DHA (docosahexaenoic acid) (15.46%)>16:4n−3 (13.14%)>16:0 (12.65%)>EPA (eicosapentaenoic acid) (6.46%)>16:1 (5.34%). In female broodstock liver and muscle, the dominant fatty acids were 16:0 (36.42%)>18:1n−9 (23.26%)>18:0 (7.50%)>16:1 (6.98%)>14:0 (5.10%)>DHA (4.98%) and 18:1n−9 (26.35%)>16:0 (24.07%)>DHA (8.38%)>16:1 (6.62%)>18:0 (5.48%)>14:0(4.44%), respectively. The dominant fatty acids in testis were as follows: DHA (29.84%)>16:0 (23.93%)>18:1n−9 (8.78%)>18:0 (7.98%)>EPA (7.96%)>ARA (arachidonic acid) (3.24%). In the liver and muscle of male broodstocks, the dominant fatty acids were 16:0 (30.14%)>18:1n−9 (25.54%)>18:0 (8.24%)>16:1 (7.24%)>14:0 (5.20%)>DHA (4.75%) and 18:1n−9 (29.51%)>16:0 (23.90%)>DHA (7.80%)>18:0 (6.34%)>16:1 (6.22%)>14:0(3.88%), respectively. The n−3PUFAs and n−3/n−6 ratios in ovary and testis of the broodstocks were significant higher than those in the liver and muscle of the broodstocks. The changes in fatty acid composition in ovary and testis as the broodstocks developed from phase III to phase V were smaller in magnitude than those in muscle or liver. It is therefore suggested that the lipid preferentially transferred to ovary from muscle during the reproductive season, and the PUFAs, such as DHA, EPA, 16:4n−3 and ARA, were selectively transferred to, and conserved in, the ovaries of silver pomfret broodstocks. [Copyright &y& Elsevier]

Abstract: This study investigated the effects of stocking density on the growth and fatty acid (FA) of Brycon insignis metabolism. Fingerlings (360) were distributed into eight ponds at two stocking densities (105 and 210g/m3). The analysis of growth showed that the condition factor (K) and the coefficient of variation (CV) for body mass were not affected by stocking density. However, final body mass and length, specific growth rate (SGR), and weight gain (WG) were higher in the low stocking density group, which also presented a higher feed efficiency (FE) and survival (S). By contrast, muscle protein levels were higher in the high stocking density group. The plasma and muscle lipid content were not affected by stocking density, but fish reared at lower stocking density presented higher lipid concentration in the liver, with no differences in hepatosomatic index values. Even with the differences observed in metabolic and growth parameters, plasma cortisol was not affected by stocking density. The FA profile in the muscle and liver neutral fraction were not affected by stocking density, but the FA in the polar fractions differed between the two stocking densities. In the liver, total polyunsaturated fatty acids (PUFA) and PUFA n−3 increased in higher stocking density, mainly due to an increase in docosahexaenoic acid (DHA). In addition, PUFA n−6 were also increased in the higher stocking density group, mainly due to an increase in arachidonic acid (AA) and docosadienoic acid (22:2n−6). In the muscle polar fraction, the saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) decreased in the animals from the higher stocking density group, and this reduction was compensated by an increase in PUFA n−3 and PUFA n−6, mainly the FA with 20–22 carbons (20:4n−6; 22:4:n−6; 22:5n−6, 22:5n−3, and 22:6n−3). A different profile was observed for the C18 PUFAs, mainly 18:2n−6 and 18:4n−6, which were higher in the lower density stocking group. The data suggest that when living in high stocking density, B. insignis differentially utilizes the hepatic lipids as energy source and remodels the membrane fatty acids, with higher amounts of DHA in the polar muscle fraction compensated for by a decrease in MUFA. The zootechnical and physiological indices reveal that the lower stocking density group achieve overall better performance. [Copyright &y& Elsevier]

Abstract: Due to economic pressures from high fish oil prices and from buyers and consumers requiring sustainable practices, the use of high levels of fish oils in aquafeeds is no longer desirable. The present study evaluated the replacement of marine fish oil (MFO) with alternative oils in a plant based diet. Litopenaeus vannamei juveniles (1.55g) were stocked into 650L circular tanks at 26shrimptank−1 and fed 13 experimental diets over a 58-day growth trial. Diets were formulated with soybean oil (SO) as replacement for MFO at inclusion ratios of 100:0, 50:50, 40:60, 30:70, 20:80, and 10:90 as MFO:SO. The next series of diets were formulated to keep n-3/n-6 ratios close to the ratio attained at 50% MFO replacement while removing MFO, this was done by increasing linolenic acid content through the use of linseed oil (LO), resulting in the following MFO:SO:LO ratios, 40:53.4:6.6, 30:56.9:13.1, 20:60:20, and 10:63.7:26.3. Three additional diets were evaluated which included a high LO (10:90 as MFO:LO) and a high soybean oil diet using a low linolenic acid acid soybean oil (LLSO) at a 10:90 ratio of MFO:LLSO. The final diet was a commercial diet which served as a reference. The results showed no statistically significant differences in final mean weight, growth, survival or FCR values of shrimp fed the various diets. Fatty acid (FA) profiles of tail muscle form shrimp fed the various lipid sources in general conformed to the lipids of the feed. Shrimp fed Diet 11, with 19.81mg of linolenic acid per gram of diet had the highest amount of this FA in shrimp tail muscle (5.61mgg−1 wet tissue) and a relatively high n-3/n-6 ratio of 1.15, but at the same time, practically the lowest content of eicosapentaenoic (4.07mgg−1 wet tissue) and docosahexaenoic (2.04mgg−1 wet tissue) acid among the dietary treatments. This response is typical for animals that cannot elongate and desaturate poly-unsaturated into highly-unsaturated FA (HUFA). As shrimp production was not influenced by lipid source or n-3/n-6 ratio, clearly a range of lipids could be used to support growth. However, as the optimal dietary approach for humans is to consume preformed n-3 HUFA by eating seafood, it would be best for farmed shrimp to retain high levels of n-3 HUFA and high n-3/n-6 ratios as found in wild caught shrimp. [Copyright &y& Elsevier]

Abstract: The biochemical composition of eggs and the nutrient dynamics during early ontogeny can provide better understanding on the nutritional requirements of both broodstock and first-feeding fish, thus constituting a valuable tool for improvement of aquaculture procedures. This study constitutes the first record of lipid composition and fatty acid dynamics during early development of seahorses. Lipid content and fatty acid profile were determined for Hippocampus guttulatus eggs and newborn juveniles, and their patterns of consumption were analyzed during embryonic development. H. guttulatus produced small broods (426±128 juveniles) but invested in the production of large eggs (2.44±0.37mm) that resulted in large fingerlings (15.53±1.28mm), which may have a high survival capacity. The total lipid content of seahorse eggs (17.6% DW) was within the typical range of marine fish eggs. Eggs were dominated by PUFA (43.9%), mainly n−3 HUFA (17.4% of DHA and 13.2% of EPA), and showed a lower MUFA content (22.5%). Extremely low AA levels (0.6%) and particularly high EPA concentrations resulted in a low DHA:EPA ratio (1.3) and high EPA:AA (22.3) and n−3:n−6 (12.2) ratios. Fatty acid consumption during embryonic development was considerably high (67.8%), reflecting the high requirements of seahorse embryos. Fatty acids were depleted at different rates, with PUFA being preferentially consumed (75.2%), while SFA were selectively retained (59.2%). PUFA constituted the major source of metabolic energy and the fatty acids 16:0, EPA and DHA were the main fatty acids to fulfill the energetic demands of seahorse embryos. Essential fatty acids (AA, EPA and DHA) were not preferentially retained, with EPA being catabolized at a particularly high rate (88.0%). These patterns of embryonic consumption resulted in newborn juveniles with an exceptionally low lipid content (5.0% DW), a predominance of SFA (41.0%) and extremely low EPA levels (5.0%). Fatty acid composition of H. guttulatus eggs and juveniles provided important clues to determine seahorse requirements, so that suitable feeding protocols could be developed. The use of broodstock and juvenile diets that reflect the lipid profile of eggs will allow the accomplishment of nutritional requirements and improvement of seahorse production. [Copyright &y& Elsevier]

Abstract: The total fatty acid composition of rainbow trout (Oncorhynchus mykiss) spermatozoa and seminal plasma was investigated in fresh and in stored semen using gas liquid chromatography. Triglycerides, phospholipids, and cholesterol were measured and the effect of fatty acids, triglycerides, and cholesterol on sperm functionality was evaluated. In seminal plasma and spermatozoa saturated fatty acids occurred in higher quantities than unsaturated fatty acids. In spermatozoa, the concentrations of monounsaturated fatty acids were higher than the concentrations of polyunsaturated fatty acids. In seminal plasma the concentrations were approximately equal. Myristic acid, palmitic acid, and stearic acid were main saturated fatty acids and oleic acid, vaccenic acid, and linolenic acid main unsaturated fatty acids of spermatozoa and seminal plasma. In spermatozoa linoleic acid, docosahexaenoic acid, eicosapentaenoic acid, arachidonic acid, and docosahexaenoic acid were found in high concentrations, too, in seminal plasma palmitoleic acid and eicosenoic acid. During semen storage the fatty acid composition changed in spermatozoa and in seminal plasma indicating that fatty acids were metabolized. Palmitic acid, the one of the main saturated fatty acids of spermatozoa and seminal plasma, and the unsaturated fatty acids, arachidonic acid and linoleic acid, which occur in spermatozoa and seminal plasma of rainbow trout, too, had a positive effect on sperm viability during immotile, unfrozen storage of spermatozoa as they increased the motility rate and average path velocity, which could be activated. Also the sperm fertility was improved by addition of fatty acids. A similar effect was found by arachidic acid, a saturated fatty acid, which was not detected in spermatozoa and seminal plasma. Therefore, semen short-term storage techniques can be improved by supplementation of storage solutions with fatty acids. Fatty acids had no effect on sperm motility duration. They had also no effect on sperm cryoresistance as the motility pattern and fertility of spermatozoa frozen–thawed with or without fatty acids were similar. [Copyright &y& Elsevier]

Abstract: The aim of the present study was to investigate how different dietary lipid levels affect growth, liver lipid deposition, apparent digestibility, apparent retention and utilization of total lipid and fatty acids in Atlantic cod. Individually tagged cod, with an average weight of 360 g, were randomly distributed in nine tanks, 49 fish per tank. Five diets with increasing dietary lipid level in the range of 80 to 268 g kg−1 were fed to the fish for 85 days, in a regression design. Increasing dietary lipid level did not affect growth of Atlantic cod, but the hepatic somatic index (HSI) increased from 7.5 to 11.8%. The liver lipid level increased from 719 to 785 g kg−1, constituting from 83 to 88% of total body lipid. Apparent lipid digestibility had an optimum level at a dietary lipid content between 138 and 180 g lipid kg−1 diet with a marked decrease at lipid levels above 180 g kg−1. Digestibility of saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) responded similar to that of total lipid, while digestibility of the n−3 fatty acids increased with increasing dietary lipid level. Apparent retention of fatty acids increased with increasing dietary lipid level, except for 18:0 and 18:1n−9. Apparent retention of 14:0 and 16:0 was low (0–60%), while the retention of 18:0 was high (150–200%), indicating that cod may elongate 14:0 and 16:0 to 18:0 and also utilize these fatty acids for energy production, particularly in low lipid diets. The low apparent retention of long MUFAs indicated that they were used for energy production. Apparent retentions of 22:6n−3 and 20:5n−3 were intermediate (50–80%) at low dietary lipid inclusion, but increased with increasing lipid level, indicating that also these essential fatty acids may have been utilized for energy production, especially in low lipid diets. [Copyright &y& Elsevier]

Abstract: The influence of dietary fish and plant oils on fatty acid compositions of Atlantic cod tissues was examined to test whether modulation of fatty acid profile following a dietary change differs between lipid-poor (fillet) and lipid-rich (liver) tissues. A dilution model [Robin, J.H., Regost, C., Arzel, J., Kaushik, S.J., 2003. Fatty acid profile of fish following a change in dietary fatty acid source: model of fatty acid composition with a dilution hypothesis. Aquaculture 225, 283–293.] was used for the test. The experiment was divided into a build-up and a restoration phase. Fish weight increased from an initial 30 g to 100 g at the end of build-up and to 300 g at termination. During build-up, triplicate tanks of fish were fed one of four feeds; LF (fish oil, 13% lipid), HF (fish oil, 18% lipid), PO (40 palm oil:20 linseed oil:40 fish oil, 13% lipid) or RO (40 rapeseed oil:20 linseed oil:40 fish oil, 13% lipid). During restoration the cod were fed either LF or HF; four groups experienced a feed change (ROLF, ROHF, POLF, and POHF), and two groups were fed either LF or HF during both build-up and restoration. There were triplicate tanks of fish for each restoration phase treatment. Samples were taken at the start, at the end of build-up, mid-way through restoration and at termination, with four fish being taken from each tank each time; tissue indices were calculated, and analyses of lipid and fatty acids were undertaken, with a focus on 18C fatty acids (18:1 isomers, 18:2n-6 and 18:3n-3) and two n-3 HUFAs 20:5n-3 and 22:6n-3. During build-up, the cod fed HF and LF accumulated relatively more liver lipid than those fed PO and RO, implying that there were differences in the ways in which the lipids in the fish oil and plant oils were digested, absorbed and metabolised. At the end of build-up the cod fed PO and RO had tissues with higher 18C fatty acid, and lower n-3 HUFA, concentrations than the cod fed LF and HF; tissue fatty acid compositions reflected those of the feed oils. The fatty acid profiles of ROLF, ROHF, POLF, and POHF cod were modified during restoration. The changes in concentrations of 18C fatty acids were more rapid than predicted by the dilution model, implying preferential metabolism of 18:1 isomers, 18:2n-6 and 18:3n-3. Concomitant with the decrease in 18C fatty acid percentages there were increases in both 20:5n-3 and 22:6n-3. At termination, fillet percentages of n-3 HUFAs were statistically indistinguishable across treatments, but feed effects on liver lipids 20:5n-3 and 22:6n-3 were still discernible; cod fed PO and RO during build-up had liver lipids with lower percentages of n-3 HUFAs than those of cod fed LF and HF throughout the experiment. The fatty acid compositions of cod tissues are modified following a change in feed oils, but there are some tissue-specific differences in the responses shown. The results indicate that it should be possible to manipulate the fatty acid compositions of cod tissues in desired directions by introducing mixtures of different feed oils at various points in the production cycle. [Copyright &y& Elsevier]

Abstract: This study assessed refined canola oil (CO) as a supplemental dietary lipid source for juvenile fall chinook salmon, Oncorhynchus tshawytscha, parr with respect to possible effects on their growth and osmoregulatory performance and body composition. Diets with equal protein (∼57%) and lipid (∼19%) content (dry weight basis) were supplemented with lipid from either anchovy oil (AO) or CO with AO so that CO comprised 0 (0CO), 11% (11CO), 22% (22CO), 33% (33CO), 43% (43CO) or 54% (54CO) of the dietary lipid content. Triplicate groups of juvenile chinook salmon were fed their prescribed diets for 104 days in freshwater (FW) and 31 days in seawater (SW) after a 4-day transition period. Dietary fatty acid compositions reflected the different proportions of AO and CO in the supplemental lipid. Diet treatment had no effect on fish growth, feed intake, feed efficiency, protein utilization, fish mortality or terminal whole body water and ash percentages. Whole body lipid percentages were higher in 11CO and 43CO fish than in 33CO fish and in 11CO fish versus 22CO fish. Whole body protein percentages were highest in 33CO, 43CO and 54CO fish and lowest in 0CO and 22CO fish. Terminal whole body fatty acid compositions were influenced strongly by the dietary fatty acid compositions. Haematocrit and muscle water percentages were not affected consistently and plasma Na+ and Cl− concentrations were unaffected by diet treatment in FW or 24-h seawater challenges during FW residency. Also, diet treatment had no effect on the physiological parameters after SW residency. We conclude that dietary treatment had no effect on fish growth performance under our experimental conditions. Also, the dietary inclusion of CO neither facilitated nor impaired the transfer of chinook salmon parr to seawater. Thus, CO was found to be an excellent and cost-effective source of supplemental dietary lipid for culture of juvenile fall chinook salmon during freshwater residency. [Copyright &y& Elsevier]

Abstract: The effects of different dietary lipids (hydrogenated coconut oil, corn oil, linseed oil, and mixtures of corn oil, linseed oil, menhaden oil, and/or soy lecithin) on the fatty acid composition of the sea urchin Strongylocentrotus droebachiensis were investigated. Dietary lipid compositions were reflected in the fatty acid profiles of sea urchin guts, gonads and shells. The shells had the highest level of 20:4n-6 and 20:5n-3, while the highest levels of monounsaturated fatty acids were seen in the guts. Tissue levels of 20:4n-6 and 20:5n-3 were influenced by the dietary levels of 18:2n-6 and 18:3n-3. The addition of soy lecithin to the diet (CLnML) enhanced the production and incorporation of 20:4n-6 in shell and gonad. Sea urchin also synthesized and incorporated 20 and 22 carbon non-methylene-interrupted dienoic fatty acids (NMIDs) in all tissue lipids. The NMID content varied among the different tissues and was influenced by the dietary lipid source. The hydrogenated coconut oil (HCO) diet resulted in the greatest NMID content, while the lowest levels were seen in sea urchins fed diets containing a mixture of corn oil, linseed oil, menhaden oil and lecithin (CLnML). The NMID content was lowest in gut and highest in the shell. Significant levels of mead acid (20:3n-9) were detected in the shells of sea urchins fed the EFA-deficient diet (HCO). The enzymatic capabilities of sea urchins to desaturate and elongate 18:2n-6 to 20:4n-6 and 18:3n-3 to 20:5n-3, as well as the capabilities to de novo synthesize NMID were hypothesized. Possible physiological roles and mechanisms for formation of NMID are discussed. [Copyright &y& Elsevier]

Abstract: This study assessed the potential of refined canola oil (CO) as a source of supplemental dietary lipid for pre-smolt spring chinook salmon (Oncorhynchus tshawytscha) over a period of 30 weeks. Triplicate groups of 320 fry (∼0.80 g), reared in flow-through well water (8–11.5 °C), were fed one of four steam-pelleted dry diets with equivalent gross energy (24.3 MJ/kg), protein (∼51.3%) and lipid (∼21.6%) content on a dry-weight basis. CO furnished either 0%, 33%, 67%, or 100% of the supplemental dietary lipid, with the remainder from a commercial blend of 1:1 anchovy oil and poultry fat (APF). Thus, CO comprised either 0% (dAPF), 25% (CO25), 49% (CO49), or 72% (CO72) of total dietary lipid content. Overall fish growth rate, feed intake, feed efficiency, protein utilization, percent survival, and terminal whole body proximate constituents were unaffected by diet treatment. Dietary lipid compositions reflected the ratios of CO and APF in the supplemental lipid and their respective fatty acid compositions. Whole body fatty acid compositions mirrored those of diet treatments. However, some essential fatty acids, namely, arachidonic acid (20:4n-6; AA), and docosahexaenoic acid (22:6n-3; DHA) were conserved in fish regardless of dietary CO level. Direct relationships were found between dietary and whole body concentrations of: 18:2n-6 (R 2 =0.94; slope=0.72), 18:3n-3 (R 2 =0.99; slope=0.58), 20:4n-6 (R 2 =0.84; slope=0.42), 20:5n-3 (R 2 =0.99; slope=0.43) and 22:6n-3 (R 2 =0.82; slope=1.25). High dietary levels of 18:3n-3, 18:2n-6, and 20:5n-3 may have been utilized for energy or converted to more unsaturated derivatives. Overall development of ionoregulatory ability, as assessed by 24-h seawater challenge tests, was unaffected by diet. However, whole body chloride content was generally inversely related to dietary CO level during early development. Our findings suggest that there is excellent potential for long-term replacement of fish oil with canola oil in the diet of pre-smolt spring chinook salmon, provided that some marine oil is present to ensure that the essential fatty acid needs of the fish are met. [Copyright &y& Elsevier]

Abstract: Dietary conjugated linoleic acids (CLA) can be successfully incorporated in several fish species but have not been evaluated in marine fish. A 12-week growth trial was conducted with European sea bass juveniles, having an initial weight of 13.96±0.16 g (S.D.). Fish were fed to satiation, twice a day, with diets containing graded amounts of CLA (0, 0.5, 0.75, 1.0 or 2%). At the end of the experiment, the daily growth index, feed intake, feed efficiency and whole body composition and tissue fatty acid profile were determined. The activity of some enzymes (glucose-6-phosphate dehydrogenase, G6PD, malic enzyme, ME, and fatty acid synthetase, FAS,) was also measured in the liver. Digestibility of the diets was determined, using chromic oxide as inert tracer, and the Guelph System for faecal collection. No significant differences were detected (P >0.05) in growth parameters, feed conversion, body composition or nutrient retention among treatments. Dietary CLA did not affect significantly the activity of the lipogenic enzymes when expressed as mIU/mg protein, but when the HSI variations were taken into consideration (IU/100 g fish) the activities of both G6PD and ME seemed to be depressed in fish fed increasing CLA levels. Dietary inclusion of CLA had no effect on tissue lipid content, but significantly affected the total percentages of polyunsaturated (PUFA) and monounsaturated fatty acids (MUFA) in both muscle and liver tissues. Dietary CLA supplementation resulted in a significant increase of the biologically active trans-10, cis-12 and cis-9, trans-11 CLA isomers in both tissues. The total accumulation of CLA was clearly higher in muscle than in liver, reaching 5.61% and 3.00% of total lipids, respectively, in fish fed 2% CLA. The results obtained in this experiment clearly suggest European sea bass can successfully incorporate CLA in both liver and muscle up to 2%, contributing to the production of a functional food. [Copyright &y& Elsevier]

Abstract: A quantitative approach is presented to evaluate fatty acid incorporation in fish. Fatty acid composition of European sea bass juvenile was studied during an experiment using 6 isoproteic (54%) and isolipidic (18%) diets containing 0.23, 0.56, 0.72, 0.86, 1.01 and 1.86% DM n-3 highly unsaturated fatty acids (n-3 HUFA). Whole body fatty acid compositions were studied at the beginning and after 52 and 81 days feeding, fatty acid profiles evolved during time under dietary influences. Incorporations of individual fatty acids into total lipids were calculated as increases in individual fatty acids as percentages of the increase in total fatty acids during growth, on a per animal basis. Relative incorporations (RI) so defined generated similar profiles for the two periods for each dietary treatment, consistent with fatty acids being incorporated in a stable way during the experiment. For most fatty acids, linear regressions could be drawn between RIs in whole fish and % of fatty acids in dietary lipid. RIs for DHA, EPA and AA demonstrated these HUFAs were incorporated in the fish in lower proportion that diet contents, in this experiment. Fractional retentions (FRs) of individual fatty acids were also calculated by dividing the quantities of given fatty acids present in lipid accumulated by the fish by the quantities of corresponding fatty acids ingested in the diet. Lipogenic activity was evidenced by 16:0 and 18:0 having FRs greater than unity. FR values greater than unity for 18:3n-6 and 20:3n-6, and 18:4n-3 in diets containing low levels of HUFA demonstrated some bioconversion capacity from 18:2n-6 and 18:3n-3 precursors, respectively. FRs for n-3 HUFA were negative in fish fed 0.2% n-3 HUFA. In other treatments FRs of n-3 HUFA were 0.5 to 0.6, lower than other dietary fatty acids as linoleic (0.75) or linolenic (0.70) acids. Results indicated a basal loss of DHA estimated around 14 μg g−1 ABW d−1 during the experiment. We conclude that dietary requirements of HUFA by marine fish comprise not only quantities required for production of polar lipids during growth, but also quantities required to replace losses probably induced by the active roles of HUFA. The results also indicate that RI and FR transformations are useful tools for better understanding fatty acid incorporations in juvenile fish. [Copyright &y& Elsevier]

Abstract: The culture of bay scallops, Argopecten irradians, is limited by a reliable and affordable supply of spat and the ability to ensure that animals attain market size within a single growing season. The main goals of our study were thus: (1) to develop growth-optimizing algal diets for implementation in hatcheries, and (2) to identify and compare bay scallop postlarval and juvenile dietary requirements, especially of lipids and fatty acids, which if met may enhance production. Nutritional needs of postlarval bay scallops (present study) are compared with those of sea scallops, Placopecten magellanicus, offered the same diets in a previous companion study. To this end, postlarval (initial shell height, SH=240 μm) and juvenile (initial SH=10 mm) bay scallops were offered 6–7 microalgal diet combinations at 20 °C, for 3 weeks. A similar growth ranking among diets was observed between the two developmental stages. A combination diet of Pavlova sp. (CCMP 459) and Chaetoceros muelleri was far superior to any other diet tested, yielding growth rates of 58 and 357 μm day−1 which were 65% and 25% higher than the next highest performing diet of Tetraselmis striata/C. muelleri in postlarvae and juveniles, respectively. The T. striata/C. muelleri diet, which is limited in the n-3 fatty acid docosahexaenoic acid (DHA), yielded very poor growth of sea scallop postlarvae in a prior study, indicating that bay scallops may have less stringent requirements for DHA than sea scallops. The Pav 459/C. muelleri diet, which also supported the highest growth of sea scallop postlarvae, is characterized by elevated levels of the n-6 fatty acids, arachidonic (AA) in C. muelleri and 4,7,10,13,16-docosapentaenoic (DPA) in Pav 459. The two diets deficient in AA and n-6 DPA, Pavlova lutheri/Thalassiosira weissflogii and P. lutheri/Fragilaria familica, yielded the lowest growth rates in both bay scallop postlarvae and juveniles. Tissue enrichment of these two fatty acids relative to the diet, as well as overall enrichment in ∑n-6 fatty acids was observed across developmental stages and dietary treatments. A similar pattern has previously been observed in sea scallop postlarvae, suggesting a dietary requirement for n-6 fatty acids in pectinids that has often been overlooked in the past. [Copyright &y& Elsevier]

Abstract: We conducted a 12-week feeding trial with LMB fed practical diets differing primarily in lipid source. We reduced the fish oil content of commercially solvent-extracted menhaden fish meal to 0.5–1.2%, and used it as the primary protein source in all test diets. Diets were supplemented with 10% lipid as canola (CAN), chicken (CHK), menhaden fish oil (MFO) or CHK+MFO (50/50%). An additional diet contained non-extracted fish meal and 10% CHK (NEF+CHK), and a commercial trout diet (SC) was also included. Growth, survival, feed utilization, body composition and health parameters were measured to assess diet effects. Weight gain, survival, feed intake, feed conversion ratio, and protein efficiency ratio of LMB fed the test diets did not differ. Weight gain of LMB fed the SC diet was higher than that of LMB fed the test diets. Muscle lipid of fish fed the diet with 10% MFO was higher than that of fish fed diets with an equal mixture of CHK+MFO or NEF+CHK, and muscle lipid of LMB fed the SC diet was higher than that of fish fed the test diets. The n-3 to n-6 fatty acid ratio of the test diets was lower than expected because the poultry meal contained 16% lipid (high in 18:2n-6). The ratio of n-3 to n-6 fatty acids was higher in muscle and liver of fish fed the SC diet than those of fish fed the test diets. Docosahexaenoic acid (22:6n-3) and 20:4n-6 were conserved in fish fed diets without HUFA, but 20:5n-3 declined sharply from initial values. The index of atherogenicity (IA) and the index of thrombogenicity (IT) of LMB fed the test or SC diets were below 1.0 (considered healthful). Lymphocytes were higher in fish fed diets with >4% n-3 fatty acids, including the CAN diet without HUFA. There were no differences in the Hk, Hb, MCHC, or serum lysozyme of LMB fed the test diets, but lysozyme was lower in LMB fed the SC diet than those fed the CHK+MFO diet. Fish fed diets with 10% MFO or CAN had higher alternative complement activity than fish fed diets with CHK. Tissue concentrations of HUFA (especially 20:4n-6 and 22:6n-6) were not depleted in 12 weeks, possibly due to conservation of initial HUFA, synthesis of HUFA from 18:3n-3 and 18:2n-6, or both. Therefore, non-fish oils might reduce diet cost with few deleterious effects for at least a quarter of the production cycle of LMB. [Copyright &y& Elsevier]

Abstract: Some of the conjugated linoleic acids (CLA), cis-9, trans-11 and trans-10, cis-12 isomers, may present a wide range of health benefits. Taking into account these beneficial effects and the relative low amounts of CLA in fish products, commercial diets for juvenile rainbow trout were supplemented with graded levels (0, 0.5, 0.75, 1 and 2%) of CLA. Duplicated groups of 5.3 g fish were fed to satiation, twice a day, over a period of 12 weeks with a CLA mixture, containing mainly the bioactive cis-9, trans-11 and trans-10, cis-12 isomers. The increase of dietary CLA levels did not affect growth performance, feed conversion ratio (FCR), hepatosomatic index (HSI) or viscerosomatic index (VSI) of the rainbow trout juveniles. Total lipids in muscle and liver were similar among treatments. In viscera, CLA supplementation reduced total lipids, but only the 0.5% CLA treatment differed significantly from the control. The fatty acid profile was affected by the dietary inclusion of CLA, resulting in a significant increase of the saturated and polyunsaturated fractions and a general decrease of the monounsaturated one, in both muscle and viscera. Nevertheless, in liver only fish fed 1% CLA had a significantly higher saturated fraction. The general decreases of monounsaturated fatty acid level in tissues with the saturated increase suggest a reduction of Δ-9 desaturase activity. CLA was deposited in all tissues and reflected the dietary CLA level. The highest concentration was attained when the 2% diet was used (6.9 g/100 g lipids in muscle). In conclusion, rainbow trout are capable of incorporating CLA in muscle, liver and viscera better than any other vertebrate, showing that this species is a potential route to increase human CLA ingestion. [Copyright &y& Elsevier]

Abstract: This work reports the interpretation of the spectra from high-resolution 1H MR spectroscopy of extracts, muscle, and whole Atlantic salmon, the latter using a MR image localization technique. It was possible to identify single chemical components, such as hypoxanthine, amino acids, anserine, lactate and some fatty acids, in extracts, whole muscle and whole fish. These techniques may have practical applications for i) the selection of live specimens for breeding, ii) the classification of both live specimens and fillets according to their qualitative and quantitative content of lipids and small molecules, which is of relevance for the nutritional value of fish, and iii) authentication analyses of Atlantic salmon. [Copyright &y& Elsevier]

Relatively little is known of the nutritional requirements of sea urchins, especially at the juvenile stages. One of the costly restrictions on feed formulation for marine fish species is the requirement for fish oils to supply the essential n-3 highly unsaturated fatty acids (HUFA). This study investigated the effects of different dietary lipid sources on the fatty acid composition and metabolism of juvenile green sea urchins (Strongylocentrotus droebachiensis). Kelp (Laminaria longicruris) served as a reference diet. Experimental diets contained 5% of: corn oil (high in 18:2n-6), linseed oil (high in 18:3n-3), menhaden oil (high in n-3 HUFAs 20:5n-3 and 22:6n-3), or 1:1 mixtures of corn oil and linseed oil, or corn oil and menhaden oil or linseed oil and menhaden oil. Unlike marine fish, the sea urchins exhibited ample ability for elongation and desaturation of shorter chain (18 carbon) polyunsaturated fatty acids (PUFA) to longer chain (20 carbon) n-3 and n-6 HUFA. Thus 18:2n-6 from corn oil in the diet resulted in high levels of 20:4n-6 in the sea urchin and similarly 18:3n-3 in the diet resulted in high levels of 20:5n-3. Even when fed kelp or diets with menhaden oil, the sea urchins did not incorporate high levels of 22:6n-3 into their lipids. In addition to the effects of dietary lipid sources on fatty acid composition of the lipids of total soft tissues of sea urchin, there were great differences in fatty acid composition among different tissues and among lipid classes of these tissues. For example, the test (shell) and associated tissue membranes, which are in constant contact with the seawater, incorporated much higher proportions of 20:4n-6 than the gonad or gut tissues. This may reflect an important role of 20:4n-6 in ion transport and osmoregulation. The sea urchins also synthesized a number of 20 and 22 carbon non-methylene-interrupted dienes (NMID) and the concentration of the major NMID was directly related to the tissue levels of 18:2n-6 and inversely proportional to the dietary and tissue levels of n-3 PUFA and HUFA. The significance of these and other interesting aspects of fatty acid metabolism in sea urchins are discussed. [Copyright &y& Elsevier]

Abstract: Wild-caught blacklip (Haliotis rubra) and greenlip (Haliotis laevigata) abalone fed a formulated feed were held from spent to gravid condition at 14 or 18 °C. Half the gravid animals were induced to spawn (using heated UV-irradiated seawater) and the remainder left untreated. All animals were then killed and samples of foot, digestive gland (DG) and gonad analyzed for lipid and fatty acid (FA) composition, as was the feed. The feed contained 5% lipid, of which the major FA were 18:2n−6 (27%), 18:1n−9 (20%) and 16:0 (16%). The lipid content of each tissue was similar for both species, ranging from 4–6%, 8–9%, 14–15%, and 30–32% in the foot, testis, DG and ovary, respectively. Each tissue had a different FA signature, with the foot, testis and ovary characterized by elevated levels of 20:4n−6 (arachidonic acid-ARA), 20:5n−3 (eicosapentaenoic acid-EPA) and 18:2n−6 (linoleic acid-LA), respectively. The proportions of LA and EPA in the DG were intermediate between those of the testis and ovary. There was no change in the lipid or fatty acid composition of blacklip or greenlip tissues in response to the two culture temperatures. Likewise, these compositions did not appear to differ between tissues from spent and gravid individuals. Tissue FA profiles from abalone fed a formulated feed are compared to those from macroalgal feeding trials to determine if the formulated feed can be further improved. [Copyright &y& Elsevier]

Gastrointestinal lipid absorption in Atlantic salmon was studied following force-feeding with a standard grower diet to which isotope-labelled free fatty acid (FFA) [1-14C]-decanoic acid (14C-10:0) and triacylglycerol (TAG) [9,10-3H(N)]-triolein (trioleic acid; 3H-18:1) were added. Following force-feeding, the 15 fish, with an average weight of 704 g, were kept in five circular tanks, three fish per tank, supplied with seawater (salinity, 32 g l−1). At 3, 6, 12, 18 and 48 h, the fish from one tank were killed, and the gastrointestinal (GI) tract was removed and divided into six segments: stomach (ST), anterior, mid, and distal pyloric ceca (PCA, PCM, and PCD, respectively), mid intestine (MI), and distal intestine (DI). The levels of radioactivity (dpm [disintegrations per minute] μg−1 tissue) from the 14C-10:0 and the 3H-18:1 substrates were measured in tissue samples from each segment, allowing an estimation of the amounts of fatty acid substrates absorbed from the lumen into the intestinal cells. The highest levels of radioactivity from both fatty acid substrates were measured in tissue from pyloric ceca (PC) 12 to 18 h after force-feeding. The level of radioactivity from the 14C-10:0 substrate was significantly higher in the PCA than in the PCM and PCD, while there was no clear difference in the level of radioactivity from the 3H-18:1 substrate measured among the different PC tissue segments and the level measured in MI. The level of radioactivity in tissue from DI was negligible to low for both fatty acid substrates. Total lipid accumulation in tissue from PCM, MI and DI was quantified morphometrically at each sampling point using light microscopy and image analysis. These results confirmed the findings from the isotope study, where the highest levels of fat were present at 12 and 18 h following force-feeding. In conclusion, PC was the most important site for fatty acid absorption in the GI tract of Atlantic salmon. [Copyright &y& Elsevier]

This study describes the evolution of tissue composition and serum metabolites of common dentex (Dentex dentex) in different maturity stages. During maturation, diet and perivisceral fat provide the materials needed for the development of gonads. Female and male fish had higher total proteins, total fat, triglycerides (TG) and cholesterol in their serum, at spawning and spermiation, respectively. The examination of dentex tissues (muscle, liver and gonad) revealed no statistically significant differences (P<0.05) in energy density and lipid content during different maturity stages and there was no conclusive evidence that energy density and lipid content differ between sexes. In muscle, liver and gonad triglycerides fraction, the proportion of saturated fatty acids (FA) was greater than the proportion of polyunsaturated fatty acids (PUFA), whereas the reverse observation was made (with the exception of liver) in the polar lipid (PL) fraction of the above tissues. In muscle and liver, the main polyunsaturated fatty acids (n-3 PUFA) were docosahexaenoic (DHA, 22:6n-3) and eicosapentaenoic (EPA, 20:5n-3) acids. The main n-6 polyunsaturated fatty acids were linoleic (18:2n-6) and arachidonic (20:4n-6) acids. Palmitic (16:0) and oleic (18:1n-9) acids were the main saturated fatty acids and monoenes, respectively. The relative concentration of the major fatty acids varied seasonally and a pattern can be seen in both mature and immature dentex. In the PL fraction of muscle, higher values of total saturated and n-3 fatty acids, palmitic acid and DHA were obtained during summer in comparison to winter samplings; this trend was also shown by the total saturated fatty acids in the TG fraction. [Copyright &y& Elsevier]

Culture of the sea scallop, Placopecten magellanicus, is constrained by a reliable supply of high-quality postlarvae, yet little is known about the diets and essential nutrients required to maximize growth and survival during these vulnerable stages. Therefore, post-settlement sea scallops were exposed to binary microalgal diets consisting of a flagellate: Pavlova lutheri, Pavlova sp. (Pav, CCMP 459) or Tetraselmis striata (Plat-P) and a diatom: Chaetoceros muelleri, Thalassiosira weissflogii or Fragilaria familica for 28–30 days. The combination Pav 459/C. muelleri provided a superior diet for sea scallop postlarvae, yielding a growth rate of up to 28 μm day−1. However, when these algae were offered singly, a 32% (Pav 459) and 64% (C. muelleri) decrease in growth rates was observed, indicating that both species made a significant contribution to the success of the mixed diet. The two species are characterized by unique signatures of n−6 polyunsaturated fatty acids (PUFAs): C. muelleri has high levels of arachidonic acid (AA), and Pav 459 (in contrast to P. lutheri) has high levels of n−6 docosapentaenoic acid (DPA). DPA was selectively incorporated into tissues of scallops fed all binary diets except the one rich in DPA (Pav 459/C. muelleri). These results, coupled with a marked increase in n−6/n−3 ratios between the diet and tissues, provide evidence that n−6 PUFAs may play an important and previously underestimated role in scallop nutrition. The diet of T. striata and C. muelleri, which yielded the lowest growth rate (8.1 μm day−1) contained dietary docosahexaenoic acid (DHA; 22:6n−3) concentrations 4.5–7× lower than any other binary treatment. Low DHA levels may thus explain the poor performance of this diet. Tissue protein and triacylglycerol concentrations reflected diet performance, with higher values generally associated with more successful diets. This work suggests that DHA, as well as the n−6 PUFAs AA and DPA, may be essential for optimizing growth of sea scallop postlarvae. [Copyright &y& Elsevier]

The fatty acid compositions of fish tissue lipids usually reflect those of the dietary lipids and tissue fatty acid profiles can be modified by altering the sources of fats and oils used in formulating fish feeds. Few attempts have been made to predict the way in which the profiles change, and the time required for the fatty acid profile to stabilise following a dietary change. The simplest model to describe the change in fatty acid composition is one in which the initial fatty acid content becomes diluted as the fish grow and deposit increasing amounts of lipid. The dilution model was tested using data relating to the influence of feed oils (vegetable vs. marine fish) and dietary fat concentrations on growth, body composition, and fatty acid profiles of the tissues (fillet, viscera and carcass) of Atlantic salmon parr and post-smolt. Fish fed feeds containing vegetable (rapeseed and linseed 7:3 v/v) oils at high (34%) or low (22%) lipid concentration during freshwater rearing (mass increase from ca. 19 to 130 g) were switched to feeds containing fish (sand-eel) oil (31% or 18.5% lipid) following parr–smolt transformation. The changes in the proportions of the three tested fatty acids (18:1 isomers, 18:2n−6 and 18:3n−3) in the total lipids of the salmon tissues during 98 days of on-growing in seawater (mass increase from ca. 130 to 380 g) conformed closely to predictions made on the basis of the simple dilution model. Practical applications, and possible limitations, of the dilution model are discussed. [Copyright &y& Elsevier]

The effects of dietary non-protein energy levels on growth, oxidative status and condition were studied in juveniles of Senegalese sole (Solea senegalensis). Four isonitrogenous diets with four energy levels were used: A—low (11% lipid, raw carbohydrate); B—intermediate (11% lipid, digestible carbohydrate); C—intermediate (21% lipid, raw carbohydrate); and D—high (21% lipid, digestible carbohydrate). Survival, relative growth rate (RGR) and feed conversion rate were not significantly affected by the dietary treatments. The fatty acid composition of the fish muscle varied little among the treatments, but trans 18:2n−6, total n−6 and EPA/DHA ratio, tended to be higher in fish fed diets with low lipid level. Cellular energy allocation (CEA) results (indicative of metabolic status and net energy budgets) showed significant differences in liver, but not in muscle samples. Livers of fish fed diet C contained the lowest carbohydrate, protein and CEA values, but the highest cellular energy consumption. Fish fed diet A had the highest CEA for growth, followed by fish fed diets B and D and then diet C. The liver and muscle peroxidation and antioxidant activity were measured by thiobarbituric acid reactive substances (TBARS) test and the enzymatic activities levels of catalase (CAT) and superoxide dismutase (SOD). TBARS values were higher for fish fed diets with high lipid content. However, no clear relation was found between HUFA level and TBARS value. The activity levels of the antioxidant enzymes CAT and SOD were higher in livers of fish fed diets with a high lipid level. Furthermore, CAT and SOD activity and TBARS values were influenced by the type of dietary starch in the diet. Higher oxidation rates were observed in fish fed diets containing raw carbohydrate. These data suggest that lipid and carbohydrate energy sources affect the oxidative status of Senegalese sole. Diets containing low levels of lipid and digestible starch reduce the susceptibility of the fish to oxidation and may enhance growth rate. [Copyright &y& Elsevier]