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Abstract Community‐based aquaculture can reduce dependence on natural resources, promote biodiversity conservation, and improve local economies and food security. However, this activity is highly dependent on local conditions regarding natural resources, such as the availability of produced organisms, adequate feeds, and environmental factors. As ectothermic organisms, fish are more susceptible to temperature fluctuations in culture conditions. A set of raw ingredients (e.g., cassava and local beans) produced or available in villages from Cabo Delgado (Mozambique) with nutritional potential for fish feed were selected to produce an experimental diet. The following objectives were defined: (1) evaluate growth performance of tilapia fingerlings fed a diet produced with local ingredients, compared with a commercial‐like diet; and (2) evaluate the response to thermal stress (18, 26, and 32°C) by tilapia fingerlings fed with tested diets. Tilapia fed with an experimental diet presented lower growth rates, lower DNA damage, higher neurophysiological, and antioxidant activity, leading to increased oxidative stress. Regarding energy budget, tilapia fed with the experimental diet presented higher protein content at 26°C and lipids at 18°C, leading to greater energy available at these temperatures. Overall, local ingredients can be successfully used as an additional feed source for tilapia production in community‐based aquaculture in earthen ponds.

Society is becoming more demanding with aquaculture’s environmental footprint and animal wellbeing. In order to potentially mitigate these concerns, feed formulations could be based on eco-efficient (circular economy-driven) or organic ingredients. This study aimed to investigate the growth performance, feed utilization, and health status of juvenile Nile tilapia (Oreochromis niloticus) when fed with such feeds. The growth trial lasted for 8 weeks, and fish had an initial weight of 31.0 ± 0.5 g (mean ± SD). Fish were fed until visual satiation, in quadruplicate, with one of three isonitrogenous and isoenergetic experimental feeds: a commercial-like feed without fishmeal (PD), a diet based on ingredients compatible with organic certification (ORG), or a feed formulated using circular economy-driven subproducts and emergent ingredients (ECO). Fish fed ECO showed a tendency for decreased feed intake, while ORG fish significantly reduced their intake compared to those fed PD. Consequently, fish fed ECO (62.7 ± 5.4 g) exhibited almost half the growth than those fed PD (107.8 ± 6.1 g), while ORG fish almost did not increase their weight (32.7 ± 1.3 g). ECO and ORG diets had a lower digestibility for protein, lipid, and energy when compared to PD. Feed utilization of fish fed ECO or ORG was also lower than those fed PD. From the health-related genes analyzed, only glutathione reductase (gsr) showed statistically significant differences, being more expressed in fish-fed ECO than those fed PD. Thus, even when such novel formulations induced extreme effects on voluntary feed intake, their impact was noted only in fish growth, but not in robustness.

Closing the life cycle of European eel (Anguilla anguilla) in captivity is targeted to provide a sustainable, year-round supply of juveniles for aquaculture. Present focus is on the nutritional requirements during the larval first-feeding period. In this study, three experimental diets were tested on hatchery-produced European eel larvae from the onset of the first-feeding stage commencing 10 days post hatch (dph) until 28 dph. Larval mortality was recorded daily, while sampling was conducted at regular intervals to record larval biometrics and analyze the expression of genes related to digestion, appetite, feed intake and growth. Two periods of high mortality were identified: the first appeared shortly after introduction of feeds (10-12 dph), while the second occurred 20-24 dph, indicating the "point of no return". This interpretation was supported at the molecular level by the expression of the gene encoding the "hunger hormone" ghrelin (ghrl) that peaked at 22 dph in all dietary trials, suggesting that most larvae were fasting. However, in larvae fed diet 3, ghrl expression was downregulated beyond 22 dph, which indicated that those larvae were no longer starving at this stage, while upregulation of genes encoding the major digestive enzymes (try, tgl, and amyl2a) advocated their healthy development. Moreover, for larvae fed diet 3, the expression of those genes as well as genes for feed intake (pomca) and growth (gh) continued to increase towards 28 dph. These results together with the registered highest survival, largest dry weight increase, and enhanced biometrics (length and body area) pointed to diet 3 as the best-performing. As a whole, this first-feeding study represents a landmark being the first to document European eel larval growth and survival beyond the point of no return, providing novel insights into the molecular development of digestive functions during the first feeding stage.

Closing the life cycle of European eel (Anguilla anguilla) in captivity is targeted to provide a sustainable, year-round supply of juveniles for aquaculture. Present focus is on the nutritional requirements during the larval first-feeding period. In this study, three experimental diets were tested on hatchery-produced European eel larvae from the onset of the first-feeding stage commencing 10 days post hatch (dph) until 28 dph. Larval mortality was recorded daily, while sampling was conducted at regular intervals to record larval biometrics and analyze the expression of genes related to digestion, appetite, feed intake and growth. Two periods of high mortality were identified: the first appeared shortly after introduction of feeds (10–12 dph), while the second occurred 20–24 dph, indicating the “point of no return”. This interpretation was supported at the molecular level by the expression of the gene encoding the “hunger hormone” ghrelin (ghrl) that peaked at 22 dph in all dietary trials, suggesting that most larvae were fasting. However, in larvae fed diet 3, ghrl expression was downregulated beyond 22 dph, which indicated that those larvae were no longer starving at this stage, while upregulation of genes encoding the major digestive enzymes (try, tgl, and amyl2a) advocated their healthy development. Moreover, for larvae fed diet 3, the expression of those genes as well as genes for feed intake (pomca) and growth (gh) continued to increase towards 28 dph. These results together with the registered highest survival, largest dry weight increase, and enhanced biometrics (length and body area) pointed to diet 3 as the best-performing. As a whole, this first-feeding study represents a landmark being the first to document European eel larval growth and survival beyond the point of no return, providing novel insights into the molecular development of digestive functions during the first feeding stage.

Gilthead seabream (Sparus aurata) tend to increase fat deposition during summer farming conditions in the Mediterranean, which may negatively affect productive performance and consumers’ quality perception of the final product. Therefore, this study evaluated the impacts of protein to lipid ratios in low fishmeal/fish oil diets on growth performance, body composition, feed conversion and nutrient utilization of seabream on-grown during summer temperature conditions. The experimental diets contained low levels of fishmeal, fish oil, and crude protein (39%), differing in crude lipid content: 16% (MF diet) or 12% (LF diet). A growth trial was performed with seabream (initial weight: 100 ± 7 g) from August to October (water temperature: 23.1 ± 2.2 ºC). A digestibility trial was also performed (at 23 ºC). Key performance indicators, whole-body composition and activities of digestive enzymes were evaluated at the end of the experiment (64 days). Low dietary lipid levels negatively affected lipid, energy, and amino acid digestibility, and as a result, fish fed the LF diet presented higher nitrogen faecal losses. Still, the decrease in nutrient digestibility was not related to dietary effects on the digestive enzyme activities. The experimental diets did not compromise the activity of pancreatic, gastric, and intestinal digestive enzymes nor feed utilization, but a slight growth impairment was observed in fish fed the LF diet, probably due to the lower amino acid and lipid digestibility. However, a potential benefit of this dietary treatment towards reducing fat accumulation in seabream during summer was observed. Nevertheless, the environmental impact of the nitrogen losses during seabream on-growing should be considered when estimating the sustainability of the production. This study demonstrated that the optimisation of diet formulations should account for the environmental conditions, especially in Mediterranean aquaculture, so the economic and environmental impacts may be correctly evaluated towards a more sustainable fish production.

The transition from endogenous to exogenous feeding is critical during fish early life, where appropriate feed availability and timing of initiation of feeding influence survival. For European eel (Anguilla anguilla), establishing first feeding culture is at a pioneering state, where successful production of larvae has recently enabled feeding experiments. In the present study, three diets and potential benefits of early feeding during the transition from yolk-sac stage to feeding larvae were explored, including molecular analyses of genes involved in digestive functions and growth. Three consecutive trials were performed using hatchery produced eel offspring. In Feeding regimes 1 and 3, expression of npy and cck (appetite regulation) was higher, while expression of pomca (food intake) was lower in non-prefed larvae, indicating increased fasting and higher starvation risk. In contrast, Feeding regime 2 led to the highest survival ever registered for European eel larvae i.e. 20% at 20 dph, in spite that prefeeding resulted in reduced survival rate during the endogenous feeding stage. This was associated with initial hsp90 (stress/repair) upregulation in larvae receiving prefeeding, however, with subsequent downregulation during exogenous feeding. Notably, the growth related gh expression was higher in prefed larvae, indicating growth benefits of prefeeding. Likewise, prefeeding resulted in pomca as well as try, tgl, and amyl2a (digestion) upregulation, providing evidence of beneficial maturation of gut functionalities. Essentially, Feeding regime 2 demonstrated a continuous upregulation of growth, appetite and digestion related genes, which in combination with the highest survival suggest that dietary requirements were partially met. Moreover, in Feeding regime 2, gh and tgl were expressed at a higher level in prefeeding larvae than in the control, indicating that prefeeding might be advantageous in spite observed mortality, but further research is needed, including timing of feed application.

An imbalance in the production and detoxification of reactive oxygen species and other oxidants can disrupt all types of cellular compounds, and lead to a state of oxidative stress. Preventing this state is essential to improve growth and health in animal production. Therefore, the aim of this work was to assess if the dietary supplementation of curcumin could improve the antioxidant status and intestine structure and functionality of gilthead seabream postlarvae, with the global objective of improving fish growth performance and robustness. Two experimental diets supplemented with different doses of curcumin (LOW and HIGH diets), and a commercial diet were fed to quadruplicate groups of postlarvae, for 20 days. At the end of the feeding trial fish fed the supplemented diets significantly improved their antioxidant status compared to CTRL fed fish. LOW and HIGH fed fish presented lower protein oxidative damage (P 0.05). In conclusion, dietary curcumin supplementation was able to enhance gilthead seabream postlarvae robustness through a modulation of the oxidative status, increasing total antioxidant capacity and decreasing protein oxidative damage. This data provide evidence that curcumin can be a suitable feed additive to promote heath status and robustness of fish at early stages of development, therefore contributing for the development and sustainability of marine fish hatchery production.

Consumption of aquatic food, including fish, accounts for 17% of animal protein intake. However, fish consumption might also result in several side-effects such as sneezing, swelling and anaphylaxis in sensitized consumers. Fish allergy is an immune reaction to allergenic proteins in the fish muscle, for instance parvalbumin (PV), considered the major fish allergen. In this study, we characterize PV in two economically important fish species for southern European aquaculture, namely gilthead seabream and European seabass, to understand its stability during in vitro digestion and fish processing. This information is crucial for future studies on the allergenicity of processed fish products. PVs were extracted from fish muscles, identified by mass spectrometry (MS), and detected by sandwich enzyme-linked immunosorbent assay (ELISA) after simulated digestion and various food processing treatments. Secondary structures were determined by circular dichroism (CD) after purification by anion exchange and gel filtration chromatography. In both species, PVs presented as α-helical and β-sheet structures, at room temperature, were shown to unfold at boiling temperatures. In European seabass, PV detectability decreased during the simulated digestion and after 240 min (intestinal phase) no detection was observed, while steaming showed a decrease (p < 0.05) in PVs detectability in comparison to raw muscle samples, for both species. Additionally, freezing (−20 °C) for up to 12 months continued to reduce the detectability of PV in tested processing techniques. We concluded that PVs from both species are susceptible to digestion and processing techniques such as steaming and freezing. Our study obtained preliminary results for further research on the allergenic potential of PV after digestion and processing.

The sustainability of the Aquaculture industry relies on optimising diets to promote nitrogen retention and maximise fish growth. The aim of this study was to assess how different dietary formulations influence the bioavailability and metabolic fate of distinct amino acids in gilthead seabream juveniles. Amino acids (lysine, tryptophan, and methionine) were selected based on their ketogenic and/or glucogenic nature. Seabream were fed practical diets with different protein (44 and 40%) and lipid contents (21 and 18%): 44P21L, 44P18L, 40P21L, and 40P18L. After three weeks of feeding, the fish were tube-fed the correspondent diet labelled with 14C-lysine, 14C-tryptophan, or 14C-methionine. The amino acid utilisation was determined based on the evacuation, retention in gut, liver, and muscle, and the catabolism of the tracer. The metabolic fate of amino acids was mainly determined by their nature. Tryptophan was significantly more evacuated than lysine or methionine, indicating a lower availability for metabolic purposes. Methionine was more retained in muscle, indicating its higher availability. Lysine was mainly catabolised, suggesting that catabolism is preferentially ketogenic, even when this amino acid is deficient in diets. This study underpins the importance of optimising diets considering the amino acids’ bioavailability and metabolic fate to maximise protein retention in fish.

This data article is associated with the research article “Evaluating the impact of methionine-enriched diets in the liver of European seabass through label-free shotgun proteomics”. Here it is described the data obtained from proteomic analysis of 36 European seabass juveniles (3 fish x 3 replicate tanks) after 18 days of feeding with experimental diets containing four inclusion levels of methionine (Met): 0.77%, 1%, 1.36% and 1.66% Met (w/w). We analysed this dataset and compared it with that obtained during the long-term feeding period i.e., 85 days. Fish liver proteins were digested with trypsin and purified peptides were analysed by LC-MS/MS. Proteins were identified with at least two peptides at 0.1% Decoy false discovery rate (FDR). In this dataset, we present the analysis of the differential abundant proteins (DAP) with significant differences across treatments after 18 days of feeding (One-Way ANOVA, p < 0.05). Treatment's comparisons were also performed between the 18- and 85-days feeding trials through Two-Way ANOVA (p < 0.05). MS/MS raw data are available via ProteomeXChange with identifiers PXD019610 and 10.6019/PXD019610 (18-days dataset); and PXD019622 and 10.6019/PXD019622 (85-days dataset). This dataset corresponds to fish sampled after 18-days of experimental trial and is made available to support the study conducted in the afore-mentioned article, by performing the analysis during a short-term period of feeding. The data presented may be further used in other nutritional studies e.g., addressing hepatic changes mediated by Met.

Fish and other marine animals have a unique and intimate interaction with their surrounding environment. Diet type or trophic level play significant roles in modulating species digestive physiology. However, little is known about how the trophic niche influences digestive activity and gut microbiota in scombrids species. The aim of the present study was to analyse and describe the digestive physiology of the skipjack tuna (Katsuwonus pelamis) and the Atlantic bonito (Sarda sarda) as bioindicator of the feeding ecology and trophic niche for both species in the Gulf of Cádiz (Spain). For that, fish proximate composition, pH of digestive organs and digestive enzymes activity levels were analysed in 10 individuals of each species to gain insight into the digestive physiological adaptations of the two species of scombrids. In addition, intestinal microbiota composition was determined for the skipjack tuna. The integration of the results suggested a clear trophic niche segregation between both species. Stomach pH was associated in both species with infrequent feeding events. Body proximate composition and digestive lipases activity patterns pointed to a high predominance of lipids in the Atlantic bonito diet, suggesting oily fish as main prey. On the other hand, results supported the skipjack tuna as a highly opportunistic feeder with a more varied diet, including fish but also crustaceans as preys. The gut microbial community in the latter species is dominated by Firmicutes and Tenericutes at phylum level, and by Mycoplasma, Blautia and Dorea at genus level. The present study contributes to advance the knowledge on the feeding behaviour and physiology diversity in fish species as a result of adaptation to a particular habitat.

New and more efficient methods to sustainably intensify Aquaculture production are essential to attain the seafood demand for direct human consumption in the near future. Nutrition has been identified as one strategy of early exposure that might affect animal early development and later phenotype. This strategy may have positive consequences in the modulation of fish digestive physiology, which will correlate with higher performance outputs. Thus, improving fish digestive efficiency will lead to higher productivity and lower biogenic emission from aquaculture facilities, minimising the impact on the environment while increasing the biological efficiency. An innovative in ovo nutritional modulation technique based on low-frequency ultrasounds was used to enhance the transport of amino acids across the embryo membranes. An early stimulus with either arginine or glutamine, both involved in gut maturation, was applied in zebrafish (Danio rerio) embryos at 3.5 hours post-fertilization (hpf). At 22 days post-fertilization (dpf), growth performance, digestive enzyme activities and gut microbiota composition were analysed to evaluate the larval nutrition-induced metabolic plasticity and the effects on fish digestive efficiency. Results showed that fish survival was not affected either by the sonophoresis technique or amino acid supplementation. Final dry weight at 22 dpf was statistically higher in larvae from glutamine treatment when compared to the control even with lower trypsin activity, suggesting a higher nutrient digestion capacity, due to a slightly modulation of gut microbiota. Higher arginine supplementation levels should be tested as strategy to enhance growth at later developmental stages. In conclusion, this study demonstrated the efficiency of sonophoresis technique for in ovo nutritional modulation and suggests that in ovo glutamine supplementation might promote growth at later developmental stage through a positive microbiota modulation.

Aquaculture has been challenged to find alternative ingredients to develop innovative feed formulations that foster a sustainable future growth. Given the most recent trends in fish feed formulation on the use of alternative protein sources to decrease the dependency of fishmeal, it is fundamental to evaluate the implications of this new paradigm for fish health and welfare. This work intends to comprehensively review the impacts of alternative and novel dietary protein sources on fish gut microbiota and health, stress and immune responses, disease resistance, and antioxidant capacity. The research results indicate that alternative protein sources, such as terrestrial plant proteins, rendered animal by-products, insect meals, micro- and macroalgae, and single cell proteins (e.g., yeasts), may negatively impact gut microbiota and health, thus affecting immune and stress responses. Nevertheless, some of the novel protein sources, such as insects and algae meals, have functional properties and may exert an immunostimulatory activity. Further research on the effects of novel protein sources, beyond growth, is clearly needed. The information gathered here is of utmost importance, in order to develop innovative diets that guarantee the production of healthy fish with high quality standards and optimised welfare conditions, thus contributing to a sustainable growth of the aquaculture industry.

Somatic growth is a balance between protein synthesis and degradation, and it is largely influenced by nutritional clues. Antioxidants levels play a key role in protein turnover by reducing the oxidative damage in the skeletal muscle, and hence promoting growth performance in the long-term. In the present study, Senegalese sole postlarvae (45 days after hatching, DAH) were fed with three experimental diets, a control (CTRL) and two supplemented with natural antioxidants: curcumin (CC) and grape seed (GS). Trial spanned for 25 days and growth performance, muscle cellularity and the expression of muscle growth related genes were assessed at the end of the experiment (70 DAH). The diets CC and GS significantly improved growth performance of fish compared to the CTRL diet. This enhanced growth was associated with larger muscle cross sectional area, with fish fed CC being significantly different from those fed the CTRL. Sole fed the CC diet had the highest number of muscle fibers, indicating that this diet promoted muscle hyperplastic growth. Although the mean fiber diameter did not differ significantly amongst treatments, the proportion of large-sized fibers (>25 μm) was also higher in fish fed the CC diet suggesting increased hypertrophic growth. Such differences in the phenotype were associated with a significant up-regulation of the myogenic differentiation 2 (myod2) and the myomaker (mymk) transcripts involved in myocyte differentiation and fusion, respectively, during larval development. The inclusion of grape seed extract (GS diet) resulted in a significant increase in the expression of myostatin1. These results demonstrate that both diets (CC and GS) can positively modulate muscle development and promote growth in sole postlarvae. This effect is more prominent in CC fed fish, where increased hyperplastic and hypertrophic growth of the muscle was associated with an upregulation of myod2 and mymk genes.

Sabella spallanzanii and Microcosmus squamiger were profiled for proximate composition, minerals, amino acids, fatty acids (FA), carotenoids, radical scavenging activity on the 2,2-diphenyl-1- picrylhydrazyl (DPPH) radical, oxygen radical absorbance capacity (ORAC) and iron and copper chelating properties. Microcosmus squamiger had the highest level of moisture and crude protein, S. spallanzanii was enriched in crude fat and ash. Both species had similar levels of carbohydrates and energy. There was a prevalence of arginine and glycine in S. spallanzanii, and of taurine in M. squamiger. The most abundant minerals in both species were Na, Ca, and K. The methanol extract of S. spallanzanii had metal chelating properties towards copper and iron, while the methanol extract of M. squamiger was able to chelate copper. M. squamiger extracts had similar ORAC values. Fucoxanthinol and fucoxanthin were the major carotenoids in the M. squamiger dichloromethane extract. Saturated FA were more abundant than unsaturated ones in methanol extracts, and unsaturated FA prevailed in the dichloromethane extracts. Palmitic acid was the predominant FA in methanol extracts, whereas eicosapentaenoic (EPA) and dihomo-γ-linolenic acids were the major compounds in dichloromethane extracts. Low n-6/n-3 ratios were obtained. Our results suggests that both species could be explored as sources of bioactive ingredients with multiple applications.

Fish hatcheries must adapt larval feeding protocols to feeding behavior and metabolism patterns to obtain more efficient feed utilization. Fish larvae exhibit daily ingesting rhythms rather than ingesting food continuously throughout the day. The aim of this study was to determine the daily patterns of feed intake, protein digestibility, protein retention and catabolism in Senegalese sole post-larvae (Solea senegalensis; 33 days post-hatching) using 14C-labeled Artemia protein and incubation in metabolic chambers. Sole post-larvae were fed at 09:00, 15:00, 21:00, 03:00 and 09:00+1 day; and those fed at 09:00, 21:00, 03:00 and 09:00+1 day showed significantly higher feed intake than post-larvae fed at 15:00 h (P=0.000). Digestibility and evacuation rate of ingested protein did not change during the whole cycle (P=0.114); however, post-larvae fed at 21:00 and 03:00 h showed the significantly highest protein retention efficiency and lowest catabolism (P=0.002). Therefore, results confirm the existence of daily rhythmicity in feeding activity and in the utilization of the ingested nutrients in Senegalese sole post-larvae.

The larval stage is highly prone to stress due to the ontogenetic and metabolic alterations occurring in fish. Curcumin inclusion in diets has been shown to improve growth by modulating oxidative status, immune response, and/or feed digestibility in several fish species. The aim of the present work was to assess if dietary curcumin could promote marine fish larvae digestive maturation and improve robustness. Gilthead seabream larvae were fed a diet supplemented with curcumin at dose of 0 (CTRL), 1.5 (LOW), or 3.0 g/Kg feed for 27 days. From 4 to 24 days after hatching (DAH), no differences were observed in growth performance. At the end of the experiment (31 DAH) LOW larvae had a better condition factor than CTRL fish. Moreover, HIGH larvae showed higher trypsin and chymotrypsin activity when compared to CTRL fish. LOW and HIGH larvae were able to maintain the mitochondrial reactive oxygen species production during development, in contrast to CTRL larvae. In conclusion, curcumin supplementation seems to promote larvae digestive capacity and modulate the oxidative status during ontogeny. Furthermore, the present results provide new insights on the impacts of dietary antioxidants on marine larvae development and a possible improvement of robustness in the short and long term.

Plant extracts are known for their high content and diversity of polyphenols, which can improve fish oxidative status. A growth trial with Senegalese sole postlarvae (45 days after hatching) fed with one of four experimental diets—control (CTRL), and supplemented with curcumin (CC), green tea (GT), and grape seed (GS) extracts—was performed to assess if supplementation could improve growth performance and oxidative status. At the end of the growth trial, postlarvae were submitted to a thermal stress to assess their robustness. Sole growth was improved by CC and GS diets when compared to those fed the CTRL. CC and CTRL postlarvae presented the lowest oxidative damage (lipid peroxidation and protein carbonylation values). Stress-related biomarkers (heat shock protein 70 and glutathione-S-transferase) decreased in CC fish compared to those fed the CTRL diet, which might be due to a direct antioxidant capacity. In contrast, oxidative damage increased in GT and GS sole reared in standard conditions. However, after a thermal stress, GT and GS diets prevented the increase of protein carbonylation content and the decrease of antioxidant glutathione, depending on exposure time. Overall, dietary supplementation with natural extracts modulated oxidative status and stress response after a short/long-term exposure to temperature.

One of the major obstacles to propagating dusky grouper, Epinephelus marginatus, is the difficulty of rearing the early larvae. We have successfully raised dusky grouper larvae in mesocosms using a mixed diet of endogenous plankton grown in the rearing tank and an exogenous supply of Brachionus plicatilis and Artemia sp. Newly hatched larvae at an initial density of 1.3 ind.l-1 were stocked in partially shaded 3 m3 circular outdoor tanks during the summers of 2007 and 2008. Before introducing newly hatched larvae, the water was left for six days to promote plankton growth. Larval growth occurred at two different rates: i) a faster rate from first feeding to the beginning of metamorphosis, and ii) a slower rate at transformation. Survival at the beginning of metamorphosis was less than 10% (33 DPH) in 2007 and between 25 and 50% (25 DPH) in 2008. High mortalities were observed during larval transformation. The estimated minimum food requirement per grouper larvae increased more than 300% from the beginning of the notochord flexion to the beginning of metamorphosis. To meet such a high feeding requirement the number of larger prey organisms/copepods in the mesocosm should be eight times higher during this time period.

Os requisitos nutricionais de larvas de peixes são ainda mal compreendidos, o que leva a altas mortalidades e problemas de qualidade no seu cultivo. Este trabalho pretende fazer uma revisão de novas metodologias de investigação, tais como estudos com marcadores, genómica populacional, programação nutricional, génomica e proteómica funcionais, e fornecer ainda alguns exemplos das utilizações presentes e perspectivas futuras em estudos de nutrição de larvas de peixes.Major gaps in knowledge on fish larval nutritional requirements still remain, what leads to high mortalities and quality problems in marine larviculture. This paper reviews a range of new tools, such as tracer studies, population genomics, nutritional programming, functional genomics and proteomics, as well as some examples of their present use, and potential future applications in the study of fish larvae nutrition.

Earthen ponds are the main production system for European seabass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) in Portugal and in Southern Spain. Production costs in this low productivity farming system are higher compared to intensive cage farms, and its economic sustainability depends on product differentiation and optimization of production. The development of new farming protocols, to enhance productivity of ponds and lagoons, or the implementation of certification processes to add value to products from extensive and semi-intensive systems, could render these activities more economics benefits and be attractive for a new generation of farmers. One clear strategy to differentiate and add value to seabream produced in semi-intensive systems is its production under organic standards. Feeds often represent 40-60% of the operational costs of fish farming. In relation to the traditional feeds, the organic certified feeds currently present a price-differential of about +30%. To assess it economic feasibility, it is therefore essential to validate if such higher feeding costs will represent an increase on productivity (fish growth and feed conversion) or can be fully integrated in the final sale price. Throughout a full production cycle of gilthead seabream (from 9 grams until >350 grams), a series of trials allowed us to assess the effects of: a) an organic certified feed; b) variable feeding levels (100 and 80% of recommendations); and c) culture density (0.5 and 1.0 kg/m3) on the overall growth performance, body composition and environmental impact at the fish farm level. Results show that growth performance (weight gain and feed conversion ratio) of seabream fed the organic feed was similar to that found in fish fed a traditional diet. With the organic feed, a reduction of the feeding level by 20% of the manufacturer recommendations led to a lower growth, while a similar reduction on the feeding level of the traditional feed had no impact on the performance of seabream. Lower culture density (0.5 kg/m3) resulted in higher overall growth performance. The impact, in terms of nitrogenous (N) and phosphorus (P) loads, among the various scenarios were calculated and clearly reinforce the environmental sustainability of these semi-intensive production systems. The use of organic feeds does not lead to a significant enhancement of the growth performance. Therefore, the additional costs associated to feeding under organic standards, need to be incorporated in the sale price, thus requiring a targeted and differentiated marketing and distribution approach. Sociedade Piscicultura Farense Lda, as other traditional aquacultures depends on the enhancement of the natural environment, combined with production fine-tuning and product positioning, rewarding the quality of the final product. The positive effects of extensive and semi-intensive aquaculture in coastal areas, including environmental protection and restoration in areas of particular ecological interest, employment opportunity and development in rural and coastal areas are highly appealing concepts for the general community, particularly to conscious consumers.

The improvement of micro diets, for fish larvae, has been a major challenge in past years; however some problems remain without a resolution. Besides its tremendous growth rates, at early developmental stages, fish larvae present an immature digestive system and a progressive metamorphic process that suggest special nutritional requirements. It is therefore essential to provide fish larvae with easy and/or quickly metabolized protein sources, like protein hydrolisates, high bioavailable forms of vitamins and trace minerals. The low molecular weight of such compounds, in association to the high surface area of the micro-particles, makes them highly soluble and prone to water leaching losses. These nutrient losses, not only makes these nutrients unavailable to the larvae, but originate an important increase of organic matter in the rearing tanks, leading to detrimental water quality criteria. The development of high-performing micro-particulate diets for fish larvae requires a delicate balance between an adequate quantitative and qualitative nutritional supply and good water stability of the feeds, without compromising the palatability and the digestive breakdown. A series of binders, protein-based (e.g. fish gelatin, wheat gluten, spray-dried plasma) and carbohydrate-based (gums, alginates, pectins, starches, dextrin, polyols) were incorporated at graded levels (1, 2.5 and 5%) in a standard formulation for seabream larvae. Diets were manufactured by a proprietary low-shear extrusion process and afterwards processed to obtain a 200-400 micron fraction. All diets were analyzed for the following criteria: water leaching of nitrogenous compounds, turbidimetry and particle water stability. An additionally approach relied on the use of various encapsulation techniques (spray-drying, fluid-bed drying and vacuum coating) to incorporate trace minerals (Zn and Mn) and amino acids (taurine, lysine and methionine). Technological results show that the beneficial effects towards nutrient leaching and physical stability of the micro-pellets after immersion in water are highly dependent on binder type and less markedly on binder dose. Through the use of selected binders (e.g. guar gum and gelatin) in association to a spray-drying encapsulation process, we were able to significantly alter the release profile of Zn, Mn and taurine. Some of these prototypes were also tested in vivo with gilthead seabream larvae and clearly suggest that microencapsulation technologies that allow a controlled release profile of nutrients result in beneficial effects to larval growth and quality criteria. The results of several specific scenarios will be presented.

The objective of this study was to evaluate the weaning success of Senegalese sole, Solea senegalensis, postlarvae when cofed a compound diet, by means of the analysis of growth parameters (relative growth rate [RGR] and condition factor [K]), survival, protein and lipid content. Total ammonia in the rearing water was also measured. The experiment lasted for 46 days (36 to 82 days posthatching). One group was fed only with enriched Artemia sp. metanauplii (Artemia treatment), whereas in another group, the Artemia sp. metanauplii were gradually replaced by the International Council for the Exploration of the Sea (ICES) diet over a period of 39 days (ICES treatment). Postlarvae were sampled on rearing days 0, 9, 23, 30, 39 and 46 for growth and biochemical analysis. Water was sampled on rearing day 30 during a 24-h cycle in both treatments. Postlarvae from the ICES treatment were weaned, though by the end of the experiment the Artemia treatment exhibited significantly higher values for growth, RGR, K and survival rates (P < 0.05). No significant differences were observed concerning total lipid content. Protein content was significantly higher for the Artemia treatment after 46 days of rearing (P < 0.05). The total ammonia nitrogen concentration in the water increased after each meal and remained below a harmless level for postlarvae.