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Gut microbiota impacts fish metabolism, nutrient utilization, and health. We know little about how temperature and diet interact with rainbow trout gut microbes. A total of 288 fish (average body weight: 45.6 g) fed four iso‐caloric, ‐lipidic, and ‐nitrogenous diets comprised crude protein (40%) and lipid (20%) manufactured as 100% animal‐based protein (AP) and blend of 50 fish oil (FO)/50 camelina oil (CO), 100% AP and 100% CO, 100% plant‐based protein (PP) and blend of 50 FO/50 CO or 100% PP and 100% CO at 14 or 18°C water temperature. Gut content was analyzed using 16S rRNA gene and shotgun sequencing. Alpha‐diversity did not change significantly. Regardless of diet, Tenericutes, Firmicutes, Proteobacteria, Spirochaetes, Bacteroidetes, and Actinobacteria dominated. At family level, Aeromonadaceae and Enterobacteriaceae dominated at 18°C, while Mycoplasmataceae dominated at 14°C. Moreover, genes relating to amino acid, carbohydrate, fat, and energy metabolisms and fatty acid biosynthesis significantly increased at 18°C. Functional profiles did not vary significantly among diets, except for a higher methionine and cysteine metabolism in fish fed plant ingredient compared animal diet, suggesting trout fed plant‐derived protein mixed with CO could be as effective as those fed fish meals mixed with 50/50 FO and CO. [ABSTRACT FROM AUTHOR]

A 9‐week feeding trial was conducted to evaluate one custom formulation and six commercially available diets when fed to juveniles of the endangered Lost River Sucker Deltistes luxatus. The seven treatments included the following: two catfish Ictalurus spp. diets, a tilapia Oreochromis spp. diet, a shrimp diet, a general warmwater fish diet, a general fish diet, and a feed formulated at the Abernathy Fish Technology Center (Abernathy sucker diet). The general fish diet produced fish that were significantly larger than the fish fed the other diets. The Lost River Suckers fed the general fish diet or the Abernathy sucker diet averaged 99.0% survival for the duration of the trial, which was significantly higher than in Lost River Suckers fed all other diets except for one catfish diet. Spinal deformities were significantly less frequent in fish fed the general fish diet and the Abernathy sucker diet. Whole‐body proximate and fatty acid composition were affected by diet. Whole‐body fatty acid profiles generally mirrored the diet profiles. The general fish diet appears to be an effective diet for juvenile Lost River Suckers, although the Abernathy sucker diet should be considered for further development as it yielded high survival and no incidence of spinal deformity. [ABSTRACT FROM AUTHOR]

The Pacific lamprey Entosphenus tridentatus is an ancestral species of critical importance to the ecosystem and indigenous cultures in the Pacific Northwest. Conservation aquaculture has been proposed as a potential technique to restore Pacific lamprey populations. Intensive culture methods and diets for this species have not been developed. A sixteen week feeding trial tested the effects of seven diet treatments on the survival, growth, fatty acid profile and whole body lipid content of Pacific lamprey ammocoetes. Dietary treatments were: active dry yeast, yeast plus fish oil emulsion, micro-algae, micro-algae plus fish oil emulsion, yeast with micro-algae, yeast with micro-algae plus fish oil emulsion and yeast with larval fish diet. Each diet was offered to five replicate tanks stocked with 20 ammocoetes that were 51 days post hatch. Survival during the trial was not affected by diet. The greatest length and weight increases were in fish fed diets containing yeast. Growth decreased as the amount of algae in the diet was increased. Lipid retention was significantly higher in fish fed yeast with larval fish diet relative to the other treatments. Feed conversion ratio was lowest in fish fed diets containing yeast. Whole body fatty acid profiles tended to reflect the fatty acid profile of the diet. Percentages of 20:5n-3 and 22:6n-3 were significantly higher in fish fed diets containing fish oil emulsion. Overall, yeast with larval fish diet provided the best growth performance in larval Pacific lamprey. [ABSTRACT FROM AUTHOR]

Transition diets, often supplemented with salt and other additives, have been used to prepare Pacific salmonOncorhynchusspp. being moved directly from freshwater to saltwater net pens for aquaculture production. However, the use of transition diets to prepare hatchery-reared salmon released into freshwater prior to out-migration to the ocean has shown mixed results. We compared the physiological (size, condition factor, Na+,K+-ATPase [NKA] enzyme activity, survival during a saltwater challenge) and nutritional (proximate composition, fatty acid profile) condition of juvenile Chinook SalmonO. tshawytschathat were fed either a standard hatchery feed or a commercially available transition diet for the final 6 weeks of hatchery rearing to determine whether the transition diet altered smolt condition. At release, NKA activity of fish fed the transition diet was higher than that of fish fed the control diet, though survival during a saltwater challenge was similar between groups. Differences were seen in the proximate composition of the fish, with increased total body moisture and decreased lipid in the fish fed the transition diet relative to fish fed the control diet. Whole-body fatty acid composition of fish was similar to the fatty acid composition of the feeds in both groups, though some key whole-body fatty acids did not follow this trend. Palmitic acid (16:0), linoleic acid (18:2[n-6]), eicosapentaenoic acid (20:5[n-3]), and docosahexaenoic acid (22:6[n-3]) varied between prefeeding trial samples and fish fed the two diets. Further research is required to determine whether the physiological changes that occurred are related to smoltification or the maintenance of osmotic balance while fish are fed additional salt. Received October 13, 2015; accepted April 3, 2016 [ABSTRACT FROM PUBLISHER]

The establishment of a propagation program is among the recommended actions of the U.S. Fish and Wildlife Service recovery plan for the endangered Lost River SuckerDeltistes luxatus. As an initial step in diet development, a feeding trial was conducted to identify appropriate dietary lipid sources to feed juvenile Lost River Suckers at a rate of 0.47 g/fish. Six dietary treatments were produced by adding the following to a basal diet: (1) marine fish oil (Fish) as a control, (2) flaxseed oil (Flax), (3) soybean oil (Soy), or a 1:1 mixture of (4) fish and flax oil (Fish/Flax), (5) fish and soy oil (Fish/Soy), or (6) flax and soy oil (Flax/Soy). At the conclusion of the feeding trial weight gain of fish fed the control diet (Fish) was not significantly different than that of fish fed the other dietary treatments. However, weight gain of fish fed Soy was significantly higher than that of fish fed Fish/Flax. Whole-body lipid was significantly higher in fish fed Soy than in fish fed Fish, Flax, Fish/Flax, or Fish/Soy, but not significantly different than that in fish fed Flax/Soy. Generally, whole body fatty acid profiles reflected the fatty acid profiles of their respective dietary treatments. These results suggest soybean oil is an appropriate dietary lipid source for the Lost River Sucker, but more research on quantitative dietary requirements is needed for successful propagation of this species. Received November 20, 2015; accepted March 4, 2016 Published online June 15, 2016 [ABSTRACT FROM PUBLISHER]

The Lost River Sucker Deltistes luxatus is endemic to the Klamath Basin in southern Oregon and northern California. Population declines led to listing this species as endangered in 1988. Its native habitat has been greatly reduced and degraded putting their future in question. If this species is to be reared in captivity to prevent extinction, the development of culture methodologies is necessary. Successful initial feeding methods are one of the first areas of culture that need to be developed. Lost River Suckers begin feeding during the larval life stage. Larval fish often require live prey at the onset of feeding; however, it may be possible to start larvae on formulated microdiets. We investigated the use of live Artemia and two commercial microdiets (Hikari and Otohime brands) as first feeds over the course of a 41‐d feeding trial. Starting on day 21 of the trial, feed sizes were increased, and the Artemia‐fed fish were offered a commercial microdiet (Otohime) while being co‐fed Artemia through day 26 of the trial (6 d cofeeding). After day 26 the Artemia‐fed fish were only offered the microdiet. The response variables of total length, weight, survival, whole‐body lipid content, and whole‐body fatty acid profile were measured during and at termination of the trial. Fish grew significantly faster when started on Artemia and also displayed significantly higher survival compared with fish fed only commercial microdiets. Fish started on Artemia transitioned well to Otohime B1, and maintained 95.2% (SD, 2.2) survival over the 41‐d feeding trial. The fatty acid profiles of the fish generally reflected the profiles of the diets they were fed. This study demonstrated that live Artemia followed by a transition to Otohime commercial feed is an effective feeding regimen for the duration of the larval phase of this species. [ABSTRACT FROM AUTHOR]

To be profitable, producers must reduce diet costs, which can be as high as 80% of the variable costs of an aquaculture expense. As vitamin and mineral premixes represent a significant cost, eliminating addition of these premixes could reduce diet costs if no adverse effects were observed for growth and production parameters. A 105-day feeding trial was conducted with juvenile Australian red claw crayfish ( Cherax quadricarinatus) to evaluate the effects of growth, survival, body composition, processing traits and water quality when red claw were fed a supplemental diet containing 28% crude protein ( CP) without vitamin and mineral premixes (and supplemented alfalfa hay) compared with red claw fed a diet (control diet) containing 42% CP, vitamin and mineral premixes, and with supplemented alfalfa hay, and compared with red claw only fed alfalfa hay when grown in ponds. Juvenile red claw (mean weight of 15.7 ± 1.0 g) were randomly stocked into nine 0.02-ha ponds at a rate of 640 per pond (3.2 per m2), and each treatment was used in three ponds. There were two feedings per day, each consisting of one-half of the total daily ration. At harvest, individual weight, percentage weight gain, specific growth rate, survival and total yield of red claw fed a control diet was significantly higher ( P < 0.05) (83.0 g, 398%, 1.53% day−1, 65.1%,and 1708 kg ha−1 respectively) compared with red claw only fed alfalfa hay (44.9 g, 202%, 1.04% day−1, 30.3% and 431 kg ha−1, respectively), but not different ( P > 0.05) from red claw fed the supplemental diet without vitamin and mineral premixes (76.2 g, 367%, 1.47% day−1, 57.2% and 1378 kg ha−1). There were no significant differences ( P > 0.05) in feed conversion ratio ( FCR) among treatments, which averaged 5.0 (based on prepared diet input). These results indicate that vitamin and mineral supplementation in a diet is not necessary when diet containing 28% CP and alfalfa hay are used in combination for pond grown red claw. These results may help reduce diet costs and possibly increase producers' profits which might allow for industry expansion. [ABSTRACT FROM AUTHOR]

A 2 × 3 factorial study was conducted to evaluate the effects of dietary lipid level on the expression of mitochondrial and nuclear genes involved in electron transport chain in all-female rainbow trout Oncorhynchus mykiss. Three practical diets with a fixed crude protein content of 40%, formulated to contain 10% (40/10), 20% (40/20) and 30% (40/30) dietary lipid, were fed to apparent satiety to triplicate groups of either low-feed efficient (F120; 217.66 ± 2.24 g initial average mass) or high-feed efficient (F136; 205.47 ± 1.27 g) full-sib families of fish, twice per day, for 90 days. At the end of the experiment, the results showed that there is an interactive effect of the dietary lipid levels and the phenotypic feed efficiency (growth rate and feed efficiency) on the expression of the mitochondrial genes nd1 (NADH dehydrogenase subunit 1), cytb (Cytochrome b), cox1 (Cytochrome c oxidase subunits 1), cox2 (Cytochrome c oxidase subunits 2) and atp6 (ATP synthase subunit 6) and nuclear genes ucp2α (uncoupling proteins 2 alpha), ucp2β (uncoupling proteins 2 beta), pparα (peroxisome proliferator-activated receptor alpha), pparβ (peroxisome proliferatoractivated receptor beta) and ppargc1α (proliferator-activated receptor gamma coactivator 1 alpha) in fish liver, intestine and muscle, except on ppargc1α in the muscle which was affected by the diet and the family separately. Also, the results revealed that the expression of mitochondrial genes is associated with that of nuclear genes involved in electron transport chain in fish liver, intestine and muscle. Furthermore, this work showed that the expression of mitochondrial genes parallels with the expression of genes encoding uncoupling proteins (UCP) in the liver and the intestine of rainbow trout. This study for the first time presents the molecular basis of the effects of dietary lipid level on mitochondrial and nuclear genes involved in mitochondrial electron transport chain in fish. [ABSTRACT FROM AUTHOR]

RosemaryRosmarinus officinalisoil has shown potential for use as a phytobiotic fish feed supplement with antioxidant properties that can inhibit the growth ofFlavobacterium psychrophilum, the pathogen that causes bacterial cold-water disease (BCWD). To determine the in vivo effectiveness of rosemary oil in preventing or minimizing BCWD, Rainbow TroutOncorhynchus mykisswere fed commercial feed top-coated with one of two concentrations of rosemary oil (1% or 3% of the feed) or a control diet for 14 d. Fish from each feed treatment were then challenged with one of two doses ofF. psychrophilumvia subcutaneous injection, and mortality was monitored for 28 d. In bothF. psychrophilumchallenges, fish treated with feed coated with rosemary oil at the 1% and 3% levels experienced significantly higher mortality than fish treated with only soybean oil–coated feed. While the use of rosemary oil as a top-coat on feed increased mortality among Rainbow Trout subjected to a disease challenge in the current study, the mechanism for this result has not been established. Received January 22, 2014; accepted April 18, 2014 [ABSTRACT FROM PUBLISHER]

Fish meal (FM) is the main protein source in aquaculture diets owing to its palatability and quality. Available quantities of FM have remained constant for the past several decades; however, demand has dramatically increased due to its inclusion in diets used for the global aquaculture industry. There are various alternative protein sources that can be used in aquaculture diets, with soyabean meal (SBM) being the most widely used plant protein ingredient; however, use of SBM as the sole protein source has often resulted in reduced fish growth. There is a growing segment of consumers who desire organically grown foods, and since Nile tilapia is one of the most-cultured fish in the world and has herbivorous/omnivorous feeding habits, Nile tilapia fed an organic diet may allow producers to enter this rapidly developing market. A feeding experiment was conducted to evaluate the combination of organic SBM and an organic yeast extract (YE) as complete replacements for FM. Five isonitrogenous, isocaloric diets were fed to small (0.1 g) Nile tilapia, Oreochromis niloticus, for 6 weeks. Diets contained various percentages (0%, 10%, 20%, 30% and 40%) of YE, with Diet 1 formulated to be similar to a high-quality commercial diet containing 0% YE and 20% FM. At the conclusion of the feeding trial, fish fed Diet 1 had statistically significantly ( p < 0.05) higher mean final weight (3.99 g) and specific growth rate (8.48% day-1), and a lower feed conversion ratio (1.40) than fish fed all other diets. Based upon the data, an organic diet which replaces FM with a combination of SBM and YE appears promising but further research is needed to refine formulation so as to have similar growth performance with a FM-based diet. [ABSTRACT FROM AUTHOR]

Successful reproduction of captive-reared fishes depends on hatchery practices and proper broodstock nutrition. Nutrient requirements and environmental conditions stimulating reproductive development are unknown for many threatened and endangered species and may differ between lineages within species. Accordingly, prior to spawning, Main Diamond Gila TroutOncorhynchus gilaebroodstock were exposed to different thermal cycles and hormonal injection to improve reproductive success. Additionally, egg fatty acid composition and hatching success of Main and South Diamond Gila Trout were evaluated to determine the extent of phenotypic differences between lineages. Thermal conditioning of broodstock accompanied with injections of exogenous luteinizing hormone releasing hormone analog (LHRHa) prior to spawning improved progeny survival over historic hatchery means as well as means for broodstock reared in raceways at constant temperatures without LHRHa. Egg n-6 fatty acid content appears to be associated with this improvement. Eggs from Main and South Diamond broodstock fed the same feeds had similar hatch rates but could be differentiated on the basis of fatty acid profile. Future trials should further evaluate the influence of dietary fatty acids on egg deposition and hatch rate, while acknowledging that changes in reproductive performance may differ across lineages. Broodstocks should continue to be conditioned with thermal cycling and use of LHRHa to induce ovulation, as these techniques resulted in significantly better hatch rates in the current study than use of only photoperiod manipulation to stimulate reproductive development. Received September 11, 2012; accepted March 14, 2013 [ABSTRACT FROM PUBLISHER]

Quantities of fish meal (FM) have remained level for the past several decades; however, demand has dramatically increased because of its inclusion in all animal production as a high-quality protein source. Soybean meal (SBM) is the most widely used plant-protein ingredient for replacing various proportions of FM in aquatic animal diets. However, use of SBM as the sole protein source has often resulted in reduced fish growth. There is a growing segment of consumers who desire organically grown seafood, and tilapia is one of the most-cultured fish in the world. As tilapia have herbivorous/omnivorous feeding habits, tilapia fed organic diets may allow producers to enter this rapidly developing market. A feeding experiment was conducted to evaluate the combination of organic SBM and an organic yeast extract (YE) as complete replacements for FM in Nile tilapia, Oreochromis niloticus, fry diets. Nine diets were formulated to contain various percentages of organic YE (0, 15, 30, and 45%) in combination with organic SBM (84-34%) with and without amino acid (methionine and lysine) supplementation. At the conclusion of the study, fry fed a control diet containing 20% FM and fry fed a diet containing 45% YE/36%SBM with amino acid supplementation showed no significant differences ( P > 0.05) in final weight, weight gain, and specific growth rate (SGR) compared to those fed all other diets. On the basis of these data, an organic diet which replaces FM with a combination of SBM and YE with added methionine and lysine is commercially feasible and further investigation into the increased use of these two ingredients as protein sources in aquaculture diets is warranted. [ABSTRACT FROM AUTHOR]

Abstract: Commercial diets fed to coho salmon (Oncorhynchus kisutch) contain high levels of fish meal and fish oil. Given concerns about future supplies and prices of these commodities, more nutritional research aimed at identifying alternative dietary ingredients for Pacific salmon is needed. Thus, utilizing a factorial design, terrestrial proteins and lipids were evaluated in practical diets fed to coho salmon. The two basal diets, containing mostly marine proteins or containing only terrestrial proteins, were extruded and top-coated with either marine fish oil or a 63:37 mixture of canola and flaxseed oils. Each of the four dietary treatments was fed to quadruplicate groups of juvenile coho salmon initially weighing 7.5g/fish. At the end of the 15-wk feeding trial, weight gain (WG), feed efficiency (FE) and survival were significantly higher in fish fed diets containing marine protein compared with fish fed diets containing terrestrial proteins. Similarly, WG and FE were significantly higher in fish fed diets containing fish oil compared with fish fed diets containing plant oils. Survival was not significantly affected by dietary lipid source. Hemoglobin, hematocrit and total protein concentrations in whole blood were significantly higher in fish fed the marine protein diets compared with fish fed the terrestrial protein diets. Hematological responses were not significantly affected by dietary lipid source. Tissue (liver, muscle and carcass) lipids in fish fed the diets with added fish oil contained significantly higher proportions of 20:5n-3 and 22:6n-3 and significantly lower 18:1n-9, 18:2n-6 and 18:3n-3 percentages compared with fish fed the diets with added plant oils. Tissue fatty acid profiles also were significantly affected by dietary protein source, as liver, muscle and whole body lipids of fish fed the terrestrial protein diets contained significantly higher percentages of 18:2n-6 and total n-6 PUFA and a significantly lower total n-3:n-6 fatty acid ratio compared with fish fed the marine protein diets. Results of this study indicate complete replacement of dietary fish meal or fish oil individually have similar inhibitory growth effects in coho salmon, but have different effects on survival, hematological responses and tissue fatty acid percentages in this species. [Copyright &y& Elsevier]

Juvenile Atlantic cod Gadus morhua (initial weight = 24.1 ± 1.4 g [mean ± SE) were fed diets in which fish meal (FM) was replaced with soy protein concentrate (SPC) and soybean meal (SBM) in isonitrogenous, isocaloric diets for 84 d. A standard marine finfish diet (3 mm, 54% protein, 14% fat) was modified to produce four experimental diets in which 50% of FM was replaced with soy at 0:1, 1:1, or 1:2 ratios of SPC:SBM and 100% FM replacement with a 1:1 ratio of SPC:SBM. No differences in mortality or feed intake were detected among treatments, and fish fed the 50% FM replacement diets, in any combination, grew as well or better than the control for all variables investigated. Cod fed the 100% FM replacement diet exhibited the lowest growth and differed from the control with respect to final body weight, growth, specific growth rate, and thermal-unit growth coefficient. No enteritis was observed in histological sections. These results indicate that 100% fish meal replacement is not recommended, but 50% replacement can be used without significant reductions in growth or condition indices. Received October 18, 2011; accepted January 11, 2012 [ABSTRACT FROM AUTHOR]

Two feeding trials were conducted in a closed system with Nile tilapia Oreochromis niloticus fry (mean weight, 0.10 g; experiment 1) and juveniles (mean weight, 2.84 g; experiment 2) to examine the effects of total replacement of fish meal (FM), with and without supplementation of dl-methionine (Met) and l-lysine (Lys), by plant protein sources. In experiment 1, fry were fed nine isoenergetic (available energy [AE] = 4.0 kcal/g of diet) and isoproteic (40% protein as fed basis) practical diets containing protein primarily from soybean meal (SBM), with and without essential Met and Lys. After 5 weeks, final individual weight (FW; g/fish) and percent weight gain (PWG) of fry fed diet 1 (control with 20% FM) was significantly higher (P < 0.05) compared with fry fed all other diets, while fry fed diet 9 containing 46% SBM and 22% feed-grade poultry by-product meal PBM) was significantly higher than all other diets (diets 2–8). Quantity of diet fed and percent survival did not differ significantly (P > 0.05) among all diets. In experiment 2, juveniles were fed six isoenergetic (AE = 4.0 kcal/g of diet) and isoproteic (35% protein as fed basis) practical diets containing protein primarily from SBM, soybean protein concentrate (SPC), feed-grade PBM, or combinations of those. After 7 weeks, mean FW, PWG, and amount of diet fed for fish fed diets 1 (control with 20% FM) and 6 (with 20% SPC and 20% PBM) were significantly higher (P < 0.05) compared with juveniles fed all other diets. Feed conversion ratio (FCR) was similar among treatments, but fish fed diet 5 (with 36% SPC and 0% FM) recorded the highest FCR value. Likewise, protein efficiency ratio (PER) was similar among treatments; however, PER in juveniles fed diets 3 (with 52% SBM and 0% FM) and 5 were significantly lower than in fish fed all other diets. Overall, no significant (P > 0.05) difference was found in percent survival, which averaged 92.6% among all diets fed. These data suggest that Nile tilapia fry cannot utilize diets containing high levels (>75%) of SBM when no animal protein ingredient is added, even with supplemental Met and Lys. However, a diet containing 20% SPC and 20% feed-grade PBM appears to be suitable for juvenile Nile tilapia, which may help reduce diet costs and allow for sustainable production. Received August 23, 2011; accepted February 14, 2012 [ABSTRACT FROM AUTHOR]

Additives are commonly used in feed to enhance fish performance, health, and well-being. In recent years, antibiotics have received increased scrutiny owing to concerns about overuse and their environmental impact. These concerns have generated a desire for naturally derived alternatives for the aquafeed industry. For screening purposes, we examined the in vitro effects of an essential oil on bacteria commonly associated with fish diseases. Six concentrations of rosemary Rosmarinus officinalis oil (0.1, 0.3, 0.5, 0.7, and 0.9 μL/μL of 1% Tween-20 and pure rosemary oil [1.0]) were used against Flavobacterium psychrophilum, Yersinia ruckeri, Aeromonas salmonicida, and three warmwater bacterial pathogens, A. hydrophila, Edwardsiella ictaluri, and E. tarda, along with a control treatment (1% Tween-20 only). After incubation, the mean zone of inhibition around the disks was measured. While most concentrations were found to inhibit pathogen growth, a concentration of 50% or more was found to have significantly higher effects on most of the pathogens tested. Rosemary oil was found to inhibit the growth of F. psychrophilum to the greatest extent and had a limited effect on the other fish pathogens. Although rosemary oil was shown to inhibit the growth of some bacterial fish pathogens in experimental trials, further laboratory and field studies are required to determine whether rosemary oil as a feed additive has any application as part of an integrated fish health management strategy. Received June 21, 2011; accepted October 16, 2011 [ABSTRACT FROM AUTHOR]

A 12-week feeding trial was conducted to evaluate a fish-meal-free, fish-oil-free diet for use with first-feeding steelhead Oncorhynchus mykiss. The marine-based control diet (marine diet) contained sardine (Sardinops spp.) meal and pollock (Pollachius virens) liver oil as the primary sources of protein and lipid, respectively. The experimental diet (terrestrial diet) contained only terrestrial sources of protein (poultry by-product meal, blood meal, canola, corn gluten, and wheat gluten) and lipid (canola oil and flaxseed oil). Each diet was administered to five replicate groups of first-feeding fry. At the conclusion of the feeding trial, fish that were fed the marine diet exhibited significantly higher weight gain and feed efficiency than fish that were given the terrestrial diet. Survival was not significantly affected by dietary treatment. However, fish that received the terrestrial diet exhibited significantly lower hemoglobin concentration and percent packed cell volume. Histological examination indicated that in comparison with control fish, steelhead that were fed the terrestrial diet exhibited a lesser degree of vacuolation in hepatocytes, mild hypertrophy and hyperplasia of the nephron tubular epithelium, and intracellular vacuolation in epithelium of the pyloric caeca. Carcass crude protein concentration was significantly higher in fish that were fed the marine diet than in fish that were fed the terrestrial diet. After 2 weeks of feeding, steelhead that received the marine diet exhibited significantly higher carcass concentrations of 14:0, 16:0, 16:1, 20:1, 20:5(n-3), 22:5(n-3), and 22:6(n-3) fatty acids but significantly lower carcass concentrations of 18:1, 18:2(n-6), 18:3(n-6), 18:3(n-3), and 20:4(n-6) relative to fish that were given the terrestrial diet. These differences in carcass fatty acid concentrations persisted throughout the feeding trial. Results of this study indicate that the current terrestrial-based diet is not a satisfactory replacement for the standard marine-based diet used with first-feeding steelhead. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented discussing digestibility coefficients of protein, lipid and carbohydrate in practical diets fed to paddlefish.

In 2006, Bio-Oregon, Inc., the only commercial producer of cold-extruded moist diets (~20-27% moisture) formulated for salmonids, announced that it would discontinue production of this diet line. One of these diets, BioDiet starter (19.5-21.5% moisture) was the primary feed used in many hatcheries that produce Chinook salmon Oncorhynchus tshawytscha. Thus, a feeding trial was conducted to identify an alternative starter diet for spring Chinook salmon. Five commercial diets were evaluated: Skretting BioVita (<10% moisture), EWOS Micro (<10% moisture), Rangen Starter (<10% moisture), Rangen Soft-Moist (14-17% moisture), and Silver Cup Soft-Moist (<13% moisture). Each dietary treatment was fed to quadruplicate groups of 200 randomly selected first-feeding fry reared in fiberglass tanks. Initial weight of the fish averaged 0.34 g/fish. The flow-through water supply was 12°C throughout the 8-week feeding trial. At the end of the study, fish fed Skretting BioVita exhibited significantly higher (P < 0.05) weight gain (3.4 g/fish) and feed efficiency (1.9 g gain/g feed) than fish fed the other diets. Fish fed Rangen Soft-Moist exhibited significantly lower (P < 0.05) weight gain (1.6 g/fish) and feed efficiency (1.2 g gain/g feed) than fish fed the other commercial diets. Survival rates were high (97-99%) and not significantly (P > 0.05) affected by dietary treatment. Carcass moisture and fat concentrations were significantly (P < 0.05) affected by the various diets. Carcass fat concentrations were significantly higher and carcass moisture concentrations were significantly lower in fish fed Skretting BioVita than in fish fed Rangen Starter, Rangen Soft-Moist, or Silver Cup Soft-Moist. Results of this study indicate that a moist starter diet is not required for rapid weight gain and high survival rates of first-feeding spring Chinook salmon. [ABSTRACT FROM AUTHOR]

Limited information is available on digestibility of nutrients in various practical ingredients used in diets for commercially important finfish species, such as hybrid striped bass. This information is especially needed for sunshine bass, Morone chrysops × M. saxatilis, to improve least-cost diet formulations and to allow effective substitution of feedstuffs. A study was conducted with large (867 g) sunshine bass to determine the apparent digestibility coefficients (ADCs) for moisture, protein, lipid, and organic matter (OM) in a variety of ingredients in floating, extrusion-processed, diets. The practical ingredients tested were menhaden (MEN) fish meal (FM), anchovy (ANCH) FM, pet-food grade poultry by-product meal, feed-grade poultry by-product meal, dehulled soybean meal (SBM), and distiller’s dried grains with solubles (DDGS). Test diets consisted of a 70:30 mixture of reference diet to test ingredient with chromic oxide (1.0%) as the inert marker. Reference and test diet ingredients were mixed and extruded on a Wenger X85 single-screw extruder to produce floating pellets. The digestibility trials were conducted in twelve 1200-L circular tanks. Diets were randomly assigned to tanks of 30 sunshine bass and were fed once daily to satiation. Protein digestibility coefficients were significantly ( P < 0.05) different among test ingredients and ranged from 86.42% for MEN to 64.94% for DDGS. Lipid ADCs were significantly different ( P < 0.05) among test ingredients and ranged from 92.14% for MEN to 57.11% for SBM. OM ADCs were significantly different ( P < 0.05) among test ingredients and ranged from 89.41% for MEN to 16.94% for DDGS. This information will assist in the formulation of more efficient, economical diets for sunshine bass. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated that fish feeds contain significant concentrations of contaminants, many of which can bioaccumulate and bioconcentrate in fish. Organochlorine (OC) contaminants are present in the fish oils and fish meals used in feed manufacture, and some researchers speculate that all fish feeds contain measurable levels of some contaminants. To determine the concentration of contaminants in feeds used in US Fish and Wildlife Service’s National Fish Hatcheries, we systematically collected samples of feed from 11 cold-water fish hatcheries. All samples (collected from October 2001 to October 2003) contained at least one polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), polychlorinated biphenyl (PCB) congener, or dichlorodiphenyltrichloroethane (DDT) metabolite. Of the 55 samples in which they were analyzed 39 contained PCDDs, 24 contained PCDFs and 24 contained DDT or its metabolites. There were 10- to 150-fold differences in concentrations of total PCBs, PCDDs, PCDFs and DDT. Although PCBs were the most commonly detected contaminant in our study, concentrations (range: 0.07–10.46ngg−1 wet weight) were low compared to those reported previously. In general, we also found lower levels of OCs than reported previously in fish feed. Perhaps most notable was the near absence of OC pesticides – except for DDT or its metabolites, and two samples containing hexachlorocyclohexane (HCH). While contaminant concentrations were generally low, the ecological impacts can not be determined without a measure of the bioaccumulation of these compounds in the fish and the fate of these compounds after the fish are released. [Copyright &y& Elsevier]

This study determined the digestibility of protein in partially dehulled sunflower meal (SFM) and then, as the main goal, the nutritive value of high-temperature extruded (≤149°C) partially dehulled SFM (SFMEX) for post-smolt Atlantic salmon Salmo salar in sea water. The digestibility study was conducted using the settling column approach (‘Guelph system’) for faeces collection as described by Hajen, Higgs, Beames and Dosanjh. In the nutritive value study, triplicate groups of 50 salmon (mean weight ∼116 g) in 4000-L outdoor fibreglass tanks supplied with 25–40 L min−1, filtered, oxygenated (dissolved oxygen, 7.0–8.5 mg L−1), 11–12°C sea water (salinity, 29–31 g L−1), were fed twice daily to satiation one of five steam-pelleted dry diets that contained 422 g of digestible protein (DP) kg−1 and ∼16.4 MJ of digestible energy (DE) kg−1 on a dry weight basis for 84 days. Low-temperature-dried anchovy meal (LT-AM) comprised 68.2% of the basal diet protein whereas in four test diets, SFMEX progressively replaced up to 33.0% of the DP provided by LT-AM in the basal diet (SFMEX≤271 g kg−1 of dry matter). Sunflower meal had 87.9% DP. Diet treatment did not significantly affect specific growth rate (1.39–1.45% day−1), feed efficiency (1.19–1.26), percentage of dietary protein retained (45.8–47.5), gross energy utilization (46.5–49.4%), per cent survival (96.0–99.3) or terminal whole body and muscle proximate compositions. We conclude that SFMEX can comprise ≥271 g kg−1 of the dry diet or ≥22.7% of the digestible dietary protein of post-smolt Atlantic salmon in seawater without any adverse effects on their performance. [ABSTRACT FROM AUTHOR]

The bonytail Gila elegans is a critically endangered cyprinid that is endemic to the southwestern United States, where it is cultured in ponds and water reuse systems as part of recovery efforts. Unlike in extensive outdoor pond culture, where natural food productivity plays a primary nutritional role, manufactured feed must provide complete nourishment for fish reared indoors in recirculating systems. The objective of this study was to determine the effects of diet on the growth and survival of juvenile bonytails fed four commercially available feeds over a 120-d period. The four treatment diets were identified as a catfish diet, a trout diet, a high-protein shrimp diet, and a low-protein shrimp diet. Significant (P < 0.05) differences in growth among treatments were observed on sampling day 102. By day 120, the average weight of fish fed the high-protein shrimp diet (36.3 g) was significantly higher than the weights of fish fed the catfish (26.6 g/. trout (24,7 g), and low-protein shrimp diets (24.2 g). The specific growth rates measured on days 102 and 120 were significantly greater for bonytails fed the high-protein shrimp diet than for fish fed the other treatments. The feed conversion ratio of fish fed the high-protein shrimp diet was significantly better than those of fish fed the trout and low-protein shrimp diets, while the protein efficiency ratio and apparent net protein retention were generally higher in the high- and low-protein shrimp diet treatment groups than in the other two treatment groups. Overall survival was high (93.5%) and did not differ significantly among treatment groups (P ≥ 0.05) through 120 d. [ABSTRACT FROM AUTHOR]

Hydraulic characteristics inside two research circular tanks (1.5-m and 1.2-m diameter) with the same volume of water were studied to understand how they might affect experimental bias by influencing the behavior and development of juvenile fish. Water velocities inside each tank were documented extensively and flow behavior studied. Surface inflow to the 1.5-m tank created a highly turbulent and aerated surface, and produced unevenly distributed velocities within the tank. A low-flow velocity, or “dead” zone, persisted just upstream of the surface inflow. A single submerged nozzle in the 1.2-m tank created uniform flow and did not cause undue turbulence or introduce air. Flow behavior in the 1.5-m tank is believed to have negatively affected the feeding behavior and physiological development of a group of juvenile fall chinook salmon, Oncorhynchus tshawytscha. A new inflow nozzle design provided comparable flow behavior regardless of tank size and water depth. Maintaining similar hydraulic conditions inside tanks used for various biological purposes, including fish research, would minimize experimental bias caused by differences in flow behavior. Other sources of experimental bias are discussed and recommendations given for reporting and control of experimental conditions in fishery research tank experiments. [ABSTRACT FROM PUBLISHER]

At two Washington State hatcheries in August 1999-2002, juvenile steelhead Oncorhynchus mykiss were size-graded and the largest fish (4.8-9.2% of the population) were coded-wire-tagged and mixed with small fish to determine whether the large fish were those that became precocious males. The results showed that the large fish in August at Merwin Hatchery tended to become precocious, although the mean lengths of the precocious and nonprecocious fish were similar at their time of release in April. At Abernathy Fish Technology Center (FTC), the large fish in August did not disproportionately become precocious, and the nonprecocious fish were significantly larger than the precocious fish at release. We suggest that precocious fish at Abernathy FTC may have committed to precocity before August whereas fish at Merwin Hatchery committed to precocity in August. Because only 0.82% of the large fish became precocious, removing the 5-10% largest fish in August at the Merwin Hatchery would be marginally successful in reducing the number of precocious males. [ABSTRACT FROM AUTHOR]

Various immunostimulants and their methods of application in fish culture are examined in this review. Important variables such as life stage and innate disease resistance of the fish; immunostim-ulant used, its structure and mode of action; and the fish's environment are discussed. Conflicting results have been published about the efficacy of immunostimulants in fish diets. Some researchers have had positive responses demonstrated as increased fish survival, others have not. Generally, immunostimulants enhance individual components of the non-specific immune response but that does not always translate into increased fish survival. In addition, immunostimulants fed at too high a dose or for too long can be immunosuppressive. [ABSTRACT FROM AUTHOR]

A 4 × 3 factorial experiment was conducted to evaluate the effects of two dietary protein sources (mixed fishmeal/plant protein-, and plant protein- based diet), two dietary lipid levels (10% and 20%) and three water temperatures (10 °C, 14 °C, and 18 °C) on the growth performance, nutrient utilization efficiencies and mitochondrial enzyme complex activities in rainbow trout Oncorhynchus mykiss (average weight ± SD, 39.5 ± 5 g) over a 180 day rearing period. At the end of the experiment, weight gain (WG), condition factor (CF), and feed efficiency (FE) were significantly affected by diet × temperature interaction (P < 0.05). Specific growth rate (SGR) was significantly affected by increasing temperature (P < 0.05). The plant protein-based diets led to a higher CF than the mixed fishmeal/plant protein-based diets. The protein productive value (PPV), protein efficiency ratio (PER), lipid efficiency ratio, (LER) and lipid productive value (LPV) were all significantly affected by diet × temperature interaction (P < 0.05). The diet × temperature interaction also had significant effects on mitochondrial enzyme complexes II, V and citrate synthase in the liver, complexes II and IV in the intestine, and complex IV in the muscle (P < 0.05). Temperature had a significant main effect on the activity of the enzymatic complexes I and III in the liver, complex III and citrate synthase in the intestine, and complexes I, II, III, V and citrate synthase in the muscle (P < 0.05). Diet had a significant main effect on complexes I and III in the liver, complexes II and III for the intestine and complexes I and II in the muscle (P < 0.05). The significant temperature x diet interaction observed has practical ecological implications explicitly demonstrating how changes in temperature regimens as anticipated in the rising global temperature can influence organismal performance in relation to changes in dietary formulations (replacing fishmeal based diet with plant protein based ingredients). To illustrate the practical application of the observations from this study, the most economical and cost effective way to produce rainbow trout would be to use 40/10PP diet at 14 °C because fish fed this treatment had a weight gain comparable to that of the fish fed the more expensive experimental diets (40/10 FM/PP, 40/20 FM/PP, and 40/20 PP). [ABSTRACT FROM AUTHOR]

A feeding trial was conducted in a closed recirculating aquaculture system with Nile tilapia Oreochromis niloticus juveniles (mean weight, 6.81 g) to examine the response to a practical diet containing protein primarily from menhaden fish meal (FM) and soybean meal (SBM) (control, Diet 1) or to diets with decreasing ratios of PBM to SBM (Diets 2–7; dose–response) as a total replacement for digestible protein from FM, and the efficacy of 1% supplemental taurine (Tau) at the highest level of plant protein inclusion by removing Tau (Diet 8). To the extent possible, the replacement diets were formulated using currently published amino acid availabilities for the ingredients of interest in order to estimate and supplement the first two limiting amino acids (Met and Lys) to match levels in the FM control diet. The test diets were formulated to contain 35% digestible protein. Fish were fed three times daily all they would consume in 30 min. All performance measures were quadratic with respect to PBM:SBM ratio in the diet. The highest weight gain, lowest average daily feed intake, lowest feed conversion, and greatest specific growth rate coincided with a dietary PBM:SBM ratio of 1.22 to 1.35 suggesting that the best tilapia performance in the current trial was achieved with replacement formula D3 that contained approximately 20% SBM, 30% PBM, and supplemental Lys, Met, and Tau. However, all growth performance measures were significantly linear and decreased with respect to increasing distance from the ideal protein amino acid profile for tilapia. Positive effects of taurine supplementation at the highest level of dietary plant protein inclusion were not observed and may have been overwhelmed by imbalances in other amino acids in the test diets. The current results provide evidence that total deviation from the ideal protein profile in tilapia is an important consideration for diet formulation when combinations of diet ingredients are used. Hence, the essential amino acid content of a fish meal control diet may be an inadequate target for optimizing fish meal replacement diets for tilapia; whereas the whole body or muscle amino acid pattern may be a more useful formulation target. Finally, while the database of ingredients that have been evaluated in tilapia is growing, the industry will benefit from more efficient diets as long-term averages of amino acid composition and digestibility accrue for a variety of traditional and novel ingredients. Statement of Relevance : The current results provide evidence that it is the total deviations from a postulated ideal protein profile that is a more important consideration for diet formulation than the combination of diet ingredients used to meet that profile. Therefore, it should be possible to formulate least-cost fish meal replacement diets for tilapia, irrespective of ingredient combinations, and diet intact protein level, as long as a reasonable amino acid model is chosen and a fairly robust set of ingredient composition and digestibility data are available. [ABSTRACT FROM AUTHOR]

Abstract: A 2×3 factorial study was conducted to investigate the effects of dietary lipid levels on growth, feed utilization and mitochondrial enzyme activities in juvenile all-female rainbow trout (Oncorhynchus mykiss). Practical diets with a fixed crude protein content of 42%, formulated to contain 10% (42/10), 20% (42/20) and 30% (42/30) dietary lipid, were fed to apparent satiety to triplicate groups of either low-feed efficient (low-FE, 105.67±3.04g initial average mass) or high-feed efficient (high-FE, 97.86±4.02g) families of fish, twice per day, for 108days. At the end of the experiment, the group of fish fed diets 42/20 and 42/30 showed higher growth and feed efficiency (FE), coupled with a lower daily feed consumption (FC), than fish fed 42/10 diet, although similar results were found with diets 42/10 and 42/30 for growth (P<0.05). With similar FC, the high-FE family showed higher growth, FE, protein efficiency ratio (PER) and protein productive value (PPV) than the low-FE family (P<0.05). Fish fed diets 42/20 and 42/30 had the highest PER and PPV (P<0.05). The lipid efficiency ratio was highest in fish from the high-FE family fed diet 42/10 (P<0.05). Fish fed diet 42/30 showed the highest visceral fat and viscerosomatic index (P<0.05). In the liver, the respiratory chain enzymatic activity was significantly affected by both diet and family for complexes I and IV, and by diet for complexes II, III and V (P<0.05). In the intestine, significant family×diet interaction effects were observed for complexes III and IV (P<0.05). There were both significant family and diet main effects on complexes I and II, whereas complex V was only affected by family (P<0.05). In the muscle, significant (P<0.05) diet×family interaction effects were observed for complexes II and IV activities; complex III activity was significantly affected by the diet, whereas complex V activity was affected by both the diet and the family main effects; the activity of complex I was not affected by the treatments (P>0.05). The overall results of this study established that feeding a 42% CP diet with a minimum of 20% dietary lipid leads to high growth, feed utilization on the one hand, and that these zootechnical parameters are coupled with high mitochondrial enzymatic function in the liver, the intestine and the muscle of rainbow trout. Also, as it was expected, the high-FE family showed higher response to treatments than the low-FE family. [Copyright &y& Elsevier]

As diets fed to juvenile steelhead (progeny of anadromous rainbow trout, Oncorhynchus mykiss) reared in conservation hatcheries contain relatively high levels of protein and lipid supplied primarily by fish meal and fish oil, a 12-week feeding trial was conducted to evaluate alternative ingredients for this species. Using a factorial design, Spirulina meal and a plant oil mixture were evaluated as partial or complete replacements of dietary fish meal and fish oil, respectively. Thus, two diets containing 0 or 50% substitution of Spirulina for fish meal were extruded and top-coated with fish oil or a 63:37 mixture of canola and flaxseed oils. Each of the four dietary treatments was fed to quadruplicate groups of 100 steelhead initially weighing 12.4 g/fish. Steelhead growth rate and feed efficiency were not significantly affected by partial replacement of dietary fish meal with Spirulina , but growth responses were significantly reduced by replacement of dietary fish oil with plant oil. Lipid and protein apparent digestibility coefficients (ADC) were significantly higher in steelhead fed the fish meal diets compared with fish fed the Spirulina diets and significantly higher in steelhead fed the plant oil diets compared with fish fed the fish oil diets. Whole body fatty acid profiles generally reflected those of the diets such that percentages of 18:2n-6 were significantly higher and n-3 polyunsaturated fatty acids (PUFA), including 20:5n-3 and 22:6n-3, were significantly lower in fish fed the Spirulina and plant oil diets compared with those fed the fish meal and fish oil diets. Plasma total cholesterol concentration was significantly reduced in fish fed the Spirulina diets and in fish fed the plant oils diets. Growth results suggest Spirulina is a suitable replacement for 50% of dietary fish meal for steelhead whereas a mixture of canola and flaxseed oil is not suitable as a complete replacement for fish oil in diets for this species. • A feeding trial was conducted to evaluate partial replacement of fish meal with Spirulina meal and complete replacement of fish oil with plant oil. • Growth responses indicated Spirulina was a suitable replacement for 50% of fish meal. • Complete replacement of fish oil with plant oil resulted in significantly lower weight gain and feed efficiency. • Dietary Spirulina and plant oil altered whole body fatty acid percentages resulting in higher 18:2n-6 and lower n-3 PUFA percentages in steelhead. [ABSTRACT FROM AUTHOR]