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Sablefish, Anoplopoma fimbria (also called black cod), is a long‐lived marine species with wide distribution extending from Baja California to Alaska, the Bering Sea, and through to the eastern coast of Japan. The landed weight of sablefish in the U.S. commercial fisheries is not large compared with other species; however, the exceptional value of sablefish has ranked it high compared with other species such as pollock, sockeye salmon, and Pacific cod. Sablefish are high in omega‐3 fatty acids and have white firm flesh with superior quality and taste. Current population levels are lower relative to historic ones and harvests have decreased within the last decade. The exceptional value of sablefish and decreases in wild populations have stimulated the development of methods to commercially aquaculture this species. Over the last 20 years, significant progress has been made in addressing the production of sablefish, and while there is still research that needs to be completed, sablefish have been commercially aquacultured by a small number of Canadian companies. In the Pacific Northwest, it is relatively easy to collect sablefish broodstocks from the wild and to transition them to land‐based rearing facilities. However, they must be maintained at cold temperatures to successfully reproduce. Captive broodstocks for genetic selection are not commercially available, though producers have begun their own development. Incubation conditions for yolk‐sac larvae have been developed and currently require long incubation periods at low temperatures, elevated salinity, and light exclusion. Although incubation times are long, they do not require very much attention during this phase. Exogenously feeding larvae currently require a regimen of rotifers and Artemia prior to dry feed habituation. However, tank characteristics, water turbidity, temperature, and illumination, as well as live feed enrichments have been studied. With the research that has been accomplished so far, survival rates of 10–40% have been routinely obtained at the larval stage. Despite a scarcity of species‐specific nutritional studies, researchers have shown that sablefish can be successfully cultured from the juvenile to the adult stage on commercial salmon feeds. Off‐the‐shelf salmon feeds have been used successfully in net‐pen grow‐out trials and are used by commercial producers. In addition, sablefish have proven to be a good cold‐water marine model for alternative feeds research. Still, research is needed to optimize nutritional requirements for all life stages of sablefish, develop practical feeds with these nutrient profiles, optimize feeding schedules, and produce life‐stage specific diets since the growth of sablefish differs according to size—most likely reflective of their complex life history. Sexually dimorphic growth in sablefish occurs during the typical grow‐out period, affecting time to harvest, the proportion of undersized (male) fish, and thus overall economic return to the producer. Production of all‐female monosex offspring at semi‐commercial scale using F‐1 progeny of neomales (XX males) generated through dietary treatment with 17α‐methyltestosterone is now possible. Results of long‐term feeding trials suggest that time to harvest at 2.5 kg from stocking at 75 g may be reduced by almost 3 months when monosex stocks are used. Econometric models reveal that internal rates of return are 11–15% higher for monosex relative to mix‐sex stocks over a 10‐year period under typical cage culture conditions. Sablefish are susceptible to diseases (furunculosis and vibriosis) brought on by atypical Aeromonas salmonicida and Vibrio anguillarum. Vaccination of sablefish using commercial vaccines to A. salmonicida (typical and atypical) has demonstrated that fish can be protected against a subsequent challenge by A. salmonicida, but this has only been effective by injection of the vaccine (not immersion) and how long the protection lasts has not been studied. More research is required to develop more effective vaccines, methods for vaccine delivery, and to understand conditions (ontogenetic and environmental) that may promote or enhance pathogenesis. [ABSTRACT FROM AUTHOR]

Turkish Towel Chondracanthus exasperates and taurine were added to alternative plant‐based feeds for juvenile sablefish Anoplopoma fimbria to evaluate the effect of these ingredients, alone or combined, on fish growth, feed intake and efficiency, whole body nutrient composition, and liver histomorphology. Fish growth was significantly increased with the addition of taurine, and to a lesser extent, Turkish Towel to the experimental feeds. Feed efficiency and protein retention were significantly improved with the addition of taurine, but were unaffected by Turkish Towel addition. As expected, whole body taurine content was significantly affected by taurine addition. Increases in whole body lipid were observed with both taurine and Turkish Towel addition, with a significant interaction between the two factors. Liver histomorphology was generally normal; however, histopathologic changes were observed in some fish at the end of the experiment. The occurrence of hepatocellular nuclear pleomorphism and clear cell foci was less among fish that had received the Turkish Towel feeds. The addition of taurine had no effect on the number of fish with a histopathologic change. Overall, results from this study reaffirm taurine supplementation is beneficial to sablefish receiving plant‐based feeds and indicate Turkish Towel may be a promising feed ingredient for this species. [ABSTRACT FROM AUTHOR]

To quantify the efficacy and cost of different soya protein ingredients, heated soya beans (HSB) and underprocessed (SB) full‐fat soya beans (FFSB), soya protein concentrate (SPC) and trim waste from Pacific whiting (Merluccius productus) were incorporated into feeds for the cold water marine sablefish (Anoplopoma fimbria). Feed ingredients for this study were processed using an experimental heated ball mill with demonstrated potential as an affordable process for rural or small‐scale feed production. The three feed treatments were formulated with equal amounts of soya protein and Pacific whiting process trim. The three feed treatments contained 46% protein and 18% lipid as dry matter. Three 480‐L tanks of 10 fish were used to evaluate each of the three feed treatments. Fish were fed to satiation every 2 days for 8 weeks. Weight gain of the treatment groups ranged between 56% and 105% over the course of the study. Fish growth was significantly better among fish receiving the feeds containing HSB and SPC than a feed containing SB. At the conclusion of the study, histomorphologic evaluations of the distal intestines of final fish were conducted. Varying levels of inflammation were measured for all three treatments. Fisher's exact test showed a significant reduction in mononuclear cell infiltration among fish fed heat‐treated full‐fat soya beans vs those receiving underprocessed full‐fat soya beans. Fish receiving HSB feed had significantly lower intestinal inflammation than SB fish. Based on our results, cost savings of $ 0.253/kg were calculated for the HSB feed over the SPC feed. [ABSTRACT FROM AUTHOR]

Sablefish ( Anoplopoma fimbria ) is a highly desired seafood product, which encourages development of sustainable aquaculture methods for this marine fish. Conventional marine fish-based feeds provide essential nutrients including long chain fatty acids for piscivorous species such as sablefish. Alternative terrestrial ingredients could reduce fishing pressures on pelagic species that are the source of fish meal and fish oil, and improve source sustainability. Using juvenile sablefish, we compared the effects of a standard fish-based diet to two diets that contained primarily terrestrial plant ingredients with flaxseed or corn oil replacing the added fish oil. After an 8-week trial feeding period, there were striking differences attributable to diet. Fish receiving the alternative feeds had lower weight gain and shorter length than fish receiving the fish-based feed, suggesting sablefish obtained lower nutrients from the alternative feeds. Among the histological differences, the intestinal mucosa was significantly less vacuolated and the frequency of intestinal mucous cells was reduced in alternative feed fish. The most dramatic lesions were observed in the liver, where severe bile duct hyperplasia (53%, flaxseed oil diet; 33%, corn oil diet), and hepatocellular lesions (nuclear pleomorphism/megalocytosis, regeneration, hypertrophy, clear cell foci) occurred in only alternative feed fish. The hepatic and biliary lesions indicate the alternative diets may be deficient or possibly harmful to sablefish. The bacterial community structures from corn oil fish showed much less diversity than those for the other diets, and the microbiome structures from the three diets were distinctly different from each other. The intestinal microbiome for the fish-based diet included the largest number of families (68), and these fish also had the largest number of unique bacterial families (11) compared to those for corn oil (two) or flaxseed oil (one) fish. Regardless of diet, the stomach and intestinal microbiomes differed significantly from each other, and the feed microbiome differed from all gastrointestinal communities, suggesting that feed is not a significant source of gut bacterial diversity. Similar to other teleosts, the sablefish gastrointestinal microbiome is dominated by Bacteroidetes, Firmicutes, and Proteobacteria. These results suggest that diet-induced shifts in microbiome can occur relatively quickly in sablefish, but the shifts may not be sufficiently adaptive or cannot overcome nutrient deficiencies. This multidisciplinary study demonstrates the utility of histology and microbiology in characterizing dietary effects for novel aquaculture species. Statement of relevance Physiological assessments such as gastrointestinal microbiomes and histopathology can provide a near-term evaluation of the nutritional adequacy of alternative feeds, such as plant-based lipid diets for marine carnivorous finfish. This is the first examination of the microbiome of sablefish, a marine species under development for sustainable aquaculture. [ABSTRACT FROM AUTHOR]

Juvenile sablefish were fed a low taurine, basal feed with seven graded levels of supplemental taurine to determine taurine requirements for growth and feed efficiency. The basal feed was plant based, formulated primarily with soy and corn proteins with a minimal (9%) amount of fishmeal. The unsupplemented, basal feed contained 0.14% taurine. Experimental feeds were supplemented with 0, 0.25, 0.50, 1.0, 1.5, 3.0, and 6.0% taurine. Using the five parameter, saturated kinetic model (5 SKM), peak weight gain was predicted at 1.5% dietary taurine. Optimum weight gain, as defined as the region of the 5 SKM curve corresponding to at least 95% of peak, was predicted between 0.4% and 5.8% dietary taurine. Peak feed efficiency was predicted at 1.1% dietary taurine with optimum weight gain predicted between 0.4% and 4.2%. Whole body and muscle tissue protein and lipid content were not affected by taurine supplementation. Tissue taurine content increased asymptotically with increasing dietary taurine supplementation. Whole body tissue became saturated at 0.25 ± 0.02% taurine, expressed on a wet weight basis. Muscle tissue became saturated at 0.34 ± 0.02% taurine. Results from this study should increase the performance of alternative, plant based feeds formulated for sablefish and enable regulatory agencies better estimate the potential human exposure to taurine from the consumption of sablefish receiving these feeds. [ABSTRACT FROM AUTHOR]