Status of sablefish, Anoplopoma fimbria, aquaculture

Abstract

AbstractSablefish, 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.