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TRIPLOID FISH welfare and production considerations Ian Mayer Norwegian University of Life Sciences Oslo, NORWAY Triploid fish Production of triploid fish Triploids are organisms with three sets of homologous chromosomes (3n). While triploids can be found spontaneously in the wild and can be easily induced in many commercially relevant species of fish and shellfish. Triploid fish Production of triploid Atlantic salmon Pressure shock: 8,500 – 10,000 psi for 5‐6 minutes Triploid fish Triploidy Diploid (¨normal¨ fish): 2 chromosome sets (2n) Triploid: 3 chromosome sets (3n) larger cells diploid triploid Triploid fish Applications The major consequence of triploidy is sterility Triploid fish are functionally sterile Triploid fish AQUACULTURE BENEFITS OF TRIPLOIDS Sterility mitigates the problems associated with: ① Early sexual maturation ② Genetic interactions with wild fish Triploid fish ① Early sexual maturation Early sexual maturation is a major production problem for many commercially important aquaculture species, including salmonids, sea bass, Atlantic cod. Early sexual maturation results in: Reduced growth: energy is diverted from somatic to gonadal growth Reduction in flesh quality Reduced immunocompetence Op mal harvest weight Growth (body weight) Precocious matura on Age Spawning season Production of triploid fish Triploid fish ② Mitigates the problems associated with escaped fish Farmed fish escape at every level of the production cycle Impact of farmed fish on wild fish: is a major environmental concern Genetic introgression results in reduced fitness of wild fish and potentially can accelerate extinction of local populations Triploid fish Genetic introgression Levels of genetic introgression in 20 Norwegian salmon rivers (Glover et al. 2013) Triploid fish ② Mitigates the problems associated with escaped fish Farmed fish escape at every level of the production cycle Impact of farmed fish on wild fish: is a major environmental concern Genetic introgression results in reduced fitness of wild fish and potentially can accelerate extinction of local populations Sterility would not solve all the problems associated with escapees but would mitigate the more serious environmental concerns (genetic introgression) Fishery Management (stock enhancement) Triploid fish AQUACULTURE CURRENT LIMITATIONS OF TRIPLOID FISH Compared to diploids, triploid fish are characterised by: ① Lower body weight at harvest size Triploid fish ① Lower body weight at harvest size Fraser et al. 2013 6000 5129 Weight (gm) 5000 4537 4482 4000 3988 3000 2000 Smolt SW transfer 1000 0 Jan 11 Apr 11 Oct 11 May 12 2n Vaccinated 3n Vaccinated Triploid fish Possible reasons for reduced triploid growth ① Ploidy differences in gut morphology In Atlantic cod, triploids had a shorter intestine and fewer pyloric caeca compared to diploid siblings. ② Ploidy differences in gut microbial community Triploid Atlantic salmon were found to have significantly higher levels of total gut microbiota compared to diploids (Cantas et al. 2011) ③ Impaired feeding behaviour Ploidy differences in brain morphology (triploids have smaller olfactory bulbs) ‐ possibly indicating that triploids have less effective feeding behaviour (Fraser et al. 2012) Triploid fish AQUACULTURE CURRENT LIMITATIONS OF TRIPLOID FISH Compared to diploids, triploid fish are characterised by: ① Lower body weight at harvest size ② Increased incidence of skeletal deformities Triploid fish Radiographic examples of vertebral deformities in adult farmed Atlantic salmon. Fjelldal et al. 2012 Triploid fish Triploid fish Increased prevalence of skeletal deformities in triploid cod Opstad et al. 2013 Triploid fish AQUACULTURE CURRENT LIMITATIONS OF TRIPLOID FISH Compared to diploids, triploid fish are characterised by: ① Lower body weight at harvest size ② Increased incidence of skeletal deformities ③ Increased heart deformities (cardiovascular performance) Triploid fish Aplasia of the septum transversum Fraser et al. 2013 Septum transversum Liver Aplasia of septum transversum (%) 40 30 20 Diploid Triploid 10 0 6 8 10 Incubation temperature (°C) Triploids have: • More cases of aplasia of the Normal Aplasia septum transversum • Aplasia occurs at lower incubation temperatures Thomas Fraser - PhD disputas - Dec 2013 Triploid fish Is triploidy the future for fisheries management and aquaculture? CONCLUSIONS ① AQUACULTURE There is growing interest in the use of triploids in aquaculture The use of triploids would mitigate the production problem associated with early sexual maturation, and additionally would minimize environmental concerns of escaped farmed fish (genetic introgression) However, there is currently a reluctance to use triploids as compared to diploids they display inferior growth rates and a higher incidence of skeletal and heart deformities (FISH WELFARE). Thank you