Sammendrag
In Norway, during the establishment phase of the Atlantic cod (G. morhua) farming industry (2000-2008), several biological as well as financial bottlenecks affected its development, profitability and sustainability. The major pitfalls were Fish juveniles’ quality, strengthening of wild cod population with increased landings and resulting price falls, precocious sexual maturation and spawning in sea cages. The attempts of controlling sexual maturation using artificial light manipulation strategies did not prove fully effective, resulting in a large numbers of fish developing gonads and releasing fertilized eggs to the environment (genetic pollution). To overcome some of these challenges one strategy is to produce selected fish which do not mature before reaching commercial harvest size. A second strategy is to produce triploid fish which are expected to be at least gametically sterile. To date, little is still known concerning the performance of triploid sterile cod. This study was undertaken to compare the growth and gut morphology of diploid and triploid juvenile cod raised over a period of 6 months. Diploid (2n) and triploid (3n) cod were produced from 3rd generation selected stocks held at the National Cod Breeding Station (Tromsø, Norway) using established rearing and treatment (pressure shocks) protocols and transported to the research station at the University of Nordland (Bodø, Norway). The fish were communally reared up to a body size of approx. 40g, individually PIT-tagged and separated into three tanks
per ploidy group. The ploidy status was verified by flow cytometry at Nordland hospital (Bodø), using blood samples.
Fish growth was similar between ploidies during most of the experiment. However, the 2n group showed higher specific
growth rate (TGC) towards the end of the trial (week 62-66) attaining a final body weight approx. 20% higher than the 3n
group (FIG. 1) (P
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