Effects of continuous light and triploidy on growth and sexual maturation in Atlantic cod, Gadus morhua

Trippel E.A., Benfey T.J., Neil S.R.E., Cross N., Blanchard M.J., Powell F.

Published date: July 2008
Volume: 32
Number: 2 suppl.
Pagination: 136-138
Publisher: Société Française d'Ichtyologie
doi: https://doi.org/10.26028/cybium/2008-322SP-057

Early maturation is considered one of the greatest problems in mariculture of Atlantic cod. We examined two approaches to impede early puberty: (i) exposure to continuous light and (ii) induction of sterility by triploidy. Use of continuous light initiated in July delayed onset of sexual maturity, in this case by ~2-3 months though cod returned to their normal spawning period when continuous light was administered for a second year. In the first year, 24 h light compared to natural photoperiod resulted in a lower percentage of mature females (73 vs 90%) compared to males (90 vs 100%). In the second year, > 88% of any gender were mature in both treatments. Using hydrostatic pressure, triploid cod were generated with a 100% success rate at a treatment of 5 min at 58,600 kPa (8500 psi) applied beginning at 30 min post-fertilization for eggs held at 6°C. No sexually mature female triploids were observed, yet 12.5% of triploid males were mature. Female triploids grew at a slower rate than diploids, and for males triploids and diploids were not significantly different in growth (body weight at age 26 mos.). A family by ploidy interaction for growth was nearly significant (p = 0.052) which underlines the importance of conducting extensive testing of the effects of triploidy among a large number of families, perhaps coincident with a selective breeding program, if one is to thoroughly evaluate the scope of this technique in assisting the cod aquaculture industry.

Keywords: Cod - Growth - Maturity - Photoperiod - Sterility - Triploidy
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