Journal Article

Continuous light delays sexual maturation and increases growth of Atlantic cod (<i>Gadus morhua</i> L.) in sea cages

G.L. Taranger, L. Aardal, T. Hansen and O.S. Kjesbu

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 2, pages 365-375
Published in print January 2006 | ISSN: 1054-3139
Published online January 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2005.10.014
Continuous light delays sexual maturation and increases growth of Atlantic cod (Gadus morhua L.) in sea cages

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Prevention of early sexual maturation is essential in Atlantic cod (Gadus morhua) farming because maturity results in reduced growth, affects flesh quality, and may lead to increased mortality. In farmed cod, almost 100% of the fish mature at two years of age and often at a size of 1.5–2 kg. Two pilot experiments were conducted with cod in sea cages at a commercial fish farm in western Norway (60°N) to test the effect of additional continuous light (LL) on the timing of sexual maturation and somatic growth compared with controls under natural light (NL). In the NL groups, 100% maturation was indicated during the natural spawning period from February to April at the age of two years. By contrast, LL treatment from 27 June (15-month-old cod) or 2 September (18-month-old cod) onwards delayed gonad development by three to five months, reduced reproductive investment, and enhanced winter growth compared with the controls. Fish held at NL decreased in body weight during the spawning season (February–April), whereas LL-exposed fish appeared to continue to grow during their spawning season (May–August). LL-treated cod reached mean body weights of 2.90–3.13 kg within 28 months of hatching, whereas the controls reached 2.20–2.42 kg during the same period.

Keywords: Atlantic cod; farming; gonad development; growth; photoperiod; sexual maturation

Journal Article.  5563 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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