Spawning energetics of Arctic cod ( Boreogadus saida) in relation to seasonal development of the ovary and plasma sex steroid levels

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Hop, Haakon, Trudeau, Vance L., Graham, Mark
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1995
• Subjects: Arctic; Canada; Arctic cod; Boreogadus saida
• Online Access: http://dx.doi.org/10.1139/f95-055; http://www.nrcresearchpress.com/doi/pdf/10.1139/f95-055

Gonadal development in Arctic cod starts in August in high Arctic Canada. Male gonads develop at a faster rate than female gonads initially, and reach maximum size about two months prior to females. Under laboratory conditions (at 1.0 °C), female Arctic cod became ripe and started to spawn in mid-February, which concurred with field observations. Ripe gonad weight increased with body size; mean gonadosomatic index (GSI) of ripe females was 47.7%, and potential fecundity averaged 26 500 eggs. At the time when ripe females started to spawn, some females were still unripe (GSI = 20.2%). Their eggs were not hydrated, and these fish had significantly higher levels of sex steroids (estradiol, 11-ketotestosterone, and testosterone) in their blood than ripe fish. Arctic cod are repeat spawners, at least under laboratory conditions, in spite of the large amount of energy allocated to reproduction (306 kJ lost from liver and muscle during gonadal development and 125 kJ as eggs during spawning). A high energy investment into reproduction, for a fish that matures at an early age, may be balanced against high predation rates on this species during the open-water season in the Canadian high Arctic.