Interaction between temperature and photoperiod on growth and feeding of Atlantic cod ( Gadus morhua ): possible secondary effects

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Imsland, Albert Kjartansson, Foss, Atle, Alvseike, Thomas, Folkvord, Arild, Stefansson, Sigurd Olav, Jonassen, Thor Magne
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2007
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; atlantic cod; Gadus morhua
• Online Access: http://dx.doi.org/10.1139/f07-006; http://www.nrcresearchpress.com/doi/pdf/10.1139/f07-006

Interactions between temperature and photoperiod on growth of Atlantic cod (Gadus morhua) juveniles (initial weight 9.1 g) were studied by rearing juvenile cod 3 months under simulated natural photoperiod (LDN) and continuous light (LD24:0) at 7, 10, and 13 °C. Juvenile Atlantic cod exposed to LD24:0 had higher growth rate and better feed conversion efficiency compared with cod reared under LDN. Optimal temperature for growth of juvenile Atlantic cod in the size range 5–50 g was influenced by photoperiod and was estimated to be 12.3 °C under LD24:0 and 15.7 °C under LDN. After termination of the laboratory study, the fish were reared in sea pens at ambient conditions for 17 months. The growth-enhancing effect of LD24:0 could be traced far beyond the duration of the laboratory trial, as the final mean weights in June 2005 of the fish reared at LD24:0 and 13 and 10 °C in the laboratory trial were 8% and 13% higher than those of the respective LDN groups. Our study indicates a physiological mechanism that might be linked to cod migrations, as maximal growth and feeding efficiency will be attained in areas during a season with extended day length or continuous light.