Effects of body size and food ration on over-winter survival and growth of age-0 Atlantic cod, Gadus morhua

This study examined the effects of body size and food ration on over-winter survival of age-0 Atlantic cod. Cod were divided into two groups based on standard length (large = 76.95 +/- 1.10 mm SL; small = 57.65 +/- 1.02 mm SL; mean +/- 1 SE) and wet weight (large = 4.02 +/- 0.21 g; small = 1.52 +/- 0.09 g). Replicate tanks (n = 2) of 10 large and 10 small cod were exposed to one of two food rations (0.25% and 1.0% body weight day(-1)) for the entire experiment (December to June). Tanks were examined daily for mortalities and feeding was adjusted accordingly. The experiment was run under ambient light and seawater conditions. All but large age-0 cod exposed to the low food ration grew over the course of the experiment. The specific growth rate (SGR) of small cod was significantly higher (0.2425% wet weight day(-1)) than that of the large fish (0.0443% wet weight day(-1)). Food ration had no significant influence on SGR or over-winter survival. Significantly more of the large age-0 cod survived the winter (58.5% of those originally introduced) compared to the smaller fish (14%). Our results are consistent with those from studies of several other fish species, and are discussed in relation to the ecology of age-0 cod, and their potential use in aquaculture in Newfoundland.