Effects of body size and food ration on over-winter survival and growth ofage-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 ent ire experiment (December to June). Tanks were examined daily for mortalitie s and feeding was adjusted accordingly. The experiment was run under ambien t 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 ra te (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 intr oduced) compared to the smaller fish (14%). Our results are consistent with those from studies of several other fish species, and are discussed in rel ation to the ecology of age-0 cod, and their potential use in aquaculture i n Newfoundland.