Stock-specific changes in growth rates, food conversion efficiencies, and energy allocation in response to temperature change in juvenile Atlantic cod

Under common environments, populations of laboratory reared (Grand Banks, G B and Gulf of Maine, GOM) and wild caught (Fortune Bay, FB and Bonavista Ba y, BE; Newfoundland) juvenile cod Gadus morhua responded similarly to tempe rature change in specific growth rates, food conversion efficiencies, condi tion factors, liver water content, and muscle water content. However, GOM c od had higher condition factors, and showed differences from GB cod in phen otypic plasticity of hepatosomatic index to temperature. These differences were not present in a different population comparison between FB and BE cod . All populations had higher growth rates and food conversion efficiencies at warmer temperatures, and exhibited compensatory growth when temperature was increased. The results suggest relatively larger genetic differences be tween GB and GOM cod than between FB and BE cod, and indicate that the fast er growth of southern populations in the wild is not due to a higher geneti c capacity for growth rate. (C) 2001 The Fisheries Society of the British I sles.