Optimal selection of temperature areas by juvenile cod (Gadus morhua L.) in the Barents Sea modelled by dynamic optimisation

trade-off between growth rate in areas with different temperatures and pred ation rates was modelled for juvenile cod living in the Barents Sea by a dy namic optimisation model. The choice of optimal temperature area of a juven ile (1-group) cod growing from a start weight (50 g, 15 cm) to a size refug e (640 g, 40 cm) was modelled for two scenarios with distributions of preda tors (4+ groups cod) similar to those observed in the Barents Sea in Februa ry 1990 and 1994, respectively, and without food limitations, The model pre dicted that when there was an overlap in distribution between large cod and younger cud (0-3 group), the younger year classes would move to areas with lower temperature and less predators. offering higher survival rates. Fish predators forced the prey to inhabit less optimal areas, and both growth a nd survival rates fell in comparison a with a scenario with fewer fish pred ators (cannibals) and less overlap. Increased fish predator density increas ed these effects. and the juveniles would stay in colder water for a longer period and their growth rate would be further reduced. Higher mortality, i ndependent of area and size, made it more profitable to stay in warmer wate r. leading to higher growth but increased mortality rates. (C) 2001 Interna tional Council for the Exploration of the Sea.