DIEL PATTERNS OF BEHAVIOR IN JUVENILE WALLEYE POLLOCK, THERAGRA-CHALCOGRAMMA

In laboratory experiments, we contrasted the behavior of juvenile wall eye pollock under dark and light conditions, comparing group cohesion, activity levels, vertical distribution, and movement into cold water when the water column was thermally stratified. At night the fish disp layed a tendency for movement into the upper water column and were les s active, with groups more dispersed than during the day. Time spent i n cold water under stratified conditions did not differ between day an d night. These results are interpreted relative to the potential ecolo gical benefits and costs of particular behaviors, and their applicatio n in designing effective sampling surveys of juvenile abundances.