A comparison of the movements of two species of gadoid in the vicinity of an underwater reef

Two saithe (35 and 38 cm) and two pollack (43 and 44 cm) were tracked simultaneously for 170 h. During the day, saithe generally patrolled over the whole of an underwater reef as part of a school, making occasional excursions off the reef to another smaller reef 250m distant. At night, saithe movements were largely limited to the reef. Pollack covered less than 50% of the reef during the study period, moving only small distances off the reef. Pollack swam more slowly than saithe during the day, but at the same speed at night.