Surfacing activity and food utilisation in the obligatory air-breathing fish Ophiocephalus striatus as a function of body weight

Abstract

Reared in cylindrical aquaria containing different depths of water (2•5 to 70 cm) the obligatory air-breathing fish Ophiocephalus striatus, belonging to different weight classes (0. 1, 0.75, 10, 20and 41 g), was forced to swim vertically a longer or shorter distance per surfacing. Surfacing frequency was a depth-dependent.activity in individuals weighing less than 20 g in all weight classes, the frequency was nearly 2 times more in the series fed ad libitum on fish muscle, than in the one where the fish were starved.