Reproduction, growth and mortality of the common bully, <i>Gobiomorphus cotidianus</i> McDowall, in a eutrophic New Zealand lake

Abstract

Gobiomorphus cotidianus in Lake Waahi, North Island, New Zealand, (37° 34'S; 175° 08'E) spawned continuously between July 1976 and March 1977. Length frequency data indicated that two, and briefly, three year classes, were present, each made up of three groups which were the progeny from successive peaks in spawning activity. Scale examination revealed checks to growth associated with spawning and stressful midsummer conditions. These and length frequency data were used in growth estimates which indicated that bullies reached 3·5‐4·0 cm after their first year, 5‐6 cm after their second but did not survive a third year. Mortality was associated with spawning and midsummer stress.