Food partitioning by small fish in a coastal New Zealand stream

Abstract

The diets and feeding periodicities of six small fish species were investigated in a New Zealand coastal stream over the diel period of 4 to 5 March 1993. Aquatic insect larvae dominated the diets of all fish except common bully, Gobiomorphus cotidianus, and longfinned eel, Anguilla diejfenbachii, which had a large proportion of ostracods in their diets. Dietary overlap was greatest between species pairs which were associated in the same microhabitats: A. dieffenbachii and bluegilled bully, G. hubbsi; torrentfish, Cheimarrichthys fosteri, and G. hubbsi; and G. cotidianus and upland bully, G. breviceps. Similar patterns in feeding periodicities existed for some of the species with associated diets; A. diejfenbachii and C. fosteri were nocturnal feeders, whereas G. hubbsi fed during daylight. Both G. cotidianus and G. breviceps were also diurnal feeders. In part, the results supported the hypothesis that species with temporal segregation of feeding are likely to have more similar dietary compositions, whereas those feeding at the same time are likely to show a greater degree of prey selectivity. © The Royal Society of New Zealand 1994.