Variety Of Prey Items Research Articles

Prey selection by torrentfish,Cheimarrichthys fosteriHaast, in the Ashley River, North Canterbury, New Zealand

Abstract The diets of two size classes of torrentfish (Cheimarrichthys fosteri Haast), taken from the Ashley River, North Canterbury, over two days in February‐March 1984, were examined. Small fish (fork length 51–64 mm) fed mainly on larval Elmi‐dae (Hydora sp.) and Chironomidae, whereas the diets of larger (71–109 mm) fish were dominated by Elmidae and Ephemeroptera (Deleatidium sp.) larvae. Aquatic larvae dominated diets of all fish; only one item of terrestrial origin was recorded. Torrentfish consumed proportionally greater numbers of slow than fast moving prey. The size range of most prey species taken was narrower than the range present in the river. Increasing fish length did not result in an increased variety of prey items consumed by C. fosteri.