The food of rainbow and brown trout in the Mohaka and other rivers of Hawke's Bay, New Zealand

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Abstract
Mature rainbow and brown trout fed mainly on drifting invertebrates.sbd.caddis larvae and terrestrial insects in summer, and mayflies and stoneflies in winter. Rainbow trout in the Tutaekuri system ate more caddis larvae and fewer mayfly and stonefly nymphs than those in the faster-flowing and more turbulent Mohaka River. The diets of the 2 spp. in the Mohaka were very similar, although brown trout ate more Nematomorpha and caddis larvae of the species Olinga feredayi and fewer of the small-cased caddis Beraeoptera roria than did rainbow trout. The overlap in their diets was considerable in both summer and winter. Rainbow trout ate more small (<EQ 6 mm) prey than did brown trout, but the modal size of the main foods of both species was virtually identical. The 2 spp. overlapped in their feedig areas and contested positions. Rainbow trout fed mainly in the head and middle parts of pools at a depth of more than 1 m. Brown trout used rapids and backwaters as well as pools, and fed mainly at a depth of less than 1 m. There was some evidence that brown trout, the larger species in the Mohaka, partially excluded rainbow trout from feeding positions in rapids and tails of pools.