Recruitment and distribution of juvenile salmonids in Lake Coleridge, New Zealand

Abstract

Rainbow trout (Oncorhynchus mykiss Richardson) and chinook salmon (O. tshawytscha Walbaum) fry and 0+ fingerlings entered Lake Coleridge, a deep, oligotrophic lake in the Southern Alps of New Zealand, in spring and early summer and dispersed throughout the shallow littoral. In contrast, most juvenile brown trout (Salmo trutta Linnaeus) remained in the tributaries for 1–2 years before migrating down stream to the lake. Juvenile salmonids (<35Omm) were more abundant in the shallow littoral (<10 m), especially near tributaries, than in the deep littoral (10–40 m), or the surface layers (0–16 m) of the limnetic zone which were populated by yearling (>150 mm) and adult salmon and rainbow trout (>210 mm). The abundance of 0+ rainbow trout in the littoral zone declined rapidly from February to August and stocks were supplemented by a migration of yearling fish from the tributaries in spring. The shallow littoral zone and tributaries are both important for juvenile trout rearing in this lake.