The Rivers Inlet Sockeye Salmon

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Abstract
The Rivers Inlet sockeye catch has averaged about 1 million fish per year, over 45 years. These are from smolts produced in a cold, deep lake, only 30 square miles in extent, and most of it heavily silted by glacial tributaries. The water has only a moderate lime content and its reaction is neutral or very slightly acid. The lake's plankton crops are small, though blooms of bluegreen algae occur in autumn in the clear uppermost basins, following on the death of large numbers of spawning sockeye. Smolts are unusually small in size, averaging about 2 grams when sampled in 1914–16 and again in 1954; almost all are age 1. The commercial gill-net fishery harvests most efficiently the salmon of intermediate sizes: the medium and large age 4 fish, and the medium and small age 5 fish. Hence escapement tends to consist of extremes of size, the larger age 5's, smaller age 4's, and almost all the age 3's. Sockeye spawning takes place in many inlet streams, along parts of the lake shore, and in the outlet river. The spawners in the various tributaries differ considerably in respect to the age structure of their runs, and to some extent in size at a given age, though the selective fishery may account for some part of these differences. Conditions for spawning and incubation in the region are still practically in their natural state.The most important management problem is to determine whether increasing the fry output into the lake would increase or decrease production of adult sockeye: the smolts are now so small that any larger numbers might possibly reduce their size below some critical level. Next in importance is to determine whether or not the present numbers of spawners are necessary to fertilize the lake for the growth of the young, and if so, whether a less valuable fertilizer might be substituted.

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