Homing of Rainbow Trout to Inlet and Outlet Spawning Streams at Loon Lake, British Columbia

Abstract

A four year field study was conducted on rainbow trout (Salmo gairdneri) spawning in the inlet and outlet of Loon Lake. Young and adult trout were trapped and marked in both streams. About 5000 fish spawn in the outlet between mid-March and June; about 22,000 spawn in the inlet between late April and July. Outlet young either enter the lake by late summer or overwinter in the stream and enter the lake next spring or summer. Most inlet young enter the lake in their first year. Return as adults, of fish which had been clipped while entering the lake as young, indicated that about 94% of fish originating from each end homed to their parent stream. Because of the large number of inlet spawners, about a quarter of the outlet spawners are strays which had hatched in the inlet. Recovery of marked fish, movement of adults within the lake, and experimental transfer of adults and young between streams, all indicate that inlet and outlet spawners do not differ genetically in their responses to current. The biological and applied significance of homing, and its possible mechanisms, are discussed.