HOMING AND SPAWNING SITE SELECTION BY SOCKEYE-SALMON (ONCORHYNCHUS-NERKA) IN ILIAMNA LAKE, ALASKA

Sockeye salmon (Oncorhynchus nerka) spawn along several island beaches and nearby streams in the eastern portion of Iliamna Lake, Alaska. We investigated the importance of homing, attraction to spawning site characteristics, and attraction to conspecifics in similar reproductive condition as factors influencing spawning site selection. Sockeye were displaced reciprocally between two similar island beaches and a dissimilar nearby stream. Few sockeye successfully homed from one beach to another (11%); those displaced to the stream from a beach displayed intermediate homing (24%) and the best homing was back to the stream (65%). More fish remained at the release site when it was similar to the capture site (25%) than when it was dissimilar (4%). Sockeye that left the release site for a beach were more often missing (68%) than those departing for the creek (30%). The use of ultrasonic transmitters revealed that four of six sockeye that departed for a beach were relocated at a spawning beach other than the capture site. Spawning site characteristics apparently play a role in spawning site selection, but the need to spawn at the capture site was more important. Homing was better to the creek, presumably because it had a unique odor and its flow made it easier to locate than the beaches.