Dynamic In-Lake Spawning Migrations by Female Sockeye Salmon

摘要

Movement studies focused on the final in-lake migration phase of sockeye salmon are generally lacking although such information is useful to resource managers and those studying evolution and ecology. We radio tagged 157 female sockeye salmon Oncorhynchus nerka as they entered Lake Clark, Alaska, and tracked them every 1-10 d to their spawning locations. Radio tagged salmon migrated along the shoreline, although some fish were detected crossing through the middle of the lake. At the Lake North and Lake South telemetry receivers, 83% of radio tagged fish were detected traveling near shore. Of these, 75% were detected along the south shore, 10% were detected along the north shore, and 15% were detected by both receivers indicating that salmon moved through the middle of the lake. Tracking data also indicate that radio tagged fish made frequent trips through the middle of the lake while migrating to spawning locations. Contrary to past research, no specific shoreline migration pattern was observed (e.g., clockwise) nor did fish enter a tributary unless they spawned in that tributary. Tributary spawning fish migrated faster (mean = 4.7 km/d, SD = 2.7, versus 1.6 km/d, SD = 2.1) and more directly (mean linearity = 0.8, SD = 0.2, versus 0.4, SD = 0.2) than Lake Clark beach spawning fish. Although radio tagged salmon migrated to within 5 km of their final spawning location in an average of 21.2 d (SD = 13.2), some fish migrated five times the distance necessary and over 50 d to reach their spawning destination. These results demonstrate the dynamic nature of this final phase of migration and support studies indicating a higher degree of homing precision by tributary spawning fish.