Downstream migrations of juvenile Pacific salmon (Oncorhynchus spp.) in a glacial transboundary river

• Published in: Canadian journal of fisheries and aquatic sciences 1997-12, Vol.54 (12), p.2837-2846
• Main Authors: Murphy, Michael L, Koski, K V, Lorenz, J Mitchel, Thedinga, John F
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Breeding; Fish; Fish migration; Freshwater; Fundamental and applied biological sciences. Psychology; Oncorhynchus; Oncorhynchus kisutch; Oncorhynchus nerka; Oncorhynchus tshawytscha; R&D; Research & development; Rivers; Salmon; Transboundary waters; Vertebrata
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f97-178

Migrations of juvenile Pacific salmon (Oncorhynchus spp.) in the glacial Taku River (seventh order) were studied to assess movement from upriver spawning areas (in British Columbia) into lower-river rearing areas (in Alaska). Differences between fyke-net catches in the river and seine catches in the river's estuary indicated that many downstream migrants remained in the lower river instead of migrating to sea. In particular, age-0 coho salmon (O. kisutch) and chinook salmon (O. tshawytscha) moved downriver from May to November but were not caught in the estuary. Age-0 sockeye salmon (O. nerka), coho presmolts, and other groups delayed entry into the estuary after moving downriver. We tagged groups of juvenile coho (ages 0-2) from the fyke net with coded-wire to determine when they left the river. One-third of all tags recovered from sport and commercial fisheries occurred 2-3 years later, showing that many coho remained in fresh water for 1-2 years after moving to the lower river. Lower-river areas of large glacial rivers like the Taku River can provide essential rearing habitat for juvenile salmon spawned upriver and are important to consider in integrated whole-river management of transboundary rivers.