Salmon escapement estimates into Togiak River using sonar, Togiak National Wildlife Refuge, Alaska, 1987, 1988, and 1990
Irving DB, Finn JE, Larson JP. 1995. Salmon escapement estimates into Togiak River using sonar, Togiak National Wildlife Refuge, Alaska, 1987, 1988, and 1990. Alaska Fisheries Technical Report Number 31. US Fish and Wildlife Service. Knig Salmon, Alaska
We began a three year study in 1987 to test the feasibility of using sonar in the Togiak River to estimate salmon escapements. Current methods rely on periodic aerial surveys and a counting tower at river kilometer 97. Escapement estimates are not available until 10 to 14 days after the salmon enter the river. Water depth and turbidity preclude relocating the tower to the lower river and affect the reliability of aerial surveys. To determine whether an alternative method could be developed to improve the timeliness and accuracy of current escapement monitoring, Bendix sonar units were operated during 1987, 1988, and 1990. Two sonar stations were set up opposite eachother at river kilometer 30 and were operated 24 hours per day, seven days per week. Catches from gill nets with 12, 14, and 20 cm stretch mesh, a beach seine, and visual observations were used to estimate species composition. Length and sex data were collected from salmon caught in the nets to assess sampling bias.
- Type
- Published Report
- Authors
- Irving, David; Finn, James; Larson, James
- Date of Issue
- 1995-02
- Publisher
- US Fish and Wildlife Service
- Units
- SWAN
- Keywords
- Alaska, Anadromous, Escapement estimates, Fish, Riverine, Salmon, Sonar, Togiak National Wildlife Refuge, Togiak NWR, Togiak River