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Alaska Department of Fish and Game


Alaska Fisheries Sonar

Sheenjek River
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In addition to using sonar to detect and record fish passage, site technicians also collect a sample of 150 to 180 chum salmon each year. The sample is used to document length, gender and age information that can be used to track long-term trends in the chum returns. Technicians collect the salmon with a beach seine net, determine gender based on external characteristics, take measurements and from each fish take three vertebra - used to determine age.

Often scale samples are used to determine fish age, but when salmon are in close proximity to their spawning sites, as they are at the Sheenjek sonar site, their scales are in poor condition and difficult to use for aging.