Ben Boettger/Peninsula Clarion
Cathy Cline, a project technician with the Cook Inlet Aquaculture Association, displays an otolith she extracted from a hatchery-raised king salmon to children dissecting fish at the Kenai National Wildlife Refuge’s “Get Out and Get Dirty” daycamp on Thursday, July 28, 2016 at the Kenai National Wildlife Refuge headquarters in Soldotna, Alaska. An otolith is a fish’s ear bone, which grows in layers of varying thickness dependent on the fish’s water temperature. Hatcheries vary water temperature to produce an otolithic “signature” identifying the fish’s origin. Cline, who describes herself as CIAA’s “otolith reader” said she microscopically examines around 10,000 otoliths per year — sampled from fish delivered to processors — to learn about the fish’s environment and the sucesses of various hatcheries.