Bering Sea pollock assessment moves to near-infrared aging, with microscopes as a check

The eastern Bering Sea pollock stock assessment is shifting its survey and fishery ages to near-infrared scanning, according to slides presented this week to the North Pacific Fishery Management Council's science committee. Microscope ages will stay on as a "tester" to check the new method's results.

Council plan teams also reported losing about 40% of their aging staff capacity, meaning fewer fish will be aged for the 2026 assessments.

Scientists determine a fish's age by counting the annual growth rings on its otoliths, or ear bones, much like tree rings. Observers and surveys collect about 45,000 otoliths a year, and researchers in Seattle read more than 30,000 of them under microscopes, according to a Sept. 28 feature from NOAA's Alaska Fisheries Science Center. "The more fish we age, the more accurate the data used in stock assessments," said Jamal Moss, the center's acting director.

With near-infrared scanning, light is focused on the otolith, and machine-learning models match the light it absorbs to the fish's age. That takes 30 to 50 seconds per otolith, according to NOAA, compared with 3 to 5 minutes to age a pollock otolith under a microscope.

The center's feature says the method increases efficiency 600% to 800%, and that conventional aging is still part of the process. NOAA has cited that same range since 2018, when it described it as a preliminary estimate for Bering Sea pollock.