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Groundfish Assessment - Survey Profile

Trawl Catch Processing and Sampling

A small catch of mixed fish and invertebrate species emptied on sorting table. Groundfish catches are hauled onboard, dumped into a sorting table, sorted by species, and weighed. Catches range in size from 1 kg to more than 5,000 kg. No two catches are exactly the same. Some catches consist mostly of a single species, while other catches can be a mix of both fish and invetebrate species. Small hauls may be sampled entirely (every fish accounted for), or subsampled if the catch quite large. Each sampled species of fish, depending on the partucular survey objectives, is further sorted by gender done by examining the gonads of each fish via a cut in the stomach), placing females into orange baskets and males into gray baskets.

A Polycorder: An electronic fish length recorder. After the catch is sorted, sampled fish are lengthed using a bar-coded length strip and an electronic polycorder with an infrared light pen (the picture at the left shows a length measurement of a shortspine thornyhead). Length data collected during groundfish surveys are analyzed to generate information about species-specific size composition.

A fish otolith Otoliths (fish ear bones) provide important information about the various ages of fish. Otoliths are extracted from priority fish species in each catch. Biologists from the Age and Growth Laboratory in the AFSC's Resource Ecology and Fisheries Management Division estimate the age of fish by counting rings in the annular pattern contained in the otoliths, similar to the process for estimating the ages of trees.


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