4.3.12 (HL)—Fish stock assessment

Stock surveys estimate what exists; landing records, observers and sensors estimate what is removed. Both are needed to judge a fishery.

Acoustic surveys, standardized trawls, tagging and models estimate abundance, age and movement. Port sampling, cameras and vessel monitoring measure catch and compliance. Each method has bias and uncertainty.

A stable landing record may hide a falling stock if effort rises; compare catch with independent abundance and effort data.

Stock size, recruitment, effort and unreported removals; catch is output, not population state.

One survey method is not a complete estimate; triangulate measurements and state limitations.