Combining trawl and acoustic surveys to assess the status of the largest U.S. fishery

Many species of fish spend some of the time on the ocean bottom, and some of their time far off the bottom, which makes them hard to survey. Acoustic surveys (that bounce sound off fish schools), can estimate the midwater component of so-called “semipelagic” fish, while trawl surveys can measure the portion on the bottom. Now a new method has been developed that combines data from both types of surveys into a single estimate using information about the environment (bottom light, temperature, sand type, and fish size). The new method has been used to assess the status of walleye pollock, which sustains the largest fishery in the United States, and was developed by Stan Kotwicki, Patrick Ressler, and Jim Ianelli at the Alaska Fisheries Science Center, and SAFS Professors André Punt and John Horne, and appears in the journal Canadian Journal of Fisheries and Aquatic Sciences.

 

Surveying for walleye pollock involves both acoustic surveys (which have a blind spot near the ocean bottom) and trawl surveys (which don’t sample midwater fish).
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