Use of concurrent trawls to validate acoustic surveys for Pacific herring

PROJECT

Use of Concurrent Trawls to Validate Acoustic Surveys

Background

Hydroacoustic surveys are a common tool for measuring the biomass of fish in an area.  The sensors used cannot tell what type of fish that are being detected and the acoustic return depends on the fish size, therefore it is important to include a sampling effort that can provide the types of fish present and their size distribution.  This project also supplies the fish samples needed by the disease, energetics, and genetics projects.

Methods

Within each bay that is surveyed a mid-water trawl is deployed at location determined during the hydroacoustic survey to collect fish.  The catch is sorted by species, the total of each species is weighed, and then up to 200 fish of each species are individually weighed and measured.  Fish are also captured using gillnets and cast nets for various projects.

What we will learn

The focus of this project is to support other projects by collecting the fish needed for analysis.  The fish capture data also provides information about changes in population composition between locations.