Comparing Relative Catch Efficiency of Survey and Commercial Trawl Gears in New England.

Hankowsky, Keith¹*, Steven X. Cadrin¹, Andrew Jones², Pingguo He¹, ¹SMAST, New Bedford, MA, ²NOAA Fisheries, Northeast Fisheries Science Center, Narragansett, RI

New England groundfish have been harvested commercially for more than 400 years. However, in the last thirty years, stocks of several important species have declined severely with a few at historically low levels. The Northeast Fisheries Science Center (NEFSC) bottom trawl survey is an essential component for stock assessment and fishery management in New England. However, many stock assessments rely on uncertain estimates of catchability. Commercial fishers’ on the water observations as well as recent studies suggest that the NEFSC bottom trawl survey is not 100% efficient for most of the species it surveys. Differences in catch efficiency and inaccurate estimates of survey catchability can result in added uncertainty for stock assessments, impacting the management process, catch limits, and the economic viability of commercial fisheries. Following other experiments in the region, this study aims to provide experimental estimates of survey efficiency for several species in the multi-species groundfish complex. In the absence of an experimental paired-gear study, an opportunistic approach was used to compare the relative efficiency of survey gears to commercial gears. High resolution fisheries dependent data from the NEFSC’s Study Fleet and Observer programs were leveraged to identify tows that occurred in the relative vicinity and timeframe of NEFSC survey tows. Catch ratios between commercial trawl gears and the NEFSC bottom trawl survey were compared and the relative efficiency for the NEFSC survey was estimated. Relative efficiency estimates can be used to help improve estimates of catchability in the stock assessment process.