Preliminary Estimates of Daytime Capture Efficiency of a Survey Bottom Trawl for Longfin Inshore Squid, Doryteuthis (Amerigo) Pealeii
NOAA’s Northeast Fisheries Science Center (NEFSC) conducts surveys twice-yearly from the Gulf of Maine to Cape Hatteras in waters deeper than 18.3m on the federal research vessel FSV Bigelow. The Northeast Area Monitoring and Assessment Program (NEAMAP) surveys strata shallower than 18.3m between Cape Cod and Cape Hatteras onboard a chartered commercial fishing vessel. Scientific trawl gear, sampling protocols, and survey timing used by both surveys are similar.
Assessment biomass estimates are adjusted for daytime bottom trawl catchability. However empirical data for computing daytime trawl capture efficiency are lacking. Following the Spring 2012 NEAMAP cruise NEAMAP and NEFSC personnel conducted a squid capture efficiency study. The study focused on quantifying escapement over the headrope because of documented rising behavior of Doryteuthis in bottom trawls. A ‘top net’ was attached directly to the standard survey net’s headrope to capture specimens which otherwise would have escaped. Gear mounted video cameras documented squid behavior near the headrope and wings. These experiments will be repeated and refined during future research cruises.