Design and Implementation of a Cooperative Research Bottom Longline Survey in the Gulf of Maine

The catchability of fish that primarily inhabit complex rocky habitat is purportedly reduced in the Northeast Fisheries Science Center (NEFSC) multispecies bottom trawl survey (BTS). Industry constituents have expressed concern that the lack of hard, ‘rough’ bottom sampling could undermine assessments of several economically important Gulf of Maine (GM) stocks sampled by BTS, including Atlantic Cod Gadus morhua, Haddock Melanogrammus aeglefinus, and White Hake Urophycis tenuis. Through the National Cooperative Research Program the NEFSC was awarded funds to conduct a pilot bottom longline survey (LLS) in the GM during 2014-2015 to address these concerns.  The LLS design was based on the BTS stratification of depth and area and further stratified by ‘rough’ and ‘smooth’ bottom type using a rugosity index. Stations were allocated based on area and bottom type. Two industry longline vessels conducted the survey, deploying a line of 1000 hooks at each of 45 stations for two hours across slack tide.  A current meter measuring speed and velocity was attached to the longline, and a video camera was deployed to verify the bottom type.  Four surveys were successfully completed, indicating increased catchability for some data-poor species, and providing additional data for assessments of several key groundfish stocks.