Windowpane Seasonal Distribution and Survey Availability on the Southern Portion of Georges Bank, USA

Abstract

The Windowpane Scophthalmus aquosus stock in Georges Bank and the Gulf of Maine is considered overfished despite the lack of a directed fishery. Windowpane stocks are assessed using an index‐based method relying on the Northeast Fisheries Science Center's (NEFSC; National Oceanic and Atmospheric Administration) fall trawl survey. From 2013 to 2016, the School for Marine Science and Technology (SMAST; University of Massachusetts Dartmouth) conducted a fisheries‐independent trawl survey on the southern portion of Georges Bank, including part of Closed Area II. Using both the NEFSC and SMAST survey catches, we examined seasonal variations in CPUE of Windowpanes as well as their relationship with depth and temperature. Windowpane CPUE was significantly higher in the spring than in the fall and was linked with temperature changes. On the southern portion of Georges Bank, the NEFSC and SMAST surveys had similar relationships between Windowpane catch and temperature. In the spring, Windowpanes were abundant at water temperatures less than 7°C, and they moved out of the area as the temperature increased. In the fall, Windowpane CPUE was higher in warmer water temperatures and decreased as the temperature decreased. As Windowpanes moved out of the area, Fourspot Flounder Paralichthys oblongus replaced them in the habitat. This distribution pattern seems to occur across the whole stock. Our findings suggest that environmental factors can affect the CPUE indices from surveys that are assumed to be consistent, and this should be considered in future assessments.