Stock Assessment of Georges Bank Yellowtail Flounder for 2017

The combined Canada/US Yellowtail Flounder catch in 2016 was 44 mt, with neither country filling its portion of the quota. This is the lowest catch in the time series which began in 1935. Despite the low catch, all three bottom trawl surveys declined. The empirical approach recommended at the 2014 Diagnostic Benchmark was applied in this year’s assessment update. The three recent bottom trawl surveys were scaled to absolute biomass estimates, averaged, and an exploitation rate of 2% to 16% was applied to generate catch advice of 20 mt to 158 mt. An intersessional TRAC conference call examined results from twin-trawl and ground gear studies and concluded that survey catchability should be 0.31 instead of 0.37 and that wing spread instead of door spread should be used when calculating the area of a survey tow. These two changes caused the average survey biomass to increase approximately three fold for the entire time series. The TRAC will discuss the appropriate exploitation rate to apply to the new time series.