Effects of a Gear Change on a Standardized Bottom Trawl Survey Time Series

A gear evaluation experiment was conducted by the Northeast Fisheries Center in 1984 to determine the effect of a trawl door change on catch rates of gear used during the NEFC bottom trawl survey. Significant door effects were found for Atlantic cod, haddock and a combined species group containing two demersal species. The conversion coefficients developed for these cases indicate that catch rates may need to be adjusted to compensate for the door change. These results are preliminary, since the data upon which the coefficients are based are limited in scope and applicability. More research is needed to accurately assess the impact of the door change on the NEFC bottom trawl survey data base.