Examination into a Vessel Effect for a Multi-Vessel Industry-Based Sea Scallop Dredge Survey

ABSTRACT Generalized linear models (GLM) and generalized additive mixed models (GAMM) were developed to examine for differences in fishing power, also referred to as a vessel effect, for three commercial fishing vessels chartered by the Virginia Institute of Marine Science (VIMS). The vessels conducted a fishery-independent sea scallop dredge survey of the MidAtlantic sea scallop resource in 2015. Surveys have continued since 2015 using a multivessel approach, and understanding the implications of a potential vessel effect on scallop catch is important for management and assessment of the resource. Surveys are conducted yearly to support annual fishery specifications and contribute biological and catch data for stock assessments. Generalized linear models tested for an effect of vessel on the total number of scallops captured and indicated survey strata and rotational area were significant predictors. Generalized additive mixed models tested for a vessel effect on scallop catch-at-length with length, vessel, strata, rotational area, and an interaction of vessel and length as fixed effects and survey station as a random effect. Two preferred GAMM were identified for the catch-at-length analysis. One model indicated that strata and rotational area had significant effects on scallop catch-at-length, whereas the interaction term was not significant. The second model did not include the interaction term or vessel as a predictor. Results presented here are consistent with previous calibration studies conducted for scallop dredge surveys suggesting that scallop catch is robust to the effect of vessel and support the use of a suite of industry vessels in the VIMS sea scallop surveys.