Evaluating Performance of a Survey Index for Stock Assessment

Selection of survey indices for stock assessment is a critical analytical decision that benefits from performance criterion. As an example of methods that can be used to evaluate survey performance, abundance indices from a fixed-station ventless trap survey off Rhode Island and Massachusetts were considered for inclusion in the scup stock assessment. We developed systematic methods to evaluate the efficacy of the survey data serving as a stock abundance index for the Northeast US scup stock. The results indicated that strong linear relationship existed between the survey index within year classes among adjacent years for ages one to four. The trap survey also had high correlation coefficients within age and year with the estimated stock abundance as well as geographically adjacent surveys. Therefore, the ventless trap survey is expected to be an informative index of abundance for the scup stock assessment. These analyses demonstrate that performance evaluation of survey indices should be a routine task for regular stock assessments.