Evaluating fisheries-independent annual recruitment indices for Spotted Seatrout in two Florida estuaries

ABSTRACT Objective The Florida Fish and Wildlife Conservation Commission’s Fisheries-Independent Monitoring Program utilizes young-of-the-year indices of abundance (IOAs) for Spotted Seatrout Cynoscion nebulosus as an index of recruitment to inform stock assessment and management decisions. However, it is unclear how well IOAs represent recruitment to the fishery. The objective of this study was to assess the ability of fisheries-independent monitoring IOAs to represent strong and weak year-classes for Spotted Seatrout. Methods We compared residuals from recruitment IOAs to catch-curve residuals for Spotted Seatrout harvested by recreational anglers in two Florida estuaries, Cedar Key and Tampa Bay. The IOAs were standardized using a delta generalized linear model to control for effects of month and localized factors at each sampling site. Spotted Seatrout used in catch-curve regressions were sampled from each estuary as two independent case studies. Results We found a positive correlation—Pearson correlation coefficient of 0.798—between catch-curve residuals and IOA recruitment residuals for the Cedar Key population. The Tampa Bay population was not a good candidate for this analysis because catch-curve residual sum of squares was relatively low, indicating weak annual variation in recruitment during the sample period. Conclusions Our results indicated that Spotted Seatrout IOAs derived from the Fisheries-Independent Monitoring Program are an accurate method for indexing year-class strength if recruitment variability is relatively high, but less variable recruitment prevented assessment of year-class strength in Tampa Bay. These results suggested that the IOAs would be expected to track strong and weak year-classes into the adult population, which is important for setting short-term harvest and catch expectations. Additionally, this study demonstrated how to incorporate charter captains in fisheries research that can inform monitoring and management programs.