Pilot evaluation of summer flounder stock enhancement potential using experimental ecology

Abstract

Stock enhancement is receiving increasing attention as a management tool to rebuild depleted fisheries. Unfortunately, proactive studies addressing the potential of stock enhancement to accomplish management goals prior to the implementation of enhancement efforts are uncommon. We outline an ecologically based, pilot protocol with which to address the potential of fisheries stock enhancement using hatchery-reared (HR) organisms, through trial releases coupled with laboratory and field experiments with juvenile summer flounder Paralichthys dentatus. Released HR fish did not persist in nursery habitats in which wild fish enjoyed relatively long residence times and high sur- vival. Multiple lines of observations and evidence suggest that the relatively rapid disappearance of released HR fish was not a result of emigration. Caging and tethering trials, coupled with previously obtained behavioral data, suggest that the poor performance of HR fish in this study was a result of increased susceptibility to predation-induced mortality, as compared with wild fish. These results suggest that post-release survival of HR summer flounder might be increased by (1) improving meth- ods of predator-conditioning, (2) releasing HR fish in sites that serve as natural refuges from preda- tors, or (3) releasing fish at larger sizes. While poor post-release survival of HR summer flounder may limit the success of stock enhancement efforts with this species, we suggest that conclusions regard- ing the potential of stock enhancement as a management tool can only be made if biological in- formation is coupled with economic information to predict economic costs associated with stock enhancement relative to costs associated with alternative management approaches.