Estimating Summer Flounder Mortality Rates Using Mark-Recapture Data from a Recreational Angler Tagging Program

Managed as a single stock along the U.S. Atlantic coast, summer flounder Paralichthys dentatus are currently under a rebuilding plan due to large declines in abundance observed in the early 1990s.  Successfully rebuilding the summer flounder population requires implementing effective management practices based on accurate stock assessments.  Currently, one major source of uncertainty in the summer flounder stock assessment is the estimate of the instantaneous natural mortality rate, which is calculated using life-history based models that have not been validated for this species.  In this paper we estimate an instantaneous natural mortality rate for summer flounder based on ten years of mark-recapture data collected by the Virginia Game Fish Tagging Program (VGFTP).  The VGFTP relies on trained recreational anglers to tag and release popular game fishes, including summer flounder, and recreational and commercial fishers subsequently report recaptures.  Over a period of 10 years (2000-2009), VGFTP participants tagged 60,647 summer flounder and 960 of these fish were recaptured.  Using these data, encounter and survival probabilities were estimated using a modified Barker tagging model.  Results from this study demonstrate how data from a recreational angler tagging program can be used to provide reliable estimates of mortality for stock assessments.