Application of Genetic Tags for Mark-Recapture in Spawning Aggregations of Red Drum Sciaenops Ocellatus Along the Florida Gulf Coast

The red drum Sciaenops ocellatus supports one of the largest and most popular fisheries in the southeastern United States.  In the last federal assessment (yr 2000), the Gulf of Mexico stock was classified as “overfished”.  However, the assessment was limited, in large part, by the lack of data for the offshore adult population.  The data gap has remained a persistent problem and the prior assessment is considered ‘highly uncertain’.  Future assessments have been postponed indefinitely until sufficient data for the adult stock can be collected. Future red drum stock assessments are likely to adopt a modified version of the age-structured population model, which requires estimates of spawning stock abundance.  Gulf red drum exhibit isolation-by-distance stock structure; i.e., dispersal and reproductive exchange occur primarily but not exclusively between adjacent bays and estuaries.  Accordingly, a meta-population approach to the stock assessment has been recommended, necessitating region-specific data for model parameters.  Genetic tagging is a technique that utilizes genetic-profile data to uniquely identify individuals within a sampled population.  By temporally surveying genetic profiles for a suitable number of individuals, recapture histories can be developed for population size and vital rate estimation.  The genetic tag-recapture approach is advantageous over traditional tagging, due to the permanence of the tags and the applicability of the data to future studies.  To demonstrate the feasibility of a genetic tagging program for adult red drum, specimens from three spawning aggregations (1,800 total specimens) were collected during a single spawning season by purse-seining.  Biological measurements and fin-clips were obtained and specimens were then released.  All specimens are being genotyped using established methods to generate individual DNA profiles and to initiate recapture histories. In this presentation, we update our findings and comment on the efficacy of this approach.