ABSTRACT

The management of Red Snapper, Lutjanus campechanus, in the northern Gulf of Mexico has caused disagreement between fishers, who expect fewer restrictions as stock improves, and managers, who need to keep restrictions in place for continued stock improvement. Therefore, accurate estimates of mortality rates are critical for proper management of the species. The present study estimated tagging mortality, natural mortality, and fisher nonreporting from acoustic telemetry of Red Snapper 76to calibrate a conventional mark-recapture study on the Alabama continental shelf in the northern Gulf of Mexico. Fishing mortality (F) estimates were higher based on acoustic telemetry in 2015 (F = 1.17), 2016 (F = 0.46), and 2017 (F = 0.37) compared with conventionally tagged fish in 2015 (F = 0.45), 2016 (F = 0.37), and 2017 (F = 0.30). Recreational fishers on private vessels captured the highest number of conventionally tagged fish. Recreational fishers on for-hire vessels and commercial fishers captured similar numbers of conventionally tagged fish. Tag return rates were significantly higher for fish released on large reefs (>25 m2) than for fish released on small reefs (<25 m2), and higher on reefs with published locations than on reefs with unpublished locations. Capture rates were also higher on reefs closer to shore (<33 km) than on reefs more distant from shore (33 to 65 km). The calibrated tag return rates for fish captured from large and small reefs were combined with a fishery-independent abundance estimate. This enabled an adjustment to F values according to reef type and an estimate of annual harvest off coastal Alabama in the northern Gulf of Mexico. Mean F for Red Snapper greater than 406 mm standard length was F = 0.22 in 2015 and 2016, with an estimated annual harvest of 212,237 fish per year. In conclusion, high-quality telemetry data allowed the calculation of calibration rates for a high-reward conventional-tagging study. Without these calibrations, the results of the conventional tagging study would have been inaccurate. Similarly, without the higher sample sizes provided by the conventional-tagging study, the results of the telemetry study alone might have been biased due to small sample sizes.