ABSTRACT
250Red Snapper, Lutjanus campechanus, have been under management since the early 1990s. At present, there are few data gathered from fishery-independent surveys that allow a comparison of stock status before and after management actions to evaluate the long-term effects of fishery management actions. The present study allowed such comparisons based on data from two fishery-independent surveys of Red Snapper over a large area of the continental shelf off coastal Alabama (United States) in the northern Gulf of Mexico. The first survey was from 1999 to 2004, and the second survey was from 2011 to 2015. In addition, potential effects of the 2010 Deepwater Horizon (DWH) oil spill on Red Snapper stocks were evaluated. The DWH oil spill occurred immediately south (~100 km) of the present study area, and the two surveys provided extensive data before and after the oil spill. In both surveys, timed hook-and-line and fish-trap sampling methods were employed. The Red Snapper stock displayed a substantial shift to higher percentage of older age fish in age frequency distribution and an increase in mean age but similar catch per unit effort (CPUE = catch/30min) between the two surveys. Also, there were differences in mean age for Red Snapper in association with reef types (i.e., small reef, concrete pyramid, U.S. army tank, and large reef) between the two surveys. The comparison of Red Snapper stocks relative to the two fishery-independent surveys confirmed that management actions had the intended effect of increasing the mean age of the Red Snapper stock in the northern Gulf of Mexico. Similarly, because of the substantial shift in the age structure accompanied by little change in CPUE relative to the DWH oil spill, there was little evidence of an oil spill effect on these species. Also, in the second survey, side-scan sonar and hydroacoustic methods were employed, which allowed absolute density estimates (rather than relative estimates) of Red Snapper over a large area on the continental shelf that had extensive artificial reefs. There were 10,885 reefs (>3 m2) in the 5973 km2 study area, which provided an absolute density estimate of 2,660,198 Red Snapper with a 3,724,277 kg total weight. These absolute density estimates allow accurate determinations of important fishery catch statistics. However, the present sonar and hydroacoustic surveys were only conducted off coastal Alabama, and additional surveys are needed to determine the absolute population size off the entire northern Gulf of Mexico.
