ABSTRACT
Densities of age-0 and age-1 Red Snapper, Lutjanus campechanus, were compared over a nine-year period (2007 to 2015), based on SCUBA visual estimates on small (1.42 m3) artificial patch reefs (patch-reefs) in the northern Gulf of Mexico. This time period included years both before and after the Deepwater Horizon oil spill 28in 2010, and provided a robust evaluation of the effect of the oil spill on this species’ initial density on patch-reefs. Densities of juvenile Red Snapper on patch-reefs were also compared with catch (number caught/H) of juvenile Red Snapper from trawl surveys by the Southeast Area Monitoring and Assessment Program (SEAMAP) that has been used as an index of juvenile density in the Gulf of Mexico. High densities of age-0 Red Snapper in 2009, 2011, and 2013 on patch-reefs indicated years of higher potential year classes of Red Snapper. The density of age-0 Red Snapper in 2010 was low at an offshore location, but similarly low densities were also observed in 2014 and 2015. The density of age-0 Red Snapper in 2010 at an inshore location was higher than the offshore location and similar to densities in other years. Also, the density of age-1 Red Snapper in June 2011 was similar to that in other years. Thus, the present study detected little effect of the 2010 Deepwater Horizon oil spill on the density of age-0 Red Snapper on patch-reefs. There was an inverse relation between the natural log density of age-0 and the density of age-1 Red Snapper in August, September, and October, indicating that older conspecifics interfered with age-0 Red Snapper movements to patch-reefs. There was no significant correlation between the density of age-0 Red Snapper on patch-reefs in October and catch per unit effort (CPUE = catch/H) of Red Snapper from the SEAMAP fall trawl surveys. However, in June, the density of age-1 Red Snapper on patch-reefs was significantly correlated with CPUE from SEAMAP summer trawl surveys, after a 2015 outlier was removed. In the present study, visual surveys of small patch-reefs were effective in estimating the density of juvenile age-0 and age-1 Red Snapper. This survey method, if applied throughout the northern Gulf of Mexico, may substantially enhance present management efforts to reliably determine initial densities on reef structure and potentially help management in predictions of year class strength.
