Modeling the spatial distribution of commercially important reef fishes on the West Florida Shelf

Abstract

Understanding the spatial distribution of a species is an important precondition to successfully managing marine populations. For reef fishes, this is of particular importance due to the patchy nature of reef communities. This study estimated the spatial distribution of five reef fish species on the West Florida Shelf: gag grouper (Mycteroperca microlepis), mutton snapper (Lutjanus analis), red grouper (Epinephelus morio), red snapper (Lutjanus campechanus), and vermilion snapper (Rhomboplites aurorubens). Estimation was done by combining large-scale fishery-dependent catch per unit of fishing effort with small scale fishery-independent video survey observation. Catch per unit of fishing effort was obtained from vessel logbook data while video observations of reef fish presence–absence and relative abundance were made by stratified random sampling on known reef and hard-bottom habitat in the Gulf of Mexico. Relative abundance estimates showed different abundance patterns for the five species depending on depth and geographical area. Variogram modeling suggested that gag grouper, mutton snapper, and red grouper were spatially autocorrelated on reef or hard-bottom habitats at short ranges of between 0.87 and 0.95km, while red and vermilion snapper were found to be randomly distributed. Range estimates for gag grouper, mutton snapper and red grouper were supported by variograms of depth soundings in the Gulf which produced range estimates of between 1.56 and 6.34km. Combining the relative estimates of abundance from catch per unit of effort with the spatial autocorrelation parameters from video surveys allowed us to provide stochastic fish abundance estimates at scales of about 2km2.