Demographic, Taxonomic, and Genetic Characterization of the Snook Species Complex (<i>Centropomus</i> spp.) along the Leading Edge of Its Range in the Northwestern Gulf of Mexico

Abstract A recent increase in the abundance of snook species (Centropomus spp.) in Texas has been generally associated with a broad-scale warming trend of Texas’ inshore waters, closure of the commercial fishery in 1987, and fairly conservative restrictions on recreational catch implemented at the same time. Despite this observed increase in abundance, little is known about the snook species complex in Texas, including uncertainty about recent changes in distribution and abundance, taxonomy, and population structure. Here, abundance and distribution data from a long-running fishery-independent (FIN) data set were analyzed in synergy with mitochondrial DNA (mtDNA) and microsatellite genotypes to answer basic questions about the snook species complex in Texas. The main findings from this work are as follows: (1) based on trends observed in FIN data, snook are increasing in abundance and expanding their range northward in Texas; (2) based on mtDNA sequencing, the two most common species of snook in Texas are the Common Snook C. undecimalis and Largescale Fat Snook C. mexicanus; (3) a third species, the Mexican Snook C. poeyi, occurs but only rarely; and (4) patterns from microsatellite genotypes suggest that the two predominant species, Common Snook and Largescale Fat Snook, probably constitute single genetic stocks in Texas, although evidence of chaotic genetic patchiness was also observed. This latter finding might be a general expectation for populations that are on the leading edge of an expanding species range and implies that management measures in Texas should be directed toward conservation of suitable habitat corridors offering environmental and habitat refugia as well as measures (e.g., stock enhancement) that increase the probability of survival of small, localized populations.