Demographic, Taxonomic, and Genetic Characterization of the Snook Species Complex (Centropomus 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.

Molecular Characterization of the Common Snook, Centropomus undecimalis (Bloch, 1792) in the Usumacinta Basin

“…Finally, our study also recovered the diversity information of mitochondrial and nuclear data that in contrast with previous studies that also shed light on the current status of the species. With the two mitochondrial markers, the genetic diversity recovered was lower (i.e., mtCox1 Hd = 0.28 and mtCytb Hd = 0.62) than previously reported for the species [18,72], and also in comparison with other euryhaline species [73,74]; for mtCox1, Hap3 was present in 80% of the samples analyzed. Similarly, in the nuclear data, the heterozygosity values obtained in our study were lower than those previously reported for 5 of our 11 microsatellite loci [25].…”

Poleward expansion of common snook Centropomus undecimalis in the northeastern Gulf of Mexico and future research needs

“…Along with poleward expansion of snook in the Gulf of Mexico (this study, [26]), there has been substantial expansion in both red mangrove and black mangrove, which provide important habitat for both juvenile and adult snook [29,49,50]. It is unclear whether the mangrove expansion northward is a mechanism for snook expansion, but clearly the habitats are shifting from salt marsh to mangroves in this region [8,14], which will further improve habitat for snook.…”

“…We hypothesize that the combination of milder winters and warmer summers has promoted the expansion of a Florida snook population into northerneastern Gulf waters. A recent study shows a similar range expansion for snook in the western Gulf [26]. We sought to quantify the changes in snook catches using a long-term standardized sampling program, to explore the spatial extent and temporal changes in size structure, assess evidence for local reproduction, and identify future research needs for an expanding range of a subtropical apex predator in the Gulf.…”

Tropicalization of temperate ecosystems in North America: The northward range expansion of tropical organisms in response to warming winter temperatures

“…These findings led to the temporary closure of the recreational snook fishery along the Gulf of Mexico coast, and recovery of the populations took up to 4 years. Since then, a decade of mild winters has allowed for expansion of the species approximately 200 km beyond its historic distribution (Anderson et al, 2020;Purtlebaugh et al, 2020).…”