The eastern oyster Crassostrea virginica is a commercially and ecologically important organism found throughout the western North Atlantic and Gulf of Mexico. Morphological differences in shell shape of eastern oysters are known to arise from environmental, genetic, and husbandry-related factors. Here, live eastern oysters were collected from 17 sites along the U.S. Gulf of Mexico coast from Texas to Florida to examine morphological differences among geographic samples. Six morphological metrics were recorded for each individual, and four different composite ratios commonly used to describe oyster shape (fan, cup, volume ratio, and weight ratio) were calculated. Principal component analysis was used to demonstrate geographic differences in ordinated shape ratios, correlating roughly with eastern (Florida), northern (Alabama, Louisiana, north Texas), and western (south Texas) samples. In Texas, differences in shape were correlated with previously described genetic population boundaries, indicating that populations north versus south of Aransas Bay had different overall shell shapes. On a broader scale, shell shape variation correlated roughly with previously described genetic population boundaries throughout the Gulf of Mexico as well as tide depth (intertidal versus subtidal reefs). Among the various factors that might act as drivers of shell shape, individual variation is important, but population structure and tide height are also significant predictor variables of shape in this species.Estuaries are highly productive ecosystems with key habitats, including salt marshes, seagrasses, mangroves, and shellfish reefs, that support spawning, nursery, and feeding functions for recreational and commercial fishery species (USEPA 1999). Shellfish reefs in the western Atlantic Ocean and Gulf of Mexico are primarily constructed by the eastern oyster Crassostrea virginica, which is a foundation species that ranges from the Gulf of St.

Two species of ladyfish occur in the Gulf of Mexico (GOM), Elops saurus and Elops smithi, that are morphologically indistinguishable except for vertebral counts but can also be identified by mitochondrial DNA haplotypes. Here we expand on previous work, most of which has occurred in Florida, and examine the demography, phylogenetics, geographic distribution, and age—structure of ladyfishes in Texas estuaries. Fishery—independent gill net data demonstrated that ladyfishes increase in abundance from north to south along the Texas coast. The abundance of ladyfishes also increased in Texas waters from 1982–2021, which coincides with recent trends of warmer winters. Genetic data confirmed that both E. saurus and E. smithi occur in Texas waters; however, E. smithi was far less common. Contrary to previous research, we observed higher levels of genetic diversity in E. saurus due to larger sample size and thorough sampling of the western portion of its geographic range. Phylogenetic analysis supported the existence of E. saurus as a distinct species but indicated that E. smithi may be paraphyletic with other species of Elops. Otolith analysis showed that the ages of E. saurus and E. smithi ranged from 0–3 years. The lack of individuals > age—3 suggests that ladyfishes migrate to the offshore GOM at age 3 and do not return to coastal areas. This study enhances knowledge of the biology of ladyfishes in inshore waters of the northwestern GOM. Future management would benefit from expanding this research to the entire geographic range of the genus Elops.