Gonadal Development and Sexual Dimorphism of Gobiomorus dormitor from the Estuarine System of Tecolutla, Veracruz, Mexico

The bigmouth sleeper, Gobiomorus dormitor, is a benthic, euryhaline species, and is very abundant in river mouths, coastal lagoons, and sites away from marine influence from south Florida to Dutch Guyana. There are few studies of its life history, ecology, and abundance, particularly within Mexican waters. Nine trips to Tecolutla estuary, Veracruz, Mexico, were taken between October 1995 and May 1998 to estimate the gonadal development and sexual dimorphism of G. dormitor. A total of 94 individuals ranging from 15-260 mm SL and 0.05-181 g were captured. Seventy-two specimens were adults (60 females, 12 males) and 22 were juveniles that did not show exter- nal sexual dimorphism. Both juvenile and adult stages of G. dormitor were captured year-round in seagrass beds and adjacent shallow, muddy or sandy areas. This study has shown that G. dormitor are resident and undergo sex- ual maturation in the Tecolutla estuary. Histological evidence suggests both males and females undergo gonadal recrudescence in the estuary and have an extended reproductive season from May through November. However, it is unclear if the species actually spawns in the estuary, since females in the final stages of oocyte maturation were not captured. Additional research on the reproductive biology and ecology of this under-studied species is necessary to determine its role in tropical estuaries in the southern Gulf of Mexico. Information learned from areas in the cen- ter of its distribution may aid in conserving the species at the periphery of its range in Florida, where it is considered threatened.