Systematics and Distributional Ecology of Etropus (Pisces, Bothidae) on the Atlantic Coast of the United States with Description of a New Species

Abstract

Etropus cyclosquamus new species, the shelf flounder and three sympatric congeners from the eastern coast of the United States-E. rimosus, E. microstomus and E. crossotus-are diagnosed and a key presented. Patterns and microstructure of the scales are sufficient to identify adults of these four species, but gill-raker counts, shapes of the body and jaws and color patterns are also useful distinguishing characters. E. cyclosquamus is distinguished from all known bothids except E. rimosus and E. microstomus by having small accessory scales on the exposed surfaces of scales on the eyed and blind sides; E. microstomus is distinguished from E. cyclosquamus and E. rimosus by having a symmetrical mandible (vs asymmetrical with upturned symphyseal knob) and less developed accessory scales; E. cyclosquamus is distinguished from E. rimosus by having cycloid scales on the blind side (ctenoid in rimosus) and relatively simple ctenoid scales on the snout that rarely extend forward beyond the nostril (vs specialized, heavily ctenoid scales extending forward beyond nostril, often to premaxillary groove). E. cyclosquamus is distributed from North Carolina to Mississippi and is most abundant at depths of 10-30 m, while E. rimosus occurs from North Carolina to northern Florida in the Gulf of Mexico with greatest abundance at depths of 30-60 m. E. microstomus is most abundant on the continental shelf from New York to North Carolina; during warmer months of the year, it interfaces sharply with E. cyclosquamus and E. rimosus near the 17 C isotherm in the Gulf Stream edge at approximately 35040'N latitude (just north of Cape Hatteras). In the winter, E. microstomus disperses southward along shore, occasionally reaching South Carolina or slightly farther; no specimens have been found from the Gulf of Mexico or the Caribbean. E. crosostus occurs from Virginia to northern South America and in the eastern tropical Pacific; between North Carolina and Texas, it is most common inshore and regularly enters estuaries.