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Alternate Title

The Occurrence of Rhopilema verrilli (Cnidaria: Scyphozoa: Rhizostomeae) on Galveston Island, Texas, and a Discussion on Its Distribution in U.S. Waters

Abstract

A specimen of the rhizostome scyphomedusa Rhopilema verrilli was stranded on the beach at Galveston Island, Texas, in the spring of 1985. Two young specimens have since been collected In the marshes on the north side of Galveston bordering West Galveston Bay. This species Is relatively rare throughout most of Its range and has only been reported once before in the western Gulf of Mexico.

Seasonal and geographic distributions from literature records are discussed in relation to temperature, salinity, currents, and life history. Occurrences along the U.S. East Coast Indicate progressively later seasonal appearances and decreased abundances from Georgia to New England. Occurrences In the Gulf of Mexico are almost all limited to the Mississippi Sound area. Collection records suggest that R. verrilli has two centers of distribution, one in southern U.S. East Coast waters and one in the northeastern Gulf of Mexico, and that occurrences outside these centers are due to transport by currents. We believe that R. verrilli's apparent rarity in the western Gulf of Mexico results primarily from a combination of wind-driven current patterns, timing of volume of Mississippi-Aatchafalaya River discharge, and temperature-salinlty tolerances of the species acting against transport into, and survival in, the western Gulf.

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