ECOLOGICAL NOTES AND PATTERNS OF DISPERSAL IN THE RECENTLY INTRODUCEDMUSSEL, PERNA-PERNA (LINNE, 1758), IN THE GULF-OF-MEXICO

Invasive mussels, Perna perna (Linne, 1758), were first detected in so uth Texas on the jetties at Port Aransas (27 degrees 50' N) in Februar y 1990 (Hicks and Tunnell, 1993). Within four years the species has co lonized jetties, navigation buoys, petroleum platforms, wrecks, and ot her artificial hard substrata as well as natural rocky shores between Matagorda Peninsula (28 degrees 35' N), Texas, and Playa Escondida (18 degrees 35' N), southern Veracruz, Mexico, a distance of over 1,300 k m. Densities of 27,200/m(2) small individuals (mean - 16 mm +/- 0.3 SE ) have been recorded from south Texas jetties. Spat settlement densiti es of up to 300/25 cm(2) (120,000/m(2)) have been recorded from algal substrata in southern Veracruz, Mexico. On oil production platforms, 6 -27 km offshore from Port Aransas, the species occurs from the interti dal zone down to depths of 9 m. Dispersal patterns interpreted from di scovery data in the Gulf of Mexico indicate a primarily southward expa nsion from the initial recording. The occurrence of P. perna in euryha line environments, such as river mouths and bay systems, demonstrates the ecological adaptability of this species.