Bottlenose dolphins of San Luis Pass, Texas: Occurrence patterns, site-fidelity, and habitat use




Maze KS; Wursig B

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Bottlenose dolphins (Tursiops truncatus) in the Galveston Bay Estuary, Texas, have been studied continuously since 1990. Most of this research has taken place in the 'Galveston Bay' area at the northeastern end of Galveston Island. In September 1995 we began a project to examine bottlenose dolphin occurrence patterns, habitat use, site fidelity, and movements in the San Luis Pass area, a relatively undisturbed area at the southwestern end of Galveston Bay Estuary; and to compare findings to previous work in Galveston Bay, approximately 48 km away. Eighty-three boat-based photo-identification surveys were conducted during 12 months in 1995-1996, totaling 349.4 h of effort, of which 94.3 h were spent in direct observation of 102 dolphin groups. Seventy-one individuals were identified, including 37 'residents' (Bay) and 34 'transients' (Gulf). These individuals were compared with 63 individuals identified in the study area in 1990. Fourteen of 71 (19.7%) animals identified in 1995-1996were present in 1990, suggesting that some dolphins exhibit long-term site fidelity to the area. Dolphins identified in San Luis Pass were compared to photographs taken during 1995 surveys of Galveston Bay. Three animals were sighted in both study areas, indicating coastal movements between sites do occur. The study area was divided into four sections based upon habitat characteristics. Season and study area section were not independent with regard to group sightings. During summer, animals were most frequently sighted in a shallow bay furthest inland, whereas during winter, they were most frequently sighted in the Gulf of Mexico. This study suggested that the San Luis Pass area, devoid of deep man-made channels and structures, is inadequate to support dolphins during winter. This is in contrast to Galveston Bay, where groups have been sighted regularly in bays and channels year-round. We suggest that food resources in Galveston Bay are present year-round due to deeper water provided by the Houston and Galveston Ship Channels, and that this habitat may therefore be more attractive to dolphins than before human restructuring of the underwater environment




Delphinidae: Animals,Cetaceans,Chordates,Mammals,Nonhuman Vertebrates,Nonhuman Mammals,Vertebrates;habitat use; occurrence patterns; seasonality; site-fidelity;Marine Ecology: Ecology,Environmental Sciences;Tursiops truncatus: bottlenose dolphin [Delphinidae];[07003] Behavioral biology - Animal behavior;[07502] Ecology: environmental biology - General and methods;[85815] Delphinidae;[85815] Delphinidae,Cetacea,Mammalia,Vertebrata,Chordata,Animalia;