Movements, Site Fidelity, and Respiration Patterns of Bottlenose Dolphins on 



the Central Texas Coast: A Report to the National Marine Fisheries Service, 



Southeast Fisheries Science Center, Miami, Florida 



By 



Bemd Wursig and Spencer K. Lynn 



Texas A&M University 



Marine Mammal Research Program 



4700 Ave. U, Bldg. 303 



Galveston, TX 77551 



ABSTRACT 



Radio-tracking of 10 bottlenose dolphins (Tursiops truncatus), from 9 July 

 1992 to 13 September 1992, and photographic surveys of 35 freeze-branded 

 dolphins, from May 1992 to June 1993, were conducted in the Matagorda Bay 

 area of Texas, in response to a mass mortality event which occurred between 

 Matagorda and Aransas Bays, Texas, during spring 1992. The primary goals of 

 the study were to assess range size and site fidelity, as well as to initiate a long- 

 term ecological study by collecting data on social and behavioral patterns. 



The Matagorda Bay dolphin population was found to be numerically 

 robust, occupying all regions of the bay surveyed. Mean range size, based on 

 radio telemetry, was 140 km^ (SD = 90.7, n = 10 dolphins). Males and females 

 had similar range sizes though males visited the extremities of their ranges 

 more frequently or for longer periods. Several generalities were observed: 

 (1) Dolphins were capable of, and often did, traverse their range in several 

 hours. (2) Dolphins traveled widely on some days, perhaps crossing their own 

 ranges, while on other days movement was very confined, within 1-2 km^. 

 This did not appear to have a temporal or geographic pattern. (3) Dolphins 

 tended to spend about 1-4 days in a particular portion of their range. 



(4) Movement tended to be more confined at night than during daytime. 



(5) Dolphins tended to visit the extremes of their ranges only in the daytime. 

 The assertions of (4) and (5) may be biased as a result of less sampling effort at 

 night, with fewer triangulations than during daytime and no visual sightings. 



Ill 



