INTRODUCTION 



In March and April 1992, 111 bottlenose dolphin carcasses were recovered 

 from the area between Matagorda and Aransas bays of the central Texas coast 

 (Fig. 1). This represented an unusually high mortality, compared to a mean of 

 14 (SD = 71, range = 5-23) deaths during March-April calculated from the 

 previous 5 yr (Elsa M. Haubold, Operations Coordinator, Texas Marine 

 Mammal Stranding Network, personal commuiucation). The die-off raised 

 questions about dolphin movement patterr\s and site fidelity on the Texas 

 coast, and on the ability of potentially locally depleted stocks to recover 

 through immigration. In response, the National Marine Fisheries Service 

 funded the Marine Mammal Research Program of Texas A&M University at 

 Galveston (MMRP) to conduct a 6-day survey of the Matagorda Bay area. The 

 primary intent of the survey was to obtain data on approximate minimum 

 numbers of animals still alive in the area by photo-identification, general 

 behavior and apparent health of live animals, and the overall feasibility of 

 conducting long-term ecological studies on bottlenose dolphin distribution 

 and habitat use in this bay system. 



The short preliminary study, carried out 15-19 May 1992, photo-identified 

 at least 67 different dolphins inhabiting the area; discovered no apparently 

 moribund dolphins among the live animals; and resulted in the strong 

 recommendation that detailed research, relying on tagging, physiological 

 studies, and long-term radio-tag and photographic monitoring were essential 

 to an understanding of dolphin use of the Matagorda Bay environs. 



Consequently, to assess the impact of the spring 1992 die-off, a National 

 Marine Fisheries Service-sponsored capture effort from 7-19 July 1992 

 resulted in collection of physiological information from 36 dolphins 

 (Sweeney 1992, Graham A. J. Worthy, Director, Texas Marine Mammal 

 Stranding Network, personal communication). The 36 dolphins received 

 dorsal fin roto-tags (Scott et al. 1990b, Sweeney 1992); 35 were freeze-branded 

 on both sides of the upper dorsum and /or dorsal fin (Odell and Asper 1990, 

 Scott et al. 1990b, Sweeney 1992); and 10 were fitted with radio transmitters 

 (Evans 1971, Wvirsig et al. 1991). 



The primary objectives of this study were to gather information on range 

 characteristics and site fidelity, and to begin a long-term study of dolphins in 

 the area by examining movement patterns, associations among individuals, 

 and other ecological data. The results of radio-tracking and photographic 

 monitoring are described here. Radio-tracking was from 9 July 1992 to 

 13 September 1992, when radio signals were no longer received. Photographic 



