SECTION IV 

 FOOD HABITS 



Nelio B. Barros 



Division of Biology and Living Resources 



Rosensnel School of Marine and Atmospheric Science 



University of Miami 



Miami, FL 33149 



An unusual mortality of bottlenose dolphins in the Gulf of Mexico (primarily along the 

 Texas coast) took place during early 1990. Due to the implication of food habits in the 

 recent mortalities of bottlenose dolphins (Geraci 1989) and humpback whales (Geraci et al. 

 1989) in the eastern coast of the United States, there was concern of a similar occurrence 

 in the Gulf of Mexico during 1990. This study analyzes the food habits of bottlenose dolphins 

 stranded along the coast of Texas during January- April 1990 and compares the results with 

 a previous study in the same area (Barros and Odell 1990). Samples obtained from 26 

 dolphins stranded in Matagorda Bay in late January 1990 were not available for examination 

 and were not included in this study. 



Methods 



Samples (entire stomachs) were collected from 38 stranded dolphins and frozen for 

 analysis (see Appendix I for details on stranding date, location, sex, age, etc.). This sample 

 was comprised of all the whole stomachs that were coUected and frozen; it was not possible 

 to determine if the sample was representative of the animals that died during January-April 

 1990. One stomach was empty and the remaining 37 had food matter (Table 1). In this 

 sample, dolphins ranged in size (total length) from 160 to 269 cm. Fish otoliths, squid beaks 

 and shrimp rostra and/or telsons were the structures utilized in prey identification, following 

 methodology outlined in Barros and Odell (1990). 



Results and Discussion 



Wet weight of the 37 stomach contents ranged from 1 to 3382 g (Table 1), with a mean 

 of 237.95 g per stomach. When only stomachs with contents weighing 10 g or more are 

 considered (see Barros and Odell 1990) this figure increases to 398.95 g (n= 22). The 

 number of prey items per stomach averaged 219.14 (SD= 287.80, n= 37) and number of 

 prey taxa 9.41 (SD= 5.49, n= 37) (Table 1). A total of 15,950 fish otoUths (13,816 sagittae, 

 2,124 lapilli, 10 asterisci), 1,681 (890 upper and 791 lower) squid beaks, and remains 

 (rostra/telsons) of 59 crustaceans were found in all stomachs, representing 7,109 fish, 915 

 squid and 59 crustaceans. The categories of prey type were: fish only (F): 9 (24%); fish and 



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