794 



Fishery Bulletin 90(4|, 1992 



intestine ~1.5m long containing extremely-hard dehy- 

 drated feces, and its stomach contained partially- 

 digested fish and bones. Two IF had peritoneal adhe- 

 sions throughout the GI tract. One of these had a 

 serofibrinous exudate on the serosal surfaces of the en- 

 tire small intestine, and the gastric compartments were 

 empty. Four animals (2 MF, 2 IM) had nematodes in 

 the forestomach and fundic chamber. Clear, crystallized 

 deposits adhered to the parietal and visceral surfaces 

 of the thoracic and abdominal cavities of all animals. 

 These deposits were < 1mm in size, felt "gritty," and 

 imparted a "sandpaper-like" texture to the surface, a 

 condition not uncommon in decomposed dolphins in the 

 region (Raymond J. Tarpley, Texas A&M Univ., Col- 

 lege Station, pers. commun., March 1990). 



Every mature animal in the Bay group had hard, 

 white, spherical deposits in the pancreatic interstitial 

 tissue. These deposits were <2mm in size and were 

 scattered throughout the central pancreas. When 

 crushed with a knife, the deposits were the same white 

 color and consistency throughout. 



Stomach contents were noted in 19 of the 23 Bay 

 animals. Stomachs of 6 animals (3 MM, 2 IF, 1 MF) 

 were void of food. Ten animals had unidentified fish, 

 bones, and scales in the stomach. Three animals (2 MF, 

 1 IM) had undigested and partially-digested fish in the 

 forestomach; in two of these animals, there was a 30cm 

 undigested fish in the esophagus. 



No other gross abnormalities were noted in the 

 respiratory, cardiovascular, renal, musculoskeletal, or 

 reproductive systems of the Bay dolphins. Eyes were 

 too decomposed for examination. Data concerning in- 

 fectious agents (viral, bacteriological, fungal, etc.) could 

 not be obtained because of advanced decomposition of 

 the carcasses. 



Discussion 



Several factors might have contributed to the East 

 Matagorda Bay dolphin mortality. First, an abnormally 

 rapid drop in water temperature which resulted in the 

 Bay freezing over; second, abnormally low tidal levels, 

 possibly preventing exit from the Bay; and third, 

 striped mullet, an important food source for the 

 dolphins, may have been significantly depleted by the 

 freeze. The poor condition of Bay dolphins was in- 

 dicated by the ~89% of males and 80% of females in 

 states of emaciation or near-emaciation, based on 

 minimum weight-length guidelines established by 

 Ridgway and Fenner (1982) (Fig. 5). In addition, 

 average blubber thickness of the Bay dolphins was a 

 third less than that of the Texas-coast dolphins during 

 winter, based on records over the previous 9-year 

 period. 



240 

 220 

 200 

 1 

 - 160 



-n ^ , 1 < I < \ < I T 



Minimum Weight (Males) 



200 220 240 2li0 280 300 



LENGTH (cm) 



220 



200 



180 



S160 



I 140 

 O 



5 120 



100 



220 240 260 



LENGTH (cm) 



Figure 5 



Weight-length data for male and female bottlenose dolphins 

 from East Matagorda Bay, plotted on Ridgway and Fenner's 

 (1982) minimum weight-length graph. 



Gunter (1941) and Gunter and Hildebrand (1951) 

 reported on the death of fishes and other organisms 

 during severe cold periods along the Texas coast. In 

 1940, water temperature fell from 18.3°C to -3.9°C 

 in 4 hours (Gunter and Hildebrand 1951). Concerning 

 dolphins, Gunter (1941) write, "It is probably worth 

 recording that two porpoises, T. truncatus, were 

 stranded in St. Charles Bay by the low tide and were 

 forced to remain there, only partially submerged, dur- 

 ing the coldest days of the freeze. They did not die and 

 it was reported that they escaped when the tide rose." 

 There are other reports of bottlenose dolphins in frozen 

 seas; for example, Manton (1986) reports that T. trun- 

 catus have been seen breaking ice in the northern part 

 of the Adriatic Sea. There are no records of dolphin 

 deaths associated with other recent freezes in East 

 Matagorda Bay, i.e., in 1983-84 or February 1989; 

 however, local fishermen stated that the only previous 

 sightings of dead dolphins (reported as 4 or 5) in the 

 Bay followed the 1983-84 storm. No data on water 



