reported strandings were >1.5 times the previous high 

 for only January and February, whereas reported 

 strandings in the remainder of the Gulf were >U 

 times the previous high for January-May. Thus it 

 appears that most of the anomalous mortality 

 occurred outside of Texas, both in terms of duration 

 and numbers. 



The increases in reported stranding rates 

 (strandings/month) in the Gulf were compared to the 

 increases observed during the 1987-89 bottlenose 

 dolphin dieoff along the U.S. east coast. Compared to 

 the prior 3-year average, the east coast dieoff 

 represented a 10 fold increase (Geraci 1989; Scott et 

 al. 1988) while in the Gulf a 2.6 times increase was 

 observed. On a state and month basis, increases along 



70 



60 



50 



40 



30 



20 



10 - 



NON-TEXAS 



• 1990 



^ 19B4-89 HIGH 



ERROR BARS 95k 



JFMAUJJASOND 



Figure 4: Compahsoo of non-Texas 1990 

 monthly bottlenoae dolphin strandings with 

 1986-89 mean, tbowing 1986-89 95% confidence 

 intervals. High monthly from 1984-89 data. 



the east coast were up to >40 times the average as compared to a maximum of about 12 

 times the average in the Gulf. Figure 5 illustrates the range of relative increases observed 

 in the Gulf and along the east coast by state and month in reference to prior 4-year averages 

 for each region. The total number of animals stranded during the east coast dieoff was about 

 twice that observed in the Gulf, but the east coast relative strandings were dramatically 

 higher. 



so 



X 



2 



20  



• ATUNTC 1987-08 



A GULF tmo 



The 1990 sex ratio of Texas strandings was 

 compared to that observed during 1984-89 for the 

 months January-June. Information on sex was used 

 only for specimens with length data. This was done to 

 avoid the possible bias that may exist in sexing animals 

 (i.e., it may be easier to sex males, even when more 

 than moderately decomposed). It was assumed that 

 specimens with length data would be reliably sexed. 

 During January-June 1984-89, sex and length was 

 recorded for a total of 334 animals, and the resulting 

 sex ratio was 1.00:0.69, males to females (range: 

 1.00:0.45 to 0.85:1.00; see Appendix III). Except for 



1989, the available data suggest that there were more 

 strandings of males than females. The sex ratio for 

 1990 for the same months was 1.00:0.98, which falls 

 within the previously observed range. A z-test, 

 corrected for continuity (Snedecor and Cochran 1973), 

 was used to test the null hypothesis that there was no 

 significant difference between the proportions of males stranded during 1984-89 and during 



1990. The results of this analysis indicated that the proportions of observed during 1984-89 

 and during 1990 were not significantly different (z = 1.545, p > 0.12). 



P t , ^ 



S 



D J F 



IIONTH 



Figiire 5: Bottlenose dolphin strandings by state 

 and month during the 1987-88 easi coast dieoff 

 and the 1990 nonhern Gulf of Modco mortality 

 event compared to prior 4-year averages. 



17 



