Offshore transport 



Monthly mean offshore transport varied significantly among years (Table 10), but 

 there was no significant relationship between overall monthly mean ofishore transport and 

 monthly mean bottlenose dolphin stranding (r^ = 0.02, P = 0.50, N = 35, Table 6). 

 Examination oi seasonal stranding and ofishore transport suggested a weak (r^= 0.08), but 

 significant (P = 0.01, N=41), inverse relationship during the spring (Figure 6). 



Tabk 10. Monthly oQshore transpon (MT/100km*ec) by yor averaged from five tutions along Toas Gulf CoaxL Negative 

 values indicate onshore transport. Values with the tame letten were not significantly diaereni (SNK test, a. ~ 0.05, A « highest 

 value, C = lowest value). 



Discussion 



Although standard statistical analyses (ANOVA) failed to estabhsh a significantly 

 higher Texas Gulf Coast bottlenose dolphin monthly mortality rate during the first semester 

 of 1990 than for the same period during the previous four years, it is clear that there were 

 a high number of dolphin mortaUties on the Texas coast during January-March 1990. The 

 low power of the significance test may explain the inability to reject the null hypothesis of 

 no significant difference between years. Further evidence that 1990 was unusual was given 

 by the occurrence of 12 bottlenose dolphin strandings in Texas in November 1990 as 

 compared to a mean of about five strandings for Novemeber 1985-89. 



Colder than normal water temperatures may directly affect bottlenose dolphin health 

 by increasing energy expenditure to maintain body temperature, or may indirectly affect it 

 by reducing local food supplies. Low sahnity, resulting from increased fresh water runoff, 

 may similarly affect prey distribution. Alternatively, unusual current patterns may result in 

 a higher than usual number of stranded dolphin carcasses with no actual increase in 

 mortahties. 



Other than an inverse relationship between winter sea surface temperatures and 

 spring dolphin mortality rate, these analyses detected no strong significant relationships 

 between bottlenose dolphin mortahties and other environmental variables. In all of the 

 relationships between environmental variables and dolphin stranding rates which were 

 examined, the power of the significance tests (1 - B) exceeded 0.99. The association of low 

 winter sea surface temperatures with an increased spring dolphin mortality rate suggests the 



41 



