NOTE Fulling et a\ Abundance and distribution of cetaceans in the US Gulf of Mexico 



929 



Stenella frontalis 



500 1000 1500 2000 2500 3000 3500 4000 4500 5000 



Perpendicular distance in meters 



Figure 4 



Plot of the detection function of pooled sightings of Stenella frontalis in the northern U.S. 

 Gulf of Mexico. 



23 dolphins (Waring et al., 2001). Using the abundances, 

 we estimated that the annual PBR would be 204 dolphins 

 for T. truncatus and 246 dolphins for S. frontalis (Table 2). 

 Although these changes in both PBRs are large, the annual 

 fishery-related mortality and serious injury for each spe- 

 cies is estimated to be <3 dolphins in the U.S. GOM OCS 

 (Waring etal., 2001). 



they were achieved after four years of effort. In cases where 

 there is human-caused mortality in a cetacean stock, abun- 

 dance estimates with a CV < 0.50 are generally required 

 to avoid incorrectly classifying a cetacean stock as "stra- 

 tegic" under the U.S. MMPA (i.e. annual human-caused 

 mortality>annual PBR) less than 10% of the time (Wade 

 and DeMaster, 1999). 



Precision 



The precision of the abundance estimates for T. truncatus 

 (CV=0.26) and S. frontalis (CV=0.27) was good, although 



Bias 



The surveys were designed to meet the assumptions of line- 

 transect theory (Buckland et al., 2001). However, the abun- 



