108 



Fishery Bulletin 88(1). 1990 



schools. While searching in the study area (Fig. 1), 

 observers on both vessels searched 27,(i(39 km and 

 detected 306 dolphin schools containing 15 or more 

 animals located within 3.7 km perpendicular distance 

 of the trackline during Beaufort sea states of 5 and less 

 (Table 1). The amount of effort and schools detected 

 varied among strata; 43% of the total trackline 

 searched and 54% of all dolphin schools detected were 

 in the inshore area. 



Abundance estimation 



The estimate of/(0) for data in the total area (pooled) 

 was 0,522. Density estimates (Di^) in the four strata, 

 calculated using the pooled /(O), ranged from 1.89 to 

 3.62 schools/1000 km^ (Table 1). Estimates of mean 

 school size (S,;.) of target species ranged from 83.97 

 to 179.04 animals (Table 1). The proportion of identi- 

 fied dolphin schools that included target species iP,k) 

 ranged from 0.744 to 0.906 among strata (Table 1). 

 The proportions of individuals of all target schools 

 that were spotted dolphins (P,^.) in the four strata 



ranged from 0.170 to 0.378 (Table 1). The proportions 

 of the other target species among strata also varied 

 greatly. For example, the proportion of common 

 dolphins ranged from 0.008 to 0.661 (Table 1). Only 29 

 spotted dolphin schools were detected in the overlap 

 region of the coastal and offshore spotted stocks. The 

 proportion (P',j) of these that were offshore spotted 

 dolphins was 0.605 (Table 1). Of 96 spinner dolphin 

 schools detected in the area of overlap of eastern and 

 whitebelly spinner stocks, the proportion of these that 

 were eastern spinner dolphin individuals was 0.703. 



The areas inhabited by each stock (/l,jj.) of each tar- 

 get species (A,^.) in each stratum (/l^.), and the over- 

 lapping areas (A',,;,.) inhabited by (1) coastal and off- 

 shore spotted dolphins and (2) eastern and whitebelly 

 spinner dolphins, are shown in Table 2. 



Relatively, common dolphins were the most abundant 

 species (Table 3). The estimate of 929,000 northern off- 

 shore spotted dolphins represented 78% of the estimate 

 of all stocks of spotted dolphins. The coefficient of 

 variation (CV) of the abundance of the northern off- 

 shore spotted dolphon stock, CV(iV|j), was 0.255. The 



