BARLOW: SHIP SURVEYS OF HARBOR PORPOISE 

 10 



0.0 



0.1 0.2 



PERPENDICULAR DISTANCE (km) 



0.4 00 

 10 



0.4 0.0 



0.2 



0.4 



0.6 



0.8 



SURVEY 3, BEAUFORT 2 



-I r 



0.1 



0.2 



1 r- 



0.3 



0.4 



PERPENDICULAR DISTANCE (km) 



Figure 3.— Probability density distributions for perpendicular sighting distances. Histograms indicate observed distributions, and solid 



lines indicate the best fit of the hazard rate model to these data. 



Table 1 .—Estimated values of the probability density functions 

 evaluated at zero perpendicular distance, ^(0). Estimates are based 

 on the hazard rate model and were made for truncation distances 

 of 400, 800, 1,600, and 3,200 m. Estimates are given only if the 

 model gave an acceptable fit to the data (P > 0.1). Asterisks in- 

 dicate f(0) values with the lowest coefficient of variation (paren- 

 theses). 



Survey 



Beaufort 

 sea state 



Truncation distance 



400 m 800 m 1 ,600 m 3,200 m 



1 

 1 

 3 

 3 



& 1 

 2 



& 1 

 2 



7.85 • 



(0.23) 



10.48 

 (0.59) 



4.51 • 

 (0.22) 



6.97 • 

 (0.19) 



5.31 

 (0.29) 



8.15 * 

 (0.21) 



3.10 

 (0.66) 



4.31 

 (0.24) 



7.09 

 (0.33) 



2.69 

 (0.31) 



5.78 

 (0.51) 



from aerial surveys (Barlow et al. 1988) show 

 roughly equal density at 0.61 and 1.85 km from the 

 shore (the latter corresponding approximately to the 

 18 m isobath). Relative density from ship surveys 

 was measured in the number of sightings per kilo- 

 meter of searching effort. Relative densities at 



Table 2.— Density estimates, D, for harbor porpoise (km"^) along 

 the 18 m isobath in each of eight geographic strata. Density was 

 calculated per Equation (2), using estimates of f(0) (Table 1) which 

 had the lowest coefficients of variation. Values are not adjusted 

 for missed animals. Standard errors are in parentheses. 



Geo- 

 graphic 

 region 



1 

 2 

 3 

 4 

 5 

 6 

 7 

 8 

 Total 



Survey 1 



Survey 3 



Beaufort 

 & 1 



Beaufort 

 2 



Beaufort 

 & 1 



Beaufort 

 2 



0.0 

 (0.0) 



1.1 

 (1.0) 



1.4 

 (0.8) 



7.9 

 (3.4) 



1.8 

 (0.8) 



2.5 

 (1.1) 



0.0 

 (0.0) 



0.0 

 (0.0) 



0.0 

 (0.0) 



2.5 

 (1.0) 



2.1 

 (1.3) 



2.0 



(0.6) 



0.8 

 (0.6) 



0.0 

 (0.0) 



1.3 

 (0.6) 



0.0 

 (0.0) 



0.6 

 (0.5) 



0.1 

 (0.1) 



0.0 

 (0.1) 



0.8 

 (0.6) 



2.5 

 (0.8) 



2.5 

 (0.6) 



0.8 

 (0.4) 



0.1 

 (0.1) 



0.1 

 (0.1) 



0.0 

 (0.0) 



6.7 

 (7.2) 



0.6 

 (0.3) 



2.6 

 (0.9) 



1.3 

 (0.7) 



1.2 

 (0.5) 



Pooled 

 estimates 



0.04 

 (0.02) 



0.51 

 (0.30) 



0.03 

 (0.03) 



2.83 

 (1.69) 



0.91 

 (0.32) 



2.22 

 (0.40) 



2.64 

 (0.78) 



1.09 

 (0.45) 



1.33 

 (0.30) 



425 



