BARLOW: SHIP SURVEYS OF HARBOR PORPOISE 



DEPTH DISTRIBUTION MODELS 



2 

 18 

 16 

 14 

 12 



1 

 0.8 

 0.6 

 4 

 0.2 







2 

 1.8 

 16 

 1.4 

 1.2 



1 

 0.8 

 6 

 0.4 

 0.2 







Primary Model 



5 15 25 35 45 55 65 75 85 95 105 115 125 135 145 





LU 

 > 



LU 

 CC 



CO 



z 



lU 

 Q 



LJJ 

 > 

 I- 

 < 



_J 

 UJ 

 CC 



CO 



z 



lU 



o 



LU 



> 



LU 

 CC 



5 15 25 35 45 55 65 75 85 95 105 115 125 135 145 



WATER DEPTH (meters) 



Figure 4.— Proposed models for the depth distribution of harbor porpoise expressed as relative den- 

 sities, 4, within 10 m depth intervals. Density at 20-30 m is assumed to be knowm and is given a 

 relative value of 1. Figures represent a) a primary model of offshore distribution, b) a high estimate 

 of offshore range, and c) a low estimate. 



5 15 25 35 45 55 65 75 85 95 105 115 125 135 145 



in each area. Both surveys show similar patterns, 

 with higher abundances in the northern strata (4-8) 

 and very low abundance in strata 1 and 3. Despite 

 similar patterns, differences between the paired 

 estimates are in some cases, large and statistically 

 significant (^tests, P < 0.05). Because region 8 was 

 not covered on the third survey, it is not possible 

 to compare estimates of total abundance for the en- 

 tire coast between surveys. The total abundances 

 for regions 1-7 (Point Conception to the Columbia 



River) are 46,550 (SE = 10,932) animals and 32,029 

 (SE = 10,906) animals for surveys 1 and 3, respec- 

 tively. The difference between these estimates is not 

 statistically significant (^test, P > 0.05). Pooling the 

 results of the two surveys, the estimate of harbor 

 porpoise abundance between Point Conception and 

 Cape Flattery in September of 1984 and 1985 is 

 45,713 (SE = 7,865) animals (Table 4). The same 

 estimate using the alternate models of offshore 

 distribution ranges from 28,769 to 78,019 (Table 5). 



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