FISHERY BULLETIN: VOL. 86, NO. 3 



transect methods assume that 100% of all animals 

 are seen directly along the trackline and use 

 statistical techniques to estimate the number of 

 animals that are missed as a function of the distance 

 from this tracWine. Line transects would require use 

 of an aircraft with unobstructed downward visibil- 

 ity through a belly window and use of a third ob- 

 server who could view animals directly under the 

 aircraft. 



Harbor porpoise are now known to occur further 

 from the shoreline than was believed at the begin- 

 ning of this study (Barlow 1988). In future surveys, 

 transect lines should be placed so as to cover a 

 greater fraction of the harbor porpoise habitat. 



ACKNOWLEDGMENTS 



Support, personnel, and flight time were provided 

 by the Southwest Fisheries Center (NMFS), the 

 Southwest Regional Office (NMFS), the California 

 Department of Fish and Game, the National Marine 

 Mammal Laboratory (NMFS), the Washington State 

 Department of Wildlife, and the Oregon Department 

 of Fish and Wildlife. The observers and data 

 recorders were R. Brown, S. Diamond, D. Hanan, 

 R. Holt, S. Jeffries, W. Ferryman, and B. Troutman 

 (also Jay Barlow, Terry D. Jackson, and Charles W. 

 Oliver). The pilots were R. Anthes, J. Cain, L. Heitz, 

 J. York, and B. Zorich. Shore observations were 

 made by M. Herter, T. LoughHn, D. Merrick, 

 R. Rowlett, D. Rugh, and B. Yerman (also Barbara 

 L. Taylor). Unpublished porpoise data from Alaska 

 were collected by P. Dawson (and Barbara L. 



Taylor). The method of adjusting for submerged 

 animals was suggested by D. Chapman based on an 

 unpublished report by R. A. Davis. Drafts of this 

 paper were reviewed by R. Brown, D. DeMaster, 

 K. Forney, D. Hanan, R. Holt, S. Jeffries, and two 

 anonymous reviewers. 



LITERATURE CITED 



Barlow, J. 



1988. Harbor porpoise Phocoena phocoena, abundance estima- 

 tion for California, Oregon and Washington; \. Ship 

 surveys. Fish. Bull., U.S. 86:417-432. 



Kraus, S. D., J. R. Gilbert, and J. H. Prescott. 



1983. A comparison of aerial, shipboard, and land-based 

 survey methodology for the harbor porpoise, Phocoena pho- 

 coena. Fish. Bull., U.S. 81:910-913. 



Kruskal, W. H., and W. a. Wallis. 



1952. Use of ranks in one-criterion analysis of variance. J. 

 Am. Stat. Assoc. 47:583-621. 

 Scheirer, C. J., W. S. Ray, and N. Hare. 



1976. The analysis of ranked data derived from completely 

 randomized factorial designs. Biometrics 32:429-434. 

 Seber, G. A. F. 



1973. The estimation of animal abundance and related param- 

 eters. Hafner Press, N.Y., 506 p. 

 Taylor, B. L., and P. K. Dawson. 



1984. Seasonal changes in density and behavior of harbor por- 

 poise (Phocoena phocoena) affecting census methodology in 

 Glacier Bay National Park, Alaska. Rep. int. Whaling 

 Comm. 34:479-483. 



Watson, A. P., and D. E. Gaskin. 



1983. Observations on the ventilation cycle of the harbour 

 porpoise Phocoena phocoena (L.) in the coastal waters of the 

 Bay of Fundy. Can. J. Zool. 61(1):126-132. 

 Wilcoxon, F. 



1945. Individual comparisons by ranking methods. Biom. 

 Bull. 1:80-83. 



444 



