EDWARDS and KLEIBER: NONRANDOMNESS ON LINE TRANSECT ESTIMATES OF DOLPHINS 



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ESTIMATED ABUNDANCE 

 OF SPOTTED DOLPHIN 



(1983) 



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1975 1976 1977 1978 1979 1980 1981 1982 198] 19B4 1985 1986 1987 



YEAR 



Figure 8. — Estimated abundance of northern offshore spotted dolphin, Stenella at- 

 tenuata, showing biologically unlikely recovery in 1984 following apparent decrease in 

 abundance during 1983 (fi-om Buckland and Anganuzzi 1988). 



tion approach identified two critical problems 

 that must be addressed if TVOD are to an effec- 

 tive source for estimates of dolphin abundance or 

 changes in abundance in the eastern tropical 

 Pacific Ocean. These critical problems are 1) the 

 effect of small-scale nonrandomness of dolphin 

 schools, and 2) the interactions between these 

 small-scale patterns (sampling frequency and 

 smoothing algorithms) on estimates of school 

 abundance or change in abundance derived from 

 line transect analysis of sightings data. Research 

 effort should now be directed toward identifying 

 and characterizing school distributions within 

 these smaller spatial (and temporal) scales, and 

 toward improving the efficacy of e.xisting 

 methods or developing new methods for analyz- 

 ing TVOD. 



ACKNOWLEDGMENTS 



Development of the model and preparation of 

 this paper have been aided significantly by the 

 sage advice and helpful criticisms of Steve 

 Reilly and Doug DeMaster. 



LITERATURE CITED 



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 Gerodette, T. 



1987. A power analysis for detecting trends. Ecology 

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 Holt, R. S., and J. Cologne. 



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875 



