Buckland et al Estimating abundance of tuna-associated dolphin stocks in the eastern tropical Pacific 



1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1983 1989 



Figure 8 



Smoothed abundance trends of central stock of common 

 dolphin Delphinus delphis in the eastern tropical Pacific. 

 Broken lines indicate approximate 85% confidence limits. See 

 Figure 1 for more details. 



1975 1976 1977 1978 1979 1980 1981 1982 1985 1984 1985 1936 1987 1988 1989 



Figure 10 



Smoothed abundance trends of pooled northern, central, and 

 southern stocks of common dolphin Delphinus delphis in the 

 eastern tropical Pacific. Broken lines indicate approximate 

 85% confidence limits. See Figure 1 for more details. 



1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 



Figure 9 



Smoothed abundance trends of southern stock of common 

 dolphin Delphinus delphis in the eastern tropical Pacific. 

 Broken lines indicate approximate 85% confidence limits. See 

 Figure 1 for more details. 



1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 



Figure 1 1 



Smoothed abundance trends of northern offshore stock of 

 spotted dolphin Stenella attenuata in the eastern tropical 

 Pacific. Broken lines indicate approximate 85% confidence 

 limits. Estimates and limits were determined from four in- 

 dependent sets of 79 bootstrap replicates, so that the plot 

 indicates uncertainty in the estimates arising from Monte 

 Carlo variation. 



If data are pooled across stocks of common dolphins 

 (Fig. 10), the 1988 smoothed estimate is significantly 

 lower than all those preceding 1981. 



Four independent sets of 79 bootstrap replicates 

 were generated for the northern offshore stock of 

 spotted dolphins. The resulting plots, one of which 

 corresponds exactly to Figure 1, are superimposed in 

 Figure 11. If an infinite number of replicates could be 

 carried out for each set, the four plots would be iden- 

 tical. Thus Figure 11 indicates the imcertainty that can 



be expected in the median and interval estimates due 

 to Monte Carlo variation. 



Discussion 



Unsmoothed estimates of relative abundance some- 

 times show larger year-to-year variation than is 



