Fishery Bulletin 90(1). 1992 



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



Figure 4 



Smoothed abundance trends of pooled northern and southern 

 offshore stocks of spotted dolphin Stenella attenuata 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 6 



Smoothed abundance trends of whitebelly stock of spinner 

 dolphin Stenella longirostris 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 1985 1987 1998 1989 



Figure 5 



Smoothed abundance trends of eastern stock of spinner 

 dolphin Stenella longirostris 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 7 



Smoothed abundance trends of northern stock of common 

 dolphin Delphinus delphis in the eastern tropical Pacific. 

 Broken lines indicate approximate 85% confidence limits. See 

 Figure 1 for more details. 



The estimated trend for whitebelly spinner dolphins 

 (Fig. 6) is similar to that for eastern spinner dolphins 

 and northern offshore spotted dolphins. There is some 

 evidence that abundance in 1988 was higher than in 

 1982 (P=0.05), but no other comparisons with 1988 are 

 significant. The 1982 smoothed estimate is significantly 

 lower than those for 1976-78. 



End effects in Figure 7 give rise to an implausible 

 trend in numbers of northern common dolphins dur- 

 ing 1975-78. Since 1980, there may have been a decline 



in this stock, but no smoothed estimates differ signif- 

 icantly. The central stock of common dolphins (Fig. 8) 

 shows evidence of a steep decline from 1977 to 1983, 

 with stability since. The smoothed estimate for 1988 

 is significantly lower than for all years preceding 1980 

 (P<0.05), but does not differ significantly from any 

 later estimates. Data on the southern stock of common 

 dolphins are sparse. There may have been a decreas- 

 ing trend (Fig. 9), but unsmoothed estimates fluctuate 

 widely and no smoothed estimates differ significantly. 



