Monitoring Trends in Dolphin Abundance in the Eastern Tropical Pacific using Research Vessels over a Long Sampling Period: Analyses of 1987 Data

Dunng 1987. the National Manne Fishenes Service conducted the second in its senes of long-term research ship S U N C ~ S to determine statusof dolphin stocks taken incidentally by tuna purse seinen in the eastern tropical Pacific Line transecf methodology was used by observers aboard two vessels for 120 days each Relative abundance estimates of northern offshore spotted dolphins are approximately I.Mo.ax) animals with a coefincnt of vanation of 0 262 This estimate was larger than the 1986 estimate of 929.MM northern offshore spotted dolphins. Relative sues of other stocks also vaned We examine reasons for these differences and discuss alternative methods of stratifying the dat