IMIS

This 1993 line-transect survey was designed to make abundance estimates of the northern stock of common dolphin, Delphinus delphis, in the eastern Pacific. This stock of dolphin is taken in the tropical tuna fishery. The index of relative abundance for this stock, computed from sightings on tuna vessels, has declined substantially in the last decade. However, because tuna vessels cover only the southern portion of the stock's range, the declines in the index may be due to a northward shift in distribution, rather than an actual decline in abundance. The 1993 survey was designed to produce the first range-wide estimates of abundance for the northern common dolphin and its recently described congener, Delphinus capensis. This survey was conducted by the NOAA Southwest Fisheries Science Center aboard NOAA Ships McArthur and David Starr Jordan for a combined total of approximately 32,000 kilometers surveyed from late July to early November 1993. This dataset provides the time-date and geographical coordinates, by species/stock, of all cetaceans detected during the survey, as well as the daily and intra-daily start and end points of the line-transect survey. Purpose The primary objective of the cruise was to survey the area inhabited by the northern stock of common dolphins, and to make an estimate of its absolute abundance in order to assess the impact of the dolphins killed by the United States and international yellowfin tuna purse seine fleet in the eastern tropical Pacific.