SWFSC Cetacean Sightings during a Marine Mammal Survey in the Eastern Tropical Pacific (1508)

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.