Estimation of density of dolphin schools in the eastern tropical Pacific using line transect methods

Aerial and research ship surveys were conducted from 1977 through 1983 to provide data to estimate density of dolphin schools in the eastern tropical Pacific. Line transect theory was used to compute estimates. Several assumptions of line transect theory were investigated for both aerial and ship data. Correction factors were developed to help accommodate violations of the assumptions. Estimates are presented for data stratified into an inshore area surveyed by planes and an offshore area surveyed by ships. These estimates were combined to determined density for the entire area. Densities for the inshore, offshore and all areas were 4.18, 2.04, and 2.71 schools/1000 km*2 , respectively. Maximum adjustments for possible biases due to adverse sea state and sun glare conditions increased the inshore estimate by 76% and the offshore estimate by 64%; however, these adjustments were based upon assumptions which were likely violated. 1984 NMFS (National Marine Fisheries Service) SWFSC (Southwest Fisheries Science Center) Library Public Domain 1930