04 Heckel FISH 98(4) - Fishery Bulletin

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Km 103 Carretera Tijuana-Ensenada. 22800 Ensenada,. Baja California, México. Guillermo A. Compeán Jiménez. Programa Nacional de Aprovechamiento del ...

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Abstract–This

study examines the question of whether the evasive behavior of northeastern offshore spotted dolphins (Stenella attenuata) during fishing for tuna (by the Mexican fleet) varies in geographic areas of the eastern Pacific Ocean (EPO). It also investigates whether evasion differs between northeastern offshore spotted and eastern spinner dolphins (Stenella longirostris orientalis). Observations recorded in the database of the Mexican Programa Nacional de Aprovechamiento del Atún y de Protección de Delfines (PNAAPD) from 1992 to 1995 were analyzed. The calculated evasion index was the estimated percentage of dolphins that evaded capture in relation to the herd’s estimated initial size in each set. Evasion index by set was averaged in 2 × 2 quadrants and then used to draw a contour map. Three areas were outlined with low (25%), medium (44.44%), and high (71.80%) median evasion indices. These areas were significantly different (P