GEOGRAPHIC-VARIATION IN EXTERNAL MORPHOLOGY OF THE SPINNER DOLPHIN STENELLA-LONGIROSTRIS IN THE EASTERN PACIFIC AND IMPLICATIONS FOR CONSERVATION

Variation in color pattern, dorsal fin shape, and body length exhibit sharp north/south gradients centered at about 5-10-degrees-N latitude and east/west gradients at about 120-125-degrees-W longitude. A conservation zone with boundaries in these regions would provide protection for the morphologically unique eastern spinner dolphin Stenella longirostris orientalis. A radial pattern of geographic variation in the eastern Pacific and a complex pattern of discordant variation outside the core range of S. l. orientalis suggest that the present separate management of "whitebelly" spinner dolphins (which comprise a broad zone of hybridization/intergradation between S. l. orientalis to the east and the pantropical spinner dolphin S. l. longirostris to the west and southwest) north and south of the Equator may not be justified on the grounds of conservation of distinct populations.