Pantropical Spotted Dolphin: Stenella attenuata

Abstract

Unspotted at birth, this long-beaked dolphin develops light spots dorsally with adulthood. Adult length is from about 165 to 260cm, varying geographically. Weight is up to about 120kg. The skull overlaps that of the Atlantic spotted dolphin Stenella frontalis in all measurements and in tooth counts. The species is a member of the family Delphinidae. It occurs worldwide in tropical and some subtropical waters. The original population of over 2 million in the eastern tropical Pacific has been reduced 80% by bycatch in the tuna purse seine fishery. It feeds on small epipelagic fishes, squids, and crustaceans and on members of the deep-scattering layer that approach the surface at night. School size ranges from a few individuals to several thousand. In the eastern tropical Pacific these dolphins associate closely with yellowfin tuna, accounting for the massive bycatches in the tuna fishery. Females reach sexual maturity at 9–11 years and males at 12–15 years. Directed fisheries exist or have existed in many areas, and bycatches also occur in fishing nets of various types throughout the tropics. Massive kills of millions of pantropical spotted dolphins by tuna fisheries have focused much attention on this species since the 1960s.