MEPS - Vol. 343 - Feature article

Populations of northeastern offshore spotted (top) and eastern spinner (bottom) dolphins in the eastern tropical Pacific have not recovered as expected. Photos: Robert Pitman (NOAA)

Wade PR, Watters GM, Gerrodette T, Reilly SB


Depletion of spotted and spinner dolphins in the eastern tropical Pacific: modeling hypotheses for their lack of recovery


Northeastern offshore spotted and eastern spinner dolphin populations have been reduced in the eastern tropical Pacific Ocean as a result of high levels of bycatch in the yellowfin tuna purse-seine fishery. Although the number of dolphins killed has been low since 1992, population modeling by Wade and colleagues indicates that both populations were still much below their carrying capacities in 2002. Both populations were estimated to be growing, but at slower rates than expected. Population modeling was not able to resolve whether the fishery was causing additional mortality or whether ecosystem changes have affected dolphin population dynamics. Effects of the fishery and ecosystem changes both remain tenable hypotheses for the lack of recovery.


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