NOAA Study Shows Eastern Tropical Pacific Ocean Dolphin Populations Improving

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Tropical Pacific Ocean Dolphin Two Dolphin Stocks May Be Recovering from Tuna Fishing Practices

The numbers of Northeastern offshore spotted and eastern spinner dolphins in the
eastern tropical Pacific Ocean are increasing after being severely depleted because of
accidental death in the tuna purse-seine fishery between 1960 and 1990, according to biologists
from NOAA’s Fisheries Service.

“These estimates are encouraging because they are consistent with what we would
expect to see if these stocks are recovering, now that reported fishery mortality has been
dramatically reduced,” said Dr. Lisa Ballance, director of NOAA’s Southwest Fisheries Science
Center protected resources division. “However, we have to be careful not to jump to final
conclusions. We need to resolve the uncertainties around these estimates before we can
definitively say these stocks are recovering.”

Between 1960 and 1990, the northeastern offshore spotted and eastern spinner dolphin
populations dropped to 20 percent and 30 percent, respectively, of their pre-fishery levels when
dolphins were caught and died in tuna purse-seine nets. Since the early 1990s, however, the
number of reported dolphin deaths has been very low because of severe restrictions on the

“We expected to see these populations begin their recovery years ago, because
fishermen have been so successful at reducing dolphin deaths,” said Tim Gerrodette of NOAA’s
Fisheries Service. “The new data are the first to indicate the beginning of a recovery, but these
initial indications are not enough to be confident that the populations will continue to grow.”

Researchers emphasize the need to continue to monitor dolphin populations at sea
through comprehensive ecosystem research cruises, and to conduct an updated dolphin stock
assessment that will include not only these most recent abundance estimates, but also
additional information on dolphin life history, fishery mortality, and the ecosystem. This
assessment will enable a more definitive interpretation of whether these abundance estimates
indicate Eastern Tropical Pacific dolphins are recovering and the degree to which the fishery
and other factors affect the conservation of these stocks.

Today’s report stems from a series of research cruises conducted since 1986. It
presents new estimates of abundance for 10 dolphin stocks for each survey year between 1986
and 2006. These estimates may be found at

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