Study shows eastern tropical pacific ocean dolphin populations improving

Jun 05, 2008
Northeastern Offshore Spotted Dolphin
The Northeastern Offshore Spotted Dolphin has a falcate, or sickle-shaped dorsal fin and light spotting on the belly. Credit: NOAA - PRD Southwest Fisheries Science Center

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 fishery.

"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. A summary of 2006 ETP dolphin abundance estimates may be found at, swfsc.noaa.gov/textblock.aspx?… tMenuId=228&id=12816

Source: NOAA National Marine Fisheries Service

Explore further: Evolution: The genetic connivances of digits and genitals

add to favorites email to friend print save as pdf

Related Stories

Lack of diversity a weak link for dolphins

Jul 04, 2014

Limited gene flow between groups of Australian snubfin and Indo-Pacific humpback dolphins in WA's north may make them more vulnerable to the environmental impacts of coastal industrial developments.

Genetic study reveals vulnerability of northwest dolphins

Jul 02, 2014

New study estimating population genetic structure of little-known dolphins inhabiting Western Australia's north coast highlights vulnerability, according to a study published in the open-access journal PLOS ONE by Alex B ...

Roebuck Bay, a special place for snubfin dolphins

May 26, 2014

One of the great scientific surprises in recent times is how an inshore dolphin with a melon shaped head and smiley mouth, was discovered as Australia's first endemic species of dolphin as recently as 2005.

Recommended for you

Scientists develop 3-D model of regulator protein bax

35 minutes ago

Scientists at Freie Universit├Ąt Berlin, the University of Tubingen, and the Swiss Federal Institute of Technology in Zurich (ETH) provide a new 3D model of the protein Bax, a key regulator of cell death. When active, Bax ...

Evolution: The genetic connivances of digits and genitals

17 hours ago

During the development of mammals, the growth and organization of digits are orchestrated by Hox genes, which are activated very early in precise regions of the embryo. These "architect genes" are themselves regulated by ...

Study: Volunteering can help save wildlife

17 hours ago

Participation of non-scientists as volunteers in conservation can play a significant role in saving wildlife, finds a new scientific research led by Duke University, USA, in collaboration with Wildlife Conservation ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.