Hi Tweets,

Looks like they finally found the cause of the heavy casualties in the
Salton Sea this year.

Peggi


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>----------------------- Message requiring your approval ----------------------
>Sender: WHadmin at nbs.gov (WHadmin)
>Subject: News Release: Dinoflagellate caused mortality at Salton Sea
>
>
> News Release
>
> Lethal Parasite Prime Suspect in Fish Kills at Salton Sea
> Investigators seeking causes of recurrent massive die-offs of fish and
> water birds at California's Salton Sea may have identified a principal
> culprit, according to Dr. Milton Friend, director of the National
> Wildlife Health Center.
>
> The finding comes as a new die-off of tilapia, the predominant fish
> species in the Salton Sea, has been reported with more than one
> million dead fish over a three-mile stretch at the north end of the
> Sea, Department of the Interior officials said.
>
> Drs. Tonie Rocke and Lynn Creekmore, scientists from the US Geological
> Survey's National Wildlife Health Center (Madison, Wis.), conducted a
> field investigation in late August that focused on collecting sick or
> freshly dead fish from locations where most of the bird mortality was
> occurring. In collaboration with NWHC studies, Dr. Jan Landsberg, a
> research scientist in aquatic health at the Florida Department of
> Environmental Protection, examined gills from 23 fish collected at the
> Salton Sea for parasites. She found 22 to be infested with moderate to
> high levels of a lethal parasite of warm-water marine fish.
>
> The parasite, a dinoflagellate known as Amyloodinium ocellatum, is
> recognized as a persistent disease-causing agent that causes serious
> mortalities in fish-farming facilities and public or home marine
> aquaria. Under closed conditions, such as aquaria and apparently also
> in the Salton Sea, the investigators reported, parasite levels can
> build up to extremely high levels in fish. Healthy fish in aquaria can
> die after only 12 hours of exposure to Amyloodinium.
>
> Like other USGS science centers, the National Wildlife Health Center
> has a primary responsibility for assisting the public land managers of
> the Interior Department. "Because a national wildlife refuge occupies
> a significant portion of the Salton Sea, the Health Center's
> assistance was sought and delivered," said USGS Chief Biologist Dennis
> B. Fenn.
>
> "Over the last five years", Dr. Friend said, " the Salton Sea has been
> the site of several major die-offs. Disease problems in birds have
> included avian cholera, Newcastle disease, avian botulism and
> undiagnosed mortality in eared grebes. Disease problems in fish have
> been less well defined, but infections with a type of bacteria known
> as Vibrio spp. have been identified as the potential cause of some of
> the massive fish mortalities".
>
> In late summer and early autumn of 1996, a large mortality event in
> birds was found to be caused by avian botulism. This outbreak resulted
> in the death of more than 14,000 fish-eating birds including 1,400
> endangered California brown pelicans and 10-12% of the west coast
> population of American white pelicans. At the same time, a die-off also
> occurred in tilapia. These fish were suspected to be the source of the
> botulism toxin for the birds.
>
> In August 1997, another outbreak of botulism occurred in fish-eating
> birds. Over 605 carcasses including 234 gulls, 138 brown and white
> pelicans, and 135 herons and egrets were picked up. Again, sick and
> dead tilapia were observed at the same time.
>
> The suspect parasite is found worldwide and infects more than 100
> species of marine fish in North America alone. In wild fish, the
> number of parasites per fish is typically very low, and they do not
> usually die from the infestation.
>
> When present at levels as high as those detected in tilapia from the
> Salton Sea, the parasite impairs respiratory function and can
> suffocate the fish. Diagnosis is based on finding the attached feeding
> stage of the parasite present in gill scrapings. Since the life cycle
> of Amyloodinium can be completed in less than one week at high
> temperatures and in high saline conditions, like those currently
> present at the Salton Sea, it is expected that massive and lethal
> infestations can develop rapidly.
>
> Now that the parasite is present in the Salton Sea, and is able to
> reproduce without control, persistent, chronic die-offs of fish may be
> expected to continue, the scientists said. High salinity is optimal
> for this parasite; it does not live in freshwater or in low salinity
> conditions. The connection between this parasite, other bacterial
> infections in fish and the occurrence of botulism in fish-eating birds
> is still under investigation. Along with environmental stressors and
> other disease-causing agents identified in fish and birds,
> Amyloodinium represents another threat to the overall health of the
> Salton Sea ecosystem.
>
> The USGS-managed Wildlife Health Center is the foremost wildlife
> diagnostic and investigative facility of its type, devoted to
> identifying causes and possible management responses for episodes of
> death or debilitation among free-ranging wild creatures throughout the
> United States and -- on a consulting basis -- other nations.
>
> --usgs/brd--
>.-
>
>
Ben & Peggi Rodgers
Aptos, CA (near Santa Cruz 122 W, 37 N)
USA
woodduck at cruzio.com
http://www2.cruzio.com/~woodduck/


"A bird does not sing because it has an answer,
It sings because it has a song"