Deadly Diseases Could Strike Bighorn Sheep plus 1 more

[USGS Newsroom <oc_web@xxxxxxxx>]

Title: USGS Newsroom

Deadly Diseases Could Strike Bighorn Sheep plus 1 more

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Deadly Diseases Could Strike Bighorn Sheep

Posted: 28 Aug 2013 10:18 AM PDT

Declining bighorn sheep populations may be vulnerable to some of the fatal diseases, including chronic wasting disease (CWD), that are found in their western U.S. habitats, according to a new U.S. Geological Survey study.

USGS National Wildlife Health Center (NWHC) research showed that bighorn sheep are likely susceptible to the deadly neurological diseases scrapie and CWD, which are occurring in or near natural bighorn sheep environments. These fatal diseases are caused by mysterious proteins called prions, and are known to infect domestic sheep (scrapie) and non-domestic deer, elk, and moose (CWD). The USGS study is published in the journal BMC Veterinary Research, and is available online.

"Bighorn sheep are economically and culturally important to the western U.S.," said Dr. Christopher Johnson, USGS scientist and senior author of the report. "Understanding future risks to the health of bighorn sheep is key to proper management of the species."

USGS laboratory tests found evidence that bighorn sheep could be vulnerable to CWD from either white-tailed deer or elk, and to a domestic sheep prion disease known as scrapie. However, none of a small number of bighorn sheep sampled in the study showed evidence of infection.

"Our results do not mean that bighorns get, or will eventually get, prion diseases," Johnson said. "However, wildlife species like bighorn sheep are increasingly exposed to areas where CWD occurs as the disease expands to new geographical areas and increases in prevalence."

The laboratory test results could be useful to wildlife managers because bighorn sheep habitats overlap with farms and ranches with scrapie-infected sheep and regions where CWD is common in deer, elk, and moose.

Bighorn sheep populations in western North America have declined from habitat loss and, more recently, epidemics of fatal pneumonia thought to be transmitted to them from domestic sheep. Prion diseases are another possible threat to this valuable species.

For more information on prion diseases such as CWD, please visit the USGS NWHC website.

Tracking Bull Trout Movement in Idaho's Arrowrock Reservoir

Posted: 28 Aug 2013 09:45 AM PDT

BOISE, Idaho — A new study released today details the migratory habits of a native and threatened population of bull trout in Arrowrock Reservoir, a critical source of irrigation water for southwestern Idaho. 

Scientists with the U.S. Geological Survey tracked the bull trout through the reservoir located in the Boise River Basin, using acoustic telemetry, in cooperation with the U.S. Bureau of Reclamation, which manages the reservoir. The study is one of several Reclamation is conducting with its partners to protect Arrowrock’s bull trout population. 

Arrowrock Reservoir is important winter habitat for the bull trout, listed as threatened under the Endangered Species Act. Scientists have known that bull trout migrate out of the reservoir in spring and summer to reproduce in the cold, clean water of the upper Boise River Basin. 

In the USGS study, eighteen bull trout were captured and implanted with acoustic tags that transmitted data about each fish's location, body temperature, and the depth at which the fish was swimming. Scientists tracked the fish from April through August 2012 in three parts of Arrowrock Reservoir: the Middle Fork Boise River arm, the South Fork Boise River arm, and the main body of the reservoir. The scientists also recorded water temperatures and dissolved oxygen concentrations in the reservoir, important factors for fish survival.

Key findings of the study include:

• Fish traveled an average distance of 5.2 kilometers (about 3.23 miles) within the reservoir.
• Fish tag temperatures on average were 3 degrees C (37.4 degrees F) lower than water surface temperatures during the study, ranging from 4.4 to 11.6 degrees C (40 to 53 degrees F).
• None of the tagged fish was detected in the deepest part of the reservoir near the dam, suggesting that passage through the dam is unlikely during the period when water releases are at their highest.
• None of the tagged fish was detected in the reservoir after June 1.
• From the first week of August through the latter part of September, little if any suitable thermal habitat remained for bull trout within the reservoir, because most recorded water temperatures exceeded 15 degrees C. 

These and other details of the study are available in the report, "Bull Trout (Salvelinus confluentus) Movement in Relation to Water Temperature, Season, and Habitat Features in Arrowrock Reservoir, Idaho, 2012."