The Whirling Disease Initiative is fundamentally a scientific research program dedicated to development of practical management solutions to maintain viable, self-sustaining wild trout fisheries in the presence of the whirling disease parasite.

More than 120 individual research investigations have been conducted since the Whirling Disease Initiative was established in 1997. In the early years, research focused on solving questions of basic biology. Increasingly, the studies have focused on management applications [more about research topics]. An extensive network of researchers at agencies and academic institutions across the country have been part of this research initiative, yielding vital information and management options to address whirling disease.

What have we learned? Read on to discover advancements in whirling disease research and management. Check out the monthly research spotlight, descriptions of past Initiative research, summaries of current Initiative research, proceedings of the annual Whirling Disease Symposium, and full research reports in our online bibliography.

Research Spotlight:

Evaluation of Management Actions to Control the Spread of Myxobolus cerebralis in a Lower Columbia River Tributary

Jerri L. Bartholomew and Antonio Amandi

WDI Funding Cycle 2003-2004 , Full Final Report [374 kb pdf]

Introduction

In the fall of 2001, the whirling disease parasite Myxobolus cerebralis was detected at a private trout farm located on Clear Creek, a tributary of the Clackamas River in northwest Oregon. While the parasite had been widely detected in eastern Oregon tributaries to the Snake River, this was the first detection of the parasite in western Oregon. Subsequent investigations determined that the hatchery was most likely infected by the surface water of Clear Creek, which was the hatchery's primary water supply. It was unknown how the parasite was introduced into Clear Creek. This investigation took place soon after the hatchery was closed in 2003.

Location

The study sites were located in northwestern Oregon on Clear Creek, a tributary to the Clackamas River which is part of the Willamette River System in the Lower Columbia River Basin. The Clackamas River is home to anadromous and resident salmonids including steelhead, Chinook salmon, coho salmon, cutthroat trout and rainbow trout.

Objectives

First, sentinel rainbow trout fry were held in Clear Creek at locations upstream and downstream of the hatchery to determine whether the hatchery was the primary source of the M. cerebralis infection.

Second, oligochaete worm populations were surveyed from the hatchery and from sites in Clear Creek. This was to determine the relative abundance of Tubifex tubifex, the alternate host of the parasite, and to determine the prevalence of M. cerebralis infection among them.

Third, outmigrating steelhead trout were collected from traps in the Clackamas River and spawning adult Chinook salmon were collected during stream surveys to determine whether M. cerebralis infections were present in those fish populations.

Summary of Findings

Sentinel Fish Exposures: No infections of M. cerebralis were detected in sentinel fish exposed at Clear Creek sites upstream of the hatchery. This indicated that the parasite was not widely established in Clear Creek and that the hatchery itself may provide the source of infection for fish downstream. M. cerebralis was detected at a distance of six miles downstream of the hatchery nine months after the hatchery closure, however infection was not detected in sentinel fish downstream of the hatchery between December 2003 and September 2004.

Oligochaete Worm Surveys: Surveys of oligochaete worm populations in Clear Creek included Tubifex tubifex in samples obtained from the hatchery and at the mouth of the river mainstem. Genetic analyses revealed these worms were of two known susceptible lineages of T. tubifex (I and III). No resistant lineages of T. tubifex were found. The form of M. cerebralis infective to fish, the triactinomyxon (TAM), was found only in water samples from the hatchery and not from samples collected in Clear Creek. The researchers concluded that it was unlikely that M. cerebralis was established in its invertebrate host in mainstem Clear Creek.

"If we assume our sampling accurately represents the composition of oligochaetes in Clear Creek, and if infected T. tubifex were eliminated from the hatchery, it is unlikely that M. cerebralis would become established in this river," researchers said,"The absence of the invertebrate host from the majority of the system limits the opportunity for myxospores from infected stray fish to propagate and currely the only apparent source of infective stages for fish are hatchery worms."

Outmigrant and Spawning Salmon Examinations: Unfortunately, no adult steelhead or outmigrant steelhead data were available for the analysis. However, 50 adult Chinook salmon were collected during spawning surveys (47 of the 50 fish were wild, 3 were hatchery fish). None of these fish had spores that could be positively identified as M. cerebralis. Other myxozoan spores found included Henneguya sp. and unidentified spores that were likely species of the genus Myxobolus. These results indicated that M. cerebralis had not been established in the river for more than three years.

Potential Management Actions

The information collected as part of this investigation supported the continued closure of the hatchery until the infected sediment and T. tubifex could be safely removed.

Further, the researchers recommended that continued surveillance of stray anadromous salmon would provide valuable information on the likelihood of future introductions into the river system.

Questions?

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