AIM: Provide finer resolution of the infectious zone in the lower Klamath River

BACKGROUND: Enteronecrosis is a leading disease of Klamath River salmonids, causing mortality in outmigrating juvenile Chinook and coho salmon. Sentinel fish studies conducted at multiple time points over several years have consistently identified the area immediately above Beaver Creek (Rkm 259) as highly infectious, but with mortality in Chinook salmon occurring as far downriver as Seiad Valley (Rkm 208). This pattern is supported by river water sampling, which targets waterborne Ceratomyxa shasta spores. However, data from surveys of the parasite's polychaete host, suggest this highly infectious zone may extend upriver to around the confluence of the Shasta River (Rkm 280; itself not a source of the infectious stage of the parasite). Characterization of the infectious zone is coarse, with consistent data available only from four index sites in the lower river, below Iron Gate Dam. This study more accurately defined this zone using developed water sampling and molecular methods.

APPROACH: In 2009, replicate water samples were collected on three days spanning a six week period at 16 sites along 79 Rkm of the lower Klamath River; a further 6 sites and 76 Rkm were included on the final day.  River water samples were taken at 3 time points at each site, at 9 or 10 am, 12 or 1pm and 3 or 4pm on May 13, June 3 and June 24. The water was filtered using a vacuum pump, the DNA that was captured was extracted using a kit and any parasite DNA present was quantified with a qPCR assay. These data produce a longitudinal map of parasite density in this section of the river for each time period which can be used to identify areas that could be targeted for control of polychaete populations.

Collaborators: Karuk Tribe, Yurok Tribe



 Barth Infectious Zone

Map of a section of the lower Klamath River (below Iron Gate Dam) showing the 16 primary sampling sites. The region encompasses the confluences of the Shasta and Scott Rivers and two monitoring index sites, Beaver Creek (KBC) and Seiad Valley (KSV). 

For the full report on the study, click here




REPEAT: The 2009 study indicated that in that year the infectious zone was more extensive than we had expected. Thus we repeated the study again in 2010, beginning the first water sampling earlier (April 26) and expanding the targeted stretch of river to include 25 sites covering approximately 180 Rkm from Orleans to east of the Shasta River.  Additional water collections occurred May 19 and June 16.  Once again, 3 x 1L water samples were collected 3 times, 3 hours apart, each day.

For a summary of the first part of the 2010 Infectious Zone study, click here


REPEAT: The position of highest parasite levels in the infectious zone differed between 2009 and 2010. The study was repeated a third year in 2011 to track this movement between years.  In response to cooler temperatures, higher flows and low parasite levels detected in the Klamath River main stem monitoring water samples, sampling occurred at only six sites (spanning 62Rkm) on April 28 and May 19.  On June 23 and August 11, intensive sampling occurred at 24 sites spanning 195Rkm.  




For a summary of the April and May sampling, click here.