Biologists note small chinook numbers; many fish are sick Biologists are seeing few young Chinook salmon on the Klamath River and its tributaries this year, and already some of them are falling sick, possibly with diseases that have killed hundreds of thousands of fish in recent years. Agencies are still waiting to hear from a laboratory exactly what's making an increasing number of fish ill. Scientists are still trying to understand the dynamics of how the Klamath fish are getting sick and what can be done about it. With a marginal run of adult Chinook this fall, fewer young salmon were apparently produced. But heavy rains in late December and January may have also wiped out many of the salmon redds, nests where salmon eggs rest until they hatch. ”We're just not seeing a lot of fish,” said Randy Brown, deputy field supervisor for the U.S. Fish and Wildlife Service's Arcata Field Office. Chinook are the mainstay of the Klamath's tribal and sport river fisheries, and for ocean commercial and recreational fisheries. This fall, so few adult fish are expected to return to the river that commercial fisheries were canceled up and down the coast, while tribal and sport fisheries were slashed. Federal legislators and California's and Oregon's governors have been pressing for government aid to buoy the latent fishing fleet and other businesses. The California Department of Fish and Game watches fish on both the Scott and the Shasta rivers, main tributaries of the Klamath. Fish and Game biologist Bill Chesney said the number of adults that returned last year wouldn't explain the low numbers of chinook being seen this year. He suspects the big winter rains roiled redds. ”They never had a chance to incubate and get out of the gravel,” Chesney said. In the tributaries, at least, there have been no obvious disease outbreaks. And one piece of good news is that there are more coho salmon -- the Chinook's threatened cousin -- than in recent years. Low juvenile numbers don't necessarily equate to poor runs three and four years out, Chesney said. If the little salmon can get to the ocean, there are currently favorable conditions, with plenty of food generated by upwelling caused by strong northwest winds. That often means that a higher percentage of the young salmon that migrate down the Klamath to the sea survive to return later. But the lower Klamath River has in recent years been hard on salmon. Outbreaks of parasites have stricken young fish, which are more susceptible to disease when they are stressed by high water temperatures or poor water quality, both common during the summer. This year, since the winter was so wet, there are higher flows in the main river than in recent years. Some believed that big flows would cut the number of tiny worms that are an intermediate host for the parasites, potentially reducing the number of “hot spots” in the river where fish are most vulnerable. Oregon State University researcher Jerri Bartholomew said it does appear that the worms are not in all the places they have been in recent years. The presence of the worms is not related to the presence of disease in fish. There are some areas where there are lots of uninfected worms, and so play no role in infecting fish. In the lower river, there appear to be fewer -- but heavily infected -- worms. The longer young fish are exposed to parasite spores the more likely they are to become infected. Also, the higher the water temperature, the more abundant the parasites, scientists believe. But if the winter rains helped, they did not eliminate the problem. ”It may not be a single-year cure,” Bartholomew said. “It may not be a cure at all.” |
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