Image provided by: University of Oregon Libraries; Eugene, OR
About Wallowa County chieftain. (Enterprise, Wallowa County, Or.) 1943-current | View Entire Issue (Feb. 12, 2020)
B8 Wallowa County Chieftain NEWS Wednesday, February 12, 2020 WHAT DO KOKANEE EAT? Ongoing Wallowa Lake study aims to find out Results can help pave the way for sockeye reintroduction By Stuart Wolpert and Daniel Stolte Univ. California, Los Angeles By Alan Moore For the Chieftain An ongoing study of Wal- lowa Lake’s kokanee and their food sources aims to improve lives of kokanee, and also help fisheries biologists understand if the lake has the resources to sup- port reintroduction of sockeye. {span}It might be easy for the casual observer to think Northwest fishery management is all about the big stuff: big riv- ers, big dams, big projects, big dollars. {/span}But at Wallowa Lake, fishery co-managers are focusing in on the little stuff, too. Not only is there hope the added perspective will help with the management of the lake’s cur- rent salmon population, it might even help inform future efforts to bring another one back. Kokanee are the salmon spe- cies in Wallowa Lake today — the same species (Oncorhynchus nerka) as sockeye. Kokanee are the land-locked version of sock- eye — or rather the sockeye who choose to stay at home and not migrate to the Pacific. (This is much the same as steelhead and rainbow trout — both the same species, but steelhead migrate to the ocean snd rainbows stay in their home streams.) the sockeye having were exterpated from the lake system about 1904 through fishing and the construction of the dam. Biologists know kokanee feed primarily on an array of tiny aquatic critters called zoo- plankton. These tiny organisms are found throughout the lake in a variety of species, abundance, densities and depths. A micro- sized shrimp called “mysis” is in the lake too, introduced in 1965 in hopes of growing big- ger kokanee. But co-managers believe mysis tend to occupy dif- ferent depths and are not a large part of the kokanee’s current diet. Pieced together with water chemistry and other factors, variables such as these com- Resistant to flu? Credit the first flu you got in childhood Hemming1952 Kokanee salmon schooling in a stream that flows into Lake Tahoe, Calif. Kokanee are the same species of fish as sockeye. They remain in freshwater rather tham migrating to the ocean. prise what biologists call the kokanee’s “food web,” some- thing co-managers hope to bet- ter understand. Not surprisingly, what happens in the food web determines much of what hap- pens with the kokanee. “Kokanee feed on zooplank- ton in the water column,” said Kyle Bratcher, acting district fish biologist for the Oregon Department of Fish and Wildlife in an e-mail. “Anecdotal infor- mation suggests that plankton abundance also fluctuates and is likely a main driver in kokanee abundance and size. This is something we are hoping to bet- ter understand with the food web study.” Since last year, a partner- ship made up of the Nez Perce Tribal Fisheries, ODFW and the U.S. Geological Survey has been conducting sampling work toward developing a working model of the kokanee food web. “We took several zooplank- ton samples in 2019 and will again in 2020,” said Shane Vat- land, research project leader with Nez Perce Tribal Fisheries in an e-mail. “We also collected kokanee stomach samples. So, we will get a clearer picture of what exactly kokanee are eating and how many are available in the lake.” Co-managers know Wallowa Lake kokanee tend to cycle in size and abundance over periods of years. In 2010, Ron Camp- bell from Pendleton landed the standing world record kokanee here (9 pounds, 10 ounces), and several other unusually large fish were caught around that time. Subsequent years saw a return more toward normal. Ongoing annual surveys mea- suring kokanee spawner size and sex offer some clues as to what might be coming in future years, but why is what co-man- agers would like to better under- stand. The hope is that the com- bination of survey data and food web modeling will give co-man- agers new tools to use in making management decisions. “The kokanee population is highly cyclical on an eight- to 12-year cycle,” Bratcher said. “The size of kokanee dropped after those years when the records were being broken. We have seen sizes increase in the last few years with some larger fish on the spawning grounds this year. Part of the food web study is to help us understand this cycle, as it appears to be highly food-driven.” In addition to knowing what kokanee are eating, another important metric in their over- all assessment is what’s eating them. Wallowa Lake does have a population of nonnative lake trout, which tend to feed vora- ciously on other fish, including kokanee when conditions are right. Bratcher said while they will continue to closely mon- itor lake trout interaction with kokanee, he does not believe lake trout predation is a large driver in kokanee abundance at this time. Recent discussions surround- ing the reconstruction of Wal- lowa Lake Dam have included the primary infrastructure changes necessary to begin to think about reintroducing sock- eye, namely passage for fish out of and into the lake at the dam site. Restored fish pas- sage would represent an enor- mous step toward that goal, but still clearly one of an unknown number facing those working to achieve sockeye reintroduction successfully. Partners working on the Wal- lowa Lake kokanee food web project say the insights gain to better understand kokanee could be useful in any future sockeye reintroduction efforts as well. Juvenile sockeye in freshwater tend to feed largely on zooplank- ton, for example, just as kokanee do. “The food web study could inform us how to approach a sockeye reintroduction in the future in terms of numbers and timing of releases,” Bratcher said. Partners expect to have a working food web model com- pleted by 2021. Why are some people better able to fight off the flu than others? Part of the answer, according to a new study, is related to the first flu strain we encounter in childhood. Scientists from UCLA and the University of Arizona have found that people’s ability to fight off the flu virus is determined not only by the subtypes of flu they have had throughout their lives, but also by the sequence in which they are been infected by the viruses. Their study is published in the open-ac- cess journal PLoS Pathogens. The research offers an expla- nation for why some people fare much worse than others when infected with the same strain of the flu virus, and the findings could help inform strategies for mini- mizing the effects of the seasonal flu. Scientists reported in 2016 that exposure to influenza viruses during childhood gives people par- tial protection for the rest of their lives against distantly related influ- enza viruses. Biologists call the idea that past exposure to the flu virus determines a person’s future response to infections “immuno- logical imprinting.” For example, people who had their first bout of flu as children in 1955 — when the H1N1 was cir- culating but the H3N2 virus was not — were much more likely to be hospitalized with an H3N2 infection than an H1N1 infection last year, when both strains were circulating, Worobey said. “The second subtype you’re exposed to is not able to create an immune response that is as protec- tive and durable as the first,” he said. Around the world, influenza remains a major killer. The past two flu seasons have been more severe than expected, said Michael Worobey, a co-author of the study and head of the University of Ari- zona’s department of ecology and evolutionary biology. In the 2017- 18 season, 80,000 people died in the U.S., more than in the swine flu pandemic of 2009, he said.
