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Scientists at the Western Fisheries Research Center, Marrowstone Marine Field Station have designed a fish swim flume to investigate the effects of fish disease on swim performance and survival. This new capacity can be used for a wide variety of applications.

Researchers condition chinook in swim flume
(Left to Right) Dr. David Paez, Joanna Salzer, Dr. Jee Youn Hwang and Bill Batts observe as Chinook salmon are conditioned in the swim flume prior to swim performance trials. Groups of juvenile Chinook were exposed to infectious hematopoietic necrosis virus (IHNV), and later tested in the chamber along with non-exposed control fish to evaluate fitness consequences of virus exposure. Swim trials were conducted both before and after the physiological transition from freshwater to saltwater.

Similar to people, disease is often not fatal for fish and instead influences their health and behavior in subtle ways. This introduces many questions about how sublethal disease impacts can still result in mortality over time. For example, can diseases affect a fishes’ ability to migrate, reproduce, and outswim predators? Can changes in the environment, such as temperature, amplify the sublethal effects of disease and reduced survival?  These are some of the questions addressed by scientists at WFRC’s Marrowstone Marine Field Station, and they’re now able to dig further into these questions with their construction of a new fish swim flume.

A swim flume is an oval loop, equipped with a propellor designed to move water at varying speeds to test the swimming performance of multiple fish at once. Like treadmills do for humans, swim flumes let us measure a fishes’ behavior, endurance, and bodily response simultaneously. Fish are placed in the flume, water flow is adjusted, and performance is measured. Scientists test fish until they fail to resist the water current and are dragged to the back of the flume (similar to falling off the end of a treadmill). At this point, the fish are removed from the flume and assessed. By using fish that were previously exposed to pathogens and fish that were not, this approach lets our scientists see how specific types and intensities of disease might be impacting the overall health of a fish population.  Water parameters such as temperature, salinity and flow duration can also be controlled and can be used to test healthy or diseased fish in a range of environments.

Our new swim flume is already being put to the test. This summer, scientists Paul Hershberger, David Paez, and Gael Kurath are using the flume to assess whether the swimming performance of young Chinook salmon is impacted by exposure to Infectious hematopoietic necrosis virus (IHNV). Hershberger and Paez are also testing whether Viral Hemorrhagic Septicemia virus (VHS) impacts the swimming performance of herring.

Future scientific applications of the flume include evaluating the impacts of pathogens and disease on fish migration through water temperatures experienced with climate change. For example, this work can help address concerns expressed by the co-managers, Washington Department of Fish and Wildlife and Washington Treaty Tribes, regarding the extent to which the health of cold-water dependent Spring Chinook salmon populations will be affected.


Fish swimming in swim flume
Chinook salmon orient into the water current of the swim flume during a performance trial. The flume provides control over current speed, which is increased at specific time intervals while fish are monitored over a period of 1-2 hours.  Swim performance is determined by speed of current and total duration that each fish swims prior to exhaustion (when fish ceases swimming). Appropriate current speeds are calculated using the average body length of fish.
Researcher preparing to sample fish from swim flume
Dr. David Paez observes as Chinook salmon undergo a swim performance trial. Water velocity in the swim chamber is increased over a prescribed period to determine time of exhaustion for each individual fish. Virus-exposed and healthy control fish are swum together in a small group and must be watched carefully. Each fish is removed promptly at the time of fatigue and the trial is over when the final fish is collected.
Researchers processing fish samples in MMFS wet laboratory
(Left to Right) Bill Batts, Joanna Salzer, and Dr. Jee Youn Hwang sample fish during a swim performance trial. Once fish have completed swim trials they are euthanized and kept fresh on ice. Sampling includes length and weight measurements, and collection of a small portion of tissues to confirm the presence of virus. Quantity of viral RNA within the tissue is compared to duration of swim performance to evaluate whether fish that have more virus also fatigue more quickly when swimming. If so, this would indicate a sublethal fitness loss for the fish due to viral infection.

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