Sources/Usage: Public Domain. View Media Details

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.