Tagging and learning about walleye in the lower Snake River

Unfortunately, this is not a good sign for salmon, steelhead, and other native fish in the Snake River. Recent work by Washington Department of Fish and Wildlife (WDFW) in the lower Snake River showed that walleye consume a lot of juvenile salmon, steelhead, and lamprey in the spring as they are moving through the reservoirs to get to the ocean. So, what has changed to cause the walleye population to grow and expand as fast as it did?

In the past ten years, numbers of several nonnative species in the lower Snake River increased, especially at and upstream of Lower Granite Dam (Figure 2). The most notable increases were seen in abundances of Siberian prawns which were first discovered in the Snake River in the mid-1990s. These prawns are only 2-3 inches long, but when there are a lot of them, they can become an important food source to fish. The WDFW diet study found they now provide an important food option for predator fishes during critical times when food was historically more scarce. American shad are another nonnative species that are becoming more prevalent in the Snake River. Walleye can now shift from eating juvenile salmonids and lamprey during the spring to prawns during the summer, then juvenile shad during the winter. A diet of prawns also allows juvenile walleye to better survive and grow to the size at which they convert to eating fish. We continue to collaborate with other agencies and tribes in the lower Snake River to learn more about walleye and ways to reduce the potential risk to salmon, steelhead, and other important species.