(Salem, OR) -- Dog owners are warned to watch their animals near Willamette Valley streams. This is the time of year when the Oregon Department of Fish and Wildlife return salmon carcasses to rivers and streams. Salmon normally spawn and then die in the rivers. When hatcheries spawn salmon for future smolt releases, the carcasses are left in rivers and streams to decompose. Their nutrients go into the river and they're eaten by animals including bears, otters, raccoons, and vultures. The decaying salmon are a threat to dogs, because they can carry a bacteria that's potentially fatal. From September through December dog owners should be vigilant around rivers.