boats are required to be inspected before launching and must have a Lake County Quagga/Zebra (QZ) Sticker on the watercraft. Shops in the vicinity carry out the inspection. At every entry to Lake County, signs warn boaters not to spread hydrilla in the county's bodies of water. Extensive management efforts have controlled the presence of hydrilla in Clear Lake, although it may return at any time. The lake is also the site of an annual "splash-in", the "oldest and largest seaplane gathering in the Western United States". The California Office of Environmental Health Hazard Assessment released an advisory statement regarding eating fish caught from the lake, based on the mercury level. Wildlife and vegetation The Clear Lake basin attracts large quantities of waterfowl, including mallards, western grebe, coots, various species of geese, ospreys, plovers, mergansers and many others. Wild turkeys, blacktail deer, gray squirrels, ground squirrels, skunks, river otter, raccoon, mink, and muskrat. There have been occasional sightings of mountain lion and ringtail. Opossums, red-tailed hawks, turkey vultures, and other species are also common. The endangered northern spotted owl is seen occasionally. Common reptiles and amphibians include the northwestern pond turtle, California king snake, Pacific gopher snake, garter snakes, northern pacific rattlesnake, common bullfrog and the rare giant salamander among many others. Much of the shoreline is developed, but parks, reserves, miles of open water and private land also exist allowing many opportunities for observing and enjoying nature. The county also hosts a growing population of the rare tule elk, recently reintroduced after being locally hunted to extinction one hundred years before. A large colony of bald eagles is found in the Cache Creek canyon. In addition to the native Clear Lake hitch (called chi by the native Pomo), the lake hosts channel catfish, white catfish, brown bullhead, crappie (both black and white species), and other native fish species, as well as Florida strain largemouth bass and carp placed by the Department of Fish and Wildlife for sporting purposes. Along the shoreline and creeks, there are aquatic growths of tule, cattail, willow, cottonwood, box elder, and many other types of riparian plant life. The streams feeding Clear lake contain Sacramento pikeminnow, California roach, and rainbow trout. Pacific lamprey are present in at least one stream, Kelsey Creek. Prior to the construction of a dam on the outlet of Clear Lake, both steelhead and Pacific lamprey ascended Cache creek to spawn