Sea Lampreys invade the Crystal River

By Chuck Olson
Sun contributor
Invasive sea lampreys are in the Crystal River. More than 50 were seen entering the river from Lake Michigan in late May and early June. Spawning pairs were found in the river on June 3 and June 25.
Sea lampreys are aggressive, attach to their prey with a suction-cup-like mouth, use several rows of rasp-like teeth to open a wound, and feed on the victim’s body fluids. Lamprey saliva contains an anti-coagulant that keeps the wound open for several hours.
Photo by Jeff Rabidoux

These predacious, eel-like fish native to the Atlantic and Mediterranean Oceans used the Welland Canal for entry to Lake Erie.
First observed in Lake Erie in 1921, lampreys quickly spread to all of the upper Great Lakes. Preying on other species of fish, including lake trout, whitefish, walleye and salmon, lampreys were responsible for the near collapse of the Great Lakes fishery. Their attacks on these native, large predators allowed the population of alewives, another invasive species, to explode. Control efforts during the ‘40s and ‘50s seemed to bring lamprey populations under control, but resurgence to pre-1950 levels has been reported for the northern portions of Lakes Michigan and Huron.
Like salmon, lampreys move into streams and rivers to spawn. Spawning begins when water temperature reaches about 50 degrees Fahrenheit and usually ends when water temperature reaches 68-70 degrees. A clean, gravelly bottom in rapid water is required for spawning and a single female may drop 60 to 70 thousand eggs. Larvae remain in the stream for several years, buried in mud or under rocks, and filter-feed until reaching a length of four to eight inches. While there, they release a pheromone that attracts adults to streams where spawning has been successful, then metamorphose into the predacious form and migrate to open water, usually in November and December. After a year or two of voracious attacks on other fish, they develop into the adult form and return to streams and rivers to spawn, after which they usually die.
Lampreys are not eels, but are classified as vertebrates even though they have no bones but a soft, cartilaginous structure. Larvae are white beneath and lead-colored to silvery above. The spawning pairs observed in the Crystal River were of two forms: an olive-green color, 24 to 28 inches long; and a darker, brownish-black color, 16 to 20 inches long. Both had seven open gills on each side, well-developed dorsal and ventral fin-folds, but no paired fins. Their mouths had 10 to 12 circular rows of hooked teeth. These three spawning pairs were observed on the gravel bar just south of County Road 675, approximately 75 yards east of the junction of M-22 and CR-675 — at the downstream end of the culverts at the last canoe-portage before the river reaches Glen Arbor.
Presence of these spawning lampreys was reported to the U.S. Fish and Wildlife Service Ludington Biological Station, the center for lamprey control in Lake Michigan. In response to some questions asked, the fishery biologists responded as follows: “Lampreys only feed on cold-blooded prey, but they have been known to attach to humans, ships, etc. The chances of wading in a stream and having a lamprey attach to your leg are probably small, but anything is possible.” They also indicated that a survey of the Crystal River will be conducted in the fall to determine if the lamprey larval population is large enough to merit treatment. Sometimes eggs do not hatch, or larval survival is so low that control measures are not warranted. The population in the Leland River, for example, was found to be great enough that it was treated this year.