Lamprey - it's a word that brings out a variety of emotions in anglers ... fear, hatred and disgust are the most common. Why? The picture of a blood-sucking creature that attaches to Great Lakes trout and salmon pops into their head. That creature is the sea lamprey, scientifically known as Petromyzon marinus, an invader from the Atlantic Ocean.
Factually, there are four "other" species of lamprey that are native to Michigan waters. These are the Chestnut, Silver, Northern Brook and American Brook lamprey. Two of these, the Chestnut and Silver, are predaceous, but cause few, if any mortality. Chestnut lamprey have not been found in the U.P. waters of Lake Superior, but are present in Minnesota streams and the north shore of Lake Superior in Ontario. They are common in Lake Michigan tributaries. Anglers, who regularly fish the Upper Manistee River, in the Lower Peninsula, are likely to encounter the Chestnut lamprey attached to a fish. The Chestnut rarely exceeds 6 inches in length as an adult and only "feeds" long enough to gain energy to reproduce.
Silver lamprey have been found in the lower reaches of the Ontonagon River. The American and Northern Brook lamprey are not predaceous, being filter feeders, eating microscopic plants and animals their entire life. They are present in many area streams and were observed spawning in the lower Pilgrim River this spring.
Sea lamprey, conversely, are a large problem and a great concern to fisheries managers. First, a history/biology lesson and then the rest of the story. Sea lamprey began colonizing the Great Lakes from their native Atlantic Ocean, when improvements to the Welland Canal were completed in 1919. They first entered Lake Michigan in 1936, Lake Huron in 1937 and Lake Superior in 1938. By the late 50s/early 60s, sea lamprey had decimated the lake trout population in Lake Superior. Sea lamprey wiped out lake trout populations in Lake Michigan by the late 1950s.
Lampreys are prehistoric jaw-less fish that superficially resemble eels, but they are not related. True eels have well-developed jaws and teeth, while lampreys have a sucker-type mouth, much like a rubber suction cup. Often they are called "lamprey eels," but that term is incorrect. Lampreys have been on Earth a very long time, actually pre-date dinosaurs and are estimated to be 500 million years old. They are very primitive, having no scales or bones, only cartilage and have a larval form.
Sea lamprey "run" up many Great Lakes streams, but not all, in late spring, when water temperatures reach 50 degrees. Portage Waterway streams, Coles Creek, Pilgrim River and Swedetown Creek, to name a few, are not invaded by sea lamprey. They build nests in gravel areas, much like steelhead and salmon, where the average female will deposit 80,000 eggs. The eggs hatch into a larval form, called an "amoceyte," and drift downstream to sandy/silty areas, into which they burrow. Here they live for from four to seven years, feeding on microscopic plants and animals, reaching a size of about 6 inches, before migrating out to Lake Superior to prey on lake trout, whitefish, steelhead, brown trout and salmon. It has been estimated that an adult lamprey will consume 40 pounds of fish during its approximate 18 months in Lake Superior as an adult. Therefore, control is a must!
Sea lamprey control in the five Great Lakes is delegated to the U.S. Fish and Wildlife Service, Marquette and Ludington offices. They expend millions of dollars each and every year on reducing numbers of sea lamprey, without which lake trout populations would disappear. Control of sea lamprey populations is an integrated approach through the use of chemicals, electricity, sterile males, velocity and physical barriers. The use of a chemical lampricide is the most commonly used technique, but physical barriers such as the one on the lower Misery River are used. Lampreys are trapped at such facilities to be used for research.
The chemical used is TFM, which for your chemists, is 3-trifluoromethyl-4-nitrophenol and is very expensive to manufacture. It is applied to streams in a liquid form, where it kills the larval lamprey living in the sediments before they mature and migrate to the Great Lakes. The chemical is very specific to lamprey, but has detrimental side affects on some fish and aquatic insects. There are 175 streams treated with TFM around the five Great Lakes, on about a four-year rotating basis.
The sterile male program is one in which sea lamprey are trapped, the males then treated with a chemical that makes them sterile. They are then reintroduced to streams where they spawn with females, with no fertilization occurring. It also is an expensive program, with mixed results. This program has been reduced in recent years.
A very promising sea lamprey control program is in development and entails the use of pheromones. What are these? They are chemicals excreted by insects and animals to trigger a social response in the opposite sex of the same species. Their use among insects, especially bees, is well documented. Typically, pheromones are literally smelled by the receptive individual in very, very low doses. Researchers at MSU have identified and isolated the pheromone male sea lamprey excrete to attract females during the spawning season. They have developed a synthetic version of the pheromone and are testing its effectiveness in attracting spawning-phase female sea lamprey. This research also led to the discovery that spawning males, which enter streams before the females, are attracted to streams by pheromones secreted by larval lamprey. It has long been known that sea lamprey do not necessarily return to the stream of their birth and provides the answer of why not. The use of pheromones may not be the "silver bullet" in the ultimate control of a creature that has survived, very successfully throughout the eons of time, but may be a less expensive and more environmentally friendly manner to reduce sea lamprey populations.