Sprol

Introduced to the Great Lakes via the Welland Canal in 1921, these primitive invertebrates, sometimes called “eel-suckers,” have become endemic in the Great Lakes, including Indiana’s portion of Lake Michigan.

Although often confused with eels because of their long, slender bodies, sea lampreys are not eels. Eels are Audrey Hepburn compared to lampreys. Instead of a face, the lamprey features a science-fiction oval mouth, packed with concentric rings of sharp teeth directly connected to a long, dark, slug-like body.

As larvae, sea lampreys utilize freshwater rivers, eating a variety of microorganisms and detritus. These baby lampreys will swim the rivers for anywhere from four to six years, just until the larvae transform into free-swimming youngsters ready to migrate into the open waters of either a saltwater, marine environment or into the freshwaters of the Great Lakes.

When these transformers, being only 13 to 15 centimeters long and silvery in color, are ready, they begin moving downstream to the Great Lakes. After they reach their destination, the newly transformed lampreys quickly attach to their first prey fish. Producing an anticoagulant substance in its saliva which prevents its victims’ blood from clotting, the lamprey uses its sharp teeth to scrape away the host’s skin so that it can begin sucking out the blood and other bodily fluids.

For this reason, the sea lamprey, is not what most of us would like to feel wrapping around our legs when wading or swimming at one of Lake Michigan’s sandy beaches. Lucky for us, lampreys do not typically have a taste for human bodies. They seem to prefer the cold, scaly flesh of unsuspecting fish.

Once in open water, the sea lamprey begins its 12 to 20 month-long adult, parasitic existence. Over this time period, while budding into mature adults, the lampreys can grow up to 46 centimeters in length.

Once a host fish finds itself with a new, attached partner, their future is quite uncertain. While the length of time the lamprey will remain attached to its host varies, there are several factors that will determine whether the host fish will survive or die as a result of its newly-found parasitic partner. The site of the attachment on the fish’s body, the time of year, and the size of the predatory lamprey in relation to its prey’s size will determine the fate of the unfortunate host fish. Oftentimes, captured lake trout may bear wounds and sometimes scars showing that they survived several attacks by smaller sea lampreys.

Sea lampreys first began migrating to the Great Lakes in the early 1920s from their native Atlantic Ocean by way of shipping canals. This parasitic vertebrate can live just fine, thrive in fact, in fresh or salt water. One of the oldest extant species of vertebrae, they are quite versatile, and have spread throughout the five Great Lakes as well as Lake St. Clair. Lake St. Clair does not present the best environment for the lamprey because of its relative shallowness and warmer temperature, which does not attract lake trout, the lamprey’s food of choice.

Over a period of 40 years, the growing sea lamprey population eventually decimated the fishing trade of the Great Lakes.

Because of their aggressive feeding style, the lampreys contributed to the serious decline of a variety of native fish species that were prime components to the Great Lakes fishing industry. In fact, prior to the invasion of the sea lampreys, United States and Canada brought in roughly 15 million pounds of lake trout from both Lake Huron and Lake Superior. But, by the early 1960s, just 300,000 pounds of this valuable fish was caught.

While the freshwater lake trout have long been the top predator in the Great Lakes, they were also the sea lampreys’ most sought after meal. The natural result was a continuing, steady decline in the number of lake trout. Over time, it became a fight between the two main fishers of the waters of the Great Lakes; sea lamprey verses the fisherman.

With lake trout numbers steadily declining, the sea lampreys turned their sites to the whitefish and other members of the whitefish family, such as chubs and lake herring. And, as lake trout and other expert predators in Lakes Huron and Michigan were eradicated, the population of a second, typically-saltwater-dwelling invader swam in from the Atlantic. The highly predatory alewife arrived, and its population seemed to explode.

Even though the alewives are quite susceptible to major die-offs in the springtime, they became very abundant and had adverse effects on a lot of the very valuable, native fish species that call the Great Lakes water system home.

As early as 1948, a special committee was formed with the idea and goal of controlling the sea lamprey population. The committee was comprised of and represented by the governments of Canada and the United States – eight American states as well as Ontario – all of the jurisdictions which border the five Great Lakes. The United States Fish and Wildlife Service, Michigan and Ontario actually led much of the research in defining the life cycle and distribution of sea lampreys. They also installed and tested physical barriers that were designed to prevent sexually mature sea lampreys from entering the very vital streams in order to spawn.

Very early in the program, the committee determined that using a chemical that was selectively more toxic to sea lamprey larvae still living and growing in streams than to “friendly,” nontarget fish and other aquatic organisms would be a must. The U.S. Fish and Wildlife Service rigorously researched about 6,000 different chemicals during laboratory testing for more than seven years before finally coming up with the chemical of choice – lampricide. TFMâ„¢ (3-trifluoromethyl-4-nitrophenol) and Bayerâ„¢ 73 (2-aminoethanol salt of 2′,5-dichloro-4′-nitrosalicylanilide) were selected for testing on the ever-growing population of lampreys. These efficient chemicals are still the major control methods used today.

Lampricide is a poisonous substance that does successfully kill the intended target, the sea lamprey; however, it also kills the many invertebrates it just happens to come in contact with along with occasional fish. Lampricide is brought to designated streams, some of which are located in populated areas, by big tanker-trucks, and is then applied to the stream waters in specific locations. This method is typically a rather expensive and labor-intensive procedure.

Later, in 1955, also formed primarily with the desire to control the growing lamprey population, the Great Lakes Fishery Commission (GLFC) was created. The GLFC is designed to work with the U.S. Fish and Wildlife Service (which is also a part of the Department of the Interior), the Department of Fisheries and Oceans Canada, the United States Army Corps of Engineers, and the U.S. Geological Survey with the goal of lamprey population control.

At this point, the GLFC estimates that the lamprey population has decreased since it peaked in the 1960s, but control of this damaging species is simply a must for the Great Lakes region. The GLFC’s principle goal is still protecting both the rich sport and commercial fishing market that is found in the Great Lakes; estimated at $4 billion per year.

Along with re-establishing and protecting the sport and commercial fishing market, the commission also has a responsibility to protect the natural environment. For this reason, the GLFC has long been eager to utilize a synthetic form of a particular sea lamprey pheromone, and thus replacing the use of lampricide poisoning, by luring lampreys to special, waiting traps and then sterilizing the males. Using the pheromone would be environmentally friendly and less expensive.

So, for the past 15 years, intensive research has been conducted with the goal of finding a safer, more environmentally-friendly method for controlling the destructive sea lamprey. What has been found is a natural chemical attractant, or pheromone, which is released by lamprey larvae that are still living and feeding in streambeds. The adult lampreys are attracted to and follow the pheromone trail with the intent on spawning until they reach streams that appear favorable.

A research team at the University of Minnesota has finally identified the three major components of the pheromone, and they have successfully synthesized the main one, which is a novel steroid much like a shark steroid that possesses anticancer properties. This special pheromone just happens to be the first migratory attractant identified in any fish.

The GLFC’s principle objective is to have the lamprey population under good control by an environmentally-safe, more effective method by the year 2010.

It is interesting to note that, generally, the freeloading sea lamprey prefers the colder, deeper waters where people do not swim. However, there has been some apparent evidence of lampreys attaching themselves to people instead of their normal fishy prey.

In Upstate New York’s Lake Champlain, a body of water with significant sea lamprey numbers, the occasional long distance swimmer has sometimes surfaced from the lake with an eel sucker dangling from one or more body parts. This gives new meaning to “stay out of the water” when swimming in waters known to support large numbers of these primitive vertebrates.