Exotic Species: The Atlantic Sea Lamprey

By:

Stephanie Poerstel

There are exotic or intrusive species all over the earth. Many of the things that we might have thought were native to our area are in fact nonindigenous. Sometimes people too can become exotic species. In this paper I will write about the Atlantic sea lamprey and its effects on the Great Lakes environment.

Exotic, intrusive and nonindigenous species are all basically the same thing. The term exotic means that a species is not native and has been introduced from abroad and is foreign. In other words exotic species are foreign species that have been accidentally or purposely introduced into a new environment. Exotic species can be harmful or helpful to the environment they are introduced to. In most cases the exotic species is harmful to its new environment. This is because the introduced species has no natural predators in its new home. It takes generations for certain animals to become totally adapted to preying on other animals. When a new species is introduced, none of the animals or plants in its environment have ever had to deal with it before, and therefore have no protection from it , or no specialized tools to aid in killing it. This leaves an enormous amount of room for the introduced species to take control over the environment. The new species will eventually change the delicate ecosystem it has invaded, forever. The old ecosystem will survive no longer and a new one will take its place.

Throughout history, exotic species have had a major impact on humans and their environment. Ever since the dawn of time species have been moving from one ecosystem to another. In the sixteenth century Columbus and other conquistadors traversed the Atlantic Ocean to establish a new trading route to the East Indies. They landed on the Americas and brought with them many new organisms from the Old World. These new organisms grew and thrived in their new home. Such things as wheat, citrus, sugar, cattle and pigs were not indigenous to the New World.

Columbus and the conquistadors were, themselves, a type of invasive species. They walked onto the soils of the Americas and almost everywhere they stepped, environmental destruction followed. They preyed upon the forests, the lakes, the ocean, the animals and the people. Kirkpatrick Sale writes that "it was sufficient for [the conquistadors] to know that God created [nature] and then gave humans 'dominion over' [it]" (Sale 75-76). The conquistadors were predators in an area of the world that had no idea how to handle them. The natives of this land had no natural immunity to these predators. However, Columbus' journey has "enabled the vast redistribution of life forms, purposely and accidentally, that has changed the biota of the earth more thoroughly than at any time...causing the extinction, alteration and even creation of species" (Sale 4).

Exotic species still reign in some area today. They bring about the destruction of old ecosystems, and the birth of new ones. For each time a species invades, it does not mean death of the ecosystem, although that can happen. Most times the ecosystem will change dramatically to incorporate its new member. The Atlantic sea lamprey (Petromyzon marinus) is an example of a destructive invasive species. The sea lamprey belongs to the taxonomic class of Agnatha. The Agnathans only have two types of fish in their class, one being the hagfish, and the other the lamprey. The fish in this group are the most primitive of all the fish. The hagfish and lampreys lack appendages, such as fins or flippers. They also lack a lower biting jaw and their skin is scaless. In short they look almost eel-like.

These fish are scavengers. They feed on the insides of dead or dying invertebrates or other fish. Lamprey's have a muscular tongue and on their tongue they have teeth-like structures. The tongue is located in the oral disc, a round opening, that is filled with numerous hook-shaped teeth. The lamprey hooks on to its prey with the round oral disc and its hooked teeth and cuts through the flesh of its host with the toothed tongue (Kardong 87). After they have taken hold of an animals flesh they tie themselves into a knot. The lampreys do this to provide leverage and stability to tear off a piece of food (Sumich 173).

Sea Lampreys are an anadromous fish. This means that in most species the adult lives in sea water, but goes up streams to fresh water to spawn, much the same as the salmon does. However the lampreys that I will talk about are land locked, meaning they no longer have access to the ocean.

The life of a sea lamprey consists of three major stages. The first is a larval stage, in which the lampreys do not feed. The larval stage lives in the river where it was born until it undergoes a metamorphosis. From this stage they migrate into the lakes. During the next twelve to eighteen months the lamprey will attack fish hosts. The last stage occurs when the lampreys are sexually mature enough to swim back into the rivers and spawn. After spawning the lampreys die (Young 100).

The Atlantic sea lamprey and the wounds it inflicts on its host species were first discovered in Lake Ontario in the 1860s (Cox 150). It invaded the lake by coming up the Hudson River and through the Erie Canal. The sea lamprey flourished in the streams leading to Lake Ontario. They did so well because the waters of these streams were warm. The lamprey then spread to the other Great Lakes. Once again man made devices made this passage possible. The lampreys reached the upper lakes by going through the Welland Canal, which allow ships to go around Niagara Falls (Cox 150).

The sea lampreys preyed upon large deep water salmonids, such as the lake trout, which is a commercially valuable fish. After the lampreys preyed upon a species to the point of extinction they moved on to another type of fish, and so on. This pattern of feeding was extremely destruction to certain fishes in the Great Lakes. In the 1930s and 1940s, in some of the lakes the lamprey devastated the populations of large top predatory fish. In some instances several species of fish became extinct in certain lakes (Cox 150).

In the 1970s efforts were started to control the growing lamprey problem. Dams were built at the mouths of the streams where lampreys regularly spawned. Also a lampricide that was supposed to kill the lamprey larvae was discovered. This lampricide was put to use immediately. At first the lamprey population dwindled and was thought to be under control. Therefore, fisheries started reintroducing the salmonids back into the lakes in hope of restoring their numbers and the ecosystem. However, with more fish no available to prey on, the lamprey population sky rocketed back up.

One other possible reason for the lamprey population increase could have been the improvement of the water quality in the St. Mary's River. The St. Mary's River, which leads into Lake Huron, is the spawning ground for more than 40 000 lampeys each spring (Young 100). Ever since 1973, when municipal sewage treatment plants were upgraded and industrial contaminants were decreased in the river, the water quality has steadily improved. This makes the habitat for all species of the lake more optimum. Also even though the combined total of sea lamprey larvae in St. Mary's River, Lake Michigan and Lake Ontario is 6.8 million, chemical lampricides can no longer be used in these areas (Swink 385).

In 1993, surveys recorded that lamprey populations were still out of control. Although the lampricides did not have as much affect on the lamprey population as scientists would have liked, other methods were tried to kill the lampreys. Electrical barriers were devised and placed at the mouths of spawning streams. These electrical barriers were designed to decrease the number of adult lampreys from reaching the spawning grounds. The combination of these efforts has kept the sea lamprey population in a delicate check and balance. The main sporting fish, lake trout and coho salmon, are now common enough to once again be fished.

The ecosystem of the world are very delicate communities. One small predator that is out of place and allowed to run wild can destroy that balance. This happened in Columbus' time, when he destroyed the balance between the natives and nature. It is still happening today as can be seen with the sea lamprey. Exotic species, whether human or animal, have a great impact on our lives. Who can tell where we would be today without the help, or destruction of exotic species.  

Works Cited

Cox, George W. Conservation Biology. 2nd ed. Iowa; Wm. C. Brown Publishers. 1997.

Kardong, Kenneth V. Vertebrates: Comparative. Iowa; Wm. C. Brown Publishers. 1995.

Sale, Kirkpatrick. Conquest of Paradise. New York; Penguin Books. 1991.

Sumich, James L. An Introduction to the Biology of Marine Life. Boston; Wm. C. Brown Publishers. 1996.

Swink, William D. "Growth and Survival of Newly Parasitic Sea Lampreys at Representative Winter Temperatures". American Fisheries Society. 1995. P 380-386.

Young, R.J; G.C Christie, R.B. McDonald, D.W. Cuddy, T.J. Morse and N.R. Payne. "Effects of habitat change in the St. Mary's River and northern Lake Huron on sea lamprey populations". Canadian journal of fisheries and aquatic sciences. 1996. P. 99-104.