Great Lakes. Sea lamprey – an alien predator

In the heart of North America, on the border of the United States and Canada, stretches the vast Great Lakes system, which has attracted travelers for years with its monumental size and extraordinary landscapes. The depths of these bodies of water also hide less visible, but no less fascinating stories, such as the one about the sea lamprey – a seemingly harmless fish that has become a threat to local ecosystems. For years, Niagara’s natural barrier protected the Great Lakes from this predator, but as infrastructure developed, its path northward was opened. The effects on the ecosystem have been shocking.

Great Lakes home to myriad life forms

The impressive Great Lakes system has fascinated travelers and explorers for centuries. The five vast bodies of water – the Upper, Michigan, Huron, Erie and Ontario – form one of the largest reservoirs of fresh water in the world, as well as a unique ecosystem.

The Great Lakes are home to hundreds of species of fish, birds and other myriad forms of life that coexist harmoniously with one another. The basins are also of crucial economic importance – a source of drinking water, a transportation route and a fishing ground. However, despite their size and power, they are also extremely vulnerable to human interference.

Man as the perpetrator of the problem

Niagara Falls, one of nature’s most recognizable wonders, was once a natural barrier, protecting Great Lakes ecosystems from the influx of invasive species. It was what allowed Ontario and the other lakes to maintain their natural balance for years. However, over the years, the progress of civilization has brought unforeseen and tragic consequences.

Human interference with natural aquatic ecosystems, through infrastructure development, opens the door for invasive species to occupy new areas where they can pose a serious threat and even lead to catastrophic changes. In their native habitats, these species usually perform an integral function in the food chain, and their numbers are controlled by their natural enemies, thus maintaining the balance of the ecosystem. However, in new environments, devoid of adequate regulatory mechanisms, their populations expand uncontrollably, leading to serious disturbances in the biological balance. As a result, ecosystems are degraded, invasive species displace native ones, destroy natural resources and reduce biodiversity.

This was also the case with the Great Lakes system. The expansion of water infrastructure such as canals and locks, and in particular the opening of the Welland Canal in 1829, connecting Lakes Erie and Ontario, had serious consequences for the Great Lakes ecosystem. The canals allowed the movement of species that previously had no access to these waters, including the ichthyofauna-threatening sea lamprey.

Sea lamprey – the parasite that kills

The sea lamprey, known as IGO, is an inconspicuous, eel-like fish that is native to the Atlantic Ocean. While it may appear harmless at first glance, its parasitic way of life poses a serious threat to freshwater fish. It plays an important role in the natural ecosystem, but the problem arises when it is introduced into new environments where it has no natural enemies. The lamprey attaches itself to fish with its sharp teeth and sucks the blood from them, which usually leads to the death of the victim.

Since lampreys appeared in the Great Lakes, populations of many fish species have declined dramatically. IGOs there hunt lake and brook trout, sturgeon and lake whitefish, burbot, pikeminnow, catfish and Pacific salmonids, among others. The action of this primitive predator affected not only the ecosystem, but also the economy of the region, in which fishing played a key role. The sea lamprey has become a real scourge, and fighting it has proved more difficult than initially thought. This fish has an extremely high reproductive capacity, and its larvae can survive in river waters for up to five years before reaching adulthood and beginning a parasitic life cycle.

Defense against a primitive predator

The fight against the invasive sea lamprey, one of the greatest threats to the Great Lakes ecosystem, has been a priority for Canadian and US authorities for years. Despite numerous attempts to completely eradicate this primitive predator, which effectively destroys freshwater fish populations, remains a challenge.

The lead organization responsible for monitoring and controlling sea lamprey populations is the Great Lakes Fishery Commission (GLFC). GLFC, in cooperation with Canadian and American institutions, uses several innovative methods. Among the most important are lampricides, such as TFM and Bayluscide, which selectively destroy lamprey larvae in streams without affecting other fish species. While these chemical methods are effective, their high cost forces the search for alternatives. Therefore, techniques are also being developed that rely on the construction of physical barriers to prevent lamprey migration, as well as the use of pheromones and alarm signals. The latter, thanks to recent research, make it possible to manipulate lamprey movement, scaring them away from key fish habitats or attracting them to traps.

Thanks to these measures, the sea lamprey population has been reduced by about 90 percent, allowing stocks of commercially important fish species such as lake trout and salmon to recover. The effectiveness of these methods is based on the integration of multiple scientific disciplines – biology, ecology and environmental engineering – which allows us to better understand the mechanisms of the spread of invasive species and counteract their destructive effects on ecosystems.

The future of the Great Lakes is still uncertain

The Great Lakes, located in the heart of North America, are a delicate and complex ecosystem that requires constant protection from the threats of human interference. The example of the invasive sea lamprey shows how quickly the ecological balance can be disrupted when alien species enter these waters. Successfully combating lamprey, which are destroying local fish populations, requires innovative methods and international cooperation.

Protecting the Great Lakes is an ongoing challenge. Maintaining biological balance and protecting fish diversity requires extensive efforts in many areas. A key element is public education about the dangers of invasive species and the need to protect aquatic resources.

If you want to learn more about the Great Lakes and the extraordinary inhabitants of this powerful ecosystem – we invite you to read future issues of Water Matters.