Creature Feature: A Fish Must Flow
One of several ways to celebrate April’s Earth Day is by performing various acts of stewardship. Stewardship can be defined as any act or deed that results in the care for something such as a community, environment, organization, etc. Here at the Johnson Nature Center, some of our more recent acts of stewardship have involved the removal of non-native invasive plant species such as common buckthorn and garlic mustard.
Invasive species do not solely take the form of plants; animals can be an invasive species too. Around and within the Great Lakes region, invasive animal species are typically aquatic in form, and are introduced to an environment unintentionally or unknowingly by humans through various means, depending on the species. While there are several to choose from to highlight for this month's Creature Feature, I am going to pick the one that seems the most…… bizarre.
So here’s the story: There is an ancient species of fish that dwells in the Atlantic Ocean. A species that has been on this earth unchanged for at least 340 million years. Each year during the spring season, adult fish of this species would travel from the ocean to freshwater rivers and streams to lay their eggs and spawn before dying. A single individual female has the potential to lay tens of thousands of eggs during this time. When the eggs hatch, the young would spend a few years in the rivers and streams before making their way back to the ocean to finish their development. Then the cycle begins again.
For those that traveled towards the Great Lakes Basin to spawn, the fish could only go as far as Lake Ontario due to a little obstacle called Niagara Falls. However, the modification of the Welland Canal (canal for ships that connects Lakes Erie and Ontario, bypassing Niagara Falls) in 1919 gave the fish an opportunity to reach freshwater lakes and systems that were unreachable before. Within 20 years, the fish were present in the other four Great Lakes and many stopped traveling from saltwater to freshwater.
The problem? As their population within the Great Lakes increased, the populations of other native fish decreased. Fish like trout, salmon, and whitefish all went on the decline, bringing the attention of anglers and fishery managers. The reason for the decline was largely due to the fact that these newly arrived fish also happen to be parasites. Once grown, they would attach themselves to other fish and slowly drain them of their fluids, just like the mosquitos that we all love.
You, dear readers, may be wondering what on earth is the name of this ancient, migrating, parasitic vampire fish that I have been going on about? The story I have told is a simplified version as to how the sea lamprey came to the great lakes. The sea lamprey is a type of jawless fish that lack pairs of fins and rely on their round suction-like mouth and rows of sharp teeth to feed on other fish. Some might compare them to an eel, but they are actually not related. To me, they look less like fish and more like the sandworms from Dune.
Sea Lamprey mouth
Since they are non-native to the vast majority of the Great Lakes Basin, sea lamprey cause an imbalance to freshwater ecosystems when too many lamprey take over an area and overwhelm the native fish populations, which in turn creates problems for us both recreationally and economically. This brings us back to the idea of stewardship from the beginning of this article. Although lamprey pose a threat to several fish species, work is done every year by many organizations throughout the region to manage and limit the population of these invasive fish through various tactics. In time, and with a little bit of additional help, species that were at risk of being replaced can come back, providing the world with a continued sense of beauty and wonder.
Sea Lamprey wound on a Lake Whitefish. Photo credit Michigan Sea Grant
Click here to learn more about the sea lamprey.
Submitted by Zach Mork, Naturalist, April 2022