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Great Lakes Invasive Species

Let's Take a Look at the Big Picture


The Great Lakes of the North-Central part of North America contains twenty percent of the fresh surface water on the planet.

It provides an economic driver for two countries, including seven States and Provinces. Shipping supplies the industries that push up against the water's edge.

What is at Stake?

Commercial fishing is becoming more difficult as fish move in response to sediment and temperature shifts. The gravel bars that once held the eggs of game and bait fish now resemble roads built between the shore and small islands.

Old timers aren't telling fish stories when they loaded their boats full with multiple ton catches. There are pictures, color pictures, so this is not so very long ago.

Today a commercial fisherman has a good catch at a few hundred pounds for a full day of work, crew wages, and fuel. We won't mention loan payments and insurance because the fisherman is often losing money by leaving the dock before these expenses.

The huge catches of fish also attracted sportsmen who came for whitefish and salmon, pike and perch. These were excellent fish and many times a box loaded with ice and fresh fish would be loaded on the train by the fishermen and picked up at one of the urban stations to the south by happy family members.

This annual pilgrimage was in place before the second world war and it took off like one of the new jet airliners once families bought cars and explored the shoreline of these inland seas.

The industries that emerged from these activities were modern commercial fishing, and recreational fishing.

Commercial fishing on the Great lakes is mostly the same as marine fishing. The catch was small enough that most lake fish was consumed in the region and other markets preferred marine fish which was more familiar to fish eating cultures.

Recreational fishing now generates more revenue than commercial fishing with both industries measured in the billions of U.S. dollars.

The Troublemakers

Invasive species that threaten many of the regional industries and cultural practices have come in waves and generally thrived for a short time before exhausting resources and becoming less prevalent.

First there was the Sea Lamprey and Alewive. Both of these creatures made it difficult to enjoy the lake since the first is a raspy tongued parasite you don't want to meet while swimming. The second is a small bait fish introduced to feed salmon that were also introduced to the lake system.

These small fish did feed the salmon and catches improved in the 1970's but the fish also ate all of the native fish food as well so about the same time we had a huge loss of native fish. The Alewive would also die and pollute water and beaches as its life cycle ended every summer after spawning.

The second wave of invasive species came in the ballast water of ships.

The Zebra Mussel and Spiny Water Flea caused great economic harm. The Spiny Water Flea is an irritating and unsightly parasite of fish. The zebra mussel forms thick encrustations on any subsurface structure destroying native fish forage and hard infrastructure like water intakes where they needed to be removed with pneumatic chisels by divers.

The third wave of invasive species consists of three forms of large carp. The native carp can grow to over 100 pounds but these are hybrid fish bred for fish farms in the south. The fish are voracious eaters with a diet that includes just about anything it can swallow including mollusks, insect larvae, and small fish.

These animal foods are not on the menu of the native carp but they are eaten by almost all game fish at some stage of their lives. This has the potential to destroy commercial and recreational fishing if the species is not controlled. The fish have already entered Lake Michigan according to genetic testing so the next hope is the fish can be controlled with a barrier on the Illinois Ship and Sanitary Canal.

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