This week’s CaliforniaWaterBlog post is an excerpt (Box 1) from a recent Delta Independent Science Board report on non-native species and the California Delta. This excerpt summarizes the experience of the Great Lakes, and how its physical and ecological management has led to waves of profoundly disruptive species invasions, resulting in a sequence of “novel” ecosystems. This sequence of invasions seems likely to continue to shape the Great Lakes. This history is a wake-up and warning for policymakers and those working on California’s Delta. Dan Eagan’s 2018 book is an excellent and readable history of these cyclic invasions and attempts to manage and cultivate them.
The Great Lakes are one of the most well-studied and invaded ecosystems in the world. Nearly every aspect of management is impacted by invaders (Egan 2018). The Great Lakes’ aquatic ecosystem developed following the last Ice Age by the recession of continental glaciers. Native species evolved from remnant populations in local and regional streams and a few that swam upstream. The Great Lakes’ topography, particularly Niagara Falls, limited species introductions to the upper Great Lakes until commercial navigation expanded in the early 1800s with the construction of New York’s Erie Canal and the Welland Canal that linked the lower Great Lakes to the upper Great Lakes.
Among these invasive species was the sea lamprey (Petromyzon marinus), which spread through the Great Lakes over several decades and depleted native predators particularly the lake trout (Salvelinus namaycush), which lacked any defenses. After years of scientific study, it was found that sea lamprey could be suppressed (but not eliminated) by treating specific stream reaches with a species-specific poison at specific times of the year when they were most vulnerable. Sea lamprey populations were reduced by about 90%, but control efforts continue, costing more than $20 million annually (Kinnunen 2018).
The herring-like alewife (Alosa pseudoharengus) also entered the Great Lakes, replacing intermediate species in the food web. With sea lamprey suppressing native predators, alewife boomed so high, they experienced massive annual die-offs that had to be removed from Chicago beaches by bulldozers. Commercial fishing began on alewife. To further help control the alewife population, several species of Pacific salmon (Oncorhynchus spp.) were introduced (Parsons 1973). Salmon survived well in the Great Lakes and triggered a massive sports fishery that bought billions of dollars annually to the Great Lakes. Annual stocking of (non-native) salmon raised in hatcheries became a major fisheries management priority and now stocking rates are tied to the production of its main prey, the non-native alewife.
The opening of the Saint Lawrence Seaway eventually brought larger, faster commercial ships and their ballast water to the Great Lakes, resulting in the new introduction of a wide range of species. Most notably, the introduction of zebra mussels (Dreissena polymorpha) to the Great Lakes in the late 1980s is considered the poster child of a successful invader. It has had profound impacts on the ecology and economy of the Great Lakes that range from clogging of water intakes for drinking and water-power operations (estimated costs into the billions) to loss of native clams to the decimation of primary production and disrupted food webs including the salmon recreational fishery. Interestingly, the invasion of the Great Lakes by zebra mussels was predicted more than a century before, based on shipping connections between the Great Lakes and areas where the mussel was well established (Carlton 1991). Quagga mussels (Dreissena rostriformis bugensis) invaded a few years later and have largely out-competed zebra mussels throughout the deeper portions of the Great Lakes. Both mussels have since spread throughout much of the Midwest and well into the west including California, Nevada, and Texas.
There is now concern about further invasions, including the movement of several Asian carp species (Cyprinus spp.) up the Mississippi River to the Great Lakes through the Chicago Sanitary and Ship Canal.
At each stage in this continuing history, local and regional interests and different state, provincial, national governments, and international bodies have acted, often out of necessity to manage these ecosystems or control major pathways such as ship ballast water. Management efforts to control invaders once established have been very limited. The entire Great Lakes ecosystem has been transformed by invasive species.
Carlton, J. (1991). Predictions of the arrival of the zebra mussel in North America. Dreissena Polymorpha Information Review, 2:1.
Delta Independent Science Board (2021), The Science of Non-native Species in a Dynamic Delta, Delta Independent Science Board, Sacramento, CA.
Egan, Dan (2018), The Death and Life of the Great Lakes, W. W. Norton & Company, 384 pp.
Kinnunen, R. (2018). Great Lakes sea lamprey control is critical. Michigan State University Extension, Michigan State Sea Grant.
Parsons, J.W. (1973). History of Salmon in the Great Lakes, 1850 – 1970. Technical Paper 68. U.S. Bureau of Sport Fisheries and Wildlife, Great Lakes Science Center.