Lake Michigan, a freshwater ecosystem, supports a diverse array of fish species. Its waters are home to a complex mix of native inhabitants, intentionally introduced sport fish, and invasive species. Understanding these groups provides insight into the lake’s ecological dynamics and fishery management.
The Original Inhabitants: Native Fish
Lake Michigan historically supported numerous fish species adapted to its cold, oxygen-rich depths. These native populations formed the foundation of the lake’s original food web and supported early commercial and subsistence fisheries. Many persist today, though often at reduced levels or in specific areas.
Lake Trout (Salvelinus namaycush) are a prominent native species, historically a top predator in the lake’s colder, deeper parts. Lake Whitefish (Coregonus clupeaformis) are another important native fish, valued ecologically and commercially. They are bottom-dwellers, feeding on small invertebrates.
Yellow Perch (Perca flavescens) are a popular native species found in nearshore areas, offering recreational fishing. Cisco, also known as Lake Herring (Coregonus artedi), were once abundant throughout the Great Lakes. Their populations have declined significantly due to overfishing, habitat changes, and competition from invasive species. Burbot (Lota lota) are unique, eel-like native fish inhabiting the lake’s deeper, colder waters.
Newcomers for Recreation: Sport Fish
Many of Lake Michigan’s most sought-after sport fish are non-native species, intentionally introduced. Introductions began in the mid-20th century to address ecological imbalances and provide recreational opportunities. These programs transformed the lake’s fishing landscape.
Coho Salmon (Oncorhynchus kisutch) were first stocked in 1966, followed by Chinook Salmon (Oncorchus tschawytscha) in 1967. These Pacific salmon were introduced partly to control invasive alewife. They quickly became popular for their size and fighting ability, establishing a major sport and charter fishing industry.
Steelhead (Oncorhynchus mykiss), migratory Rainbow Trout, and Brown Trout (Salmo trutta) were also introduced and thrive in Lake Michigan. Steelhead are known for their strong fight and often migrate into rivers to spawn. Brown Trout are also popular for lake and river fishing, prized for their wariness. Walleye (Sander vitreus) are found in various parts of Lake Michigan, particularly in shallower, structured areas like Green Bay.
Unwelcome Guests: Invasive Species
Lake Michigan’s ecosystem has been significantly impacted by numerous non-native species. These invaders disrupt native food webs, compete with indigenous fish, and alter habitats. Managing them is an ongoing challenge for the lake’s health.
The Sea Lamprey (Petromyzon marinus) is one of the most notorious invaders, entering the Great Lakes through canals. They prey on large native fish by attaching and feeding on their blood. Control efforts, such as lampricide treatments, limit their impact on fish populations. Alewife (Alosa pseudoharengus), though now a food source for introduced salmon, initially caused significant ecological problems due to population explosions and massive die-offs.
Zebra Mussels (Dreissena polymorpha) and Quagga Mussels (Dreissena bugensis) arrived in the Great Lakes via ballast water in the late 1980s. These filter feeders remove plankton, altering the food web and increasing water clarity, impacting native species. Round Goby (Neogobius melanostomus), also a ballast water invader, compete with native fish like Yellow Perch for food and habitat. While not yet established in Lake Michigan, invasive Asian Carp (Bighead, Silver, Grass, and Black Carp) remain a significant concern, with ongoing efforts to prevent their entry.
A Changing Environment: Lake Michigan’s Fish Ecosystem
Lake Michigan’s fish populations exist within a dynamic environment, shaped by natural processes and human interventions. The current fish community reflects historical conditions, management strategies, and the persistent influence of invasive species. This balance impacts the lake’s food web and species success.
Human management plays a significant role in sustaining the lake’s fishery, including stocking programs for introduced salmon and trout. These programs maintain populations supporting a thriving sport fishing industry. Control measures against invasive species, particularly Sea Lamprey, are also implemented to protect vulnerable fish stocks.
Lake Michigan’s food web is in flux, with introduced species relying on invasive prey like alewife, while native populations contend with competition and habitat alteration from other invaders. Filter-feeding mussels, for example, have significantly changed nutrient cycling and water clarity, affecting the entire aquatic community. Understanding these interconnected relationships is key to conserving and managing Lake Michigan’s diverse fish ecosystem.