Lake Michigan, a vast freshwater expanse, hosts a diverse array of salmon species. These salmon, though not originally from the Great Lakes, have become a significant part of the lake’s ecosystem and a popular target for recreational anglers. Their presence is the result of deliberate management efforts, transforming the lake’s fishery.
Major Salmon Species of Lake Michigan
Chinook and Coho salmon are the most prominent species in Lake Michigan, alongside smaller populations of Atlantic and Pink salmon. Each species has distinct characteristics, habits, and sizes.
Chinook salmon (Oncorhynchus tshawytscha), often called King salmon, are the largest salmon in Lake Michigan and a popular sport fish. They have a silvery body with black spots on their back and on both lobes of their tail fin, and their lower jaw gums are black. Chinook salmon in Lake Michigan weigh between 10 and 20 pounds, though some can exceed 30 pounds. These fish primarily inhabit deep, open waters during summer, moving to river mouths in the fall for spawning. Their diet primarily consists of alewives once they reach a certain size.
Coho salmon (Oncorhynchus kisutch), also known as Silver salmon, are smaller than Chinooks but are also a popular game fish. They have a silver body, a dark blue-green back, and black spots mainly on their back and the upper lobe of their tail fin. White gums at the base of their teeth are a distinguishing feature. Coho salmon in Lake Michigan average 4 to 6 pounds in weight and 11 to 26 inches in length, with some reaching up to 10 pounds or more. They spend most of their lives in deep, open water, moving to nearshore areas in spring and then to tributary streams in the fall for spawning, and primarily consume alewives, smelt, and aquatic invertebrates.
Atlantic salmon (Salmo salar) are less common in Lake Michigan compared to their Pacific counterparts. They have a silvery body with distinct black, X-shaped spots, mostly above their lateral line. Their caudal fin is slightly forked, and their pectoral fins are dark. Atlantic salmon in Lake Michigan weigh between 5 and 12 pounds, with some individuals growing larger, and can be found near eastern shorelines and river mouths of Lake Michigan. These salmon eat crustaceans, smelt, alewives, and other forage.
Pink salmon (Oncorhynchus gorbuscha), often called Humpies due to the pronounced hump developed by spawning males, are the smallest salmon species in Lake Michigan. They have a mostly silver body with large, oval black spots on their tail and back, and their mouth and gums are dark. Mature adults are in the 20-inch range and weigh 2 to 7 pounds. Pink salmon were introduced into Lake Superior and have established self-sustaining populations, occasionally appearing in Lake Michigan. They are plankton feeders as juveniles and consume a variety of fish and other aquatic animals as adults.
The History of Salmon in Lake Michigan
The presence of salmon in Lake Michigan stems from stocking programs initiated in the mid-20th century. These Pacific salmon species are not native to the Great Lakes basin.
In the 1960s, Lake Michigan faced an ecological imbalance due to the rapid proliferation of invasive alewives (Alosa pseudoharengus). These non-native fish experienced massive die-offs. To address this nuisance and establish a new sport fishery, state agencies began introducing Pacific salmon.
The first successful introduction occurred in 1966 with Coho salmon, followed by Chinook salmon in 1967. These stocking efforts aimed to control the abundant alewife population by introducing a new predator, while creating a valuable recreational fishing opportunity. Continued stocking by various state agencies around Lake Michigan followed.
Their Role in the Lake Michigan Ecosystem
Salmon play a multifaceted role in the Lake Michigan ecosystem, acting as apex predators and supporting a significant sport fishing industry. Their introduction altered the lake’s food web dynamics.
As top predators, Chinook and Coho salmon primarily consume alewives, which helps manage the population of this invasive prey species. This predator-prey relationship is important for maintaining ecological balance, as an unchecked alewife population can negatively impact native fish species by competing for food resources. The reliance of Chinook salmon on alewife makes them sensitive to fluctuations in alewife abundance.
The introduction of salmon also fueled a significant sport fishing industry around Lake Michigan, contributing to the regional economy. Anglers target these species, contributing to charter boat operations, tackle sales, and tourism. This economic contribution highlights the human aspect of salmon management in the lake.
Managing salmon populations involves balancing predator and prey numbers, particularly between Chinook salmon and alewives. Agencies continuously monitor salmon health and growth, adjusting stocking levels to ensure a sustainable fishery and a stable ecosystem. Challenges include fluctuations in prey availability and the need to manage diseases that can affect salmon populations.