Surprise find: The rediscovery of the shortnose cisco in Lake Superior

The shortnose cisco, a freshwater fish from the salmon family, had been considered extinct since 1985. After almost 40 years, it has now been rediscovered in a place where no one expected it: Lake Superior, the largest of North America’s five Great Lakes.

Once, the shortnose cisco (Coregonus reighardi) was widespread throughout the Great Lakes, but a combination of commercial overfishing, competition from invasive species such as the sea lamprey, zebra mussels and quagga mussels, and the deterioration of water quality and habitats led to its disappearance. These factors affected both its survival and its reproduction until it was regarded as extirpated from its original range from the 1980s onward.

Although numerous fisheries surveys were carried out in potential habitats over the past decades, the shortnose cisco remained untraceable. Its last confirmed sightings date to 1964 in Lake Ontario, 1982 in Lake Michigan and 1985 in Lake Huron. Without new findings, the species faded from view while scientists turned their attention to other challenges in managing fish populations.

The International Union for Conservation of Nature (IUCN) has listed the shortnose cisco since 1996 as “critically endangered (possibly extinct).” The U.S. Fish and Wildlife Service (USFWS) and Ontario’s Ministry of Natural Resources officially declared the species extinct because there had been no records since 1985. The surprising rediscovery in Lake Superior now raises new hope—not only for the shortnose cisco, but also for the ecosystems of the Great Lakes.

A surprise from the depths of Lake Superior

In July 2022, scientists from the United States Geological Survey (USGS) made a discovery: during a fish population survey near the Keweenaw Peninsula in Lake Superior, they unexpectedly encountered three juvenile shortnose ciscoes. It was a remarkable find, because the species had not previously been documented in this lake—no modern scientist had ever recorded shortnose ciscoes in Lake Superior. This discovery was made possible by modern capture and analysis techniques. Further investigations eventually also turned up adult specimens, indicating that a small, stable population may have established itself in this unexpected habitat.

This rediscovery not only sparked joy in the scientific community, but also rehabilitated Walter Koelz, the American naturalist who first described the shortnose cisco in 1924. In his 1929 work Coregonid Fishes of the Great Lakes, Koelz assigned the species to Lake Superior. For decades, it was assumed that he had been mistaken, because subsequent researchers found no shortnose ciscoes in that lake. But almost 100 years later, it has become clear that Koelz was right. The recent catches were examined both morphologically and genetically and identified as shortnose ciscoes.

Significance of the rediscovery of the shortnose cisco

The rediscovery of the shortnose cisco, believed extinct, is a sign that ecosystems can recover—even after decades of pressure from human impacts and invasive species. This species, which plays a central role in the Great Lakes food web, is important for the stability of the ecosystem. A healthy population of native fish could help mitigate the damage caused by invasive species in the long term.

Targeted conservation measures show that reintroduction programs are crucial for preserving threatened species. Since 2018, the Michigan Department of Natural Resources (DNR) has been collecting fertilized eggs from remaining wild populations, for example near Drummond Island in Lake Huron, and raising them in a hatchery. Around one million juveniles are released into Saginaw Bay every year—a region where ciscoes were once abundant before they disappeared. At the same time, scientists monitor whether the fish not only survive but also reproduce successfully. Such programs, such as the planned reintroduction of ciscoes into New York waters of Lake Erie, demonstrate how targeted support for native species can contribute to the resilience of the entire ecosystem.

While the shortnose cisco is back, other fish species from the Great Lakes are probably irretrievably lost—such as the blue walleye. It was once endemic to Lakes Erie and Ontario before disappearing for good around 1965 because of overfishing and invasive species.

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Source

• Matheny, K. (2024). Great Lakes fish thought extinct for decades rediscovered – in an unexpected place. Detroit Free Press.