Bumper hatch of forage fish in Superior

by Jeff Helsdon | August 24, 2023
School of Alewife, Lake Michigan ENGBRETSON UNDERWATER PHOTO

The right combination of environmental factors created conditions for an above-average hatch of cisco and bloater in Lake Superior.

Final numbers are still being calculated, but researchers believe the 2022 hatch is the strongest in the 40 years assessments have been taking place in Canadian waters. The strongest to date were the 1988- and 1989-year classes.

Superior always has a cisco hatch, but typically survival rates are low. It’s suspected that colder water temperatures in winter and spring 2022 contributed to the high number.

“Although there is not one clear cause for strong recruitment events, cold winters and ice cover have long been suspected to play a role,” said Fritz Fischer, assessment supervisor at the Upper Great Lakes Management Unit, Fish and Wildlife Services Branch, MNRF.

Positive signs

Fischer said this is a positive sign for the health of Lake Superior. Although large cisco hatches occur, Fischer said the time between these events has been increasing. “It is also positive that a recruitment event of this magnitude can occur given climate change,” he said.

Asked about the significance of this for the sport fishery, Fischer said by 2025 the cisco will be 15 inches long and will be too large for prey for most species. However, for the time in between cisco will provide an increased forage base, which will be a boon to some species, resulting in quicker growth rates.

“The increase in growth rates will likely be most noticeable in short-lived fish, for instance, chinook salmon,” he said. “Other relatively short-lived species like coaster brook trout may also see increased growth rates and ultimate size.”

With a life span of up to 20 years, the adult cisco will also provide angling opportunities. The cisco abundance will also make it tougher for invasive prey species like smelt or alewife. 

“The next 20 years is going to be a tough time to be an invasive planktivorous fish like smelt or alewife in Lake Superior as they have to compete with this bumper crop of cisco,” Fischer said.

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