Researchers say something happens in the Niagara River starting around 9 p.m.
The lake sturgeon get active.
For the first time outside of a laboratory, Great Lakes scientists at Chicago's Shedd Aquarium proved sturgeon tend to be nocturnal creatures. Their data showed the sturgeon's greatest activity occurs between about 9 p.m. and 3 a.m. – with an average peak time of 10:32 p.m. That time period is when sturgeon prefer to feed on leeches, snails and clams.
The scientists tracked the sturgeon using satellite tags attached to the fish as part of ongoing research supported by the U.S. Fish and Wildlife Service and the state Department of Environmental Conservation.
What researchers have learned shows such promising results that the DEC said it could begin de-listing the threatened lake sturgeon no later than 2024.
“We’re constantly catching them,” said Lisa Holst, the rare fish unit leader in the DEC’s bureau of fisheries. “The numbers are very promising.”
The discovery, which will be published in the Journal of Great Lakes Research, is the latest in a five-year long push by state and federal environmental officials to learn more about the biological patterns of the prehistoric species.
Why is it so important?
“It helps you mitigate potentially negative interactions between the fish and humans,” said Andy Kough, a research biologist at Shedd Aquarium.
That can help guide the DEC's future rules to protect the fish and its habitat from the effects of boating, hydroelectric generation or other activities.
It also answers questions about what environmental factors influence sturgeon activity and why biologists might tend to find more or fewer sturgeon at certain times of day and in different places.
“Knowing when and where lake sturgeon are active or static allows us to consider potential barriers to their recovery and helps managers design for comprehensive recovery strategies,” said Jonah Withers, a fish biologist with the U.S. Fish and Wildlife Service.
The data show the Niagara River's sturgeon are most active overnight, but there are outliers, researchers said.
Shedd’s data showed around-the-clock activity.
“Fish, in many aspects, are like people – not everybody is the same,” said Phil Willink, Shedd’s senior research biologist.
Added Kough: “Some are active at 7 a.m. I kind of call them the ‘coffee drinkers.’ ”
The Shedd study used satellite tags affixed to the body of sturgeon to track temperature, water depth and its movements in the upper and lower Niagara River, Lake Erie and Lake Ontario. In the upper Niagara River, that was mainly near Buffalo Harbor. In the lower river, sturgeon swim upstream from Lake Ontario to spawn; otherwise, they hang out mostly in lake shoals near the mouth of the river at Youngstown.
Researchers said the satellite tags are common in marine ecosystems, but this study also showed they can be used successfully in highly mobile freshwater species and in such dynamic conditions as the flow of the Niagara River.
Researchers said that since humans can’t survive underwater and can’t see at night, studying the time, place and movements of sturgeon like this was really only possible because of the space-age advances in technology.
“If you tried to do this back in the 1960s and 1970s, we might not have been able to do this project,” Willink said.
Mathematical calculations peg the numbers of lake sturgeon in Buffalo Harbor between 450 and 1,250.
That’s a whole lot more than when the species was added to the threatened species list in 1983, but more science is needed to narrow that to a more precise estimate.
“The error bias is pretty big,” said the DEC's Holst.
For the lake sturgeon to be taken off the state’s list of threatened species, the DEC’s proposed Lake Sturgeon Recovery Plan requires at least 750 sexually mature sturgeon to be documented in six of the DEC’s seven management units statewide as well as evidence of at least three years of wild reproduction of the fish over a five-year period.
Lake Erie – including Cattaraugus Creek, Buffalo Harbor and the upper Niagara River – is considered to be one of those six areas.
Lake Ontario, from the lower Niagara River and the lake to about Rochester, is another.
In the St. Lawrence River, the lake sturgeon has come all the way back. More than 1,000 sturgeon have been located at Massena.
It was that discovery – and vast new research into the lake sturgeon’s spawning tendencies, range and other data – that prompted the DEC to revisit its recovery plan for the fish that was last updated a dozen years ago.
The plan suggests Lake Erie has a lot going for it.
The sturgeon there are fish who have naturally reproduced. None of the fish was stocked, unlike at some other spots in the state.
Their numbers really started coming back in the early 2000s. It was first noticeable near Buffalo Harbor.
“We just started hearing from fishermen along the jetties complaining ‘we’re fishing for walleye and we keep hooking sturgeon, what are you going to do about it?’ ” Holst said.
It wasn’t known how low the once massive sturgeon population in eastern Lake Erie got – estimates are as a low as 1 percent of its pre-19th century number – but when the DEC started looking for the fish at Buffalo Harbor in 2012 using gillnets, they caught 13 sturgeon in five days.
The recovery plan calls for continued annual gill net surveys in the harbor during the spring spawning season until the DEC can confidently say population estimates are no lower than 500 sturgeon. It also proposes verifying spawning reports and analyzing the sturgeon’s size, age and populations for signs of trends.
Getting accurate counts of adult sturgeon is especially important.
Unlike most other wildlife species, the ecological health of sturgeon populations are determined by its adults, not by the numbers of its young.
That’s because the long-lived fish take a long time to sexually mature. Males can’t reproduce until they’re 8 to 10 years old. Females not until they’re 16.
And, they don't spawn every year. Fish and Wildlife data show males spawn every two to seven years, females only once every four to nine years.
“You get more bang for your buck when you have productive adults,” Holst said. “Once they get to a certain size, nothing eats them.”
Sturgeon live a long time. Males usually live up to 55 years, but females can live up to 150 years.
And, some stay frisky into their advanced years.
In 2014, the DEC documented an 84-year-old female sturgeon spawning with much younger fish in Buffalo Harbor.
That female, who became known to the agency’s fish experts by her tag number, 2336, was probably hatched around 1930. She survived a lot of the 20th century’s industrial pollution, enjoyed the lake’s improved water quality and watched native and invasive species come and go.
“She’s seen a lot,” Holst said. “She’s been through a lot.”
If there’s something that concerns Holst, it’s the ages of the fish that are most often found during the DEC’s annual surveys.
They’d like to consistently find 8-year-old sturgeon.
Most caught in Buffalo Harbor are males between 12 and 15. They’re a little younger in Lake Ontario.
Does that mean there was a sturgeon baby boom a dozen years ago? Has reproduction hit a lull? If so, why?
“I worry about that,” Holst said.
It’s too early to know for sure. More studies will be needed.
“We are still exploring those potential recruitment bottlenecks,” said Withers, U.S. Fish and Wildlife Service fish biologist. “If the environment’s supportive of recovery, it would still likely take a number of years to reflect a change in the population since lake sturgeon exhibit slow growth and long generation times.”