Minnesota, Ontario complete first phase of sturgeon study
Minnesota and Ontario fisheries crews tagged more than 1,300 sturgeon 40 inches or longer this spring to wrap up the first part of a major population study of the species on Lake of the Woods and Rainy River.
According to Phil Talmage, area fisheries supervisor for the Department of Natural Resources in Baudette, Minn., crews completed the tagging phase of the “mark-and-recapture” study in late May.
Next up, Talmage said, they’ll go back out with sampling gear later this month and begin recapturing a similar number of sturgeon in the Rainy River and the southeast portion of Lake of the Woods. By comparing the ratio of tagged to untagged fish in the recapture effort, biologists then can calculate a population estimate.
Sturgeon on the Minnesota-Ontario border lake and river are on the rebound after nearly being decimated by overfishing in the early 1900s and later, declining water quality that hampered production. A remnant population of sturgeon survived, and the passage of clean water legislation in the 1960s improved spawning habitat.
Today, the sturgeon population on Lake of the Woods and Rainy River has reached short-term recovery goals set by Minnesota and Ontario fisheries managers. Those goals called for male sturgeon to age 30 and females to 50 years old, with fish larger than 70 inches and 30 year-classes of fish in the population.
The DNR and Ontario’s Ministry of Natural Resources last teamed up on a major sturgeon population study in 2004. DNR fisheries crews from Baudette and International Falls, Minn., along with MNR fisheries personnel from Fort Frances and Thunder Bay, Ont., have been sampling sturgeon this time around, Talmage said.
The tagging portion of the study got off to a slow start this spring because of a late ice-out and high water levels. But once conditions straightened out and crews could set nets and, in some cases, hand-grab sturgeon at spawning sites, the tagging effort quickly fell into place, Talmage said.
“I think our first 500 fish took us five or six weeks, and the last 800 or 900 we got in a matter of a week,” he said. “We had one pod we were working where we must have tagged about 10 fish in 20 minutes.”
Crews also tagged the largest sturgeon ever sampled on Lake of the Woods and Rainy River, Talmage said — a 72½-inch behemoth with a 30-inch girth “through a good chunk of its body” that weighed an estimated 105 pounds. That fish was sampled below the Clementson Rapids on the Rapid River about 10 miles east of Baudette.
Crews also sampled a few fish more than once, Talmage said. In one case, a sturgeon caught May 1 at the mouth of the Rainy River was recaptured May 22 in Big Falls, Minn., on the Big Fork River, a Rainy River tributary about 110 river miles away.
The river in Big Falls is a key spawning site for Lake of the Woods and Rainy River sturgeon.
“It was down there in the rapids, and we hand-grabbed him out,” Talmage said of the sturgeon, which measured 44 inches long. “We don’t know whether it’s a male or female, but we’re guessing probably a male. It shows you that fish obviously had something on its mind where he or she wanted to go. When you think about it, it swam past other spawning populations to get there.”
Talmage said the crews aged about 1,500 sturgeon during the first phase of the study but only tagged fish measuring 40 inches or longer.
Back to work
Heavy rains and high water will delay recapture efforts in upstream portions of the study area, Talmage said, but crews working the lower Rainy River and Lake of the Woods are scheduled to begin June 23.
Sampling fish at randomly selected sites, they’ll continue to catch sturgeon until they approach the goal of 1,400 fish, Talmage said. If crews don’t reach that number by the end of July, they’ll take a break and resume the effort in October, he said.
Sampling sturgeon during the middle of the summer when water temperatures are warmer increases the risk of mortality, Talmage said, something the research crews don’t want to happen.
“Ideally, we’d have it wrapped by the end of July,” Talmage said. “If we can get it wrapped up by then, we won’t have to worry about those water temperatures. We’ll just see how it goes.”