GRAND FORKS, N.D. -- Fisheries crews from the Department of Natural Resources in Baudette, Minn., are getting their fill of behemoth fish these days as they study lake sturgeon populations on Lake of the Woods and Rainy River.
Two sturgeon surveys are under way this spring, said Tom Heinrich, large lake specialist for the DNR in Baudette. Both focus on the recovery of a population nearly decimated in the early 1900s by pollution and overfishing. One is an annual assessment, and the other takes place every five years.
Fishheries crews recently wrapped up the less-frequent assessment in Four-Mile Bay, where the Rainy River enters Lake of the Woods. The survey, which involves capturing and tagging sturgeon, is designed to monitor populations in comparison to a set of long- and short-range goals Minnesota and Ontario fisheries managers established in the late 1990s.
The DNR since 1990 has tagged about 6,000 lake sturgeon on Lake of the Woods and Rainy River.
The main criteria, Heinrich said, are the age and length of fish in the sturgeon population. Short-term goals include male fish to age 30 and female fish to age 50, while long-term goals include male fish to age 40 and females to age 70.
The population isn't changing very fast, Heinrich said, so conducting the survey on a five-year rotation is adequate.
Within the same survey, managers every 10 years develop a population estimate. They do this, Heinrich said, by comparing the number of tagged fish to the number of returns reported by anglers or documented in subsequent netting surveys. The most recent estimate, from 2004, was that Lake of the Woods and Rainy River has a population of about 60,000 lake sturgeon 40 inches or longer, Heinrich said.
"I don't think we'll ever get back to where the lake sturgeon population was when white people started to settle; I just don't think that's going to happen," Heinrich said. "What we're doing is monitoring how sturgeon are aging and how the size structure is changing" and how that compares with the recovery plan.
Sturgeon have been on the rebound since the 1960s. And short-term, at least, the recovery goals appear to be on track, Heinrich said.
"We're well on the way to recovery for the population being where it's at," he said. "That's something we're pleased with."
Heinrich said the study targets Four-Mile Bay because the area attracts large numbers of both adult and immature sturgeon each spring. The goal this spring, Heinrich said, was to tag at least 200 sturgeon in Four-Mile Bay, and the DNR crews ended up tagging about 260.
The gear is most effective at sampling sturgeon 30 inches and larger, he said.
"For whatever reason, fish spending a lot of their time in the lake are coming into Four-Mile Bay in the spring for awhile before they head back to the lake or run upriver to spawn," Heinrich said.
The thought, he said, is that Lake of the Woods and Rainy River each hold discrete sturgeon populations.
Heinrich said the number of tag returns reported by anglers this spring suggests the population hasn't changed much since 2004. About one in every 12 sturgeon that anglers catch is tagged, he said, a ratio that's consistent with the 2004 estimate.
More recently, Heinrich said, DNR crews have been sampling spawning sturgeon at the mouth of the Rapid River, which flows into the Rainy at Clementson, Minn., east of Baudette. Crews from the Ontario Ministry of Natural Resources conduct a similar annual survey on a Canadian tributary of the Rainy.
"The reason we're following these spawning fish is that's the oldest, largest segment of the population," Heinrich said. "And that's what a lot of the recovery goals are based on."
Heinrich said the survey crews this spring have sampled two spawning females that measured 66 inches long and 30 inches around, which would put them at about 84 pounds and 42 years old.
Those are big fish, to be sure, but Lake of the Woods historically had sturgeon weighing more than 200 pounds. Only time will tell whether that happens again. It's like asking, Heinrich says, how long it would take to regenerate a 500-year-old forest that's been leveled.
"That's really what we're up against with the sturgeon population, too," he said. "That's just the reality -- to be a 200- or 250-pound fish, you're going to need some in the 100-year-old range. And right now, the oldest are in that 60-year-old range."
"Hopefully, that's within the realm of my lifetime to get into something like that."