By Louie Stout
Dwindling results in fall surveys of St. Joseph River walleye stockings have biologists scratching their heads.
Indiana, with the help of the Michiana Walleye Club, stocks the river every other year. On non-stocking years, the biologists return in the fall to survey success from the previous year’s stocking.
Last fall’s capture of one-year-old fish declined, just as it has for the past few years.
“We’re trying to figure out why,” says DNR Fisheries Biologist Matt Horsley. “My initial reaction is it could be the stocking location. We’ve been stocking in the lower part, closer to the dam, so maybe the fish are migrating out of that impoundment and moving downstream.”
In 2023, the DNR moved part of the stocking farther upstream and saw slightly better results.
“I’d like to see a couple more years of data from upstream stockings before making a decision,” says Horsley.
The biologist also noted that the timing of the surveys could be impacting the results.
“We typically start surveying in early October, but with the warmer falls, maybe we should start surveys a little later,” he adds.
Biologists use electro-fishing boats that shock fish to the surface where they can be captured, counted, aged and released back into the river. However, the boat is only effective in water six feet or less.
“Maybe we need to look at metrics from a different time of year and get a better sense of what the fishery is doing,” Horsley offers.
The DNR plans to start doing spring surveys on some waters this year to measure a difference.
Other potential factors
Another possibility is an issue with the genetics of walleyes being stocked. The downturn in one-year-old survival is being seen in walleye lakes as well. The DNR raises a small portion of the walleye at its hatcheries, but the bulk come from purchasing fish from private hatcheries.
While St. Joseph River anglers admit to catching walleyes, the complaint is that catching keepers – 16 inch fish – is a lot harder. River fish generally hit that 16-inch mark by age 3.
“That’s another reason I’m beginning to question our sampling methods,” says Horsley. “I don’t get complaints from anglers about not catching walleyes.”
One area where the DNR has found a variety of walleye sizes during previous years’ fall surveys is around the Baugo Creek area.
But that is changing.
“We’ve noticed an influx of starry stonewart is replacing the milfoil in those shallows,” the biologist says. “That plant provides an edge, but fish can’t get up into it like they can with milfoil.”
Starry stonwart is an invasive plant species that grows thick like a Brillo Pad and makes it difficult for fish to use as cover.
Yet, Horsley says they are seeing a lot more bluegills and pumpkinseed panfish in Baugo than they did before. However, he adds, they don’t see the suckers and carp there.
“Maybe the forage base has changed in that area and the walleyes are migrating out,” he says. “These are just some of the things we’re looking at to see what adjustments need to be made.”