- Associated Press - Sunday, June 8, 2014

PIERRE, S.D. (AP) - The inch-long black radio transmitter slipped neatly into the small incision despite the patient’s lack of cooperation.

It was a large adult gizzard shad caught in the northern end of Hipple Lake and was expressing its displeasure at being outfitted with a radio transmitter by flopping out of its surgical cradle. Game, Fish and Parks Department Senior Fisheries Biologist Mark Fincel, meanwhile, was struggling to keep the shad still as he sewed the hole shut.

The fish was the last of the day’s take from the Hipple Lake and would spend the next few months of its life sending radio pings from its new transmitter to receivers located up and down Lake Sharpe as part of a first-of-its-kind study of the lake’s primary baitfish.

“Right now there isn’t a lot of information about gizzard shad movement,” Fincel said.

The new study has two goals. The first is to determine how important Hipple Lake is to gizzard shad spawning. The Hipple Lake is connected to Lake Sharpe through a narrow channel between Farm Island and the shoreline. The second goal is to figure out where the warm water bait fish weather South Dakota’s harsh winters, Fincel said.

“We think we have the bulk of our reproduction in Hipple Lake,” Fincel said. “We don’t know where they (go) over winter.”

Gizzard shad make up more than 90 percent of the prey eaten by Lake Sharpe’s walleye and small mouth bass. There are so many shad hatched each year that both species don’t have to compete for food. And that is what Fincel is trying to preserve with his study.

“One of the largest spawn areas that we know of is Hipple Lake,” said Fisheries Program Administrator Geno Adams. “The question that came up is how important is that to the river . That was the impetus behind the study.”

Hipple Lake’s connection to Lake Sharpe was nearly silted in during the 2011 flood. Now less than two feet of water connects the lakes and biologists are worried that the link could be lost completely. If that happens and Hipple Lake turns out to be a major source of Lake Sharpe’s gizzard shad, the result could lead to a population crash of every species that preys on them.

“We want to be proactive and not reactive,” Fincel said.

What makes the gizzard shad such an important species for Lake Sharpe is that it reproduces in mass quantities, females can release up to 500,000 eggs each, Adams said. A few months after those eggs hatch the new fish are big enough to interest game fish, which actually causes the fishing on Lake Sharpe to get tougher for anglers because there’s so much food.

“They are the fuel that feeds the walleye fishery,” said Brian Graeb, a South Dakota State University fisheries researcher. “If they would spawn a little earlier in the year they’d be perfect.”

When winter hits the vast majority of young gizzard shad die off, Graeb said. That’s because shad are a warm water species that don’t stand up well to long periods of cold water. That’s good, Graeb said, because if there are too many shad they can out compete other baby fish for plankton.

“They never reach extremely high densities of adults,” Graeb said.

That sensitivity is also driving the second goal of the study. Fincel wants to find out where the shad that do survive spend their winters. He thinks there’s a series of warm water springs that provide just enough heat to keep a small number of adult shad alive to spawn the next year.

“We think that they are finding those springs,” Adams said.

Fincel hopes to be able to identify the springs shad are using so they can be protected from silting over. That way shad can continue to provide stable baitfish populations, and avoid the wild swings that are often seen on Lake Oahe.

“It’s kind of what makes Lake Sharpe a consistent lake,” Fincel said of the lake’s gizzard shad.

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Information from: Pierre Capital Journal, https://www.capjournal.com

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