Familiar denizens of the deep will return to Stansbury Lake next spring as the Stansbury Park Service Agency works to reduce weeds in the body of water.
During its meeting last Wednesday, the service agency board voted to return triploid grass carp to the lake in April 2018 after Stansbury Park Service Agency manager Randall Flynn suggested using the fish, in addition to harvesting using the lake mower and adding dye to reduce photosynthesis.
Flynn laid out a number of different options for the board that could improve the lake, ranging from simple, cheap fixes to more complex and expensive options.
The best, long-term solution for the health of the lake and to reduce weed growth would be to drain the lake and excavate the shallow regions, Flynn said. The problem: Such a project might take more than a year and would cost as much as $10 million.
Flynn laid out other options as well, including using diquat herbicides in the lake. He said the herbicide would kill the weeds but they could come back and a quick, widespread elimination of weeds could cause oxygen levels in the lake to decrease.
While it was part of his recommendations, Flynn said dye to reduce photosynthesis and improve the appearance of the lake hadn’t been used enough on the lake to ensure it was successful.
“The reason we stopped using dye is because we wanted to flow water through the lake,” Flynn said.
Stansbury Lake is high in dissolved solids and water is run over a weir to simulate movement in the lake to reduce its salinity, Flynn said. Stansbury Lake is fed by the Mill Pond and wells and does not have a natural inlet or outlet.
With the lake flushed frequently, the dye would only remain in the lake for a short period of time, Flynn said. An application would cost $2,500 to $4,500 per month and likely run March through October.
Flynn ultimately suggested the triploid grass carp, dye and lake mowing as the cheapest and most effective combination to treat the weed problem in the lake. He said the service agency put too many grass carp into the lake when they were first put in the lake prior to the mass fishkill in 2013. A total of 3,000 grass carp, which can grow up to six feet long, were put in the lake over a two-year span in the first stocking.
“Our lake, for the size of it, would probably be better suited to about 800 grass carp,” Flynn said.
The grass carp actually did too good of a job eliminating lake weeds, Flynn said, as they eventually eradicated the weeds. The resulting decrease in oxygen in the water led to the fishkill during a hard freeze.
It would cost between $15,000 and $20,000 to restock the lake with grass carp. The fish don’t reproduce and don’t stir up the bottom like true carp species do.
“I didn’t think I’d ever recommend putting those carp back in,” Flynn said.
The service agency unanimously voted to approve up to $20,000 to restock the lake with the triploid grass carp, on a motion by board member Mike Johnson. The dye for the lake, expected to cost about $25,000 for the year, was also approved by the board. Neither treatment would begin until the spring of 2018.