Vegetarian fish?

Many methods are being tried to control weeds on Lake Hopatcong and Hopatcong Mayor Michael Francis is suggesting one that involves bringing Triploid Grass Carp to certain areas of the lake.

“It’s not a silver bullet,” Francis was quick to say.

The carp love the taste of milfoil, which is the biggest weed problem on the lake, Martin Kane of the Lake Hopatcong Foundation said. He gave a slide presentation to the Lake Hopatcong Commission at its Monday, February 12 meeting.

Martin Kane of the Lake Hopatcong Foundation tells the Knee Deep Club about grass carp. (Photo: Jane Primerano)

Kane said he became a convert to the carp cause when Francis took him and Donna Macalle-Holley of the Commission to visit a Connecticut lake that is the scene of a carp experiment. He said the carp like leafy plants. They don’t eat water lilies or algae. They tend to remain in their feeding area. Kane suggested Crescent Cove and the canals as a good place to introduce them.

The carp developed by Western Connecticut University are sterile. They grow to about 25 pounds and 36 inches long. They don’t look like the carp lake denizens are familiar with. Their bodies are sleeker and their dorsal fins are smaller. Their faces are also shaped for front feeding rather than feeding below. They go dormant in winter.

Kane said they live about 10 years with a 10 percent die-off of those introduced, partially because when they are small they would be attractive to the lake’s large muskies.  

Fred Lubnow of Princeton Hydro, the commission’s environmental consultant, said his firm has experience with grass carp in lakes in New York and Pennsylvania. New Jersey doesn’t allow them in lakes larger than 10 acres. The other states require a barrier so the fish don’t escape downstream, although Lubnow said they rarely stray from their feeding area.

“The fish don’t know they’re sterile,” Tim Clancy of the Knee Deep Club pointed out from the audience, noting they might try to find spawning grounds. Lubnow said they may travel along the shoreline, but won’t go into open water. During times of drawdown, Lubnow said, they will head away from the shore where there is still enough water but not far.

He said they stay away from boats which is why Landing Channel, which has a milfoil problem, would probably not be a good place for them. Francis said when they feel vibrations such as from a boat they drop straight down like a submarine.

Members of the KDC were invited to the meeting for the presentation because their support would be needed to try a grass carp program.

“I’m not speaking for the club,” Clancy said. “I’m not convinced they will stay in the area we want them to stay. He said he read of a place they lived for 15 years and caused a loss of native species, although it was temporary. “I’m not against this, but it’s got to be part of a holistic approach,” he said.

“I see on the internet people are saying the carp are going to solve all the problems of the lake,” Clancy said.

Francis, Lubnow and Kane all emphasized that grass carp only work in areas with certain species of plants such as milfoil and tapegrass and won’t touch planktonic growth or cattails or phragmites. They stay away from deeper parts of the lake. The advantages are a lower cost than some other methods of weed control  because one the carp are purchased and put in the lake there is no more cost. The weed harvesters which would still have to be used in the main parts of the lake, are very expensive to maintain.

The Commission will consider the recommendation for implementing grass carp, Chairman Ronald Smith said.

Hopatcong Mayor Mike Francis describes the success of the grass carp program in a Connecticut lake. (Photo: Jane Primerano)

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