Is It Time for Lake Hopatcong to Reconsider Triploid Grass Carp?

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The summer is half over and boats are starting to go back in the water after such a long hiatus due to the pandemic. Of course, we can not forget the tragedy of Curt Mulch who lost his life after the harvester capsized only a few weeks ago. Unfortunately, the overgrowth of weeds in Crescent Cove is still an issue. So the question becomes is it time to reconsider Triploid Grass Carp.

Grass carp is a long, slender, silver-colored fish.  They feed almost exclusively on aquatic plants. They can eat 2-3 times their weight each day and may gain 5-10 pounds in a single year. Grass carp can grow up to 100 pounds. The larger they get, the more plant material they consume.

triploid grass carp and aquatic plant management lSince grass carp cannot reproduce in ponds and lakes, they are an excellent biological control agent. They can only affect the impoundment during their individual life span. They are usually most effective after their first growing season until around age eight. Due to this growth period, weed decline is usually not apparent in a pond until the end of the second year, depending on the number of fish stocked.

Although grass carp will probably not reduce mature stands of aquatic flora, they may eat the new sprouts and prevent further expansion by these plants. Their preferred plants are pondweeds, milfoil, coontail, waterweeds, muskgrass, waterlilies and cattail. Quite a few of these vegetations shown above are present in the crescent cove area.

Most of the time Grass Carp are used in ponds and contained areas but they have been used successfully. Candlewood Lake in Connecticut introduced over four thousand grass carp in two batches starting in 2015. Residence did see a reduction of invasive plant life over the next few years. 

When using Grass Carp in larger bodies of water such as a lake there can be challenges. They have been known to travel outside of the desired area so containment barriers (netting at the Dam) can be used. Depending on the barrier it could hinder boating. Also, grass carp can be fussy eaters. They eat what they like first. So, if there is other vegetation in the cove they prefer they may eat that before eating what we might want them to eat. 

Candlewood Lake – Proof of Concept in a Large Lake:

Candlewood Lake is the largest lake in Connecticut and also the most popular lake for recreation in the State. At 8.4 square miles, it is the largest lake in Connecticut. Here is a past video regarding their use of Triploid Grass Carp.

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The state of New Jersey does have guidelines in regards to Triploid Grass Carp

Taken directly from the DEP Website-

Permission to stock will only be given for the “Triploid” form. 

  • They must be obtained from one of the hatcheries on our list of approved hatcheries, where the US Fish and Wildlife Service certify them as “Triploid”.
  • We will allow for the stocking of waters of 10 acres or less in size, and where it can be reasonably expected that the fish can be prevented from escaping.
  • A minimum of 40% of the lake surface be covered with vegetation that is palatable to the species before it will be considered for stocking.
  • Stocking of grass carp will not be approved in areas identified as sites of endangered or threatened species, plants, or animals.

Now you know more about Triploid Grass Carp then you probably ever wanted to know. 

More about Sterile Grass Carp at Southland Fisheries:

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So, again we ask… Is it time to reconsider Triploid Grass Carp? 


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