We don't presume to know how many weed-eating Asian grass carp are needed to eradicate the hydrilla threat in Lake Wylie, but we hope 500 will be enough.
The grass carp is desirable because it likes to eat hydrilla, an invasive, non-native plant that can grow as much as a foot a day. It can quickly choke out native species and make lakes, canals and other waterways unusable by boaters, swimmers and anglers, and can even effect the quality of drinking water.
Hydrilla, which probably was introduced to Lake Wylie from a home aquarium, has established itself on the North Carolina side of the lake near the Interstate 85 bridge. It now covers about 20 acres.
An initial plan had called for introducing 1,600 sterilized carp to attack the plant. But officials on both sides of the state line now have compromised on 500 fish.
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This project will be funded by the state of North Carolina, the marine commission and Duke Energy. But officials with the S.C. Department of Natural Resources were involved in negotiations about how many fish would be needed.
South Carolina officials argued that some anglers like the idea of hydrilla because it provides a good place to cast for fish. They think 500 fish will be enough to control the hydrilla while reducing the chance that the too many carp would turn to eating native plants, too.
We hope 500 fish is enough, although that seems to be a sharp reduction from the 1,600 originally planned. But, as Duke officials note, they always can add more.
In any event, the decision to use carp to attack the encroaching hydrilla looks sound. It has been used successfully elsewhere and is a much better method than using chemicals to kill the plants.
This also is an opportune moment to advise people not to introduce aquarium fish or plants or other non-native species to the lake. As the problem with hydrilla illustrates, one plant can upset the natural balance of the entire lake.