(Provided by IDNR)
Recent heavy rains that flooded northeast Indiana ditches could create problems for anglers.
DNR fisheries biologists say flooding can create better conditions for non-native common carp to move into lakes, rivers and wetlands.
Introduced in Indiana in the 1880s, common carp have spread throughout the state and caused widespread damage to water quality, fish habitat and fishing. Carp roil the muck and silt on lakebeds and riverbeds, muddy the water, uproot aquatic plants and destroy nests of other fish.
They also compete for food and space with sport fish and upset the natural food web.
"They are the No. 1 nuisance fish in Indiana," DNR biologist Jed Pearson said.
Pearson has dealt with carp problems at three lakes in Noble County.
In the 1980s, he managed a DNR-funded project to eradicate carp from Sylvan Lake and many of its headwater lakes and streams. Carp became so abundant at the lake that few anglers fished there, and residents were unhappy with the muddy water.
After the renovation, water quality improved, fishing boomed, and lakefront property values increased.
Carp grow rapidly and within the first year are too big to be eaten by predator fish.
"Fortunately Sylvan and many other lakes have enough predators to control carp reproduction," Pearson said. "But when high water levels in ditches allow more adults to get into lakes, that increases chances carp numbers will rise."
Carp also have caused problems at Bixler Lake in Kendallville. Located upstream from Sylvan, it was renovated in the 1970s and developed into an outstanding fishery.
DNR officials installed a barrier in the outlet to block carp from returning to the lake from Henderson Ditch, but DNR later removed it due to maintenance issues. Carp numbers increased after removal, but not enough to warrant another renovation.
"Weíve been monitoring the lake ever since," Pearson said. "Weíre looking into the possibility of re-installing a barrier, however, we recognize the time and cost it would take to properly design, get approval for, install, and potentially maintain it in order for it to be effective."
The likely source of carp problems at Bixler and Sylvan lakes is Henderson Lake, a small lake that sits in the watershed between the two. Henderson Lake has been renovated twice, but poor habitat conditions prevent the redevelopment of a healthy sport fish population.
In general, biologists do not like fish barriers because they also block the movement of popular species. Pearson suspects Bixler Lake gets an influx of walleyes during high water from stockings downstream at Sylvan Lake. He caught four walleyes at Bixler during a fish survey there last summer.
But local conditions and can override this concern.
"Carp are the biggest problem at Bixler," Pearson said. "If a barrier is installed, walleyes could always be stocked later directly into the lake."