Learn MoreSlideshow / South Fork Rivanna Reservoir Mitigation UpdateSouth Fork Rivanna Reservoir helped by trees and fishReservoir task force adopts final report calling for selective dredging only after specific goals and locations are identified
Lurking below the water of some of Charlottesville–Albemarle’s lakes and reservoirs are grass carp that have made quick work of invasive water vegetation. Called hydrilla, the plant often hinders boaters, anglers and water intake systems, and localities frequently stock lakes and ponds with the carp in order to manage its growth.
Despite improvements in water access and usability, some fishermen say they aren’t catching fish in the same numbers they used to, and they wonder if the absence of hydrilla is the culprit.
“I used to catch 10 [or more] fish per trip on Lake Albemarle and Chris Greene Lake,” said Bill Maupin, a lifelong Albemarle resident and bass fisherman. “Now, fishing the mostly barren lakes, I feel fortunate to catch one or two.”
But Johnathan Harris, a biologist with the Virginia Department of Game and Inland Fisheries, points to data that show increased bass populations.
For example, between 2008 and 2015, bass populations in Lake Albemarle have jumped from approximately 150 catches per hour to nearly 350 per hour. However, the catch rate for large bass 15 inches or longer dropped from almost eight per hour to almost four per hour.
The decline in larger-sized bass, Harris said, is the result of a growing bass population. Because bass in many of Albemarle’s lakes have few predators and a low mortality rate, there are large numbers of smaller bass but decreasing numbers of bigger bass.
“They’re eating everything that’s available, but there are so many mouths to feed that they’re just not growing fast,” Harris said.
One reason for the high numbers of fish in the water, Harris said, is that anglers are releasing fish back into the water after they are caught.
“It’s been engrained in all the anglers’ heads to catch and release bass,” Harris said. “When you have good reproduction and low mortality, you have a real heavy stockpile.”
With respect to the absence of hydrilla, Harris said that could lead to a change in fish behavior — thus making it harder to catch fish — but not to a decreased bass population.
“Some people, when they’re used to fishing hydrilla beds and then the hydrilla is removed, they have a hard time catching the fish, even though the fish are still there,” Harris said.
Regardless, Maupin questions the decision to use grass carp to remove the vegetation outright.
“We need to think about whether aesthetic feelings toward aquatic vegetation and human needs, such as valid uses for outboards etc., … are the primary reasons we decided to destroy aquatic vegetation,” Harris said. “I would like to see us better balance the needs of human uses and aesthetic desires with fishermen who are concerned about the health of our fisheries.”
The decision to introduce grass carp depends on the situation, Harris said. For example, if a reservoir is being used as a water supply, the intake needs to be kept clear. In instances where a lake is used for recreational purposes — like Lake Albemarle — Harris said you would use carp if vegetation was prohibiting that use, or if hydrilla appeared in one-third of the water.
“When it starts interfering with the boat landings, and people getting in and out of the boats, then we have to manage for that,” Harris said.
Moving forward, Maupin is hopeful public perception over using carp will change.
“I believe public attitudes toward aquatic vegetation, which are admittedly evolving, will change over time,” Maupin said.