In the past, hydrilla carpeted whole swaths of Lake Austin. The invasive plant ruined recreation and damaged ecosystems on the lake. So to counteract that, the City of Austin occasionally introduced tens of thousands of sterilized grass carp to eat the hydrilla. But the city is now on the lookout for unintended consequences.
You’ve got to hand it to the grass carp: They did their job swimmingly. There’s no hydrilla problem in the lake right now, but there is concern the thousands of hungry fish have turned their attention to native plant species, and even other fish.
“Yeah, some of the anglers have talked about while they’re off fishing that they’re actually able to catch grass carp on crank baits. So, that’s what really got their hackles up,” says Dr. Brent Bellinger, an environmental scientist with the Watershed Protection Department. “Well, if they’re going after something that looks like shad on crank baits, they might be going after shad in general.”