Spawning Grass Carp Means it’s Time to Move on Separation

Spawning Grass Carp Near Lake Erie Underscores the Urgency of Keeping Bighead and Silver Carp Out of Lake Michigan.

News that the United States Geologic Survey (USGS) has confirmed the verified spawning of grass carp in the Lake Erie Basin should be an alarm to the US Army Corps of Engineers and Illinois leaders considering options for the permanent separation of the Lake Michigan and Mississippi River watersheds. Grass carp are an invasive species and pose a threat to the Great Lakes, but the bighead and silver carp found near Lake Michigan would be substantially more damaging to the Great Lakes ecosystem. These new findings followed the lack of preventative action and confirm the need for a plan against new invasive transfers.

Sterile populations of grass carp have been found in 45 states throughout the U.S. and have inhabited the Great Lakes system for years. However, the recent findings that this species is capable of reproducing reinforce the impracticality of controlling non-native species after they have been introduced into a system.

Despite grass carp’s widespread distribution, the populations are primarily present in inland lakes and are considered less threatening than other Asian carp species, most notably bighead and silver carp. Disruption to aquatic vegetation represents the primary impact from grass carp populations, leading to a reduction in available habitat. Bighead and silver carp, in comparison, are the species most commonly referenced as “Asian carp” and could yield extensive ecological devastation. As voracious feeders, populations of these species can vastly outcompete native fish species, disrupting entire food chains throughout the Great Lakes.

Grass carp spawning serves as a warning of the impending risk from other, more destructive Asian carp species. The fact that grass carp gained entry into the Lake Erie basin reminds us that aquatic invasive populations are on the move, growing, and likely to enter the Great Lakes unless permanently stopped. If connections into Lake Michigan remain exposed, bighead and silver carp will continue to have the opportunity to enter our Great Lakes, at which point they could colonize the entire Great Lakes and sustain high-density populations.

Grass carp entering the Lake Erie basin through the Sandusky River is bad news, and a new threat to the Great Lakes. However, it is a separate threat from that posed by bighead and silver carp. We cannot allow the Chicago Area Waterway System to be another point of entry for even more damaging species. We hope that the forthcoming Great Lakes and Mississippi River Interbasin Study (GLMRIS) from the Army Corps will prioritize hydrological separation, and launch aggressive, innovative planning for a permanent solution before it’ too late.

Posted October 28, 2013