Carp Feast on Zebra Mussel in Mississippi

From January, 1996 (Update #26)

There was widespread media attention this fall about common carp feeding on zebra mussels. (See Cliff's Notes for more on the subject.) The stories were inspired by the findings of John Tucker, a biologist with the Upper Mississippi River Long-Term Resource Monitoring Program in Alton, Ill. Given all the hoopla, we contacted Tucker and he sent this intriguing response: "I was fishing with my daughter near Brussels Ferry, Ill., this summer when we caught a common carp 290 mm long. To satisfy my daughter's curiosity, we took it home to dissect. When we examined it, we found that the fish's gut was completely packed with fragments of zebra mussels. "Because the common carp had not been reported to feed extensively on zebra mussels in the United States, I asked station biologists to collect carp from the Mississippi River, just below the confluence with the Illinois near Grafton, Ill. This collection site has been monitored for zebra mussels since 1992 and is known to be heavily colonized by them. "Of the 31 common carp examined (ranging in size from 243-559 mm), 26 contained the remains of one or more zebra mussels. With few exceptions, the zebra mussel shells were crushed and well fragmented by the carp. Staff members determined the number of zebra mussels present in each gut by halving the number of internal septa found. The number of zebra mussels consumed ranged from 0 to 204. Measurements are incomplete at this time, but the largest carp contained specimens of zebra mussels estimated to have been 15-18 mm in shell length, based on septa lengths. Smaller fish contained zebra mussels estimated to be less than 12 mm in shell length." Tucker said he publicized his initial findings because some aquaculturists have suggested releasing other exotic carp species to control zebra mussels. Substantial common carp predation further diminishes the rationale for introducing another exotic carp to prey on zebra mussels, he said. Moreover, predation evidence can be collected without killing the fish by expressing feces from the vent of the carp. The feces can then be examined for zebra mussel shell fragments. Further investigation into the phenomenon appears warranted, agreed Steve Gutreuter, director of monitoring and research at the National Biological Service Environmental Management Technical Center in Onalaska, Wis. "It is far too soon to tell whether carp might help control zebra mussel populations," he cautioned. "The fact that zebra mussels and carp are both abundant in some areas of the upper Mississippi River suggests that carp are unlikely to be controlling the densities of zebra mussels. However, in areas where zebra mussels may already be limited by lack of suitable conditions, the additional mortality from carp predation might be important.".

ID: 199601-3.

The Zebra Mussel Update was a 4- to 8-page quarterly national newsletter published by the University of Wisconsin Sea Grant Institute from May 1990 through May 1997. The ZMU documented the spread of the zebra mussel -- an exotic nuisance mussel -- through North America's freshwater environments, especially the Great Lakes, and on efforts to control it.