Where’s the Carp?

By Pamela Eyden

Common carp are an exotic species that was brought to the Upper Mississippi River basin so long ago (the 1880s) that most of us take them for granted. Despite the fact that carp are a desirable food fish all over the world, few anglers on the Upper Mississippi River want to catch them.

Uncommon carp?

Commercial fishermen do pursue carp. Common carp have been important to commercial fishing on the river since it began, a couple decades after carp got established. Commercial fishermen sell common carp, buffalo and catfish to wholesalers who process and ship most of it out of the region, to Chicago, the East Coast and Europe.

Mike Valley, who fishes commercially out of Prairie du Chien, Wis., said in January, “There have been no carp in our stretch of river since last fall. We hauled in 3,000 pounds of buffalo and there were only a couple of carp in there. Where have they gone?”

Cate Bell and her husband Keith started K & C Fisheries in Wabasha, Minn., in early 2012 to process carp to ship overseas. She buys carp from local fishermen, but, she said, “There aren’t the quantity that there used to be.”

Jeff Ritter, who fishes commercially and processes his catch at a small factory north of Prairie du Chien, agreed. “There are not such huge numbers of carp anymore. Years ago you could seine 50,000 pounds of fish at a time from under the ice, but not anymore. The max now, I’d say, is 5,000 to 10,000 pounds.”

Ritter now takes his two boats and four-man crew to the St. Louis area to fish three days a week. He usually brings home 13,000 to 15,000 pounds of rough fish.

Larry Stoller of Stoller Fisheries in Spirit Lake, Iowa, is the third generation in his family to process and ship carp and other wild-caught freshwater fish for human consumption.

“There’s been an overall decline in the number of carp in both the river and the inland lakes,” he observed.

“We don’t take much out of the Mississippi River anymore — partly because the fishermen are fickle and the supply is irregular.”

How many carp are in the river?

State and federal agencies do not sample or track carp numbers, as they do game fish and fish of special interest, such as paddlefish. So, biologists can’t say if there are more or fewer carp in the river than 20 or 50 years ago.

The Upper Mississippi River Conservation Committee (UMRCC), a consortium of scientists from five states, has kept records of wild fish taken by commercial fishermen since 1953. The records show that the number of carp caught in the river has bounced up and down, but has generally decreased for a long time. In 1956, the total catch was 1,101,746 pounds, although that count included smallmouth buffalo. In 1971, the carp catch was 4,104,270 pounds. In 1990, the catch dipped to 541,830 pounds, then it rose again to 2,072,692 pounds in 1992. In 2000 the number dropped below a million pounds and has stayed below ever since. In 2013 the catch was 366,453 pounds.

Andy Bartels, fisheries specialist with the U.S. Geological Survey’s Upper Midwest Environmental Sciences Center in La Crosse, Wis., summarized the catch data by saying that “the data shows a definitive long-term decline in the number of carp.”

Fisheries biologist Michelle Marron of the Wisconsin Department of Natural Resources, who maintains commercial harvest data for the UMRCC, cautioned that those numbers reflect more than just the number of carp.

“A lot of factors affect the carp harvest,” she said. “There was a big drop in demand in the 1970s, when PCBs were discovered in the river and in fish. We lost a lot of commercial fishermen at the same time, and now we’re down to just five major wholesalers that fishermen can sell to.”

Speculation

Biologists and fishermen can only spec ulate about causes of the apparent decline in the carp population. Some possibilities are:

• New, sophisticated fishing and seining technology has enabled bigger catches and put a permanent dent in the population. Submersible ROVs (remotely operated underwater vehicles), for example, can easily find the deep holes where fish gather under the ice and help corral them into nets.

• Chemicals and pollution in the water may be affecting reproduction of rough fish.

• An infestation of the spring viremia virus (swim bladder virus) in 2004 hit common carp hard, and the extreme summer heat in 2005 added to the damage. The virus is still persistent. (It is not harmful to humans.)

• River water is cleaner now than a couple decades ago. Water level drawdowns in some pools have encouraged plant growth. Increased aquatic vegetation has decreased the roiling effect of wind and waves that keeps the water muddy, which carp tend to prefer. Zebra mussels have also filtered the water, making it less ideal for carp.

• Parts of the river may be improving ecologically, increasing opportunities for native species and putting invasive species, like carp, at a disadvantage.

Marron said her agency has never looked at the number of carp, except in relation to the spring viremia virus, but she saw a lot of small carp last year, so they may be rebounding.

“That’s good for fishermen, not necessarily for us,” she laughed.