Looking at a pond or lake, we sometimes see aquatic scum or plants moving over the surface, propelled by something beneath them. It’s possible to imagine, say, the presence of a large snapping turtle–but no turtle would explain why, at certain times of the year waters are so turbulent they look like they are boiling.

According to Jeff Braunscheidel, a DNR fisheries biologist whose responsibilities include the Huron River watershed, the most likely cause is the common carp.

Carp are big fish. The state record weighed more than sixty pounds, and specimens three feet long and weighing thirty or forty pounds are common. They’re relative newcomers to America, introduced from Europe in the nineteenth century to replace native species depleted by overfishing. But they’ve never had the cachet of native sport fish. Messy bottom feeders, they suck up and spit out sediment, causing turbulence that destroys the nests of other fish species; they also eat other species’ eggs.

The greatest carp commotion occurs when they spawn, locally in late May and early June. We were over at South Pond behind the city’s Natural Areas Preservation office on E. Huron River Dr. (see Ann Arborites, p. 25) during this period of time looking for wood ducks. While we didn’t have much luck with the ducks, we did see water and mud splashing up in the shallows, as though someone had popped the corks on hundreds of magnums of champagne at the same time. Looking closer, we could see the unmistakable scaly backs of spawning carp.

Carp will be active near the surface again when mulberries are ripe in July or August. According to Braunscheidel, the fish come up to feed on the berries that drop into the water from overhanging branches.

While most Americans do not consider carp a game fish, many still fish for them. Since they are not fussy eaters, bait may include various dough ball concoctions or corn. Of late carp have developed a following among fly fishermen and even archers: Braunscheidel says they hunt at night from boats, their bows equipped with lights and their arrows with lines to reel in their catch. This evokes an �xADancient tradition: according to the website of OSU’s American Indian Studies program, “The Potawatomi used spears to fish at night with torches of cedar soaked in pine pitch and splint baskets for holding fish.”

Braunscheidel notes that some fishers smoke or can their catch. Carp also can be ground up to make patties or balls and is an ingredient in some varieties of gefilte fish. (Bob likes his smeared with a thick layer of horseradish; Jorja prefers hers put in the trash.)

If you do eat carp, Braunscheidel recommends eating small ones. Because they are bottom feeders, carp are “contaminant concentrators” that absorb pollutants from sediment; the bigger they are, the longer they’ve been sucking them up. On a more positive note, he says they make excellent garden fertilizer.

Given the contaminant issue, we probably would pass on using them for this purpose in a vegetable garden. We’re happy to just observe the movement of the waters and know what lurks beneath the surface.