Winter Kill Reports

blake · Mar 24, 2009

PMA Memberships & Renewals and IBA Memberships & Renewals

From the IDNR:

 Reports of Winter Kills in Lakes and Ponds Coming in as Ice Melts
by Joe Wilkinson

The calls come in about this time of year. Winter ice has melted and a pond owner or early season angler heads down to check things out. Dead fish? Not a good sign.

"I'm getting lots of calls. We had a fairly hard winter again and people are calling about fish kills on ponds," relays Scott Gritters, fisheries management biologist for the Department of Natural Resources. You can expect a few fish to die each winter. However, a deep blanket of snow can mean problems. "Heavy snow-and we had a lot of it through December into January--keeps sunlight from penetrating through the ice," notes Gritters. "That causes algae in the pond to die back, which depletes oxygen."

In Iowa, there are about 90,000 ponds. Most are farm ponds, holding water from surrounding slopes or hillsides. They often provide watering holes for livestock. A growing number of ponds are showing up in towns, too; especially as developers and city planners work to contain runoff.

Well managed ponds are excellent fisheries. A strong zooplankton/insect base feed the bluegills or other panfish. Most of them end up as dinner for larger predator fish. However, as thousands of their siblings are consumed, the rest grow to decent sizes; delighting anglers young and old. And with a good forage base, those predators-- largemouth bass for instance-hit trophy sizes. Throw in some channel catfish, which aren't choosy about whether their food is still living, and you can develop a balanced 'back 40' fishery.

So now, after a hard winter, you have to assess the damage. "I ask people to walk around the pond and see what kind of fish are dead," says Gritters. "If it's mostly large fish, then the smaller fish-which need less oxygen-might have survived. As they grow, they should fill that big fish gap. If the shoreline is littered with dead fish of different sizes then that indicates a widespread die off."

In that case, restocking may be your next move. Private hatcheries and other commercial vendors--even some farm supply stores--offer various fish stocking options. The DNR does as well; though the pond stocking program revolves around that three species combination. Young-of-the-year bluegill and catfish are shipped early in the fall. By the next summer, largemouth bass are available. The pond owner is charged $25 an acre for the stocking and certain other requirements must be met; such as pond acreage, depth and whether livestock are kept out. Information is available at http://www.iowadnr.gov or by calling your area fisheries biologist.

Oh, and to nip in the bud one of the most commonly asked questions, 'No, you do NOT have to let anyone fish in your pond just because the DNR stocked it.' But since angler license sales help offset the cost of pond stocking, it is always appreciated if pond owners do allow some angler access.

Of course, prevention is better than restocking. An inspection of your pond can determine whether it is too shallow, or perhaps whether it has too much nutrient-load or chemical runoff entering it. Any of those factors can lead to problems.

If it is in good shape, the best prevention comes in the winter. "A lot of people look at aerators for their ponds. That is a viable solution," says Gritters. "A cheaper method is just to scoop the snow from the ice; to let light penetrate." He admits, though, repeated shoveling after each heavy snowfall can get old in a hurry.

From there, as long as you don't upset the balance in the pond, lunker bass and hand-sized bluegills can be common. Biologists usually advise setting up a catch and release policy for any big bass. Some have to remain in the pond to eat into the forage base. Otherwise, an overpopulation of stunted bluegills, for instance, will appear. Likewise, catfish do not readily reproduce in such confined settings and you shouldn't take too many.

Maintain a balance in that pond-whether it is in a cattle pasture or a subdivision-and the payoff will be great fishing across four seasons.

PM
Ron Wyllie
Southwest Iowa IBA Area Representative
rwyllie@iowawhitetail.com

Winter Kill Reports

blake

Life Member