Spring thaw washes up ponds of suffocated fish

SALEM, Ohio – As the temperatures rise and the snow and ice melt, some pond owners are getting a big surprise: dead fish.

With ponds covered in ice and thick blankets of snow for months, the fish suffocated and are now washing up as the water thaws.

Ice alone wasn’t the culprit, says Andy Burt, fisheries biologist with Ohio Department of Natural Resources. Instead it was the snow.

With piles of snow sitting on the pond, sunlight couldn’t penetrate the ice. That sun was essential to the fishes’ survival, Burt said.

Without sunlight, photosynthesis could not occur in the water’s plants. Photosynthesis is what provides oxygen to the fish when ice covers the surface, Burt said.

The fish suffocated, he said, because they were using the oxygen without more entering the water.

In past years, the die-off hasn’t been as severe because of breaks in the winter weather and less snow.

Worried owners. Ever since the temperatures warmed up, Burt says there have been daily calls from concerned pond owners. Although many of them say all their fish are dead, Burt says this isn’t the case.

Although there isn’t oxygen for all the fish in a snow-covered pond, usually there’s enough for some of the fish to live. And because larger fish typically need more oxygen, they are the first ones to die.

Add fish? Although it’s too late to do anything this year, pond owners can take heart in knowing that they don’t necessarily have to restock their ponds.

Give it time for the bass and blue gill to grow and reproduce. Within a year or two, Burt says the pond will be stocked with about the same number and size of fish as before the die-off.

Precautions. Pond size doesn’t matter. All owners, from small farm ponds to 5-acre ponds, are at risk for this type of die-off.

For next year, Burt says to remember to shovel the snow off the pond often.

He says all the snow doesn’t have to be removed. For example, he says a 30-foot area on a small pond is plenty.

(Reporter Kristy Hebert welcomes reader feedback by phone at 1-800-837-3419, ext. 23, or by e-mail at khebert@farmanddairy.com.)