The first warm days of spring brought a surprise to anyone who ventured out into the Nyquist-Harcourt Bird Sanctuary on Huguenot Street in New Paltz: dozens and dozens of dead fish, floating on the surface of the pond there. A number of readers reached out to the New Paltz Times to find out what could have caused this dying off.
The phenomenon is known as winterkill, according to Department of Environmental Conservation spokesperson Wendy Rosenbach. “DEC received reports of dead fish in this portion of the Wallkill River this year, as well as similar reports from last year,” she said in a statement. “DEC Fisheries staff investigated and attribute this to a natural phenomenon associated with severe winters both this year and last year (long period of ice cover with a significant amount of snow), resulting in fish being trapped in shallow water and running out of oxygen under the ice.
“In most cases, fish kills that become evident when the ice melts can be attributed to a natural phenomenon known as winterkill. Winter die-off of fish, or ‘winterkill,’ is caused by oxygen depletion in the water through the winter. Ice that accumulates on ponds or lakes prevents wind action from adding oxygen to the water. If there is significant winter snow accumulation on top of the ice, sunlight is prevented from reaching plant life in the pond. Without adequate sunlight, the oxygen-creating process of photosynthesis cannot occur. Shallower ponds or shallower areas of a river are particularly susceptible to winterkill, due to their low storage capacity for oxygen. With the exception of extreme situations, it is rare that all fish in a pond or shallow area of a waterbody will die as a result of winterkill. Typically, larger fish are more susceptible than smaller fish.”
The larger fish do seem to have taken the brunt at the bird sanctuary, and according to Tom Nyquist of the Nyquist Foundation, the same thing happened last year, too. “Most years we get flooding, sometimes so deep it covers the bridge” over the pond, he said, and that’s how the fish get there in the first place. He hadn’t seen this year’s winterkill when he was reached for comment, but recalled that it was “mostly carp,” which fell victim last year to the phenomenon. Nyquist handles virtually all of the construction and maintenance at the sanctuary himself, and has since the foundation preserved it in 2011.
The DEC subsequently released a statement addressing the problem of winterkill generally, which advises that the best prevention is to deepen the pond in question to 12 feet or more. It further advises that, should restocking be necessary, a permit to do so must be obtained through the Region 9 office, which is located on South Putt Corners Road.