A thousand or so dead sunfish were bobbing in and around Field Pond, bleaching a sickly white under the sun. Fearing an act of pollution or some impending ecological disaster, visitors to Harold Parker State Forest were quick to call authorities.
But the fish kill the past two weeks was neither toxic release nor apocalyptic sign. As alarming as it was to the dozens of callers, it was a natural event, the combination of spawning stress and warming waters, state fisheries officials say.
"When someone comes across a lot of dead fish, the logical conclusion is something must be wrong with the water," said Richard Hartley, a state fisheries biologist who investigated. "It's kind of the canary in the coal mine."
However, the water quality is fine and fish and wildlife are OK, he assures. And local anglers tell him the fishing is good. Still, something about the sight of all those blue gills, and the smell of it, kept Hartley busy fielding calls from area residents.
He issued an advisory to satisfy the curious and to educate the public on the seasonal events. Because it is a natural phenomenon, the state allows nature to take its course in such events. The remaining fish are consumed by birds and other scavengers, while some decompose. The dead, which ranged in size from 3 to 5 inches, are a fraction of the overall fish population, he said.
"To us it looks something absolutely horrific," said Hartley. "But to natural scavengers, this is a bounty. It's like going through the drive-through."
The dead fish became the talk of Andover at one point a week ago. Robert Douglas, conservation director for the town, said the town received a couple dozen inquiries. He offered reassurances, as well as some agreement about the peculiarities of nature.
"It is natural, but it's always disturbing to see so many dead fish," he said.
Hartley attributes any hyper sensitivity in the public to greater knowledge of various human impacts on the environment. He welcomes the calls, whether for one dead fish or the 1,000-plus he estimated he found at the 59-acre pond within the state forest just off Route 125 in Andover. The state does not stock fish in Field Pond, a popular spot for boaters with small recreational watercraft.
The greater awareness is the result of decades of environmental rallies, regulations, and stewardship, agreed Jack Clarke, director of public policy for the Massachusetts Audubon Society.
"People's personal behaviors have changed," he said, pointing to greater recycling and personal consumer actions, better and more efficient uses of energy, and less use of harmful everyday chemicals, like certain lawn fertilizers. He said people know that if they put something down the drain, it is not out of sight and out of mind, that it potentially goes right into their local water supply.
Hartley said the public reaction to the Field Pond fish kill is also related to a trend of modern life -- that most people do not encounter much wildlife. As the coordinator of fish-kill response for the Massachusetts Division of Fisheries and Wildlife, Hartley monitors a database with four decades of reports. This is the first fish kill reported in Field Pond, though he said it has probably occurred in the past without a report being filed. He has tracked about 20 episodes this year, with all but one or two being natural, seasonal events.
Most fish kills reported are typically the result of spawning stress, fish diseases, or low oxygen levels in the water. When pond temperature increases, the water holds less oxygen, Hartley said. Vegetation growth also consumes oxygen.
The spawning stress can be incredible. During late spring and early summer, sunfish and other species crowd into shallows along the shore to compete for the best sites. The concentration of biomass is susceptible to disease outbreaks and what the biologist calls an unavoidable fish kill.
If Hartley had discovered that the fish died because of pollution or intentional or accidental dumping, he would have called the state Department of Environmental Protection for analysis and a formal investigation, he said.