If you’ve walked or rowed along the Charles River the last few weeks, you may have been subjected to a grotesque scene: Several dead fish floating in the water.
But Jason Stolarski, an aquatic biologist and the “fish kill coordinator” for MassWildlife, says he’s not concerned about the number of dead carp reported in recent weeks.
“They’re very active when they spawn, so they expend a lot of energy. They’re also releasing eggs and sperm into the water, and it costs energy to create those reproductive products,” Stolarski said. “By the end of this activity, when they’ve all spawned, they’re just gassed, right?”
Essentially, he said that the carps’ defenses were down after the seasonal breeding activity. So when the record-breaking heat wave tore through the Boston area last month, they were vulnerable to the high temperatures, or low oxygen in the water, or disease.
“These fish died probably a few weeks ago, but they’re still kind of just kind of floating around and being consumed by secondary predators and turtles and things like that.”
For passersby who see — or smell — the carp, there’s really nothing to do. Still, Stolarski acknowledges it’s upsetting.
“Obviously when you see dead fish, particularly when you see aggregations of dead fish, your mind immediately goes to kind of the worst-case scenario — the river turned to poison, ... there’s some sort of agent that’s killing things at will. And that’s often not the case,” he said. “It’s not the end of the world, and the carp will be just fine.”
Marielena Lima with the Charles River Watershed Association says it’s been a “noticeable” amount of fish — and she wants to make sure people don’t get up close and personal with bacteria-laden decomposing organisms.
“Definitely don’t touch it,” she said.
“It’s such an early fish kill. Usually it happens later down in the summer when it’s really hot,” she added. “But we’ve been in a drought for months now, so I think it’s just kind of all these compounding effects on fish in our watershed.”
Stolarski said it’s been a rough season, and offered another cause for the many dead fish on the river. The unusually cold winter led to way more fish than usual dying under thick layers of ice and snow in ponds across the state. So when the ice started melting a few months ago, those dead fish all rose to the surface, she said.
“Usually it’s a pretty quiet job ... but this year it’s been quite busy,” Stolarski said. “They’re all natural, and it’s all a function of how we treat how we treat the watershed that we live in.”
On the Charles, the fish being impacted appear limited to one species and aren’t native to the area, so Lima isn’t worried about environmental consequences.
“Thankfully, it’s only been invasive carp,” Lima said.
