ELLSWORTH, Maine — River herring are dying in droves this month in Ellsworth after passing through Leonard Lake Dam, according to a Maine conservation group calling for safer passage for the fish.

“Community members have reported seeing hundreds of dead fish floating down stream below the dam and the Route 1 bridge on multiple occasions over the past 12 days,” said Brett Ciccotelli of the Downeast Salmon Federation. “Dead fish have been seen as far downstream as the city’s Harbor Park.”

Some of those fish appeared to have parts chopped off, while others suffered slashes across their sides or were missing eyes, indicating they struck turbines in the dam, according to the group.

The federation says “thousands” of adult river herring have been killed since early this month while returning from their spawning grounds farther upriver. The group made similar claims following another large-scale fish kill back in October.

“Their life history — needing fresh water to lay their eggs and returning to the same rivers year after year — makes dams without safe downstream passage particularly dangerous to river herring,” Ciccotelli said.

Brookfield Renewables, the parent company that owns the Ellsworth dam, is in the midst of a five-year process for renewing its federal license for the dam for another 30 years.

Ciccotelli argued that one requirement of that renewal should be an upgrade to the fish passage through the dam to reduce the number of fish kills.

Brookfield did not immediately return messages Friday requesting comment.

In October, Brookfield said in a news release that it was “constantly working to minimize the potential environmental impacts associated with our operations and activities.”

“We’re going to be working with Brookfield to assess this situation and will continue to evaluate fish passage at the Brookfield site as we go through the relicensing process,” Maine Department of Marine Resources spokesman Jeff Nichols said in an email Friday.

Defending its environmental record, Brookfield said it moved more than 650,000 river herring around the Ellsworth dam in 2016 and, in response to concerns raised by Downeast Salmon Federation, made easing the passage of out-migrating eel a priority.

Brookfield officials also have said that federal officials determined that the company is already taking steps required by federal regulators to minimize fish mortality at the Ellsworth dam.

Follow Nick McCrea on Twitter at @nmccrea213.

BDN writer Bill Trotter contributed to this report.