The Maine Department of Marine Resources has reduced its estimate of Atlantic salmon returns to the Penobscot River by nearly 200 fish, but the final estimate for 2020 — 1,440 salmon — is still the highest annual return since 2011. In November, state fisheries scientists announced an estimated 1,603 Atlantic salmon had returned to the Penobscot River.
Jason Valliere, a marine resource scientist for the DMR, said each of his regular reports filed since July have included a disclaimer explaining that the official year-end estimate of returning fish was subject to change. Those counts are adjusted after data becomes available, taking into account individual fish that are captured, returned to the river to free-swim to spawning grounds, then re-captured by fisheries staffers at the Milford Dam.
The 2020 total was up from 1,152 in 2019, and is the largest run of salmon since 3,125 salmon returned to the river in 2011. The average run for the eight years from 2012 to 2019 was just 708 salmon per year.
Valliere explained that with more salmon returning this year, he had expected more fluctuation between the November estimate and the one he issued this week, after more data had been analyzed. The fact that more fish were in the river this year led to more fish being available to possibly be counted more than once.
The breakdown on this year’s run: 578 males, 666 females and 196 grilse, or salmon that had spent only one winter at sea before returning to the river, were counted. Of those, 64 males, 126 females and 31 grilse were taken to Craig Brook National Fish Hatchery in Orland to serve as broodstock in the ongoing restoration effort. A total of 1,215 salmon — 513 males, 536 females and 166 grilse were returned to the river to spawn naturally.
The summer weather created some challenges for the fisheries crew, Valliere said.
“The hot dry summer prevented us from handling fish a few weeks earlier in the summer than normal, which resulted in more fish being counted by video,” Valliere said. “In-season recaptures cannot be documented by video so they are prorated based on a subsample of known tagged fish in the river which are detected electronically. This is then extrapolated out to the rest of the video count.”
Atlantic salmon in most Maine rivers have been protected under the federal Endangered Species Act since 2000. Federal protection was expanded to all Maine rivers in 2009, with the addition of the Penobscot, Androscoggin and Kennebec rivers. Among the results of the federal listing: Fishing for Atlantic salmon is not allowed on any Maine river.
Earlier this year conservation groups and individuals were rebuffed when they asked the state to consider listing fish on the Maine endangered species list to strengthen the protections the federal listing has provided.
In November, Valliere said plenty of salmon restoration work remains to be done.
“It’s going to take more time before we can truly assess the success of recent restoration efforts like dam removal and improved fish passage for salmon,” Valliere said. “It takes many generations to do this due to natural population variation year to year due to weather and ocean conditions. We hope the run continues to increase, most importantly the naturally reared component of the run, and that the needle continues to move toward restoration target goals.”