October 27, 2015 — For 178 years, dams stood across the Penobscot River here, obstructing salmon and other river-run fish from reaching the watershed’s vast spawning grounds, which extend all the way to the Quebec border.

Now, two years after the dam’s removal, the salmon’s proponents fear the fish face a more fearsome threat: a warming sea.

In recent years, the Gulf of Maine has been one of the fastest-warming parts of the world’s oceans, and climate change models project average sea surface temperatures here to increase by another 5.5 degrees Fahrenheit by 2065, a development that could extirpate Atlantic salmon and other cold-loving species, many of which already find Maine at the southern edge of their ranges.

“We’re all for taking down the dams and all the things that are going on to restore habitat, but how much are they looking at the evidence?” asks Gerhard Pohle of the Huntsman Marine Science Center in St. Andrews, New Brunswick, co-author of a study predicting how the changes are likely to affect 33 commercial species over the next 75 years. “Distribution of salmon in the Gulf of Maine would be such that there wouldn’t be many left at all.”

The warming gulf is already presenting challenges to many of its cold-loving denizens. Scientists at the National Marine Fisheries Services, or NMFS, have recorded the steady retreat of a range of commercially or ecologically important fish species away from the Maine coast and into deep water in the southwestern part of the gulf, where bottom water temperatures are cooler.

The retreat, which intensified over the past decade, includes cod, pollock, plaice, and winter and yellowtail flounder. Other native species that once ranged south of Long Island – lobster, sand lance and red hake – have stopped doing so, presumably because the water there is now too warm.

“You can imagine that when you have species at the southern end of their ranges, they will be really sensitive to these changes,” says Michael Fogarty, chief of the Ecosystem Assessment Program at the NMFS Northeast Fisheries Science Center in Woods Hole, Massachusetts. “They will either shift distribution or their survival rates might change.”

Read the full story at Portland Press Herald