August 9, 2013 — For more than 100 years, conservationists have tried to restore stocks of Atlantic salmon in Maine rivers, including the Penobscot. Many river-specific threats to salmon, including pollution and barriers to passage in the form of dams, have been studied and demonized over the years.
Today, Maine’s rivers flow cleaner than they have in decades. Dams are being torn out, both on the Kennebec and Penobscot rivers. Salmon should be flocking back. Or should they?
Earlier this month, Katherine Mills, a research scientist at the University of Maine and the Gulf of Maine Research Institute, along with peers Andrew J. Pershing, Timothy F. Sheehan and David Mountain, published a paper that paints a grim picture of the challenge facing Atlantic salmon at sea.
In that paper, Mills points out that climate change and a decline in available food — the relocation or reduction of plankton and fish called capelin — have helped lead to a decline in salmon stocks that has been taking place since 1990. And the outlook for the future is not too bright.
“What we really are seeing is that changes in salmon can be most strongly linked to the loss of capelin as a prey source for them in the Labrador Sea, but can also be tightly linked to [water] temperature,” Mills said.
Salmon in North American rivers take different routes on their migration paths, but eventually end up — or aggregate — in a few key spots. One is the Labrador Sea, where they spend summers. Another is off west Greenland, where they spend winters. Eventually, usually after two winters at sea, Atlantic salmon swim back to the rivers where they were born or stocked.
Read the full story at the Bangor Daily News