Forage fish food key to survival.

• Position: Puffins

The connection among the condition and survival of puffin nestlings, climate change, and commercial fisheries is demonstrated in a study by the National Audubon Society, New York. 'There have been some good years and some bad years but, overall, we're seeing a decline in puffin chick body condition and this leads to fewer chicks surviving to breeding age," says coauthor Stephen Kress, director of the Audubon Seabird Restoration Program and Project Puffin.

"You can protect the islands where puffins nest, but that's not enough if the forage fish and marine habitat are not protected as well."

As part of this study, Atlantic puffin populations and chick weights at three Maine islands were examined between 2005-14. Because puffins return to breed at the same island each summer, they are good indicators for changes in forage fish species. Kress and coauthors Paula Shannon, Audubon Seabird Sanctuary manager, and Christopher O'Neal, senior model validation analyst and statistician at Synovus, Columbus, Ga., liken a puffin colony to "a community-based fishery that fishes near home, samples nearby waters, and is vulnerable to local conditions."

White hake, a cold water species, is by far the most common fish delivered to puffin chicks, but they are shifting northward as the Gulf of Maine warms. Atlantic herring, the second most important forage fish, also has declined in puffin diets. Meanwhile, butterfish, a warm water species, has increased, but large butterfish often are too large for the chicks to swallow, resulting in starvation. This especially was obvious in 2012, the warmest water year ever recorded for the Gulf of Maine.

"Puffin chicks can only fit certain sizes and shapes of fish into their beaks," explains Kress. "They have to swallow them...