In trying to untangle a mysterious herring collapse from the aftermath of the Exxon Valdez oil spill, scientists in Prince William Sound are revealing just how resilient—and unpredictable—marine ecosystems can be.
On a cold day in June, Scott Pegau leans toward the passenger window of a Cessna floatplane and peers out at the teal waters of Prince William Sound. The glacier-rimmed pocket of seawater on the southern coast of Alaska is protected from the open ocean by a string of rugged islands. It is both moody and alluring. Clouds dally on the snowy peaks and fray against the forested hillsides. The sea is flat and frigid, except for a single row of waves lapping at the rocky shore.
Pegau aims his gaze at the shallow waters behind the breakers. After a few minutes of searching, above a deep bay on one of the outer islands, he finally spots what he’s looking for: a school of juvenile herring. Pegau can distinguish them from other schooling species by the unique way they sparkle—an effect produced by sunlight playing off their silver flanks as the fish bank and roll. Try as I might, I can’t make out any twinkling, just the inky splotch of a few tons of small fish swarming below the surface.
“Small H1,” Pegau says into the headset microphone, tucked snugly under his thick, grey mustache. That’s code for a small school of one-year-old herring. He enters the location on his computer; huddled in the back seat, I make a tick mark on the backup tally. It’s the first of dozens of schools we’ll see on our flight.
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