In streams winding through Alaska's Tongass National Forest, the largest national forest in the United States, the salmon are running.
They do this every year: the adult fish struggle upstream, sometimes hundreds of kilometers from the ocean. They are going back to the freshwater streambeds where they hatched years earlier. There they will mate, lay their own eggs and die.
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Every year, the U.S. Forest Service puts a camera in the water to capture the salmon's journey.
“These fish come right up to the camera sometimes," said Tongass National Forest biologist Pete Schneider. "You get to see how they chase other fish away, or you can see them digging their nests in the rocks and gravel. You can be at their level and look at them almost eye to eye."
Schneider has been running the salmon cam every year since 1997. This year, he has put it in Steep Creek, where sockeye salmon mate and lay their eggs. The camera shows bright red and green sockeye pairing up and swimming endlessly against the stream's current.
Sockeye is a particularly delicious species of salmon, though the fish can be difficult to catch. “Their meat is highly prized, it keeps very well, so a lot of the native tribes would seek out sockeye in particular because it cans and smokes very well," said Schneider.
Humans aren't the only ones who go after sockeye. After the salmon have spawned, they die in Steep Creek, and the forest's predators all come to the stream for the feast. Grizzly bears, bald eagles and even wolves thrive on the fish. But salmon are a keystone species - the entire coastal ecosystem depends on them.
“It goes beyond just the eagle and the bear and the humans," Schneider said. "It feeds the insects and the plants, and the soils benefit from it, and all the microbes and invertebrates - they all indirectly benefit from the salmon.”
The salmon's bodies fertilize the stream banks and nourish the forest. Later, when the eggs hatch, small fish and animals will feed on the fry. The young salmon travel downstream to the ocean, where they become prey for larger fish, seagulls, seals, whales and fishermen. In a few years, the cycle will start again, and the surviving salmon will battle upstream once more.