News / Science & Technology

    The Salmon Show, Live from Alaska

    A sockeye salmon scurries through shallow water in the Adams River in British Columbia, Canada, Oct. 11, 2006.
    A sockeye salmon scurries through shallow water in the Adams River in British Columbia, Canada, Oct. 11, 2006.
    Megan McGrath
    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. 

    Watch the Migration Show Live
     

    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.
     
    The salmon cam is hosted by the U.S. Forest Service.

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    Comment Sorting
    Comments
         
    by: Cranksy from: USA
    July 25, 2013 2:51 AM
    Why do salmon ( some species only I think) die after they spawn? I have researched this question in the past, but I didn't get very far. If any ichthyologist or serious amateur reads this, please give some degree of explanation of the cause of death.
    In Response

    by: Cranksy from: USA
    August 03, 2013 1:04 PM
    Pete Schneider, thanks again. Your second reply is closer to the intent of my original question why do salmon die after they spawn. I was asking for a pathologist's sort of answer. You wrote they [salmon] stop eating once entering fresh water. A guess, but only a guess, is that they die of starvation.
    In Response

    by: Pete Schneider from: Juneau, Alaska
    August 01, 2013 7:44 PM
    On this system, the black bears usually get first crack at the returning salmon. Once the salmon become plentiful, the bears begin to "high-grade" and focus on pre-spawned female salmon. They are after the eggs. We commonly see female fish with only their belly eaten. They also like the fat-rich brains. Bears are joined by river otters and mink as the primary mammals on this system. Bald eagles, ravens, and crows are usually next in line and often go for the eyes first, then any remaining flesh.

    Regarding being edible for humans- it depends how hungry you are. A rule of thumb up here for sport fishing is to get the salmon when they are still bright (silver) from the ocean. The quality of their meat decreases once they obtain their full spawning colors. Since they stop eating once entering fresh water, they rely on their fat reserves and muscle tissue for energy on the spawning grounds.
    In Response

    by: Cranksy from: USA
    July 31, 2013 12:48 AM
    Hi Pete, and thank you. A component of your reply is ...[S]cavengers have consumed the carcasses.... Do mammals eat them? Are they edible for human beings when they are dying and/or dead?
    In Response

    by: Pete Schneider from: Juneau, Alaska
    July 30, 2013 12:39 PM
    Death after spawning is one of the characteristics that make a salmon a salmon. Salmon have evolved with this basic mechanism in their lifecycle which works for them and it is actually very beneficial to their young. Unlike most mammals, birds, and some reptiles, most fish can't or don't "care" for their young in any manner. Salmon compensate for this somewhat by producing numerous offspring. Less than 5% of the eggs laid will survive to reproduce. By dying on the spawning grounds, the salmon indirectly benefit their young (and the young of their cohorts) with literally all they have- their bodies. Their nutrient-rich bodies support the ecosystem by fertilizing the stream and adjacent stream banks. Once scavengers have consumed the carcasses, plants, fungi, microbes, and insects all utilize whatever is left. This creates a robust ecosystem foundation that will, in turn, benefit the salmon fry once they emerge in the spring from their gravel nests. Healthy plant and insect populations provide shade, cover, clean and cool water, and a food base for the growing juvenile salmon. It makes for a perfect cycle as the adult fish move out of the way for the next generation.
    In Response

    by: Yoshi from: Sapporo
    July 25, 2013 6:04 PM
    Hi, Crankcy, how do you do. I have never think about it. I also wonder why and can not find an answer. Could someone inform us?

    by: Yoshi from: Sapporo
    July 24, 2013 8:20 PM
    Oh, it is already time for salmon to start migration in Alaska. Some of them must be native of Hokkaidou, northern part of Japan. We are looking forward to welcomig them this autumn in their native rivers and wish good lick to spawn fry.

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