Making a Connection: Salmon as Networker
I have been watching Cosmos a lot. It’s got wide appeal in my house–children and adults are equally enchanted. Cosmos reminds me of our connection to all living things–all of us born of stardust. I hadn’t thought about that in a long time.
Most of us don’t dwell on the mysteries of the universe, but they matter. Our interconnectedness, in particular, matters for people–and for wildlife out there in those wild places. Some species are more linked than others. In Malcolm Gladwell‘s world, we’d call them “connectors.” In science, they’re called “keystone species.” These animals, and even some plants, have a large impact on the creatures surrounding them–so large that the habitat would be fundamentally different without them.
Salmon are amazing connectors; they connect to more than 190 plants and animals. So when salmon go missing, it’s like the life of the party has suddenly disappeared–everyone feels it. It may not surprise you to learn that salmon are an important food for orcas, sharks, sea lions, seals, otters, and bears.
But did you know that birds, amphibians, and even insects consume salmon carcasses and eggs? Salmon are so connected that they benefit plants, even vineyard grapes.
How, you ask? It’s all about their journey.
Pacific salmon are marathon swimmers–beginning in the briskly cold freshwaters of the Snake, Klamath, and Sacramento Rivers, and other rivers and their tributaries. From these rivers, they spill into the open expanse of the Pacific Ocean. Some go on to swim all the way to Japan.
Near the top of the food chain, salmon eat and absorb nitrogen from creatures unlucky enough to be lunch. The nitrogen in these ocean-dwelling animals is unique. Scientists call it “marine-derived nitrogen,” or (MDN for the techies at heart). And when salmon swim all the way back to our roaring rivers of the West, scientists can track the impact of salmon by this special marker–the MDN–in other animals and plants.
When a salmon dies, that marker works its way through the habitat–from the colossal grizzly to the little bug. Bears and wolves fish the salmon out. They carry the carcasses further upstream. Parts of the carcasses are often left behind for other animals and insects to scavenge. The animals that eat salmon also then do what animals do in the woods… and, as a result, this nitrogen gets absorbed by the soil and works its way into algae, mosses, herbs, shrubs, and the royalty of plants–ancient trees.
Scientists are discovering remarkable things. When more salmon reach their spawning grounds, the MDN, not surprisingly, gets more widely dispersed into the watershed. This, in turn, creates wild places that are healthier and more diverse–more bugs, more birds, more plants. And playing the role of Sherlock Holmes, scientists can track the impact of MDN from tree core samples to an otter’s whiskers.
But many salmon are becoming an endangered species. What happens when salmon disappear from these ecosystems and the ocean? Very bad things. Just ask the endangered Southern Resident Killer Whales or orcas (Orcinus orca), which live in Puget Sound and the Pacific Ocean from Southeast Alaska to California. These whales are going hungry, and the impacts mean life or death for individuals and for the population as a whole.