By John Roach Humans are a big burden on sockeye salmon populations.
Scientists now say natural climate variability also wreaks havoc on the fish.
Devoured at the dinner table, blocked by hydroelectric dams and crowded out by urban development, sockeye salmon face a big burden in humans. And now it turns out that natural climate variability also wreaks havoc on the fish, according to research in today's Science . But climate change is a regulator in the population cycle going up and down. Sockeye gain 99 percent of their body mass while at sea on a diet of plankton, squid and small fish. When the fish return to freshwater lakes to spawn and die, their carcasses release the isotope nitrogen-15.