Every year, millions of adult salmon return from the ocean to their home streams, where they lay eggs and produce the next generation of fish. But far fewer sockeye salmon are making it back to their freshwater mating grounds compared to a few decades ago, and that’s seriously affecting population sizes of the species throughout the Northwest, from Alaska to Washington State.
The discovery suggests that changing ocean conditions may be making life harder for some groups of wild salmon -- possibly by reducing their food supply or increasing populations of predators.
“We found that substantial reductions in productivity of over 50 percent have occurred in the last two decades in a wide geographical area,” said Randall Peterman, a fisheries scientist at Simon Fraser University in Burnaby, Canada. “We were quite stunned to see these results.”
“We’re telling researchers that in order to really explain the decline in a give population, you should be looking at what is causing the decline in productivity in other populations,” he added. “Depending on which mechanism is the cause of the decline, we may or may not be able to do anything about it.”
Continued: http://www.livescience.com/21517-sockeye-salmon.html
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