Researchers from the Simon Fraser University in Burnaby, Canada have found substantial reductions in sockeye salmon populations over the last two decades. 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. Changing ocean conditions could be based on increased acidification of ocean waters, increases in water temperature, or is being impacted by man made pollution. The researchers did not provide a clear-cut reason, but there is some speculation that warmer temperatures may be the leading cause. Thought the water is not warm enough to hurt the salmon, it may be sufficient to reduce the supply of zooplankton, a main source of food for the salmon. Warm water also increases the populations of tuna, mackerel, and sea lions, which eat young salmon. Researchers plan on zeroing in on the reasons for the decline, in an effort to help facilitate a rebound in sockeye salmon populations.