More salmon are returning to Pacific rivers than ever before, and that’s a good thing for coastal ecosystems, new research shows.
A study published in the science journal Nature this week reviewed data from 1976 to 2015, and found the amount of salmon returning increased overall by 32%. Researchers found that has increased beneficial nutrients in watersheds where salmon spawn and die, increasing dissolved nitrogen and phosphorus, which are essential for aquatic life.
However, it also means an increase of human-caused contaminants such as mercury and PCBs, which accumulate in salmon flesh and persist in the ocean after decades of dumping them at sea during the past century.
The good news, they say, is the benefits of eating salmon, for all creatures, outweigh the potential negatives from trace contaminants.
“Eating Pacific salmon provides a net benefit to people,” researchers say, although they call for more research into the effects of contaminants to ecosystems, which remain largely unknown.
The research found the BC and Washington Coast region has seen the largest increase in nutrient and contaminant inputs, 142 per cent since 1976.
The overall amount of salmon in the Pacific has been increasing since around 1976.
“Populations of pink salmon, sockeye salmon and chum salmon are larger now than they have been in recorded history, with modern increases corresponding to the 1977 ocean regime shift and expanded hatchery production,” the study says.
The increase is mostly driven by pink salmon, which now account for more than half of all salmon in the Pacific, and which are thriving in response to climate change, the study says.
The study is titled “Continental-scale nutrient and contaminant delivery by Pacific salmon” and is available online in its entirety.
