Good to see a story like this showing up in mainstream media. Some points I took from it:
"Competition with other marine mammals for the same food may be a bigger problem than fishing, at least in recent years, for southern resident killer whales that spend time in Washington state's Puget Sound, a new study suggests.
Researchers used models to estimate that from 1975 to 2015, marine mammals along the U.S. West Coast ate dramatically more Chinook salmon – from 6,100 metric tons to 15,200 metric tons, according to a study published Monday in the journal Scientific Reports.
In the same period, salmon caught by commercial and recreational fishing from Northern California to Alaska declined from 16,400 to 9,600 metric tons.
"This really quantifies yet another pressure on recovering the salmon population," said co-author Isaac Kaplan, a research fishery biologist with the Northwest Fisheries Science Center, part of NOAA Fisheries. Other threats to salmon include habitat damage, dams and pollution.
The emphasis typically has been on managing how fishing affects salmon. But this study brings the rest of the ecosystem, including predators, into the picture, Mr. Kaplan said.
Researchers have known marine mammals gorge on salmon in certain hot spots, including the Columbia River between Oregon and Washington. But the predators may be eating even more in the ocean than thought.
The authors estimated how much salmon in different life stages four marine mammals ate based on a number of assumptions, including their weight, diet and size. The species included California sea lions, Stellar sea lions, harbour seals and fish-eating killer whales.
The study does a very good job of accounting for who eats Chinook salmon during its various life stages, said Andrew Trites, professor and director of the marine mammal research unit at the University of British Columbia. He was not involved in the study. "They've identified some of the major players, but they haven't identified them all," such as other fish, marine birds and porpoises, he said.
The study found killer whales, which increased from 292 to 644, ate the most salmon in terms of biomass, or weight, while harbour seals ate the greatest numbers of salmon, mostly juvenile fish."
This something that DFO and their masters the Federal Government has to start paying attention to!
