Page 28 - ARUBA TODAY

A28 SCIENCE
Tuesday 21 November 2017

Endangered orcas compete with seals, sea lions for salmon

By PHUONG LE tion efforts including the
Associated Press Marine Mammal Protection
SEATTLE (AP) — Harbor Act in 1972 have meant
seals, sea lions and some good news for other popu-
fish-eating killer whales lations. Harbor seals, for ex-
have been rebounding ample, increased 210,000
along the Northeast Pacific to 355,000.
Ocean in recent decades. Puget Sound orcas con-
But that boom has come sume adult chinook salmon
with a trade-off: They’re - also called king salmon
devouring more of the because they’re the larg-
salmon prized by a unique est - that migrate back to
but fragile population of Puget Sound waters.
endangered orcas. “Every other one of those
Competition with other ma- predators has a chance
rine mammals for the same to eat that salmon before.
food may be a bigger prob- In this Sept. 2017, photo made with a drone, a young resident killer whale chases a chinook They’re the last ones to
lem than fishing, at least in salmon in the Salish Sea near San Juan Island, Wash. sit at the table and get a
recent years, for southern Associated Press chance to eat,” said Bran-
resident killer whales that don Chasco, lead author
spend time in Washington include habitat damage, The study does a very good salmon. of the study and an Or-
state’s Puget Sound, a new dams and pollution. job of accounting for who But the orcas that spend egon State University post-
study suggests. The emphasis typically has eats chinook salmon during time in Puget Sound ate doctoral student.
Researchers used models been on managing how its various life stages, said about the same volume Meanwhile, harbor seals
to estimate that from 1975 fishing affects salmon. But Andrew Trites, professor they did 40 years ago, feast on millions of smaller,
to 2015, marine mammals this study brings the rest of and director of the marine mostly because their num- juvenile salmon as they mi-
along the U.S. West Coast the ecosystem, including mammal research unit at bers have been relatively grate to the ocean from lo-
ate dramatically more chi- predators, into the picture, the University of British Co- constant. cal rivers.
nook salmon - from 6,100 Kaplan said. lumbia. He was not involved Puget Sound orcas, also “They’re first in line to eat
metric tons to 15,200 metric Researchers have known in the study. “They’ve iden- known as southern resident the prey before they be-
tons, according to a study marine mammals gorge on tified some of the major killer whales, face greater come adults,” Chasco said.
published Monday in the salmon in certain hotspots, players, but they haven’t challenges than their orca “The question is whether
journal Scientific Reports. including the Columbia identified them all,” such as counterparts farther north those fish would have died
In the same period, salmon River between Oregon and other fish, marine birds and because they have a nar- in the ocean, or if they’re
caught by commercial and Washington. But the preda- porpoises, he said. rower menu of fish stocks taking prey out of the
recreational fishing from tors may be eating even The study found killer and fewer available fish mouths of predators farther
Northern California to Alas- more in the ocean than whales, which increased compared with what they downstream.”
ka declined from 16,400 to thought. from 292 to 644, ate the need, Kaplan said. The authors say efforts to
9,600 metric tons. The authors estimated how most salmon in terms of bio- These whales have strug- restore threatened salmon
“This really quantifies yet much salmon in different life mass, or weight, while har- gled due to lack of food, runs may be masked by the
another pressure on recov- stages four marine mam- bor seals ate the greatest pollution and impacts from increasing numbers eaten
ering the salmon popula- mals ate based on a num- numbers of salmon, mostly boats since they were listed by these marine mammals.
tion,” said co-author Isaac ber of assumptions, includ- juvenile fish. as endangered in Canada The study was paid for by
Kaplan, a research fishery ing their weight, diet and Scientists also found certain in 2003 and 2005 in the U.S. the Pacific Salmon Com-
biologist with the Northwest size. The species included populations of fish-eating There are now just 76, down mission, which was formed
Fisheries Science Center, California sea lions, Stellar resident killer whales in from a high of 140 decades by the governments of
part of NOAA Fisheries. sea lions, harbor seals and southeast Alaska and Can- ago. Canada and the United
Other threats to salmon fish-eating killer whales. ada waters ate a lot more Marine mammal protec- States in 1985.q