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A sick and malnourished sea lion pup is examined at the Marine Mammal Center in Sausalito, Calif., on Wednesday.Justin Sullivan/Getty Images

Record-high sea-surface temperatures in the Gulf of Alaska and die-offs of sea lions and seabirds on the West Coast are raising concerns about changing conditions in the Pacific.

A report released this week by the U.S. National Oceanic and Atmospheric Administration (NOAA) says a massive "warm blob" of water that is up to 3 C higher than average is spreading south from Alaska. That, together with other environmental factors, could make the ocean less productive for many species, including salmon.

The changes are occurring in addition to an El Nino event that developed in the Pacific this winter, and which brought warmer water north from the equatorial Pacific. The warm waters in Alaska developed about one year ago.

"We are seeing unprecedented changes in the environment," Toby Garfield, director of the environmental research division at the U.S. Southwest Fisheries Science Center said in a statement.

The report states that, in addition to higher sea-surface temperatures, there have also been weaker upwellings of cold currents. Those upwellings bring nutrients up from deeper ocean levels, enriching the base of the marine food web.

The NOAA report states that last summer and fall, the weights of California sea lion pups were below average in some rookeries, and many pups died, apparently from starvation.

"That trend has continued into winter, along with strandings of dead pups. It is possible that another UME [unusual mortality event] will be declared soon in 2015," the report states.

The NOAA report also says that Cassin's auklets, especially juveniles, have been dying in large numbers.

"Many dead auklets appear emaciated. Cassin's auklets prey on zooplankton, and this die-off may be a leading indication of suboptimal feeding conditions," the report states.

Dr. David Bradley, B.C. program manager of Bird Studies Canada, said Wednesday there is "definitely a spike in [marine bird] casualties in B.C. this winter."

But he said "it's a big mystery" as to why the birds have been dying and he is waiting to see whether U.S. researchers can confirm a correlation between marine-bird deaths and warmer sea-surface temperatures.

Dr. Richard Beamish, an emeritus scientist with the Department of Fisheries and Oceans, said the NOAA study suggests a significant shift of oceanic conditions is taking place.

"Some of us, me in particular, believe there are these major climate, ocean events which we've been calling regimes," he said. "We had a major regime shift in '77 and then in '89, probably another around 1998 … and since they [are] occurring roughly every 10 years … most of us have been expecting we'd see a change."

Dr. Beamish said regime shifts can have a dramatic impact on salmon production, causing stocks to crash.

But some fish species thrive under warmer conditions, and fish rarely seen off the West Coast can become plentiful.

"We could have a bizarre season, perhaps with tuna up as far as Alaska," he said.

Aaron Hill, executive director of Watershed Watch Salmon Society, said the changes are worrying.

"It's certainly concerning, because there are a number of factors in addition to this that are conspiring against B.C. salmon populations," he said, noting low snowpacks this winter will lead to reduced river levels. "If we get another hot summer on top of that, it will be really bad [for spawning salmon]."

Mr. Hill urged government to restrict commercial catch levels this year.

"I'd like to see [Fisheries and Oceans] take a more precautionary approach to salmon populations under these conditions," he said. "They are basing management decisions on the assumption we have a certain level of productivity in our salmon populations. But with these environmental conditions right now, that seems like a brash assumption."