Unusually high water temperatures throughout the North Pacific Ocean have brought concerns from researchers about how it could affect native species of fish as well as sightings of uncommon species.
The three areas of the North Pacific with the most notable warming trend include the Gulf of Alaska, the Bering Sea and an area off the coast of Southern California down to Baja California, Mexico, with temperatures as high as 5 degrees above average.
These sea surface temperature anomalies have remained this way for more than a year, one of the longest stretches on record, according to researchers with the National Oceanic and Atmospheric Administration (NOAA).
The warmer water has prompted questions about how it will impact the marine food web, said Laurie Weitkamp, a research fisheries biologist with NOAA's Northwest Fishery Science Center in Newport, Oregon.
A big concern for native species of fish, such as salmon, is that the primary food items they eat may no longer be available, Weitkamp said.
Potentially adding further stress to the situation, warm water also increases the metabolic rate of the fish so they have to eat more in warmer water, but there may not be enough to eat because the conditions are not suitable for their food items, Weitkamp said.
Nate Mantua, leader of the landscape ecology team at the NOAA Southwest Fisheries Science Center, attributes these conditions in the Gulf of Alaska to the same ridge of high pressure that's believed to have contributed to California's extreme drought. Storms and winds that commonly cool and stir the sea surface have been quelled by the ridge.
"If the warming persists for the whole summer and fall, some of the critters that do well in a colder, more productive ocean could suffer reduced growth, poor reproductive success and population declines," Mantua said in a NOAA Fisheries article.
"This has happened to marine mammals, sea birds and Pacific salmon in the past. At the same time, species that do well in warmer conditions may experience increased growth, survival and abundance," Mantua said.
Another effect likely brought about by the noticeably warmer waters is observations of different species of fish that are not known for frequenting this part of the ocean.
Earlier this past summer, a research vessel found a thresher shark in the Gulf of Alaska, which was the northernmost documented catch of the species, according to Michael Milstein, a spokesman for NOAA Fisheries.
"Thresher sharks are know for preferring warm waters," Milstein said.
In August, a skipjack tuna was caught in a salmon net off the Copper River in Alaska, a region not known for warm-water species such as tuna. The book "Fishes of Alaska" has only one confirmed documentation of the species which was back in 1981.
Additionally, a mola, also known as an ocean sunfish, was spotted in the Prince William Sound in the Gulf of Alaska.
Seeing a sunfish in that part of the ocean is "completely unheard of," said Weitkamp.
Farther south, fishermen in the San Francisco Bay unexpectedly caught a rare green sea turtle in mid-September. The species, normally found in Mexico, was about 2,000 miles off course according to an article on SFGate.com. The turtle was later released.
"Fish are really sensitive to water temperature and they have their preferred water temperatures and that's where they like to stay," said Weitkamp.
Milstein said the Bering Sea and Gulf of Alaska serve as seafood baskets for the rest of the world, supplying much of the world's fish protein.
The warmer water temperatures can have a huge impact on a lot of these species, despite water temperatures varying 4 to 5 degrees from normal, Weitkamp said.
"It doesn't sound like a very big difference, but it really is [a] pretty significant impact on a lot of species," Weitkamp said.
Already, one report published in July by NOAA Oceanographer Bill Peterson indicated that spring chinook salmon and steelhead trout that migrated into the Gulf of Alaska this past spring "may experience very poor survival this year."
The last time there was a similar warming in these waters was 2005, but what's unusual about this situation is how extensive the warmth has become and how long it's been occurring.
"It's not clear when it's [going to] end either," Weitkamp said.