One size does not fit all when trying to understand salmon survival in the Pacific Ocean, Laurie Weitkamp of the NOAA Fisheries Northwest Fisheries Science Center, Newport, Oregon, office, told the Council in a report in January.
And the unique life history characteristics of each species can be further complicated by changing and sometimes hostile conditions in the ocean, as has happened in recent years as the result of a warm water anomaly known as The Blob.
Normally, each species uses the ocean differently. They enter the ocean at different times, go to different places, eat different things, and return to the Columbia River to spawn after spending different amounts of time in the ocean. Collectively, this determines their ocean survival, that is, how many fish return to spawn as adults.
For example, juvenile spring Chinook, chum, sockeye, and some coho move rapidly northward along the continental shelf to the Gulf of Alaska, where they will feed and grow. Fall Chinook and some coho, by comparison, remain in local waters off the coasts of Washington and Oregon. Steelhead are the long-distance travelers of the anadromous fish world, heading rapidly straight out into the ocean directly west and traveling sometimes nearly to Russia. Steelhead tagged as juveniles at the Dworshak National Fish Hatchery in Idaho have been caught in driftnet fisheries off the coast of Japan.
When they return as adults, Columbia River fish follow similar patterns, Weitkamp said. Fall Chinook, and possibly chum and sockeye travel south along the Continental Shelf from the Gulf of Alaska. Coho travel north along the coasts of California and Oregon, and steelhead and Spring Chinook tend to move rapidly onshore from west to east to the mouth of the river.
Complicating this already complex mix of life histories, atmospheric and ocean conditions can affect salmon survival and the availability of food. The warm water anomaly known as The Blob, a mass of warm water in the middle of the North Pacific, formed in the winter of 2013/2014 and created a ridge of high pressure over the northern Pacific that was “ridiculously resilient,” Weitkamp said. The practical effect of The Blob was to create warm, low-nutrient surface waters, which left much of the ocean a food desert for Columbia River fish. Many juvenile salmon are believed to have starved. By January of 2018, maps showed sea surface temperatures had returned to normal, but the damage had been done and its effects continue.
There was a broad response to the warm water created by The Blob, from ocean conditions to marine species, Weitkamp said. In 2015, fish normally found in the tropics were being caught off the Northwest coast; young Chinook salmon were noticeably skinny and obviously malnourished. In 2016, red pelagic crabs, a warm water species typically only found south of San Diego, were found off Oregon, and changes to the food web, first noticed in 2015, continued. In 2017, crab and clam fishery closures that began in 2015 continued, there was an explosion of warm-water pyrosomes, also known as sea pickles, from California to Alaska, and the cod abundance in Alaska crashed. More California sea lions than usual migrated to the Columbia River estuary from southern California, where their pups were starving. From about 1,500 counted in 2014 in the Astoria area, the 2016/2017 count was nearly 4,000.
In 2017, the annual survey of waters off the coast found extremely low numbers of juvenile Chinook and coho salmon. Researchers have no idea what happened, as the number of juvenile fish in the Columbia River estuary was within the normal range. There were other anomalies in 2017 – the second-lowest sockeye and pink salmon returns ever to the Fraser River, the lowest steelhead returns to the Oregon coast ever, the closure of fisheries for Chinook from Washington, Oregon and British Columbia in Alaskan waters, but the highest chum salmon harvest ever in Alaska, and strong returns of pink and sockeye salmon to Alaskan waters.
Weitkamp said she expects the biological effects of warm ocean conditions to continue for several years, at all levels of the marine ecosystem. The low counts of juvenile coho and Chinook in 2017 do not bode well for adult returns in 2018 and 2019, but the prediction for cooler coastal waters this spring should be good for juvenile salmon entering the ocean, she said.