Threat to listed species, threat to regional investments
The population rebound is very good news for the species, but the way in which the population has expanded its presence in the Columbia River is not good news for Columbia River spring Chinook, an endangered species. NOAA Fisheries research conducted since 2010 between Astoria and Bonneville Dam has identified an “unexplained mortality” of the fish that varies from year to year but has not been lower than 11 percent of the run (in 2010), which translated to 34,688 fish in that year. In 2017, the unexplained mortality was estimated at 24 percent, which given the below-average run size, translated to 24,242 fish. The highest mortality as a percentage of the run was in 2014, when an estimated 104,333 fish, or 43 percent of the Upper Columbia spring Chinook run entering the river that year (242,635 fish), were lost between Astoria and the dam to the unexplained mortality, which the chief researcher, Dr. Michelle Wargo-Rub, said can be attributed to sea lions.
In contrast, Columbia River fisheries – sport, commercial, and tribal – are much more constrained in terms of protecting weak species. Commercial and recreational fisheries in the lower Columbia River, the same area where sea lions prey on salmon and steelhead, target hatchery fish and are restricted to an incidental take of no more than 2 percent of the annual wild-fish return.
Video: U.S. Army Corp of Engineers
Every year since 2002, the U.S. Army Corps of Engineers has observed sea lions killing salmon, sturgeon, and lamprey in the area immediately downstream of Bonneville Dam between the first of January and the end of March, the time period when the largest number of sea lions are present and adult spring Chinook are migrating upriver. In 2017, the Corps estimated that sea lions consumed between 4,759 and 5,227 salmonids (salmon and steelhead) at that location. During that period, NOAA researcher Dr. Wargo-Rub estimated that 24,242 salmonids were consumed by sea lions, about 6,000 of them within four miles of the dam, which is farther downriver than the Corps observers are able to see from their positions around the dam. So the numbers are similar.
Sea lion with unfortunate sturgeon
Salmon and steelhead recovery in the Columbia River Basin costs around $300 million a year, and nearly all of that is paid by electricity ratepayers of the Bonneville Power Administration, which has a legal obligation to protect and enhance fish and wildlife affected by hydropower dams in the basin. Bonneville Dam blocks the river, and while adult fish are able to pass using fish ladders, the presence of the dam and the limited number of fish ladders provide an ideal location for sea lions to prey on fish. NOAA Fisheries, Bonneville, the Council, and others are concerned that the increasing sea lion predation on ESA-listed species is offsetting the large investments in salmon recovery associated with habitat, dam operations, harvest, and hatcheries.
The Columbia River spring salmon run includes 32 distinct populations of Chinook that are listed as threatened or endangered under the federal Endangered Species Act, as well as many non-listed populations. Of particular concern are upper Columbia spring Chinook, listed as endangered, and Snake River spring/summer Chinook, listed as threatened.
“Our panel of independent scientists is alarmed by the steady decline in survival of ESA-listed, upper Columbia spring Chinook salmon in the Columbia River estuary, where research indicates predation by sea lions on these fish is intense,” said Guy Norman, a Washington member of the Council and chair of the Council’s Fish and Wildlife Committee. Before being appointed to the Council in 2016, Norman directed the Southwest Washington division of the state Department of Fish and Wildlife.
The danger to these runs, particularly upper Columbia spring Chinook, was highlighted in a February 2018 report by the Independent Scientific Review Board, a panel of scientists that advises the Council, NOAA Fisheries, and Columbia River Indian tribes. In their report, the ISAB cited predation by sea lions in the lower Columbia River as one of the threats that may be contributing to the continuing low numbers of Chinook.
“The continuing temporal increase in pinniped [sea lion] numbers [in the lower Columbia] may be an important factor limiting Upper Columbia spring Chinook abundance,” The ISAB reported. The ISAB report continued: “Surprising new evidence indicated a steady decline in estuarine survival of the combined runs of adult middle and Upper Columbia River spring Chinook and Snake River spring/summer Chinook (from 90 percent in 2010 to 69 percent in 2013). Survival was consistently higher for Chinook arriving late in the run compared to those returning early or at the peak, when predation by pinnipeds would have been more intense. The declining survival rates also coincided with the growing presence of sea lions and seals in the estuary.”
Not everyone agrees predatory sea lions need to be removed. The Humane Society of the United States, which has litigated to prevent the lethal removal of the most aggressive sea lions in the Columbia, say sea lions are unfairly targeted because they contribute only a small percentage of the total take of Chinook salmon. In an April 2016 blog post headlined "Eating Salmon Is A Crime – But Only If You’re a Sea Lion," the Society stated, “We humans are responsible for a far larger share of the mortality” through impacts such as sport and commercial fishing, hydropower dam operations, predation by introduced non-native species like Bass and Walleye, and failed culverts that block fish passage to spawning and rearing habitat.
Data for tables: U.S. Army Corps of Engineers, NOAA Fisheries
There is no question the population of upper Columbia Spring Chinook has been historically impacted by a number of factors including dam passage, habitat degradation, bird predation, and fishing, but the impacts from those factors have been reduced to aid recovery while sea lion predation on adult salmon is increasing at alarming levels. According to the 2018 Joint Staff Report: Stock Status and Fisheries for Spring Chinook, Summer Chinook, sockeye, steelhead, and other species issued by the Oregon and Washington departments of fish and wildlife in February, the 2017 upriver (destined to spawn upriver from Bonneville Dam) spring Chinook return to the mouth of the Columbia River, which includes fish destined for Snake River tributaries, totaled 115,821 adult fish. Of these, 11,156 were designated upper Columbia River fish, and of these, 2,514 were considered "natural origin" (wild) fish.
According to the recovery plan for ESA-listed upper Columbia spring Chinook, developed by the Upper Columbia Salmon Recovery Board in coordination with NOAA Fisheries, the species will be considered recovered when annual returns are at least 4,500 successfully spawning natural-origin adult fish across the three primary populations — 2,000 in the Wenatchee, 500 in the Entiat, and 2,000 in the Methow. These numbers are considered reasonable considering the estimated smolt production capacities and smolt/spawner ratios, historical production levels, and general conservation guidelines of the rivers.
Current numbers provided by NOAA and reported on the Council’s website, are far lower. In 2017 the number of natural origin spawners was estimated at 154 (excluding jacks) in the Methow; 121 (excluding Jacks) in the Wenatchee, and no adults but 63 jacks in the Entiat.