By Dr. Deborah Giles, May 16, 2015
Ten years ago, the Southern Resident orca population was officially listed as endangered under the Endangered Species Act (ESA). In the decade since, the Southern Residents have declined in number in the face of numerous threats and a continually diminishing food source. The survival of this unique orca population is closely linked to the abundance of their preferred prey – Chinook salmon – and WDC is proud to be part of a developing coalition that is working to save both the Southern Residents and the salmon they need to thrive. These two species, iconic images in their Pacific Northwest home, and recognized and revered worldwide, are vital parts of their ecosystem, and they are in need of recovery efforts on an ecosystem-wide scale to ensure their future.
This Whale and Dolphin Conservation guest blog is from Dr. Deborah Giles, a research affiliate with UC Davis who has been studying the Southern Resident killer whales for over a decade. She is a founding member of the Salish Sea Association of Marine Naturalists (SSAMN) and the Southern Resident Killer Whale Chinook Salmon Initiative (SRKW CSI). As part of the coalition, we are working on restoring rivers in the Pacific Northwest, starting with the Snake River – one of the key components for the survival of Chinook salmon and the Southern Residents.
What else do the Southern Residents need to survive? Read on to find out….
The recent births of four calves in the federally listed endangered Southern Resident killer whale population are worthy of celebration because this small population of whales has been declining since 2010, and they haven’t had a surviving calf for more than two years. Also worth noting is that at least one of the new calves – J50, born in December 2014, has been confirmed to be female. The Southern Resident orca population is in desperate need of more female calves because since 2006, there have been twice as many surviving male calves than females ones. This skewed ratio of male to female means there will be less genetic diversity in the whale population in the future. After reaching breeding age, female killer whales only produce a calf every 4-5 years, so there needs to be a lot of females in a population if it is to increase in number; if most of the babies being born now are male, then the population will have even less chance of recovery in the future.
When the Southern Resident killer whales were listed as endangered in 2005, the federal government set a recovery goal of a population increase of 2.3 percent annually for 28 years. With 88 whales in the population when they were listed, they have not come near this goal, and have in fact declined significantly to a mere 77 individuals as of the end of 2014, according to the Center for Whale Research’s most recent census. Therefore, while these four calves are certainly excellent news for this struggling population, we must balance those gains against the loss of four other whales in 2014, which leaves the population at 81 individuals, assuming all four of the new calves survive. The whales need our help to increase the amount of food available to them year-round and throughout their entire known range in order to ensure the survival of whales of all ages, and especially of these new additions.
Research continues to illustrate the importance of Chinook salmon to the fish-eating Southern Residents. The amount of food required for each whale depends on myriad whale-related variables including age, sex, and reproductive status, as well as fish variables such as species and age. Pregnant or nursing females require more calories because the mothers are providing all the nutrients for their calves, too. According to their federal recovery plan, adult Southern Residents need to consume 28-34 adult salmon daily; younger whales need 15-17 to meet their basic energetic requirements. Therefore, approximately 739,000 salmon are needed annually just to maintain the current population of 81 whales in the Southern Resident population; significantly more would likely be required to increase the population. Having enough prey available to the whales throughout their entire range and at all times of the year is vitally important for the recovery of this population.
Typically the Southern Resident killer whales can be found from May – September in the inland waters of the Salish Sea (Puget Sound), designated by the federal government as “core summer critical habitat.” During this time of the year, 80-90% of the whale’s diet would normally consist of Chinook salmon bound for the Fraser River watershed in Canada. Interestingly, at least five Southern Resident calves, including the four mentioned above, were conceived between June and September 2013, when the whales were remarkably absent from their inland core range. In 2013, the whales were documented on less than half the number of days in this core habitat compared to past years. Given that 2013 was the second worst (2012 was the worst) year for Chinook returning to the Fraser River, it is reasonable to speculate that the whales were instead foraging on the reportedly high numbers of Chinook salmon (both wild and hatchery) returning to the mouth of the Columbia River during the same time period.
Columbia River Chinook
Once the biggest wild salmon-producing river system in the world, the Columbia River Basin is thought to have produced between 10 and 16 million wild salmon annually. Today, the entire Columbia Basin produces a meagre 2.5 million fish per year, and more than two-thirds of those are hatchery salmon. Wild Chinook are estimated to be less than 2% of their historic numbers. Dams in the Columbia/Snake River system are a major factor in the decimation of the salmon runs. The Southern Resident orca whales, like all other killer whales, are top predators that have evolved over millennia by eating high quality, abundant prey items throughout their natural ranges. In the past few years, several satellite-tagged Southern Resident killer whales have been documented traveling down the Pacific coast as far as California, and regularly spending significant amounts of time foraging at the mouth of the Columbia River between Oregon and Washington states.
This population of apex predators likely historically utilized the once abundant and nutritionally rich Chinook salmon of the Columbia Basin. In the recovery plan for Southern Residents, the federal government stated “Perhaps the single greatest change in food availability for resident killer whales since the late 1800s has been the decline of salmon in the Columbia River basin.” This statement clearly highlights the need to concentrate on increasing the number of wild Chinook salmon from the Columbia Basin.
Within the Columbia Basin Watershed, the Snake River provides the best potential for recovering healthy and abundant Chinook salmon runs in the Pacific Northwest, given the river’s historic salmon production. Indeed, the Snake River watershed once produced about half of all salmon from the Columbia Basin. Today however, myriad dams stand between the Pacific Ocean and salmon spawning grounds, resulting in only about 1% of Snake River salmon returning home to spawn. Fortunately, half of the eight dams that block Snake River salmon from their spawning grounds are prime candidates for breaching. Dam breaching is the act of removing enough “dam” material (often the earthen berms) to allow a now-freed river to resume its natural course and flow. Breaching is a significantly less expensive and faster way to remove the barriers than removing the structural material of the dams entirely, allowing the river to reconnect the ocean and the wilderness acres that create the best in-stream spawning habitat for salmon. Breaching the four lower Snake River dams would open the gateway to a vast, 5,500-mile expanse of intact spawning and rearing streams that run through more than 15 million acres of wilderness. These high-elevation streams are considered to be some of the most climate change-resistant salmon spawning streams in the entire lower 48 states.
Breaching the lower Snake River dams would greatly increase a critical food source for the Southern Resident orcas, not only in the fall and winter months, but also in years when the Fraser River salmon populations are insufficient throughout the spring and summer months. Although the whales were “lucky” in 2013 to find Chinook returning to the Columbia River to spawn (thanks to court-mandated increased spill from Columbia River dams starting in 2005 and favorable ocean conditions) we can’t assume that will be the case in the future. In fact, there is every reason to believe the fish returns throughout the entire Southern Resident range are going to get significantly worse in the near future due changes in ocean variables. Already the 7-degree hotter pool of water known as the “warm blob” located off the west coast of the US between Alaska and Mexico has had a significant impact on the food web and those that rely on the cool coastal waters.
It is probable that breaching the four lower Snake River dams is the single most important measure that we can take in the United States to recover abundant salmon and steelhead in time to permit the Southern Resident orcas to survive.
The Southern Residents face many threats to their recovery, including prey depletion, pollutants and toxins, and noise. These threats amplify the effects of the others – when faced with prey shortages, the orcas metabolize their blubber, releasing toxins accumulated there; noisy oceans mean they have to use more energy to communicate and forage, which means they need more food. Making sure they have enough Chinook to eat helps them with these other stressors, though it certainly doesn’t solve all the issues. WDC is working for ecosystem recovery in the Pacific Northwest to ensure the survival and protection of both salmon and the orcas that depend on them. From our support of Klamath River restoration to our work with the coalition to breach the dams on the Snake River, we want to see salmon bounce back on the west coast and ensure an abundant food source for the Southern Resident orcas.
WDC is grateful to our guest bloggers and value their contributions to whale conservation. The views and opinions expressed by our guest bloggers are those of the author, and do not necessarily represent those of, and should not be attributed to, WDC.