Hey, seals and sea lions! Quit eating so much endangered orca food... or else.
Politicians and wildlife managers are engaged in a fresh debate about whether to intervene in nature to save an imperiled species. The question is whether humans can get seals and sea lions to lay off Chinook salmon so there's more for killer whales to eat.
Chinook — or king — salmon are the preferred food of the critically-endangered Pacific Northwest orcas. But growing numbers of sea lions and the robust population of harbor seals eat Chinook too.
"This is that classic mix of the predators being a protected species and the prey being a protected species," said Nate Pamplin, policy director for the Washington Department of Fish and Wildlife. "We don't know the level of consumption in terms of whether or not humans should intervene."
The current population of 75 southern resident killer whales is near the record low of the past thirty years. Whale scientists have identified lack of sufficient salmon to eat as a major contributing factor to the orca population decline along with environmental pollution and disturbance from vessel traffic and noise.
Earlier in the current Washington legislative session, a bipartisan group of state representatives argued that culling seals and sea lions would have an immediate impact on boosting Chinook salmon, the favorite food of the orcas. They introduced a measure to direct WDFW to seek a federal permit for "maximum lethal take" of seals and sea lions. It passed out of one committee and then died in February.
Now lawmakers are haggling over funding to implement a prior recommendation from the Washington governor’s southern resident killer whale task force. The task force urged state and federal agencies to evaluate how to reduce predation by seals and sea lions on the valuable fish.
The state Senate proposes to spend millions of dollars for biological studies, analysis of management options and possibly blocking or removing some log rafts and docks where seals haul out to rest in Puget Sound. The proposed House budget, however, allocated zero dollars to this. The two chambers have to reconcile their spending blueprints before the governor can sign a two-year budget into law, presumably next month.
"We would definitely like to have resources in the final budget to address seal and sea lion predation of salmon," said Democratic Rep. Joe Fitzgibbon, the state House Environment Committee chair. "We know that is a significant pressure on Chinook salmon populations and that has an impact on orcas as well."
Fitzgibbon said other initiatives to increase the orca food supply are moving ahead, including funding to temporarily increase Chinook production at selected salmon hatcheries and increased protection for salmon spawning and rearing habitat.
"We just have to make hard choices sometimes about what we can and can't afford," Fitzgibbon added in an interview Thursday.
Southern resident killer whales and multiple Chinook salmon runs are listed under the Endangered Species Act. By contrast, sea lions and harbor seals are abundant in the region, but Pamplin noted the pinnipeds are shielded too by a different federal law.
"Congress, in 1972 when they passed the Marine Mammal Protection Act, treated marine mammals as a very special species and gave them really strong protections," Pamplin said in an interview. "There are very limited opportunities to actually do removals for management purposes. Furthermore, we know this will be highly scrutinized."
Meanwhile, a different population of orcas known as transients, or Bigg's killer whales, are being seen more often in Pacific Northwest waters. Unlike the resident orcas, these visitors prey on seals and sea lions, a welcome habit in the current context.
The marine mammal-eating orcas are putting a modest dent in the local harbor seal population, according to a recently published paper. Volunteer researchers led by Monika Wieland Shields of the Orca Behavior Institute in Friday Harbor, Washington, estimated transient orcas consumed 1,090 seals in the Salish Sea in 2017 — or more than 2 percent of an estimated harbor seal population of 51,000 in the Strait of Georgia and Washington's inland waters.
"The population controlling effects of transient killer whale predation on harbor seals should be considered when evaluating any pinniped management actions in the Salish Sea," Shields and her co-authors wrote.
A longer-running discussion about the same issue in the Columbia River has resulted in expanded sea lion cullings. Since 2008, state and tribal wildlife biologists have removed an average of 19 California sea lions per year that were observed repeatedly preying on salmon and steelhead below Bonneville Dam. Some of the sea lions were shipped off to aquariums, but most were trapped and then killed by lethal injection.
The removals have not ended the toll on salmon at the dam, so late last year Congress passed a law to give wildlife managers more latitude to remove sea lions upstream of the I-205 bridge and expanded the target list to include Steller sea lions.