The distribution of 10,000 simulated trajectories with means and SD of the population size for northeastern Pacific Ocean Southern REsident Killer Whales (SRKWs) projected for 100 years, based on demographic rates observed from 1976 through 2014, applied to a starting population as it existed in 2015. Graphic: Lacy, et al., 2017 / Scientific Reports

By Lynda V. Mapes
27 October 2017

(The Seattle Times) – Orca whales are on a path to extinction within a century unless they get a big increase of chinook salmon to eat, and significantly quieter seas in which to find their food, a new study has found.

The research, published in the journal Scientific Reports, evaluated the relative importance of known threats to the survival of southern-resident killer whales, the salmon-eating whales that frequent Puget Sound.

An international team of scientists reviewed 40 years of data and the threats of lack of food, pollutants, and excessive noise under different future scenarios.

A clear finding emerged: lack of food, specifically chinook salmon, was the orcas’ biggest threat to long-term survival, so much so that a 30 percent increase in chinook above average levels is needed to recover the orca population. That increase could be cut to 15 percent if vessel noise also is reduced by half.

Otherwise, the populations will continue to decline and there is a 25 percent chance the whales will be lost within 100 years, the scientists found. […]

“The very first thing we should be doing is holding the line, and not increasing threats and harms that are already there, clearly we don’t want to be adding to the problem,” said Paul Paquet of the Raincoast Conservation Foundation in Sydney, B.C., a lead author on the paper.

“There is an urgency here that is not well-appreciated; they are certainly in jeopardy,” he said of the orcas. “There is no doubt about that.”

Bob Lacy, a conservation biologist with the Chicago Zoological Society, and another lead author on the paper, said the southern residents are “just holding on; the population is too fragile to withstand any increased threats.

“It is not a cheerful story, but it is a wake-up call.”

Lynne Barre, Seattle branch chief of the Protected Resources Division at NOAA Fisheries West Coast Region, said the agency is well aware of the orcas’ predicament, as their population — at the lowest numbers since the 1980s — continues to drop. They are listed as endangered under the Endangered Species Act.

“We are moving in the wrong direction,” Barre said. The agency is looking for partners at every level — local, state, federal and across the border in Canada, to ease threats to orca survival she said. [more]

Orcas headed to extinction unless we get them more chinook and quieter waters, report says


ABSTRACT: Understanding cumulative effects of multiple threats is key to guiding effective management to conserve endangered species. The critically endangered, Southern Resident killer whale population of the northeastern Pacific Ocean provides a data-rich case to explore anthropogenic threats on population viability. Primary threats include: limitation of preferred prey, Chinook salmon; anthropogenic noise and disturbance, which reduce foraging efficiency; and high levels of stored contaminants, including PCBs. We constructed a population viability analysis to explore possible demographic trajectories and the relative importance of anthropogenic stressors. The population is fragile, with no growth projected under current conditions, and decline expected if new or increased threats are imposed. Improvements in fecundity and calf survival are needed to reach a conservation objective of 2.3% annual population growth. Prey limitation is the most important factor affecting population growth. However, to meet recovery targets through prey management alone, Chinook abundance would have to be sustained near the highest levels since the 1970s. The most optimistic mitigation of noise and contaminants would make the difference between a declining and increasing population, but would be insufficient to reach recovery targets. Reducing acoustic disturbance by 50% combined with increasing Chinook by 15% would allow the population to reach 2.3% growth.

Evaluating anthropogenic threats to endangered killer whales to inform effective recovery plans

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