Dams, pollution and development have taken a toll on salmon populations in Washington State. Now researchers find that the lack of fish is causing pregnant orcas to miscarry, further imperiling the endangered killer whales.
(From NewsDeeply/ by Hanna Brooks Olsen) — Writing in 1916, conservationist John Muir noted that “there is not a ‘fragment’ in all nature, for every relative fragment of one thing is a full harmonious unit in itself.” A century later, in the Pacific Northwest, land managers, tribal leaders, environmental stewards, lawmakers and business interests are locked in a fight over which harmonious units and relative fragments can be rearranged to satisfy all parties.
But while they grapple over the details of regulations and policy changes, and the various perceived and demonstrated economic effects any such legislation may have, whales continue to miscarry at an unprecedented rate.
In the salty waters off the coast of Seattle, the region’s orca population is spontaneously miscarrying the majority of its pregnancies, according to a recent study by researchers at the University of Washington, published in PLoS One. By studying the feces of orcas through the use of detection dogs, the researchers tracked the whales’ hormones over time. Their findings were stark: 69 percent of all detectable orca pregnancies ended with miscarriage; 33 percent of those pregnancies failed in the late stages of gestation or immediate postpartum.
While the temperature of the ocean, boating and commercial shipping are often looked to as identifiable reasons for orca stress, one of the most important places to look for answers may actually be on land, where the human footprint has choked off the primary food source of the Southern Resident killer whale population – the Chinook salmon.
The Center for Whale Research, which has been surveying Puget Sound killer whales for decades, reports that Chinook make up about 80 percent of the average orca’s diet; each whale must consume between 18 and 25 salmon per day just to retain its energy levels. To feed the entire population of Southern Resident killer whales, the Puget Sound and surrounding waterways must provide at least 1,500 salmon per day.
But since the Pacific Salmon Commission began tracking salmon in 1984, it has noted a 60 percent reduction in the population of Chinook. The commission estimated that under half a million were left in the Salish Sea in 2010 – less than a year’s supply of fish for the orca.
While researchers have known for years that the reduction in supply has a direct effect on the area’s killer whale population, the University of Washington study sheds light on a new, previously underdiagnosed problem: It appears that lower numbers of salmon put undue burden on pregnant whales, who need even more of the high-fat, high-protein fish to feed both themselves and their growing babies.
“Low availability of Chinook salmon appears to be an important stressor among these fish-eating whales as well as a significant cause of late pregnancy failure, including unobserved perinatal loss,” the University of Washington researchers note.
Researchers have already noted a decline in orca population – a survey in 2012 found that the Puget Sound pods had posted some of their lowest numbers since the 1970s. Still, the high incidence of miscarriage came as a surprise, largely because…