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NW Fishletter #384 August 1, 2018

[3] Columbia River Chinook Rate High On List Of Stocks Needed For Orca Recovery

With their sights set on saving the dwindling population of southern resident killer whales, NOAA Fisheries scientists have rated 31 populations of Chinook salmon based on how useful they may be to recovery of the orcas, which rely on the fish for food.

And while fall Chinook from both northern and southern Puget Sound come out on top, Chinook from the Columbia and Snake rivers make an impressive showing on the list, which was developed to help managers prioritize salmon-recovery efforts.

Of the top 10 populations, five are from the Columbia and Snake, and all seven Columbia and Snake stocks are on the list's top 15.

A higher-priority rating will mean extra effort--and potentially additional funding--will go toward recovering those stocks through projects like habitat protection and hatchery production, said Lynn Barre, NOAA's recovery coordinator for southern resident orcas and a member of Gov. Jay Inslee's task force formed in March to help recover this population of whales.

While killer whales are doing well worldwide, a Puget Sound population known as south resident killer whales is struggling. They were ESA-listed as endangered in 2005, but the population has continued to decline and is now believed to include just 76 individuals. Barre said NOAA Fisheries now considers the southern resident population as one of the eight most at-risk marine species nationwide for becoming extinct.

Scientists have identified three major threats to the orca's recovery--a lack of its preferred prey--Chinook salmon; noise and overcrowding from boat traffic; and water pollution that causes contaminants to build up in their blubber, resulting in immune system and reproduction problems.

The task force is working on all three problems, and expects to complete a list of comprehensive recommendations by October.

Barre said NOAA Fisheries has been studying the population's diet for several years in an effort to better understand what they eat, and when. The priority list offers new information on which Chinook salmon runs the orcas depend on most.

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Source: NOAA Fisheries

Developed by NOAA scientists, the prioritization model is based on three factors.

One factor is the orca's observed diet, gathered every summer since 2004 by following the orcas and collecting tissues and scales from its prey, and fecal samples left in the water, which are genetically identified to determine the specific Chinook stock.

Another factor is the proportion of each specific Chinook stock the whales are eating during their more vulnerable months in fall, winter and spring.

And finally, consideration is given to overlap between the whales and each Chinook stock, both in location and duration.

Mike Ford, head of the conservation biology division at NOAA Fisheries' Northwest Fisheries Science Center, said that while southern resident killer whales prefer Chinook, they eat other salmon and fish species, including coho, chum, steelhead, halibut and lingcod. The population makes its home in Puget Sound for some of the year, and then migrates along the West Coast from Northern California to southeast Alaska.

Most of NOAA's data on the population's diet has been gathered in the summer months. Ford said once the orcas head to Washington's outer coast after spending the summer in Puget Sound, there's less data to indicate what they're eating. However, he noted, existing data suggests it includes a significant amount of Columbia River Chinook--largely from the lower Columbia River, but also some from the upper Columbia and Snake rivers, along with Chinook from rivers on the Olympic Peninsula and from the Sacramento River. Scientists don't know, he said, how important extirpated stocks--like the Chinook runs that no longer exist above Hells Canyon or Grand Coulee dams--once were in the orca's diet.

Ford noted that while several Chinook runs in the Columbia River Basin are threatened, based on total returns of Chinook to the Columbia River in the last decade or so, "it has not really been bad, and the whale's behavior may be reflecting that. They seem to be spending more time out in the coastal area, and a little less time in the Salish Sea."

He said the priority list is weighted more heavily toward whether the Chinook population is in the right place at the right time to serve as prey for these orcas. "If it's present in their diet, there's an extra bonus if they have a large time-space overlap with the whales," he said, adding there's still much to be learned, and the priority list will be updated as new information becomes available.

In the meantime, agencies and organizations can look to the list to help prioritize salmon-recovery projects, or to develop new ones, Barre said.

In addition to providing the list to Inslee's task force, it has also been shared with the National Fish and Wildlife Foundation, and will be made available to other salmon recovery partners.

Under the governor's proclamation, the Washington Department of Fish and Wildlife was also asked to identify the highest-priority areas and watersheds for orca prey "in order to focus or adjust, as needed, restoration, protection, incentives, hatcheries, harvest levels, and passage policies and programs."

Initially, Barre said, NOAA Fisheries hopes the list will be used to prioritize habitat-recovery projects, and to guide decisions about hatchery production, although many more factors will be considered when prioritizing actions besides how much it can help the orca's recovery.

These added benefits to killer whales may help some Chinook recovery projects get past hurdles they are facing, whether in funding, permitting or other obstacles. Projects to improve runs of higher-priority salmon also have new funding potential, through the task force or other organizations, she said.

Barre said it may seem challenging to try to save an endangered species by boosting populations of its prey, many of which are also listed as threatened, but taking steps to help one may do a lot to help the other. "We're trying to look at things in more of that ecosystem scale, and not just the relationship between killer whales and Chinook salmon," she said, adding, "It's all interconnected." -K.C. Mehaffey

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Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: K.C. Mehaffey
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