[3] Estuary Science Confab In Astoria
Scientists and policymakers from the Northwest Power and Conservation Council met in Astoria last week to hear about the Columbia River estuary and the work being done to improve conditions for fish.
It's an area of the Columbia that has been singled out by BiOp judge James Redden, who said last May that more work needs to be done there before he gives the new hydro BiOp a passing grade.
But the estuary had been getting more scrutiny long before District Judge Redden made much of it.
In 2005 and 2006, initial results from survival studies of acoustic-tagged juvenile salmon showed it might be a giant bottleneck to salmon recovery, with mortality to juvenile fish per kilometer much higher than in the hydro system itself.
Since then, researchers say, improved technology has reduced the original mortality numbers, and narrowed down the region where most fish disappear. Geoff McMichael of the Pacific Northwest National Laboratory said the lowest 50 kilometers in the river between Bonneville Dam and the ocean is still where most acoustic-tagged salmon seem to die.
But why that is remains a mystery, since the scientists estimate only about 10 percent of that 25- to 30-percent mortality can be explained by avian predation -- even with more than 20,000 cormorants now nesting near the mouth of the river.
McMichael says that an added receiver array had been placed at the Astoria Bridge to help unravel the puzzle, along with a mobile tracking project staffed by NOAA personnel. So far, no simple answers have been found.
McMichael said young spring chinook tagged at Bonneville generally make it to the ocean in less than four days, with later-migrating fish moving even faster. In April, they average 60 km a day. Later on, they speed downstream, covering about 100 km a day. But at the widest part of the estuary, around the Astoria bridge, they seem to slow down to about 25 km a day and eventually only about 70 percent of them make it to the ocean.
For the much smaller subyearling fall chinook, the trip doesn't take much longer. But the later migrating fish take their time -- about 36 percent of the subs were tracked in off-channel habitats, compared to 29 percent for yearlings. Eventually, though, most made it to the mouth -- 90 percent in 2008, according to McMichael.
However, some subyearlings may hold over in the estuary for the entire winter and head out to sea the following spring. That's one reason why the Corps of Engineers and PNNL have added a receiver array to track fish in the freshwater plume beyond the mouth of the river.
McMichael said researchers are still wondering about the higher juvenile mortality near the ocean -- they don't think it can be pinned on a tag effect since they don't see much difference in mortality on the bird islands between PIT-tagged fish and PIT-tagged fish that sport the surgically implanted acoustic tags.
Tom Karier, Washington's Northwest Power and Conservation Council member, asked about making the connection between where the most mortality occurs and where "we can focus the dollars."
But NOAA Fisheries scientist John Ferguson said that wasn't the right way to look at the situation.
"Ultimately, to get to recovery you need to figure out what the response is in terms of adults," Ferguson said. "And you back up from there and you look at how juveniles respond to habitat changes, how those responses propagate up through the life cycle and turn into adults coming back. And adults coming back in a way that they can adjust to a variable environment -- that's the issue of persistence of the populations and that's the issue of bio-complexity that leads to persistence. That's what the scientific literature is telling us we need to do."
To do that, he said, complex habitats are needed because "we have lots of different types of fish using the habitat."
Ferguson said using survival as the measure is the wrong way of looking at it. "It is a measure, but it is not the measure," he said.
If restoration work were focused on the lower end of the estuary where most of the acoustic tag data on mortality shows up, Ferguson said, "we would ignore the upper end of the river where a lot of different stocks that weren't tagged, that aren't in those survival estimates, are using those habitats," such as the Willamette stocks and the Snake River fall chinook that may be overwintering there.
This means, he continued, that "we need to step back and be clear that you have a set of information that is only as good as how representative those fish are of the whole composite array of stocks and pops and life-history diversities that are out there."
Ferguson said the tagging data that have been collected are very good but relatively narrow, since they only include active migrators at Bonneville Dam at least 95 mm long. A lot of fish inhabiting the estuary's off-channel habitat are only 50-60 mm, too small for these tags.
Other scientists are still sorting out which stocks do spend more time hanging out rather than using the estuary as a simple conduit to the sea.
Ferguson said preliminary genetic data suggests that chinook stocks may not be distributed uniformly from the mouth to Bonneville Dam, with Upper Columbia stocks more prevalent in the upper estuary, and most restoration work now concentrated on the lower estuary.
Preservation and restoration of shallow-water habitats are important to maintain food webs that support these smaller fish from natural populations, said NOAA Fisheries scientist Ed Casillas. He said work is being done to determine how much more such habitat is needed to improve diversity and spread the risk for fish populations, especially as climate change will make it more difficult for less diverse populations to cope.
Other researchers brought council members up to speed on contaminant issues and ecosystem restoration in the lower Columbia.
BPA's estuary lead Tracy Yerxa outlined a new way the BiOp is being implemented to improve monitoring and help guide estuary restoration efforts using a complicated tool being developed by the University of Washington, the U.S. Geological Survey, and the Estuary Partnership.
The tool classifies the ecosystem using geology, topography, bathymetry and land cover in order to focus on the most effective actions that will help improve ESA-listed stocks in the Columbia Basin.
NOAA's Ferguson said there are other questions that need to be answered, such as why smolt-to-adult return rates vary with ocean entry timing -- that is, what conditions in the river plume boosting survival can measured and used to tune actions in the fresh water, such as timing of hatchery release, barging fish, and flow augmentation.
He also noted more study needs to quantify the effects of marine mammal predation on returning adults -- 1,500 sea lions may be eating 20,000 spring chinook every year.
He supported Canadian researcher David Welch's ongoing ocean tracking project that so far has shown no evidence of delayed mortality, and said more scrutiny should be focused on the use of Rogue River chinook in a lower-river netpen fishery, since it's an out-of-basin stock that has strayed and spawned in two lower river reaches. -B. R.
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