COLUMBIA?RIVER - The Corps of Engineers' attempt to re-engineer breeding grounds for salmon-munching birds in the Columbia River estuary has been a partial success, according to Oregon State University researcher Dan Robey.
Speaking at the Corps' four-day marathon research review in Portland in early December, Robey said an alternative colony site developed for Caspian terns at Crump Lake in Warner Valley attracted 430 nested pairs, including five terns branded at the estuary 500 kilometers to the northwest.
But the old "build it and they will come" adage didn't hold for a new site created near Eugene. Not one tern nested there this year, though nine different ones showed up late in the nesting season.
Robey also said the Corps studied another tern nesting site in San Francisco Bay for possible expansion, where more than 800 breeding pairs already hang out. About 10 percent of their diet is made up of migrating juvenile salmonids-mostly hatchery-reared, non-ESA-listed fall Chinook smolts from netpen release sites in San Pablo Bay.
With that much salmon in the Bay terns' diet, fish managers are concerned that moving some birds from the Columbia could adversely impact ESA stocks from the Sacramento River Basin.
Meanwhile, the tern colony at the mouth of the Columbia has kept growing, though not by much over last year's count. In 2008, 10,800 nesting pairs were counted on East Sand Island, where they had been relocated from an upriver site at Rice Island a few years ago.
The terns' diet seemed to be similar to that in previous years-about 29 percent juvenile salmonids. The researchers hadn't finished crunching 2008 numbers, but they said total consumption was probably similar to 2007, when the terns gobbled up an estimated 5.5 million smolts.
But terns haven't been the only avian headache for the Corps in that stretch of the river. Nearly 11,000 pairs of double-breasted cormorants also nested on Sand Island this year.
The population was down about 20 percent from 2007. However, the scientists reported that breeding success was pretty high, at about 2.3 chicks per breeding pair. An estimate of salmonid impacts is still in the works, but researchers expect it will be similar to 2007's, when the cormorants ate more than 9 million salmonids.
That year, most of the cormorants' diet of young salmonids was made up of subyearling Chinook (5 million), along with coho (2.7 million), steelhead (1.3 million), and spring Chinook (1.1 million).
Recent tagging efforts have also shown that other cormorant colonies in northwest Washington and southwestern British Columbia have contributed new recruits to the site in the Columbia estuary. The Corps is developing another program to move some cormorants from the Columbia.
In another presentation during the meeting, NOAA Fisheries scientist Doug Marsh reported on the latest results from fish transportation studies. Most of the spring Chinook and steelhead are back from the 2005 outmigration. Adult returns were meager, due likely to poor ocean conditions that greeted the juvenile fish when they reached the ocean in 2005.
Marsh said only 28 wild adults returned from nearly 13,000 that were PIT-tagged and barged downstream, which represented a SAR [smolt-to-adult return rate] of 0.22 percent. That's down nearly 10 times from results just a few years ago, when ocean conditions were very good.
Only three wild non-detected (fish that passed dams via spillway or turbines) spring Chinook returned to Lower Granite this year, out of 748 tagged fish - a SAR of 0.40 percent.
Nearly 6,000 wild fish that went through bypass systems at dams had a SAR of only 0.12 percent.
Marsh also said that fewer transported and bypassed Chinook made it back through the hydro system as adults compared to inriver migrants, about 80 percent compared to nearly 100 percent, respectively.
Marsh also said the Chinook transported as juveniles took longer to make it back through the hydro system as adults.
As for wild steelhead, they seemed to benefit from barging, with a SAR of 0.38 percent, while bypassed inriver migrators returned at only 0.11 percent. None of the 200 or so non-detected juveniles evidently returned.
The bypassed steelhead also made it back through the hydro system as adults at nearly a 100-percent rate, while about 60 percent of the transported fish successfully made it all the way back to Lower Granite Dam.
Marsh noted that fish tagged in 2006 and 2007 have already shown evidence of much higher survivals of jacks and two-ocean returns (fish that stayed in the ocean two years) than the 2005 outmigration, but SARs for the 2006 migration year won't be known until three-ocean Chinook return next year.