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November 17, 2006, Columbia Basin Bulletin

Sea lions were, for the most part, undeterred in their pursuit of salmon in the waters below Bonneville Dam this past spring and early summer despite efforts of biologists, and noise-making devices to shoo the large marine mammals away.


Sea lion exclusion devices installed at the entrances to fish ladders at the dam did do their job, however, keeping sea lions out while presenting no apparent hindrance to migrating salmon and steelhead.


Those assessments were among the many delivered this week during the annual Anadromous Fish Evaluation Program conference. The event sponsored each year by the U.S. Army Corps of Engineers was held Monday through Thursday in Portland.


The event drew non-governmental, state, federal and tribal researchers involved with the Corps' program for fish passage research out of both its Walla Walla and Portland districts over the past year. The presentations represented $60 million worth of research. The program has been funded annually since with congressional appropriations


AFEP funds evaluation and monitoring studies designed to provide biological information and insights related to fish passage and survival at hydropower dams. Studies include such topics as effects of juvenile fish transportation, evaluation of fish guidance devices and surface collection, effects of gas supersaturation on fish, adult fish passage at the dams, the effects of predation on salmon populations and other topics.


That research is used to focus fish passage improvements and operations at the eight federal lower Snake and Columbia river hydro projects through operational changes and capital improvements.


Among the research results previewed during the four-day session was a detailing of the growing presence of avian predators on salmon, Caspian terns and cormorants, in the Columbia River estuary. The tern colony has been characterized for nearly 10 years as the largest in the world. Research presented this year notes that the largest known breeding colony of double-crested cormorants nests at the same site, East Sand Island.


The research led by Oregon State University's Dan Roby and consultant Ken Collis says that the tern colony, which forms each year at East Sand for the spring breeding season, has been relatively stable in size since 2000 after a decade of rapid growth. The 2006 count was 9,200 breeding pairs, slightly higher than last year.


The cormorant colony, however, showed considerable growth in a year's time, up by 10 percent over 2005 to an estimated 13,740 breeding pairs. Since monitoring began in 1997 that colony has grown by 275 percent, according to the study's abstract presented to AFEP.


The tern and cormorant presence has concerned fish managers because together they ate an estimated 6.5 million salmon and steelhead smolts last year. Many of those passing juvenile fish are stocks that are listed under the Endangered Species Act. A plan has been devised to try disperse the tern colony, but has been delayed because the Corps lacks, at this point, the authorization to implement it. That authorization must come from Congress. Management options for reducing cormorant take of listed salmon have yet to be considered.


Likewise, the presence of sea lions in the lower Columbia has grown over the past few years, as has their predation on salmon and steelhead and other fishes.


A Corps study led by Robert Stansell judged the effect of a full-fledged hazing effort carried out this past year had on sea lion activities below Bonneville.


"Non-lethal deterrence measures used in 2006 proved ineffective in reducing predation on salmonids, but more intensive and directed hazing efforts may reduce pinniped presence near fishway entrances," according to that abstract.


A delayed arrival of this past spring's spring chinook salmon run -- the prime sea lion target -- raised concerns that the hazing, and SLED installation, may have been causing the fish to pause before climbing the dam's fish ladders. But a study carried out by the University of Idaho and NOAA Fisheries Northwest Science Center concluded that neither appeared to impede salmon passage.


An ongoing NOAA Fisheries smolt survival study showed that chinook survival through the entire Columbia/Snake system this past year was 58 percent, the highest since PIT tag studies began in 1993. Steelhead survival was 37 percent through the 750 kilometer stretch from the Snake River trap near Lower Granite Dam to the Bonneville tailrace.


"During 2006, a high flow and spill year, survival through individual reaches averaged 93 percent for chinook salmon and 88 percent for steelhead (decreasing through successive reaches)," the abstract said.


A NOAA Northwest Science Center Study to document downstream passage histories of returning Snake River fall chinook indicates that a great share of those fish leave their natal waters as subyearlings, but do not actually leave the freshwater until they are yearlings. Two "life histories" for the Snake River fall chinook have been identified in recent years -- ocean-type that migrate to the ocean in summer as subyearlings and reservoir-type that holdover in the freshwater system until winter before outmigrating. Little is known, however, about where the reservoir-type fish spend the winter.


The research led by Douglas Marsh found that 79 percent of the 118 PIT-tagged adults recaptured at Lower Granite Dam during 1998-2005 had entered saltwater as yearlings after making their way downstream in-river. Of those fish (93) 27 were conclusively shown to have spent their first winter in reservoirs and the other 66 had wintered in unknown freshwater locales.


Of 20 recaptured adults that had been transported through the system in summer to below Bonneville, , 35 percent appear to have wintered in freshwater downstream of the Columbia's lowermost dam. Of the 33 recaptured adults that were transported downstream as subyearlings in the fall, 61 percent overwintered in freshwater.


Scale samples of the recaptured fish were analyzed to determine their age of entry into the ocean.


Presentations included transportation studies and fish survival and tracking studies. The conference opened with general presentations on what has been taking place in the full river system and cover programs designed to look at the history of how fish pass and how they return to the basin. Additional presentations covered specific details of a particular project or species.


Anadromous fish live in the sea, but breed in fresh water. The best-known anadromous fish are salmon, which hatch in small freshwater streams, swim to the sea and live there for several years, then return to the same streams where they were hatched to spawn.


For more information on the conference, research presentations, and research abstracts, visit http://www.nwp.usace.army.mil/pm/e/conference


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