Tuesday, December 17, 2013
Last week, the U.S. Army Corps of Engineers held its annual research review at Walla Walla Community College. The program, continuously funded research since 1953, included 50 studies for 2013 on adult salmon passage, bird predation, lamprey passage, juvenile fish survival at dams and related subjects.
Many interesting results came from juvenile salmon tagged with passive integrated transponders (tiny radios without a battery). Returning adults were detected at the dams and in many tributaries.
Millions of PIT tags are put in juvenile salmon each year. Sockeye tagged in Idaho are returning up the Snake River at over 98 percent per dam project. Results were similar for Snake River spring Chinook. In all cases, wild fish returned at higher rates than hatchery fish.
The Indian tribes want to return Pacific three-toothed lampreys to Columbia River tributaries. The Umatilla, Yakama and Nez Percé tribes have reintroduced these three-foot parasites into streams where their ancestors fished for them for food.
Unlike salmon, lampreys do not necessarily return to their natal stream and they lay over a year before spawning. After the eggs hatch, larvae spend three to five years buried tail first in the mud filtering food from the water as it goes past. Then they metamorphose into six-inch parasites and hitch a ride to the sea where they attach to larger fish for a couple of years before returning. Fish passage is being improved at the dams to increase lamprey returns.
PIT tags also come into play estimating how many salmon birds eat. Caspian terns take millions of juvenile salmon in the Columbia Estuary.
Now the effects of cormorants, gulls and several other fish-eating birds are being studied. Researchers collect PIT tag data from the islands and nesting areas where the birds pass the tags.
By energizing the tags, they return 10 digit codes for individual fish that can then be analyzed from the PIT tag database. Birds take over 30 million juvenile salmon yearly.
Spill for fish was analyzed with the overflow spillway weirs passing the majority of the juvenile salmon, Survival over the weirs was higher than under the normal spill gates, but due to Judge James Redden’s edict, spill was still provided at all gates even though it reduced potential survival. Turbine bypass systems have very high survival and transported fish survived at a higher rate than migrants spilled down river. With the spill program, transport was reduced.