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  1999 Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River PDF Format - [2.52MB]
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Hanford Reach Salmonid Entrapment Research 1999 Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River Executive Summary
The Washington Department of Fish and Wildlife (WDFW) in cooperation with the Bonneville Power
Administration (BPA), Grant County Public Utility District (GCPUD), Pacific Northwest National Laboratory
(PNNL), University of Idaho (U of I), Streamside Programs Consultation (SPC), United States Geological
Survey Biological Resources Division (USGS/BRD), and Yakama Nation (YN) performed the 1999 Evaluation
of Juvenile Fall Chinook Salmon (Oncorhynchus tshawytscha) Stranding on the Hanford Reach of the
Columbia River. The 1999 evaluation was the third year of a multi-year study to assess the impacts of water
fluctuations from Priest Rapids Dam on rearing juvenile fall chinook salmon, other fish species, and benthic
macroinvertebrates. The field effort was performed from March 5 through September 29.
The objectives of the 1999 evaluation were to collect basic information on the physical parameters of the
Hanford Reach, evaluate the extent of stranding and entrapment of juvenile fall chinook salmon and other fish
species, and identify critical habitat zones. The information will be used to develop a model for determining
susceptibility of juvenile fall chinook salmon to stranding and entrapment due to flow fluctuations. WDFW
subcontracted U of I and SPC to assess the effects of flow fluctuations on the benthic macroinvertebrate
communities and USGS/BRD to study the effects of heat stress on the survival, predator avoidance ability, and
physiology of juvenile fall chinook salmon.
River and meteorological conditions on the Hanford Reach during the 1999 juvenile fall chinook salmon
emergence and rearing period (March–July) were marked by above average river flows, below normal ambient
air temperatures, below normal precipitation, and above average solar radiation levels. Priest Rapids Dam
(Rkm 639.1) discharges averaged 161.4 kcfs from March 8 through June 30. Hourly discharge ranged from
61.9 to 261.3 kcfs. Mean daily fluctuation during this period was 42.1 kcfs.
Scanning Hydrographic Operational Airborne Lidar Survey (SHOALS) system bathymetry data collected by the
United States Army Corps of Engineers (COE) in 1998 on 35.1 km2 of the Hanford Reach from Rkm 571.3 to
Rkm 606.9 was processed in 1999. SHOALS data was used in conjunction with the Modular Aquatic
Simulation System 1D (MASS1), a one-dimensional unsteady flow model for the Hanford Reach (Richmond
and Perkins 1998), to characterize the Hanford Reach at stage discharges from 40-400 kcfs.
The Hanford Reach produced an estimated 8,405,936 fall chinook salmon fry in 1999. Juvenile fall chinook
salmon were first captured in nearshore areas on March 5 and last sampled July 21. Peak abundance was
observed between April 28 and June 2 with the largest catch of the season occuring on May 13. Juvenile fall
chinook salmon with fork lengths at or below 42 mm (emergent fry) comprised 30% or more of the fish
sampled each week through May 26. Fish with fork length greater than 59 mm (size threshold thought to be
less susceptible to stranding or entrapment) began to appear in nearshore samples on May 5 but did not occur in
large numbers until June 2.
Field crews located 1,026 stranded and entrapped juvenile fall chinook salmon in random plots in 1999. Fish
were first encountered in random plots on March 20 and last observed June 12. The majority of stranded and
entrapped fish were sampled during the weeks of March 21-27, April 4-10, April 11-17, and May 23-29. These
time periods coincided with lower flows (<120 kcfs) and large flow fluctuations (>80 kcfs).
Stranded and entrapped juvenile fall chinook salmon had a mean fork length of 45.6 mm and ranged from 36
mm to 66 mm. Indivduals less than 60 mm comprised 96.9% of the juvenile fall chinook salmon measured.
Fish were found throughout the SHOALS defined study area in a variety habitats and flow bands but the highest
concentrations were found at the island complex areas of Locke Island (600-605 Rkm) and 100 F Islands (590-
595 Rkm) at flows of 80-120 and 120-160 kcfs in random plots with gravel to cobble substrates, low substrate
embeddedness, and absent to medium vegetation density.
The estimated total number of juvenile fall chinook salmon stranding and entrapment mortalities within the
SHOALS defined study area (Rkm 571.3 to Rkm 606.9) in 1999 was calculated to be 125,695 with a 95%
confidence interval between 50,724 and 200,666. Juvenile fall chinook salmon placed at risk of mortality due
to stranding and entrapment was calculated to be 381,897 with a 95% confidence interval between -347 and
764,141.
Other fish species found stranded and entrapped in 1999 included northern
pikeminnow (Ptychocheilus oregonensis), threespine stickleback
(Gasterosteus aculeatus), smallmouth bass (Micropterus dolomieui),
sculpin (Cottus spp.), mountain whitefish (Prosopium williamsoni),
sucker (Catostomus spp.), bluegill (Lepomis macrochirus),
lamprey (Lampetra spp.), peamouth (Mylocheilus caurinus),
dace (Rhinichthys spp.), and walleye (Stizostedion vitreum).
The stranding of lamprey in 1999 is of special interest because pacific
lamprey (Lampetra tridentatus) and river lamprey (Lampetra ayresi)
are listed as federal species of concern and river lamprey are also designated
as a Washington State candidate species. Lamprey were also found stranded
in 1998.
Long-and short-term studies of the effects of dewatering on artificial substrates, indicate water level fluctuations
affect nearshore community structure, density, and biomass of macroinvertebrates in the Hanford Reach. Longterm
tests on the effects of fluctuations clearly show that benthic macroinvertebrates within the river fluctuation
zone were severely limited in density and biomass compared to the communities on continually inundated areas.
Total invertebrate density was approximately 4 times higher on bricks never de-watered than on substrates
exposed only 1 to 24 hours. Mean total invertebrate density and biomass were reduced by 59% and 65%,
respectively, from substrates exposed up to 24 hours to substrates never dewatered. Effects of short-term
exposure scenarios revealed that a dramatic decrease in survival was found with even short duration exposures
to air. Artificial exposure tests revealed that survival of macroinvertebrates on substrates exposed to air
decreased dramatically with increasing duration of exposure, with only 50% survival after 1 hour of exposure.
Changes in discharge and water levels also catastrophically entrained macroinvertebrates into the drift outside
of behavioral diel periodicity.
USGS/BRD thermal tolerance tests showed thermally-stressed juvenile fall chinook salmon had little direct
mortality and no increased vulnerability to predation. However, these fish showed transient increases in plasma
concentrations of cortisol, glucose, and lactate, and a dramatic (25-fold higher than controls) and persistent
(lasting 2 weeks) increase in levels of liver hsp70. It is not known what the consequences of exposure to
multiple, cumulative stressors may be to the fish.
An emergency management team (EMT) consisting of WDFW and YN personnel was organized in 1999 to
monitor primary fall chinook salmon rearing areas to identify flow fluctuation events that pose risks (imminent
drainage of entrapments, lethal water temperatures) to large numbers of entrapped juvenile fall chinook salmon.
The EMT monitored 119 entrapments from April 17 to June 21. A total of 8,240 juvenile fall chinook salmon
were seined from these entrapments. Field crews recorded 166 direct mortalities at the time entrapments were
sampled. Projected mortalities were estimated at 428 based on drainage or lethal temperatures monitored in
entrapments. Criteria for emergency action were reached on four days (April 17, May 18, May 22, and May
23). GCPUD provided additional water to re-inundate (or increase river elevations) on each of these
occurrences except May 22.
Based on the results of the 1999 evaluation, the Hanford Policy Group recommended, with the exception of
eliminating the rewetting of entrapment zones after large fluctuations, that the operation constraints imposed in
1999 should be repeated in 2000. Operational constraints recommended for the 2000 juvenile fall chinook
salmon emergence and rearing period include limiting flow fluctuations from Priest Rapids Dam to a range of
40 kcfs on a daily basis (60 kcfs on a daily basis during flow augmentation for outmigrating juvenile fish under
NMFS Biological Opinion) when weekly average flows are less than 170 kcfs at Priest Rapids Dam and
restricting flows to an hourly minimum of 150 kcfs when weekly average flows are greater than 170 kcfs at
Priest Rapids Dam.
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