|
|
  2000 Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River PDF Format - [391K]
|
Hanford Reach Salmonid Entrapment Research 2000 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 2000 Evaluation of Juvenile Fall Chinook Salmon
(Oncorhynchus tshawytscha) Stranding on the Hanford Reach of the
Columbia River. The 2000 evaluation was the fourth 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 13 through
August 28.
The Hanford Reach experienced slightly warmer to near normal air temperatures
and wetter than normal conditions during the 2000 juvenile fall chinook
salmon emergence and rearing period (March–July). Solar radiation levels,
a good indication of cloud cover, were above the 20-year mean (1980-1999)
each month during this time period with the exception of March. River
flows during juvenile fall chinook salmon emergence and rearing period
were below the 10-year mean flows (1990-1999) for each month with the
exception of April when flows were 30.6 kcfs above the previous 10-year
mean.
Emergence of wild juvenile fall chinook salmon in 2000, as calculated
under the terms of the 1988 Vernita Bar Settlement Agreement (GCPUD 1988),
was estimated to start on March 20 and population index surveys were subsequently
initiated on March 13. Implementation criteria were met on March 19 and
the 2000 Interim Protection Program began March 21. Random sampling to
assess the effectiveness of the 2000 Interim Protection Program began
on March 20 and ended June 25. The protection program continued through
June 26.
Priest Rapids Dam (Rkm 639.1) discharges averaged 147.7 kcfs from March
21 through June 26 in 2000. Hourly discharge from the Dam ranged from
62.1 to 293.2 kcf. Mean daily fluctuation during this period was 50.0
kcfs. The primary period of susceptibility of juvenile fall chinook salmon
to stranding in 2000 based on fish recorded as “mortalities” and “at risk”
in random samples and length frequency distribution from index sampling
appears to be from the start of emergence to May 21. Mean daily flow fluctuation
from Priest Rapids Dam during the primary period of susceptibility was
46.5 kcfs with 9 days of relatively stable flows (fluctuations < 20 kcfs)
and 33 days of flow fluctuations greater than 40 kcfs including 8 days
of flow fluctuations greater than 80 kcfs.
A total of 709 juvenile fall chinook salmon were sampled from random
plots in 2000 including 138 stranded and 571 entrapped individuals. Field
crews recorded 156 direct mortalities consisting of the 138 stranded and
18 thermal induced fatalities. Projected mortalities were estimated at
625 based on revisitation of previous sites to determine if the entrapments
drained or reached lethal temperatures (>24°C). Fish were first encountered
in random plots on March 24 and last found on June 2. The majority of
juvenile fall chinook salmon were sampled from March 26-April 15 and April
23-May 6.
The estimated total number of juvenile fall chinook salmon stranding
and entrapment mortalities in 2000 was calculated to be 72,362 with a
95% confidence interval between 34,270 and 110,454. The number of mortalities
estimated by revisitation of entrapments was 209,997 with 95% confidence
interval between –20,483 and 440,476.
Juvenile fall chinook salmon placed at risk of mortality due to stranding
and entrapment was calculated to be 255,222 with a 95% confidence interval
between 17,743 and 492,701. Juvenile fall chinook salmon collected in
random plots had a mean fork length of 41.7 mm and ranged from 33 to 86
mm. Individuals less than 60 mm comprised 99.2% of the juvenile fall chinook
salmon measured. Juvenile fall chinook salmon were found throughout the
SHOALS defined study area at a variety of flow bands but the highest concentrations
were found at Locke Island (595-605 Rkm) and the downstream end of 100
F Islands (585-590 Rkm) at flows of 120-200 kcfs.
An estimated 16,293,584 fall chinook salmon fry were produced on the
Hanford Reach in 2000. Sampling to assess juvenile fall chinook salmon
abundance and fish size began on March 13, just prior to the estimated
start of emergence on March 20 (Carlson 2000), and ended on June 26. A
total of 5,624 juvenile fall chinook salmon were seined during this period.
Juvenile fall chinook salmon were collected from six index locations once
per week during this period. Peak abundance was observed from April 24
to May 29. The largest catch of the season was obtained on May 29 when
870 individuals were sampled. Juvenile fall chinook salmon with fork lengths
at or below 42 mm comprised 30% or more of the fish seined in the Hanford
Reach until May 15 and fish of this size remained in the samples through
June 19. Juvenile fall chinook salmon with fork lengths greater than 59
mm, the size threshold that individuals are thought to become less susceptible
to entrapment (Nugent et al. 2001a and 2001b), began to appear in the
samples on April 24 but were not collected in considerable numbers until
May 23.
The emergency management team (EMT) monitored entrapments in primary
fall chinook salmon rearing areas from March 20 to June 24. A total of
10,705 juvenile fall chinook salmon were seined from 158 entrapments during
this time period. Many of the same entrapments were sampled on multiple
days in conjunction with EMT monitoring. Field crews recorded 311 direct
mortalities at the time entrapments were sampled. Projected mortalites
were estimated at 4,451 based on drainage or lethal temperatures monitored
in entrapments. Criteria for emergency action were reached on 10 days
(March 27, April 2, April 6, April 15, April 27, April 30, May 2, May
6, May 26, and June9) in 2000. GCPUD provided additional water to re-inundate
(or increase river elevations) entrapments on six of these days (March
27, April 2, April 6, April 15, April 27, and June 9).
Minimum numbers of fish other than fall chinook salmon were sampled during
the implementation and evaluation of the Interim Protection Program in
2000 (March 13-June 26). Spring chinook salmon (Oncorhynchus tshawytscha)
and at least 10 other species of fish were collected in nearshore sites
and random plots during the spring and early summer sampling period. Resident
species found consisted of mountain whitefish, northern pikeminnow, peamouth,
redside shiner, sculpin, smallmouth bass, sucker, threespine stickleback,
dace, and yellow perch. Spring chinook salmon, peamouth, smallmouth bass,
dace, and yellow perch were not represented in random plots.
In 2000, the summer and early fall sampling program began on July 11
and ended August 28. Species collected in nearshore sites during this
time period consisted of American shad, common carp, peamouth, northern
pikeminnow, dace, redside shiner, undetermined minnow species, sucker,
threespine stickleback, bluegill, smallmouth bass, undetermined bass species,
and sculpin.
|