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Clean hatchery water going back to the Clearwater |
A lot has been happening at Dworshak National Fish
Hatchery recently!
We currently have just shy of 4 million Chinook, 400K Coho, and 2.2 million
steelhead on station. There are also 2.6 million eyed Chinook eggs, and around
1.2 million Coho eggs in incubation.
How did we get here?
For several years, Dworshak has been struggling to meet its NPDES permit
(National Pollutant Discharge Elimination System). The Environmental Protection
Agency ( EPA), Army Corps of Engineers (Corps), Fish and Wildlife Service (FWS),
and Nez Perce Tribe entered into a Federal Facility Compliance Agreement (FFCA)
to work towards a solution to this problem. As part of the FFCA, Dworshak
needed to treat cleaning effluent from System 3 Burrows Ponds. In 2011, the
System 3 solution was reducing the number of Burrows Ponds in production so
that a limited volume of wastewater could be diverted to the old re-use system
for treatment.
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Steelhead Smolts |
As a result of the reduction of System 3 availability, Dworshak increased the
density of steelhead smolts reared in the 50 remaining Burrows Ponds to meet a
release target of 2.1 million smolts. As part of the density increase,
management also increased the flows to each Burrows Pond substantially; from an
average of 450 gallons per minute (gpm) to over 850 gpm. This flow increase
also corresponded with several other key water management changes including:
1. Replacement and rebuilding of the main pumps;
2. Reduction of leakage around the ladder supply valve and corresponding change
to re-use water for the ladder and holding ponds;
3. Utilizing re-use in the Chinook raceways.
In 2011, System 3 was retrofitted with gates and protocols were developed to
divert cleaning waste to the defunct biofilter for the 9 ponds in production.
As part of the FFCA-driven System 3 shutdown, the Coho were also moved to the
Raceways. This displaced 6 raceways of Spring Chinook production. The densities
of the remaining Spring Chinook raceways were increased to maintain the 1.05 million
smolt release goal.
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The sad results of an IHNV outbreak |
During the 2011 rearing, the Hatchery staff was very pleased with the Burrows
Pond steelhead rearing and Raceway Chinook/Coho rearing. Approximately 300K
steelhead were destroyed due to an infectious haematopoietic necrosis virus (IHN)
outbreak, but this was traced back to a breach in the Nursery supply water and
only affected the first take of steelhead. No other steelhead contracted IHN in
2011 due to early rearing on reservoir water in the System 1 Burrows Ponds.
After early rearing, the steelhead fingerlings were split into final rearing
numbers in August through September in the 59 Burrows Ponds. The staff immediately
noticed the benefit of higher flow rates in the Burrows Ponds. The increased
flows created a cleaner rearing environment and greater swimming velocities for
the smolts. Survival in the Burrows Ponds again topped over 90% for the second
year in a row, after the dismal 50% survival of BY2009.
Brood Year 2010, 2011 and 2012 steelhead have been
produced using reservoir water beginning in May of each respective rearing
cycle. BY 10 and 11 were released in full numbers achieving or exceeding
the 2.1 million smolt release target. We are positioned well for the SST
BY 12 numbers on station to meet or exceed the 2.1 million smolt release target
in the April 2013.
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Burrows Ponds at Dworshak National Fish Hatchery |
In early summer of 2012, the Hatchery Management was
much more comfortable with the System 3 cleaning operations. They made plans to
return the Coho production to System 3, and increase the Spring Chinook
production by 300K smolts and 300K parr at the request of the Lower Snake River
Compensation Program (LSRCP). The Steelhead production was slated for 50
Burrows Ponds in Systems 1 and 2, and 10 Burrows Ponds in System 3, along with
the 5 Coho Burrows Ponds. All of this would be supported with increased flows
per rearing unit, based on the key water management changes from 2011.
Stay tuned. Next week
we will talk about what happens when things don’t go as planned….