Friday, December 7, 2012

Ten Million Fish, Part 1

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.
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.
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.
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….

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