ITEM: |
INFORMATIONAL ITEMS/STAFF REPORTS |
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25. |
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Meeting Date: |
January 29, 2009 |
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N/A |
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General Manager |
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Cost Estimate: |
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General Counsel Approval: N/A |
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Committee Recommendation: N/A |
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CEQA Compliance: N/A |
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AQUATIC HABITAT AND FLOW
CONDITIONS: During November and
December 2008,
During November
2008 the mean daily streamflow recorded at the District’s
SLEEPY HOLLOW STEELHEAD REARING FACILITY: The first rescued fish were brought to the Facility on May 14, 2008. Of the approximately 47,657 rescued fish brought to the Facility, 1,022 fish died during the initial quarantining and the grow-out of very small young-of-the-year (YOY) fish from predation, injury, or disease. By the end of July 2008, 46,635 fish had been placed in the Facility’s 800-foot long rearing channel. This was nearly two times the number of fish ever stocked in the channel before (approximately 26,000 in 2003 and 24,000 in 2005). Because of the record number of juvenile steelhead that needed to be rescued in 2008, over 84,000 fish, the District, with the support of the National Marine Fisheries Service (NMFS) and the California Department of Fish and Game (CDFG), decided to only rear up to 48,000 fish at the Facility.
Compared to 2007, the 2008 YOY fish brought to the Facility were much larger and were rescued earlier in the season, so their initial stress and disease levels were probably lower. These facts, coupled with cooler summer water temperatures, led to much lower mortality due to disease: 20% in 2008 versus 60% in 2007 (when all the fish were reared in small tanks). Unfortunately, the percentage of unaccounted-for fish mortality was very high in 2008, 49%, a potential consequence of the high stocking densities. The 12-year Facility average is 36% unaccounted-for fish. While there have been three other years that had greater than 50% unaccounted-for fish, this year’s result is particularly discouraging since so many steps were taken to reduce the likelihood of intra-specific predation and other fish losses.
In the summer of 2008, one of the
largest fires in
The smaller fish (<150 mm FL) from the rearing channel were transported downstream and released in several locations between lower Garland Park (RM 10.8) and CAW’s Manor Well (RM 7.1) (mostly below Scarlett Well (RM 9.1). The lower 2 miles of this reach had dried over the summer and the fish were rescued. It began re-wetting in late October, but had few fish in it at the time the Facility’s fish were released there. We estimate that we restocked this 3.7 mile reach of mostly rewetted habitat with approximately 0.6 fish per lineal foot of habitat, which is a very low stocking density.
A total of 14,721 fish were captured from the rearing channel over four weeks in December with 3,620 (25%) larger fish being held temporarily in Tank 3, and 11,101 (75%) smaller fish being released back into the lower river (Exhibit 25-A). The average condition factor (K) (the ratio of fish weight to fish length) of fish reared in the channel was excellent, 1.16, at the time of release and the fish looked extremely healthy and fit. The average fish at release was 151mm fork length (FL) and weighed 45g. This is considered “smolt size” (Exhibit 25-B). Overall steelhead survival at the Facility during the 2008 rearing season was 32%. The Facility’s 13-year average survival is 39%.
EXHIBITS
25-A Sleepy Hollow Steelhead Rearing Facility 2008 Summary
25-B SHSRF Average Fish Sizes at release
U:\staff\word\boardpacket\2009\20090129\InfoItems\25\item25.doc