Biological Opinions - Bureau of Reclamation

The April through September 4,034.60 ft (1229.75 m) minimum elevation was set, in part, to
provide access to spawning areas below Anderson-Rose Dam (USFWS 2008). Spawning runs
have occurred in years that Anderson-Rose Dam spills or releases water. Releases were required
as provisions of earlier biological opinions (USFWS 1992, 2001, 2008). In 2006 and 2007,
USFWS entered into an agreement with Tulelake Irrigation District to provide releases during
the spawning season, but high flows in 2006 flushed out newly placed spawning gravel, and no
further efforts were made to support spawning below the dam. As a result, in 2009, the 2008
biological opinion was amended and minimum flows were no longer required at Anderson-Rose
Dam. Successful egg incubation and survival of larvae to swim-up below Anderson-Rose Dam
has been infrequent in recent years and, because only two juvenile suckers were captured in Tule
Lake in recent years, natural recruitment is thought to be very low or nonexistent (Hodge and
Buettner 2008, USFWS 2008). The 2013 Revised Recovery Plan and the 2012 Final Rule for
Critical Habitat both emphasize that agencies should continue to evaluate the feasibility of
restoring spawning habitat and self-sustaining populations of suckers in Tule Lake. Reclamation
has put suckers salvaged from the California portion of the Project into Sump 1A as part of their
efforts to meet BiOp canal salvage requirements. This has occurred on a yearly basis since the
early 1990s and numbers of suckers placed here varied from 2 to 625 between 2006 to 2010, and
averaged 444 per year.
Water depths of Tule Lake Sumps 1A and 1B are shallow (mostly less than 4 ft [1.2 m] deep),
and consequently there is a lack of adequate depth for suckers in large portions of the sumps.
Additionally, gradual sedimentation is a potential threat to adult suckers that require water depths
greater than 3 ft (1 m) to avoid predation by fish-eating birds, particularly pelicans (USFWS
2008).
During severe winters with thick ice cover, only small, isolated pockets of water with depths
greater than 3 ft (1 m) exist in Sump 1A, increasing the risk of winter die-offs (USFWS 2008).
However, the April 1 to September 30 minimum elevation of 4,034.60 ft (1229.75 m) was set, in
part, to provide rearing habitat in Sump 1A, and the October 1 to March 31 minimum elevation
of 4,034.00 ft (1229.56 m) was set to provide adequate winter depths for cover and to reduce the
likelihood of fish die-offs from low DO concentrations below ice cover (USFWS 2008).
Water quality also is considered a threat to suckers in Tule Lake sumps. Tule Lake is classified
as highly eutrophic (enriched) because of high concentrations of nutrients and resultant elevated
aquatic plant productivity (Dileanis et al. 1996). Because Tule Lake is shallow and the nutrient
content high, photosynthesis and respiration by aquatic plants and algae causes large fluxes in
DO and pH. During the irrigation season, water reaching the sumps has been used multiple
times on agricultural lands, which leads to increases in nutrient and pesticide concentrations
(Orlob and Woods 1964, Dileanis et al. 1996).
Reclamation has documented surface temperatures up to 26 ºC (79º F); DO levels from
supersaturation (>15.0 mg/L to near zero); and pH occasionally exceeds 10.0 (Reclamation
2009). During the winter, most inflow to Tule Lake is from localized runoff and water quality
conditions are relatively good, except during prolonged periods of ice-cover when DO levels
decline.
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