Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Endangered Suckers: Effects of the Proposed Action on Endangered Suckers
to a lesser extent, the action of storage and delivery of water on water quality and
larval sucker entrainment.
Upper Klamath Lake Habitat
In UKL, sucker access to suitable habitat may change with water management
decisions and lake elevations. Each life history stage demonstrates a specific
habitat requirement in UKL:
• Larval suckers enter the lake environment April through July where they
occupy habitats that are characterized as shallow, nearshore, and
vegetated, except in systems that lack nearshore vegetation (NRC 2004).
Submergent vegetation appears less important for larval rearing than
emergent vegetation (Cooperman 2002). Suckers continue to occupy
habitats with these characteristics in common until they reach juvenile
stage, which typically occurs at about a total length of about 20 to 25 mm
(~0.75 to 1 in) in late July (USFWS 2002).
• Juvenile suckers use nearshore habitats. A general characterization of
juvenile nearshore habitat use is more difficult, as different studies
indicate juvenile suckers may use several different nearshore substrate
types (Buettner and Scoppettone 1990, Simon et al. 2000, Hendrixson et
al. 2007a, 2007b). Juvenile suckers become increasingly difficult to
observe using standard sampling gear during late summer and fall and
may shift toward offshore or deeper water at this time of year (Terwilliger
2006).
• Adult suckers appear to occupy habitats in the northern end of UKL from
June through late September that are defined, in part, by water quality
thresholds for the species (i.e., temperature, DO, and pH [Martin and Saiki
1998, Loftus 2001]) and depth. In general, both adult Lost River and
shortnose suckers selected for depths between 3 and 5 m and avoided
depths < 2 m (Reiser et al. 2001, Banish et al. 2007) until lake water
quality conditions deteriorated or adults were redistributing throughout the
lake in autumn (Banish et al. 2007). When water quality conditions
deteriorated below thresholds in Loftus (2001), adult suckers were
observed in habitats of improved water quality, such as near or in Pelican
Bay, regardless of depth (Banish et al. 2007).
Clear Lake and Gerber Reservoirs Habitat
Sucker habitat requirements are less understood for endangered sucker
populations in both Clear Lake and Gerber reservoirs. In USFWS 2002 BO,
minimum lake elevations in these two reservoirs were proposed and evaluated for
volume and depth of the remaining pool to provide juvenile, subadult, and adult
habitat and access to spawning habitat in the reservoirs’ tributaries. The current
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