Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Endangered Suckers: Environmental Baseline for Suckers
in the lake. Increased survivorship at earlier life history stages may increase the
number of individuals recruiting into the adult populations.
Levees surround the TNC property, known as Tulana Farm, keep lake and river
water from flooding the agricultural lands inside the levees. The agricultural
lands within the levees have subsided through the years as a result of farming and
the nature of the soil type dominating the area. The Nature Conservancy has
attempted to restore wetland vegetation prior to removing the levees and
inundating the fields. At present, TNC estimates approximately 800 to 1000 acres
of established wetland vegetation at elevations that will remain as emergent
wetland following levee breaches (Elseroad 2004, M. Barry, Williamson River
Preserve Director TNC, Williamson River Preserve, pers. comm.).
While it is certain that water depth in the new areas of emergent vegetation will
fluctuate with lake elevation, it is relatively uncertain how much of the 800 to
1000 acres of vegetation will be available to larval sucker use at any one time.
Recognizing that depth is a component of sucker habitat in and near emergent
vegetation, previous work has indicated that larval suckers use emergent
vegetation habitat, nearshore in shallow water (Dunsmoor et al. 2000, NRC 2004,
Markle and Dunsmoor 2007). Assuming that only half of the presently
established vegetation (800 to 1000 acres) is accessible to larval suckers
following levee breaching and the average depth of water in this area is 1 ft at the
time larval suckers arrive in the habitat during spring 2008, then emergent
vegetation habitat is available in a volume of about 7,424,000 to 21,780,000 ft 3
(493,392 to 616,740 m 3 ). Although emergent habitat volume is influenced by
lake elevation, the increase in emergent vegetation habitat that will be readily
available to larval and juvenile suckers in northern UKL during spring 2008 is a
substantial increase after levee breaching than prior to levee breaching (Dunsmoor
et al. 2000).
Elseroad (2004) estimated the surface area to be colonized by particular
vegetation communities based on surface elevations of the Williamson River
Delta area and UKL water management of the 2002 BO (USFWS 2002). The
estimates of unvegetated open water, deep water wetland, emergent wetland,
riparian/wet prairie, and upland plant communities varied with lake elevation.
However, the most stable vegetation community by surface area through the four
water management scenarios of the 2002 BO was emergent vegetation (Elseroad
2004). The estimated nearly 2200 total acres of emergent vegetation yet to
establish on the Williamson River Delta is a large increase from the existing
estimates of emergent vegetation in this area (Dunsmoor et al. 2000). Should
only a fraction of this habitat be used by larval and juvenile suckers, the habitat
increase could result in increased survivorship and numbers of suckers at the two
earliest life history stages. This becomes especially true if habitat has been a
limiting factor for sucker survivorship in UKL.
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