Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Endangered Suckers: Review of Proposed Action
reproductive organs, reduced juvenile growth rates, and high incidence of external
parasites and lamprey infestation (Reclamation 1994). Overall fish body
conditions were improved with increased body weight and fewer external
parasites and lamprey wounds at higher lake levels in 1993-1995 (Scoppettone et.
al. 1995). Reclamation proposes to provide a minimum lake elevation of 4520.6
ft at Clear Lake. This elevation is 1.2 ft above the conditions in 1992.
Lower lake levels may also result in degraded water quality, including higher
water temperatures and lower DO levels. However, water quality monitoring
over a wide range of lake levels and years documented water quality conditions
that were adequate for sucker survival (Reclamation 2000 Water Quality). The
major concern for harmful and/or lethal water quality conditions is associated
with winter ice cover periods. Low lake levels have an increased risk of low DO
and potential winter die-off during ice cover conditions. During the winter of
1992-1993, Clear Lake was ice-covered for several months at an elevation of
about 4519.5. However, DO concentrations during the ice-cover period that year
remained at adequate levels for sucker survival (>4 mg/l; Reclamation 1994).
Because of the relatively low recharge rate in Clear Lake, lake levels may remain
relatively low for several years. These conditions may adversely affect sucker
through crowding and the associated increases in stress, competition for food and
space, predation, and disease. Extended drought may result in complete or nearly
complete desiccation of Clear Lake, especially if the lake drops below 4520 feet
for extended periods. However, model simulations demonstrate that if the surface
elevation of Clear Lake is at least 4521 feet on October 1, it is unlikely that the
lake will drop below 4519 feet in the following year. Delivery of water that
results in a lake level of less than 4521 feet before October 1 will be curtailed.
In the 2002 BO, USFWS agreed with Reclamation that water operations resulting
in a minimum lake elevation at Clear Lake of 4520.6 ft above sea level was
permissible (USFWS 2002). In a memorandum from USFWS to Reclamation on
4 March 2003 (memorandum #1-10-03-I-075), USFWS concurred with
Reclamation’s effects analysis that a minimum elevation of 4520.6 ft is needed to
protect Lost River and shortnose suckers at Clear Lake and that Reclamation’s
operation of Clear Lake was permissible (USFWS 2003 Amendment).
Water management action at Clear Lake may affect suckers; however, it is
unclear what the effect may be. The proposed water management at Clear Lake is
unchanged from the USFWS 2002 BO and its amendment (USFWS 2003
Amendment). Water management at Clear Lake during the last 5 years would
have appeared to provide a benefit to the sucker populations there as evidenced
through recruitment into the adult populations and the relatively large and stable
population of suckers present in Clear Lake (Leeseberg et al. 2007, Barry et al.
2007 Lost).
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