Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Endangered Suckers: Review of Proposed Action
Reclamation’s proposed action may affect suckers at Clear Lake. The effect on
suckers may be beneficial or detrimental.
Gerber Reservoir
The proposed water management at Gerber Reservoir is unchanged from the
USFWS 2002 BO and its amendment (USFWS 2003 Amendment). The proposed
minimum elevation for Gerber Reservoir is 4798.1 feet above mean sea level.
During years when the surface elevation of Gerber Reservoir is less than about
4805 feet above mean sea level from February through April, access to spawning
areas in Barnes Valley and Ben Hall creeks is restricted (Reclamation 2001). The
seasonal minimum elevation at Gerber Reservoir is likely to occur during summer
or fall. Gerber Reservoir is typically able to refill to at least 4805 feet from a
minimum of 4798.1 feet during late fall and early winter, so access to spawning
tributaries is re-established by the spring months when suckers typically spawn.
However, in dry years these streams typically have very low flows that may not
provide adequate for the upstream passage of spawning adults regardless of lake
elevation (Reclamation 2001).
During dry years when minimum elevations reach 4801.7 feet above mean sea
level, the surface area of Gerber Reservoir shrinks to about 750 acres, reducing
sucker habitat to less than a third of the full reservoir area. When juvenile and
adult rearing habitat shrinks to low amounts, suckers are likely stressed by poor
water quality (high temperature and low DO); increased competition; and
increased incidence of disease, parasites, and predators. Effects of low lake levels
on larval and juvenile suckers are likely to be greater than adults since they have
lower food reserves, higher metabolism, and lower mobility, and are more
vulnerable to predators.
At a minimum elevation of 4798.1 feet above mean sea level, suckers may
become concentrated in the remaining pool and experience stress. Lower lake
levels may result in degraded water quality including higher water temperatures,
higher pH values and lower DO levels. However, water quality monitoring over a
wide range of lake levels and years documented water quality conditions that
were generally adequate for sucker survival except in 1992, when Gerber
Reservoir dropped to a minimum elevation of 4796.4 (Reclamation 2000 Water
Quality). The proposed minimum elevation is likely to maintain a sufficient pool
of water that will likely have less of an effect on the population of shortnose
suckers that reside in Gerber Reservoir than in 1992. In the 2002 BO, USFWS
agreed that operations resulting in minimum lake elevation at Gerber Reservoir of
4798.1 ft above mean sea level were 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 4798.1 foot is needed to protect shortnose suckers at
Gerber Reservoir and operations for diverting available water to irrigation was
permissible (USFWS 2003 Amendment).
136