7918

• UCREFRP Catalog Number: 7918
• Author: Scoppettone, G. G., M. Coleman and G. A. Wedemeyer.
• Title: Life History and Status of the Endangered Cui-ui of Pyramid Lake, Nevada.
• USFW Year: 1986.
• USFW - Doc Type: \
• Copyright Material: NO

cans (predation by pelicans is discussed later), or
that died of injuries in the FPB; a few specimens of
selected sizes were sacrificed. Fecundity estimates
were made by volumetric displacement, as
described by Raney and Webster (1942). For each
fish, we took five egg samples along the gonads,
each sample consisting of at least 1 mL of eggs from
complementary sites in both ovaries. The mean
number of eggs per milliliter was counted for the
five samples, and the volumetric displacement of
the ovaries determined. The total number of eggs
in the ovaries was then estimated by direct
proportion.
Fecundity estimates ranged from 24,000 eggs for
the smallest female, 432 mm long, to 196,000 for
the largest, 657 mm long (Fig. 5). The relative con-
sistency of estimates for the 2 years leads us to
believe that fecundity was lower in 1983 than in
1982. Least squares analysis showed that a female
558 mm long (the average length) produced 104,000
eggs in 1982 and 76,000 in 1983. The reduction in
eggs in 1983 paralleled a reduction in relative gonad
weight, from 18% of total body weight in 1982 to
15% in 1983.

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Spawning Habitat

Cui-ui, like other catostomids, spawn in groups,
depositing their eggs over a broad area (Scoppettone
et al. 1983). The tracking of radio-tagged fish
released above MB dam revealed the location of
15' more or less discrete spawning areas during the
3 years of study. One to five depth and water
velocity measurements were taken at each area,
depending on the size of the area and the relative
concentration of eggs; more measurements were

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Fig. 5. Cui-ui fecundity as a function of fork length of
44 females in 1982 and 2S in 1983.

Fig. 6. Frequency of use of spawning sites as a function
of stream depth, stream velocity, and near-bed velocity,
1982-84.