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

18

Table 4. Estimated number of cui-ui in the pres pawning aggregation in Pyramid Lake in 1982 and 1983.

Year

Item

1982

1983

Tagging
Dates
Number of fish
Recoveries in FPB
Dates
Percent of total tagged
Estimated prespawning aggregation
Number
95% confidence limits

3/17-6/16
1,092

4/6-6/16
1,122

5/15-6/11
7.1

5/22-6/8
5.7

187,065
151,883-236,451

103,407
82,270-134,161

short-term loss of tags among fish entering the FPB.
Using a modified Schnabel population estimator for
our computation (Ricker 1975), we estimated the
prespawning aggregation of cui-ui to be 187,000 fish
in 1982 and 103,000 in 1983. The large number of
cui-ui offshore in 1982 and 1983, compared with
much smaller runs at the FPB, indicated that the
fishway was not totally effective in letting fish pass,
In 1982, 13,804 fish-only 7.4% of the estimated
offshore population-entered the FPB; in 1983, this
number was 5,994 (5.8%).

Food

Adults

To determine food of adult CUl-Ul ill the
prespawning aggregation, we collected gut samples
from fish captured at offshore gill-netting stations.
The guts were immediately removed and preserved
in 10% formalin, and the contents of the anterior
third of the intestinal tract were later determined.
We used a dissecting microscope to count the

Table 5. Stomach contents of 14 adult cui-ui collected from the 1983 prespawning aggregation
(T = trace, less than 0.5%).

Stomach contents

Total
number
(%)

Frequency of
occurrence
(%)

Total
carbon
(%)

Macroinvertebrates
Chironomidae
Chironomus sp. (larvae)
Pseudochironomus sp. (larvae)
Zooplankton
Copepoda
Cyclops verna lis
Diaptomus sicilis
Nauplii
Cladocera
Ceriodaphnia quadrangula
Algae

T 21 T
T 36 T
T 21 T
46 100 71
T 57 T
54 100 29
T 86 T