7918 ‎(2)‎

• 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

20

sample was collected and preserved in 10% forma-
lin each week. The largest cui-ui taken was 28 mm
long and had remained in one of the channels for
5 weeks. We later identified and counted the con-
tents of the entire gut. (Larvae captured at our plank-
ton net stations were not used for food analysis
because they were held overnight before being sepa-
rated from the tangle of filamentous algae taken
with them in the collecting net.)
Of a sample of 51 young cui-ui 12-28 mm long,
42 contained food. Chironomids were found in
86%, copepods in 69%, and algae (primarily
diatoms) in 70% (Table 6). Numerically, cladocerans
accounted for 32% of the food items eaten,
followed by chironomid larvae (26%). In terms of
energy potential, chironomid larvae were the most
important food item, representing 56% of the total
carbon consumed, followed by copepods (18%),
and cladocerans (15 %).
Larvae 12-20 and 21-28 mm long generally ate
the same food except that only the smallest fish
(12-13 mm long) ate copepod nauplii, and the
larvae longer than 20 mm ate larger numbers of the
cladocerans and ostracods that are typically
associated with the benthos. These organisms were
rarely eaten by smaller fish.
Cui-ui larvae were rather selective in their
feeding, taking individual organisms from the water

column, as has been observed in other catostomids
(Willsrud 1971; Corbett and Powles 1983). In most
other catostomids, however, the mouth shifts to a
more ventral position when the postlarval stage is
reached and the fish become more bottom oriented
and feed less discriminatively; sand and silt are
ingested, together with algae and invertebrates
(Moyle 1976; Marrin 1983). There is no morpholog-
ical change in the mouth parts of cui-ui at the onset
of the postlarval stage (Miller and Smith 1981), and
our limited data on yearlings suggested that they,
too, feed on zooplankton.
Four yearling cui-ui collected from Mud Lake
Slough in 1981 had apparently passed through the
Indian Ditch irrigation diversion as larvae in 1980,
and moved into Mud Lake Slough with agricultural
return water. We preserved the fish in 10% forma-
lin and later identified and counted the contents of
the anterior one-third of the gut (as previously
described for the adults). Zooplankton made up
over 97 % of the food items and 90 % of the total
carbon (Table 7). Diatoms and filamentous green
and blue-green algae were noted in the guts of all
four fish but were of negligible importance in terms
of energy potential.
Since food is linked to both environmental
conditions and food availability (Vondracek et al.
1982; Marrin et al. 1984), specific food items eaten

Table 7. Stomach contents of four yearling cui-ui (104-120 mm long) collected in Mud Lake
Slough on 31 March 1981 (T == trace, less than 0.5%).

Stomach contents

Total
number
(%)

Frequency of
occurrence
(%)

Total
carbon
(%)

Macroinvertebrates
Chironomidae
Larvae
Pupae
Amphipoda
Nematoda
Annelida

Zooplankton
Copopoda
Cladocera
Ostracoda
Rotifera
Nauplii

Algae

2 75 7
T 25 T
T 25 1
1 75 1
T 25 T
9 100 14
59 100 72
T 25 T
28 100 4
T 50 T
T 100 1