7400

• UCREFRP Catalog Number: 7400
• Author: Valdez, R. A.
• Title: The Endangered Fish of Cataract Canyon
• USFW Year: 1990.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

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Ne = (N/(A x Vm X 1)) X 1000

where:

Ne = estimated number of drifting fish in 1000 cubic feet of water,
N = actual number of fish recovered from a drift sample,
A = area of net opening in square feet (1.5 square feet),
V m = average water velocity in feet per second at the net opening during the set, and
T = total time of set in seconds.

All sample material collected in these drift nets was preserved in 10% formalin and placed in labeled
Zip IocR plastic bags for later sorting at the BIO/WEST laboratories. Preliminary identification was made
of these fish and all samples were sent to the Larval Fish Laboratory (LFL) in Fort Collins, Colorado, for
verification and further identification. In the laboratory, each rare fish was measured for total length and
classified by developmental phase (protolarva, mesolarva, metalarva, juvenile); the nontarget fish were
only classified by phase. The first. three classifications of protolarva, mesolarva, and metalarva were
combined in this st.udy into the age category of larva, while those individuals termed .juveniles. by LFL
were placed into the YOY category.

3.4 Measurements of Gila Specimens

Because of the morphological variation in the genus Gila of the Upper Colorado River Basin, each
juvenile and adult chub captured was photographed on a white background marked with a 1-cm grid
pattern. Also, the following meristics were measured using calipers, and counts were made on each
chub longer than 200 mm (Figure 10): (1) total length, (2) fork length. (3) distance between insertion
of pectoral and pelvic fin, (4) nuchal depth, (5) minimum caudal peduncle depth, (6) caudal peduncle
length, (7) head length, (8) length of dorsal fin base, (9) length of anal fin base, and (10) dorsal and
anal fin ray counts. These measurements are recommended by FWS in the ISMP. Additionally, the
following meristics were recorded: (11) maximum caudal peduncle depth, (12) maximum body depth,
and (13) snout length. Each fish was also weighed in grams. These meristics were used in principal
components analysis (Humphries et a1. 1981; Kim and Mueller 1978) as a tool in segregating distinct
forms of Gila.

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Figure 10. Morphometric measurements taken from each chub (Gila spp.) longer than 200 mm.

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