1108

• UCREFRP Catalog Number: 1108
• Author: Valdez, R. A.
• Title: Fisheries Biology And Rafting Annual Summary Report - 1987
• USFW Year: 1988.
• USFW - Doc Type: ‎(Contract no. 6-CS-40-03980)‎.
• Copyright Material: NO

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growth of these fishes. The surface area seined by each sample effort was
measured and the CPE was computed for each species as the number of fish per 10
square meters of area sampled. An average CPE was computed for each species
using the CPE's from each sample, including zeros, where the species was not
captured in a given sample.

Kick Screens

Kick screens were used in a few concavities and isolated pools where seines
could not be used. Each screen consisted of a 4-foot length of 1/32-inch mesh
tacked to two hand-held brailes. No CPE statistic was computed for sampling
done with this gear.

Drift Nets

Larval drift nets were used to capture larvae and YOY being transported
downstream by river currents. These fine-mesh nets were designed from the
prototypes developed by Haynes et al. (1985). Each net is 10 feet long with a
12 by 18-inch opening. The mesh is 560 micron Nitex plankton netting. Drift
nets were placed in sets of four in water 3-4 feet deep, along the shoreline.
Most sets were left in the water only 15-20 minutes to prevent clogging and
backup from the large volume of detritus carried by the river. A Marsh-
MCBirney current meter was used to determine average velocity at the mouth of
each drift net during the duration of the set; a reading was taken at the
beginning of the set and one at the end. The total volume of water filtered by
each net during a set was computed as the basis for estimating the density of
drifting fishes (Valdez et al. 1985). CPE was computed as the number of fish
in 1000 cubic feet of water by using the following formula:

Ne = (N/(A x Vm x T)) 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),

Vm = average water velocity in feet per second at the net opening
during the set, and

T = total time of set in seconds.

An average CPE was computed for each species using the CPE's from each drift
sample, including zeros, where the species was not captured in a given sample.

Larval drift nets were set only during trips 2, 3, and 4, from June 23 to
August 3.

All sample material collected in these drift nets was preserved in 10% formalin
and placed in labeled Ziploc plastic bags for later sorting at the BIO,IWEST
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

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