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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The numbers of fish by species and age category were recorded on field data sheets at the end of
each sample effort. As with all sample efforts, each fish was classified into one of four age categories;
(1) larvae = LAR, fish without complete muscle and fin development and either a yolk sac or yolk slit
present; consist.ent with the Larval Fish Laboratory (1987) definition, (2) young-of-the-year = YOY,
postlarvae less than one calendar year of age, (3) juvenile = JUV, immature fish greater than one year
of age, and (4) adult = ADU, sexually mature fish.

A summary of sample efforts associated with each general gear type by year is presented in Table
3, and a dletailed breakdown of sample effort by specific gear type for each year is presented in Tables
D-1 througlh D-4. .

Table 3. Summary of fish sample efforts by year.
YEAR CA1"EGORY YEAR
1985 1986 1987 1988
Electrofishing Runs 71 95 170 140
Gill Net Sets 106 180 452 388
Trammel Net Sets 86 142 129 158
Seine Hauls 191 137 204 318
Larval Drift Net Sets 62 132 116 0
Dip Nets 3 0 0 0
Kick Screens 2 4 8 1
Minnow Trap Sets 0 26 0 0
Hoop Net Sets 0 0 0 9

3.3.1 Electroflshlng

Electrofishing was used primarily to sample adults and juveniles along shorelines. A 22O-volt DC
system was used from the 18-foot Havasu raft (Photo A-41). The system was powered by a 4.5-kilowatt
EMS Honda generator, and controlled by a Coffelt WP-15 variable voltage pulsator. The normal
operating level was 180-220 volts and 6-12 amps. Three-pronged anodes of 1/4-inch st.ainless st.eel
braided cable were used. Efforts were made to replace the cable anodes with spherical anodes in light
of the conc:em over possible injury to fish from electrofishing (Carouthers and Sharber 1988). The
swiftness of most. habitats in Cataract Canyon hampered efficient electrofishing using the spherical
electrodes primarily because of the drag resistance which hung the spheres on rocks and prevented
accurate st.eering of the boat.

Throughout this investigation, only the three principal BIO/WEST biologists operated the electroflShing
syst.em. Each exercised much care in monitoring voltage and amperage levels as well as fish reaction
during each electrofishing operation. '" effects were seen with only two fish. One was an adult
flannelmouth sucker that appeared to have a spinal injury, and the second was a juvenile Colorado
squawfish that received overexposure to the anode. The actual cause of death for this fish was not
known. Other than these two fish, no adverse effects were obselVed with fish captured by
electroflShing. In other studies (Valdez and Nilson 1982; Valdez and Masslich 1988) using similar
electrofishing syst.ems, no ill effects were seen even after fish caught by electrofishing were radiotagged
and monitored over periods of several months.

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