7715

• UCREFRP Catalog Number: 7715
• Author: U.S. Fish and Wildlife Service, C. R. F. R. T.
• Title: Bonytail Chub Recovery Plan.
• USFW Year: 1990.
• USFW - Doc Type: \
• Copyright Material: NO

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Reservoir

life history data on bony tail chub in reservoirs have been collected by a
number of biologists and summarized by Minckley (1985). Bony tail chub in lake
Mohave generally occupy lacustrine habitat rather than upstream riverine
habitat near Hoover Dam. William Minckley (Arizona State University, pers.
comm.), believes the cold hypolimnetic water from lake Mead precludes use of
the riverine habitat in lake Mohave by bony tail chub. Wagner (1955) reported
that the species was the most common one collected in gill nets and was
usually found in areas over a clean, sandy bottom with reverse eddy current.
The diet of bony tail chub in reservoirs appears to be primarily plankton and
algae, although extensive food habit studies have not been carried out
(Minckley 1973). Stomach analysis of specimens collected from lake Mohave
indicated they had re ed u on recentl socked rainbow trout less
63.5 mm (~.5 in.) T in size agner 1955).

Spawning behavior of bony tail chub was observed in lake Mohave (Jonez and
Sumner 1954), but no young have been reported. Shortly after impoundment of
lake Mohave, approximately 500 bony tail chub congregated over a gravel bar in
water up to 9 m (29.5 ft) deep. Generally, females were escorted by three to
five malps and fertilized eggs were apparently deposited randomly. No effort
to guard the spawning areas by either sex was observed (Jonez and Sumner
1954). Based on egg development, Wagner (1955) concluded spawning began in
late spring or very early summer.

Hatchery

The majority of the collecting efforts in lake Mohave since 1974 have been
carried out to obtain bony tail chub for culture purposes, producing a total of
24 fish (Minckley 1985); another 8 fish were heavily infested witb the
parasitic cooepod Lernaea cYDrinacea (Bozek et al. 1984). Six female and five
male bony tail chub obtained from Lake Mohave were artificially spawned in
water temperatures of 200e (680F) at Willow Beach National Fish Hatchery
(Willow Beach), Arizona, in 1981 (Hamman 1982a). Most eggs (90 percent)
hatched 99 to 174 hours later. Only 55 percent of eggs placed in 16-17oe
(600-630F) water hatched (between 170-269 hours) and 4 percent hatched at
12-130e (540-550F) (between 334 and 498 hours). Marsh (1985) incubated
bony tail chub eggs at 50e (90F) intervals between 50e and 300e (410F and
860F). The hatching success was 35 percent at 150e (590F), 32 percent at 20De
(680F), and 0.5 percent at 250e (770F); no eggs survived at 50e (410F), 100e
(500F), or 300e (860F). Mean total length at hatching was 6.0-6.3 mm (.24-.25
in.). Total length of normal fry at swim-up was greatest at 200e (680F) (8.6
mm [.34 in.]), ~ompared with 8.1 mm (.32 in.) at 150 and 250e (590-770F). The
incidence of deformed fry was highest (4 percent) at 150e (590F) (Marsh 1985).

Bony tail chub fry produced at Willow Beach in 1981 were reared at the Dexter
hatchery (Hamman 1982b). Spawning trials on 2-year-old bony tail chub were
carried out in 1983 (Hamman 1985) when 24 females were spawned over a 4-week
period using carp pituitary extract to induce ovulation. The fish ranged from
45 to 227 grams (1.6-8 oz) with a mean weight of 127 grams (4.5 oz).
Fecundity ranged from 1,015 to 10,384 eggs per fish with a mean of 4,677.
Average number of eggs per kilogram of body weight varied from 2,302 to 13,576

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