7341

• UCREFRP Catalog Number: 7341
• Author: Valentine, J. J.
• Title: Hatchery and Laboratory Phase of the Colorado River Endangered Fishes Study.
• USFW Year: 1981.
• USFW - Doc Type: \
• Copyright Material: YES

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For the most part, eggs deposited in the raceways were not dis-
turbed but were allowed to hatch. tfuen the fry swam up, they were
gathered with a fine seine and transfered to fertilized ponds. Numbers
of fry were estimated at this time. As the fish outgrew their food
supply of zooplankton, they were successfully converted to trout feed.
These fish grew very slowly taking about 100 days to grow from 7 to
50 rom.

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Humpback chub - In 1978 through 1980 adult humpbacks were collected
from the Little Colorado River in Arizona and from the Black Rocks area
of the Colorado River in Colorado and brought to Willow Beach to make
two lots of 14 and 18 fish respectively. The raceway systems and metho-
dologies were nearly the same as those used for the squawfish. However,
these fish did not spawn naturally. Instead they were removed from
their pond in late of 1980 when they showed signs of maturation. They
were injected with carp pituitary and a few eggs were collected and
fertilized by hand stripping. By late May, only 750 fry resulted from
this effort.

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Badly needing these fish, a special expedition was planned into
Black Rocks to collect eggs from wild fish there. Fortunately, from
several ripe females and males, captured on June 1 and 2, 18,000
eggs were collected (Valdes 1980). These were air shipped to Willow
Beach, where about 82% hatched successfully. Swimming fry were trans-
ferred to fertilized ponds and were gradually converted to dry food
as the supply of natural food organisms diminished.

Their growth was faster than the squawfish and some grew 1 mm per
day. They reached an average of 50 rom in 72 days, although there
was a large variation in size. A harvest of about 12,000 fingerlings
was expected, but only 6,200 appeared in the final inventory. Approx-
imately 1,000 were air shipped to Utah FES and 5,200 to the University
of Idaho. Those at Idaho are now 100 rom in length where the water
temperature is a constant 190 C. At Logan they reached 75 rom in
September, but have stopped growing since the water temperature dropped
to 62 0 F.

Bony tail chub - Five Mojave bony tail adults were collected and
brought to Willow Beach in 1979 and 1980, but none tutned out to be
males. In 1979 they produced eggs, but these were discarded. In 1980
the eggs were fertilized in May with sperm from round tails and hump-
backs. As many as 22,000 eggs were taken from a single female.
Hatching success was 75% for the roundtail and 62% for the humpback
crosses. About 12,000 roundtail and 8,000 humpback hybrid fry were
shipped to Dexter NFH for rearing in June. Growth of the humpback-
bony tail hybrid was phenomenal. They reached 125 mm by December. On
the other hand, the roundtail hybrids were less than 75 rom at that time
and some had deformed backbones.

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