9666

• UCREFRP Catalog Number: 9666
• Author: VanHaverbeke, D. R. and Robert L. Simmonds Jr.
• Title: Final Report - The Feasibility of Developing a Program To Augment the Population of Humpback Chub ‎(Gila cypha)‎ In Grand Canyon.
• USFW Year: 2004.
• USFW - Doc Type: Flagstaff, AZ.
• Copyright Material: NO

removal of larval humpback chub (<20 mm) should have less impact on the wild
population than removal of an equal number of 50 mm fish. In addition, growing fish
from 50 to 150 mm rather than from 30 to 150 mm will take less time in the hatchery
(perhaps a month). Two important considerations are to 1) attempt to keep fish held on
station for only a year (or less) in order to logistically accommodate the arrival of the
next year's stock (i.e., prevent stacking of year classes at a facility), and 2) minimize the
time that fish are held in captivity in order to minimize behavioral changes.

Larval humpback chub can be captured with dipnets in the LCR; however, identification
to species can be problematic in the field (Childs et al. 1998). Humpback chub 50 to 70
mm can be easily identified by most field personnel, and can be captured and handled
with minimum mortality using seines, minnow-traps, or hoop nets.

Table 1. Age (in years), mean total length (mm), and estimated wild annual survival
rates for humpback chub. Data provided by C. Walters.

Age

2

3

4

5

6

7

8

9

10

Mean length

93 134 171

204 232

258 280 300 318

334

Estimated survival rate

0.35 0.52 0.61

0.67 0.71

0.73 0.75 0.77 0.78

0.79

Another alternative could be removing 1-year old fish during spring. These fish would
be -93 mm, and could be grown larger (e.g., 200 mm), for increased survivorship.
However, removal of a sufficient number of fish of this size may be more problematic,
and should be expected to depress wild recruitment mor~ than removal of smaller fish.

Other considerations will include the logistics of obtaining fish from a variety of
locations, the gear types for collecting a desired length of fish, and the logistics of
keeping fish alive from the time of collection to arrival at their captive destination.
As discussed in the captive broodstock section, collection of fish should be performed
on appropriate temporal and spatial scales in order to maintain the maximum likelihood
for retention of genetic integrity. Protocols will need to be established to ensure
mortality is kept to levels specified in permits. For instance, holding pens will need to be
established at each camp, and methods will need to be established for moving fish
safely from capture sites to the holding pens. An alternative to setting up holding pens
in the river may be large plastic coolers (e.g., 178 quart capacity Gott coolers) supplied
with a power source (small Honda generators) and pumps for supplying fresh river
water. Aeration of standing water in coolers during the hot ambient air temperatures of
July and August is not advised as mortality would occur. Rather, a constant supply of
fresh river water is preferred. Fish will need to be treated according to the most recent
protocols to relieve stress. Specifics on amounts and types of approved chemicals
used to treat fish and relieve stress need to be included in camp protocols, but this

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