7016

• UCREFRP Catalog Number: 7016
• Author: Larval Fishes Laboratory.
• Title: Development of Marking and Otolith-ageing Techniques for Colorado Squawfish
• USFW Year: 1986.
• USFW - Doc Type: Report on Study-Phase 1.
• Copyright Material: NO

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may be troublesome, i.e., extraction of otoliths
and detection by U-V light microscopy.
--Otoliths are the ideal calcium-containing tissue
for TC marking because calcium turnover rate is
low. Moreover, loss of TC tag does not occur
because otoliths are in effect "biological internal
tags".
Procedures
-Test fish--three potential test species, in order of
preference: (1) Colorado squawfish- eggs/larvae may
be obtained through Dexter (New Mexico) National
Fish Hatchery if arrangements are made in advance
(contact Buddy Jensen); typically, Dexter begins
culture of Colorado squawfish in early-mid June.
(2) Roundtail chub (Gila robusta robusta)- early-life
stages similar to Colorado sgauwfish; brood stock
can be field collected and striped and young reared
in the laboratory (Muth et al. 1985). (3) Fathead
minnow (Pimenhales promelas)- if neither Colorado
squawfish or roundtail cliub eggs/larvae can be
obtained, this species seems eggs/larvae
be the best
alternative; eggs may be obtained from Environmental
Research and Technology, Fort Collins, Colorado
(contact Dan Keefe).
-Facilities--all laboratory experiments will be
conducted at Colorado state University in the
Experimental Wet Laboratory, Room 04, Natural
Resources Building (see Muth et al. 1985 for
description of wet lab facilities). The wet lab. is
supplied with well water at a constant temperature
of 19-20C.
-Experimental design (see Figure 1)
--Goals of the experiment: (1) determine optimal
TC concentrations and treatment times, (2) evaluate,
mark retention time, (3) determine effects (if any)
of marking on fish survival, (4) evaluate the
potential of ageing larvae using daily growth rings
on otoliths.
--incubation and rearing procedures will be similar
to those described in Muth et al. 1985.
--Tetracycline hydrochloride (TC) will be used as
otclith marker; concentrations (mg/1) of TC-200,
350, and 500 in distilled water; treatment times
(hours) for each TC concentration- 4, 12, and 36;
pH of TC solutions will be adjusted to near
neutral with Tris buffer (TC solutions are
initially acidic; an electronic pH meter will be
used to measure pH); total of nine treatements per
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