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

A. It
B. Trace element marking. Potential markers include:
analysis of natural trace element content of otoliths to
identify stocks, examination of Sr/Ca ratios, and
introduction of artificial trace elements to mark otoliths
and other fish tissues--potential elements include copper,
zinc, flouride, strontium, and various rare earths (e.g.,
Terbium chloride hydrate). Depending on treatment used,
methods of mark detection include the use of atomic
absorption spectrometry and the electron microprobe, and
SEM in conjunction with the electron microprobe and X-ray
spectrometry. Otolith preparation for these analyses is
complex and relatively expensive and time consuming.
C. Tetracycline marking. This compound is a well-known
marker for calcified structures. Detection of mark
requires examination of otoliths with U-V light microscopy.
Incident illumination gives superior results. Preparation
of otoliths for viewing, especially in larger specimens,
might require grinding or etching. Tetracycline marks are
known to be somewhat light-liable; however, good marks may
persists for several years in internal structures such as
otoliths (Blacker 1974).
Conclusions
Given the requirements of the larval drift/marking
program being planned by the CDOW, tetracycline marking is
clearly the "best" method for marking otoliths Colorado
squawfish embryos and larvae. According to procedures
described in the literature, tetracycline marking has the
following beneficial attributes: (1) fish can be marked by
immersion treatment (suitable for mass marking), (2)
marking procedure is relatively simple (useable in the
field), (3) mortality-is low, (4) mark retention time is
relatively long (at least 105 days, Tsukamoto 1985; maybe
even for years, Blacker 1974), (5) mark detection
relatively simple (U-V microscopy), (6) overall cost
relatively low, (7) proven technique for marking fish
embryos and larvae approximately the same size as Colorado
squawfish (see Tsukamoto 1985 and Hettler 1984), and (8)
essentially meets all of our guidelines for an "optimal"
mark.
RECOMMENDED EXPERIMENTAL PROCEDURES FOR MARKING STUDY
Primary literary sources used in establishing the
experimental design were Weber and Ridgeway (1967), Campana
and Neilson (1982), Hamman (1982a and 1982b), Hettler
(1984), Brothers (1985), Muth et al. (1985), and Tsukamoto
(1985). Most information strictly pertaining to (TC)
tetracycline marking of fish embryos and larvae was drawn
from Hettler (1984) and Tsukamoto (1985); a summary of
these two papers follows:
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