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.?

year, the LFL agreed to begin work prior to contract
confirmation. This report covers work conducted under
under Phase 1 of the overall study.
GENERAL SCOPE OF PHASE 1
Phase 1--Determination and set-up of laboratory
procedures
A. Survey literature, contact researchers familiar
with larval fish marking/ageing techniques, and
assess the available methods; reference list
will be developed.
B. After completion of Phase 1A, determine the
"best" methods with applicability to Colorado
squawfish larvae; a report of Phase 1A and 1B
findings will be prepared and submitted for
consideration.
C. Based on conclusions/recommendations from Phase
1B report, set up experimental design and order
materials/supplies.
RESULTS OF PHASE 1A and 1B
In cooperation with Thomas Nesler, we first defined
guidelines for an "optimal" mark for larval Colorado
squawfish. These guidelines were based on and largely
restricted by overall CDOW project-objectives. It was
decided that an "optimal" mark should have the following
attributes: (1) fish must be marked during the embryo
period or early protolarval phase (prior to feeding or
swim-up), (2> because of restrictions of #1, marking
probably will have to be accomplished by some sort of
immersion treatment, (3) treatment must be suitable for
mass marking, (4) low mortality during and initially after
marking (mark should not affect normal activity/life of
fish, e.g., increased predation due to higher visibility of
larvae or altered behavior), (5) mark should be retained
and detectable for at least 4-6 weeks (preferably 6-8), and
(6) marking procedures developed in the laboratory must be
useable in the field. During the literature survey we were
cognizant of the guidelines and strictly structured our
assessment of available methods around them.
A considerable amount of literature exists on marking
techniques for fish (see Stott 1968; Laird and Scott 1976;
and Wydoski and Emery 1983 for general overviews of fish
marking techniques). However, relatively few marking
procedures have been described for fish embryos and early
larvae (especially for freshwater fishes), and only a small
percentage of these have attributes (all or in part)
aligned with our established guidelines. After a detailed
a
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