7937

• UCREFRP Catalog Number: 7937
• Author: Chart, T. E. and E. P. Bergerson.
• Title: Methods for Long-term Identification of Salmonids
• USFW Year: 1988.
• USFW - Doc Type: A Review.
• Copyright Material: NO

opercula, and mandibles soon after administration. The
mark forms a band in the bony material, invisible in
normal light but which fluoresces yellow under
ultraviolet light. Three forms of TC have been used for
marking fish, including the pazent form, oxytetracycline
(OTC) and chlortetracycline. Oxytetracycline is
commonly used in the hatchery system because it does
not affect palatability of the diet, and mazk retention is
high (Weber and Ridgeway 1962, 1967; Weber and
Wahle 1969; Odense and Logan 1974; Koenings et al.
1968).
Tetracycline is typically administered in one of three
ways: ingestion of TC-dosed diet, intraperitoneal
injection, or immersion in a TC solution. In the dietary
method, the most widely used (Moring and Fay 1984),
efficiency increases as the calcium content of the feed is
reduced. Glucosamine, dimethyl sulfoxide, and
terephthalic acid (referred to as potentiators) can assist
in the uptake of TC from the diet and incorporation into
calcified structures (Weber and Ridgeway 1967;
Schidmore and Olsen 1969).
Contrary to the fmdings of Weber and Ridgeway
(1962,1967), Koenings et al. (1986) determined that the
length of the feeding period was secondary in
importance to marking fish at a size above which a lazge
percentage of the OTC assimilated was not
incorporated. Kcenings et al. (1986) suggested that
juvenile sockeye salmon (Oncorhynchus nerka) must be
larger than 40 mm (0.6 g) before orally administered
OTC produces a functional mazk. They also reported a
new fluorometric technique that detects OTC in the
skeletal structure before a visible ring is formed. This
new technique offers the additional advantage of being
able to distinguish the different forms of TC, increasing
its usefulness as a tagging agent.
The immersion process has not been as useful as
orally administered TC for tagging fish (Choate 1964;
Schidmore and Olson 1969; Hettler 1984); however,
encowaging results were reported recently when eggs
and larvae of ayu (Plecoglossus altivalis) were immersed
in TC solutions (200300 mg/L for 248 h for eggs and
200-300 mg/L for 3-24 h for larvae). Mark retention was
100% at 100 d post-immersion, with no special
preparations for detection (Tsukamoto 1985).
Injections of tetracycline have been used successfully
in marking killifishes (Bevelander and Goss 1962) and
flounders and cods (Jensen and Cummings 1967);
however, mazk incorporation may be slow with this
method (Moring and Fay 1984).
Moring and Fay (1984) listed the following
advantages and disadvantages.
Advantages
1. Marks aze essentially permanent (Jensen and
Cumming 1967; Weber and Ridgeway 1967; Weber and
Wahle 1969; Trojnaz 1973; Odense and Logan 1974).
2. Effect on survival and growth or behavior is limited
(Arnold 1966; Weber and Ridgeway 1967; Weber and
Wahle 1969; Schidmore and Olson 1969).
3. No handling or anesthetic is required, unless fish are
injected (Weber and Ridgeway 1967; Trojnar 1973;
Odense and Logan 1974).
4. Lazge quantities of fish can be tagged with relatively
little effort.
5. Coding and data processing aze simple.
6. Life stages and sizes from egg to smolt can be marked
(Trojnar 1973; Tsukamoto 1985).
7. Long-term storage of samples is possible (Trojnar
1973).
Disadvantages
1. Limited permutations for mazked groups (Weber
and Ridgeway 1967; Thomas 1975; Raymond 1974).
2. Wild fish are difficult to mark.
3. Lack of an external identifier, although external bony
parts (fms and opercles) fluoresce for a short period
(Choate 1964).
4. Fish must usually be sacrificed to enable detection.
5. Extraction and mark identification are tedious.
6. Sunlight deactivates TC fluorescence until
melanophores are developed (Choate 1964; Trojnar
1973; Odense and Logan 1974).
7. TC marks aze more readily detected in the fin rays of
small fish and the bones of larger fish (Trojnar 1973).
8. Hatchery stocks treated with TC for disease are
inadvertently tagged -which can be a source of
confusion in mazking studies.
Fluorescent Pigments
When fish are marked with fluorescent pigments, the
objective is to spray pigment granules onto or beneath the
skin (beneath the scales) and later detect their presence
under ultraviolet light. This method was first described in
1959, when it was used to mark landlocked Atlantic
salmon (Jackson 1959). Thereafter the technique was
used on a variety of species (Andrews 1979).
In the marking of smolt-sized salmon, pigment
granules aze sprayed through asand-blasting apparatus
at pressures of 7.0 to 8.4 kg/cm2, at a distance of 20 to
46 cm from the fish (Pribble 1976; Everhart and Youngs
1981; Evenson and Ewing 19$5). Fish aze typically dip-
netted onto an inclined, plastic-lined trough (Moring
and Fay 1984; Evenson and Ewing 1985) or conveyor
belt (Pribble 1976) on which they pass under the pres-
surized spray. Marking rates are high and have been
reported to be 32,000 sockeye salmon smolts per hour
by athree-person crew (Everhazt and Youngs 1981); or
25,000 juvenile Chinook or 40,000 juvenile rainbow trout
(Salmo gairdneri) on a conveyor system (Pribble 1976).
And recently, 35,000 spring Chinook salmon and sum-
mer steelhead were tagged per hour by afour-person
crew at the Cole River Hatchery on the Rogue River,