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

1. As judged by survival data, tag retention, and tissue
response, the PIT tag could be injected and retained in
the body cavity of juvenile salmonids weighing as little
as 1.3 g.
2. Implantation of the tags at a pelvic or pectoral
insertion was satisfactory in juveniles, but pectoral
insertion is recommended due to the eventual position
of the tag in the body cavity.
3. The tag did not appreciably affect survival in any of
the test groups.
4. Growth was not significantly affected in any of the
tagged test groups.
5. Tag retention was not markedly different between
pectoral and pelvic treatments; however, the pectoral
site tended to be slightly better.
6. Tag wounds appeared to close sufficiently within 8 to
12 d after implantation to prevent tag loss or wound
infection.
7. If the gut was perforated with the tagging needle,
there was an immediate change in fish color or behavior,
usually followed by death within 5 d.
8. If a tag was lost (not retained in the fish), it was
usually lost within 3 d after implantation.
9. There was nolong-term behavior difference between
tagged and untagged fish; however, this observation
should be tested further (Prentice et al. 1986).
In 1984, NMFS, which began studying the efficiency
of juvenile PIT tag monitors under simulated field
conditions, found the equipment to be more than 90%
efficient. In 1985, NMFS conducted field tests on a PIT
tag monitor system for juvenile fish at the McNary Dam
on the Columbia River (see Figures 10 and 11 in
Prentice et al. 1986). Results of a series of tests with
juvenile spring and fall Chinook salmon (Oncorhynchus
tshawytscha) indicated that the monitor functioned at
95% efficiency and 99% accuracy.
In 1986 and 1987, NMFS continued research with the
newly developed glass-encapsulated PIT tags (Earl
Prentice, personal communication). The glass tags are
about 1 to 2 mm longer than the polypropylene model
(a size increase that was necessary to accommodate a
more economically efficient, automated connection
between the antennas and the microchip), but have
proven superior to their predecessors in three ways:
1. Excellent retention; no sign of mesentery tissue
attachment, as was occasionally noticed with the
polypropylene tags.
2. Improved tag longevity due to a more reliable
moisture seal.
3. Greater range of transmittance; tags have been
decoded at a distance of 10 cm from the fish's body (an
improvement over the polypropylene tags).
The PIT system was recently compared with the more
traditional tagging methodology of freeze-branding.
Prentice et al. (1986) indicated that survival and
behavior of juvenile Chinook salmon implanted with PIT
tags or freeze-branded were not significantly different.
In addition, the number of test fish could be reduced by
90%-95% in a PIT tagging study to attain the same
results and statistical significance. Fish tagged with PIT
tags are handled once during a complete study, whereas
other tagging methods require handling of both tagged
and untagged fish during each detection effort.
Inasmuch as most PIT-tagged smolts released to the
sea have been tagged with the polypropylene tags, the
detection rate of the returning adults is not expected to
be high. The first adults with the glass tags are expected
to return in 1988; however, there was only one detection
station (McNary Dam on the Columbia River near
Umatilla, OR) by late 1987. The emphasis of the study
to this point has been directed at the basic feasibility of
the tags and detection system, the effect of this type of
tagging on fish physiology and behavior, and preliminary
research with the PIT tag as a tool for studying
outmigrations of juvenile anadromous salmonids.
Passive Integrated Transponder tag dctection
devices have been incorporated into existing CWT
trapping facilities, and adult salmonids can be
automatically checked as they pass through detection
systems in Denil fish ladders (Prentice et al. 1985).
Passive Integrated Transponder reading efficiency can
be expected to exceed 95%; it has been as high as 100%
in migrant adult steelhead, Salmo gairdneri (Prentice et
al. 1986).
With current equipment, an experienced PIT-tagging
crew can tag fish at a rate of more than 100 juvenile
salmonids (1.3-3.5 g) per hour. Personnel at NMFS have
recently designed agravity-fed tag-to-syringe loading
device that may increase this rate to 400 per hour.
As would be expected with a system that incorporates
state-of-the-art technology and body cavity
implantation (a PIT jaw tag has also been used to
monitor adult salmonid movements), its high cost and
slow tagging rate may limit its utility. Cost per tag
decreased after recent design modifications, and
depends partly on the number ordered. The NMFS in
1987 procured 100,000 tags at a cost of $3.50/tag- a cost
that may decline further as technology advances. The
initial cost of detection systems varies with the
complexity of the operation.
The usefulness of the PIT tag is being investigated in
Norway, Sweden, and Australia, and is being considered
in New Zealand. Most research has been done byNMFS
in the Pacific Northwest. There has been more
preliminary research into the effects of this tag on the
behavior and biology of the target animal than for
perhaps any other tagging system (Earl Prentice,
personal communication).
The PIT tagging system will not replace traditional
tagging methods (branding, attached tags, coded wire
tags, etc.), but should provide the researcher with a new,
versatile tool to complement these methods. Inter- and
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