North American Journal of Fisheries Management 28:386–393, 2008 American Fisheries Society 2008 DOI: 10.1577/M06-019.1
[Management Brief]
Performance of Commercially Available Passive Integrated Transponder (PIT) Tag Systems Used for Fish Identification and Interjurisdictional Fisheries Management S. ADAM FULLER*1 U.S. Fish and Wildlife Service, Mora Fish Technology Center, Post Office Box 689, Mora, New Mexico 87732, USA
JAMES P. HENNE U.S. Fish and Wildlife Service, Bears Bluff National Fish Hatchery, Post Office Box 69, Wadmalaw Island, South Carolina 29487, USA
JOHN SEALS U.S. Fish and Wildlife Service, Mora Fish Technology Center, Post Office Box 689, Mora, New Mexico 87732, USA
VINCENT A. MUDRAK U.S. Fish and Wildlife Service, Warms Springs Regional Fisheries Center, 5308 Spring Street, Warm Springs, Georgia 31830, USA Abstract.—Passive integrated transponder (PIT) tag systems are commonly used in identification and monitoring programs with fisheries applications. Transponders of different frequencies, sizes, and code formats are available from numerous manufacturers, and there is increasing concern regarding the need to coordinate tagging efforts with appropriate equipment. Given the high cost of PIT tag systems and the adverse management implications of using incompatible equipment, we evaluated the performance of 20 transponder models and 11 transceiver models currently used in the United States. Compatibility among transceivers ranged from 14% to 81% when evaluated with the 20 transponders in this study. The maximum read distance across all tags and tag readers averaged 9.5 cm (range, 2.0–31.3 cm), and there were significant differences among reader and tag type combinations. Both transponder size and frequency significantly affected the maximum read distance, but transceiver model choice appeared to allow for the greatest practical increase in read distance. These results should assist resource managers with decisions regarding the coordination of tagging efforts that use PIT tag systems, particularly those involving longlived or interjurisdictional species.
Passive integrated transponder (PIT) tag systems are radio frequency identification devices consisting of transponders (tags) and transceivers (tag readers) * Corresponding author:
[email protected] 1 Present address: U.S. Department of Agriculture, Agricultural Research Service, Stuttgart National Aquaculture Research Center, Post Office Box 1050, 2955 Highway 130 East, Stuttgart, Arkansas 72160, USA. Received January 20, 2006; accepted April 16, 2007 Published online March 6, 2008
coupled with an internal or external antenna. Tags are implanted into host organisms, and readers acquire digital codes from the tags by scanning for them with a short-range electromagnetic field. This technology was evaluated for fisheries applications in the early 1980s (Prentice and Park 1983), and the use of PIT tags to individually mark salmonids in the Columbia River basin began in 1987 (Hauser 2003). Since PIT tags are near-permanent internal tags that have few negative effects on host organisms, they have become an integral component of many investigations involving the biology, ecology, and conservation of fish and wildlife species (reviewed in Gibbons and Andrews 2004). Research incorporating PIT tag systems has provided fisheries managers with valuable assessments of fish habitat use (e.g., Bell et al. 2001), migration (e.g., Achord et al. 1996), survival (e.g., Skalski et al. 1998), social organization (e.g., McCormick and Smith 2004), and restoration efforts (e.g., Axel et al. 2005), with no apparent deleterious effects to growth or survival (Prentice et al. 1993; Zydlewski et al. 2001). There are three major PIT tag frequencies (125, 134.2, and 400 kHz) available for use in the United States today, another frequency (128 kHz) being more common in Europe and South America. The 400-kHz frequency was one of the first frequencies used in mass-produced PIT tags, but is being phased out of use as newer technology emerges. Currently, tags using the 125- and 134.2-kHz signals are the most popular. The 134.2-kHz tags have been developed to meet the International Organization for Standardization (ISO) protocol for code format. These regulations provide a
386
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TABLE 1.—Organizations participating in data collection for the compatibility and transponder interaction components of this study. Organization
Location
Connecticut Department of Environmental Protection, Marine Fisheries Division Delaware Department of Natural Resources and Environmental Control, Division of Fish and Wildlife Delaware State University, Department of Agriculture and Natural Resources Florida Fish and Wildlife Conservation Commission, Stock Enhancement Research Facility Maryland Department of Natural Resources, Fisheries Service New York Department of Environmental Conservation, Hudson River Estuary Program, Fisheries Unit South Carolina Department of Natural Resources Marine Resources Division Wildlife and Freshwater Fisheries U.S. Fish and Wildlife Service Bears Bluff National Fish Hatchery Maryland Fishery Resources Office Mora National Fish Hatchery and Technology Center Northeast Fishery Center Warm Springs National Fish Hatchery U.S. Geological Survey Center for Aquatic Resource Studies Conte Anadromous Fish Research Center Leetown Science Center University of Maryland Center for Environmental Science, Horn Point Chesapeake Biological Laboratory
standard method to decrease the probability of duplicate tag codes. This diversity of tag frequencies and code formats from multiple manufacturers has the potential for widespread incompatibility between PIT tags and PIT tag readers (Gibbons and Andrews 2004). Additionally, read distances of some transponder– transceiver combinations may be too short to effectively read tags in large fish when the tags are embedded deeply inside the animal (e.g., shortnose sturgeon Acipenser brevirostrum; J. P. Henne, unpublished observations). These issues can have serious implications, particularly when management involves long-lived or interjurisdictional species. For example, Smith et al. (2002) suggested that recaptures of shortnose sturgeon Acipenser brevirostrum previously implanted with PIT tags may have been underreported because (1) the original PIT tags used sometimes produced altered alphanumeric codes and (2) the inherently short read distances of the original transponder–transceiver combination combined with the subsequent equipment change to a transceiver model optimized for a different tag frequency may have lowered tag detection efficiency. Evaluating the performance of PIT tag systems would provide resource managers with decision-making information and improve coordination of tagging efforts to maximize equipment compatibility and project success. Therefore, the objectives of this study were to evaluate commonly used PIT tags and PIT tag readers for compatibility, transponder interaction, and maximum read distance.
Old Lyme, Connecticut Dover, Delaware Dover, Delaware Port Manatee, Florida Stevensville, Maryland New Paltz, New York Charleston, South Carolina Bonneau, South Carolina Wadmalaw Island, South Carolina Annapolis, Maryland Mora, New Mexico Lamar, Pennsylvania Warm Springs, Georgia Gainesville, Florida Turners Falls, Massachusetts Kearneysville, West Virginia Cambridge, Maryland Solomons Island, Maryland
Methods This study was conducted at the Bears Bluff National Fish Hatchery (U.S. Fish and Wildlife Service, Wadmalaw Island, South Carolina) in cooperation with state, federal, and academic institutions that performed additional equipment testing at their respective laboratories (Table 1). Twenty commercially available PIT tag models that varied by size, manufacturer, code format, and frequency (Table 2) were used in this study, with nine replicate tags for each model. Individual tags were approximately centered relative to diameter and length inside schedule-20 polyvinyl chloride (PVC) pipe sections (12.7 cm long 3 1.9 cm in diameter) filled with common insulating foam. The ends of the pipe sections were sealed with PVC caps, which were externally labeled with unique three-digit alphanumeric identifiers for tag reference. Tag codes were inscribed inside the PVC pipe sections in the event that a tag lost function during the study. All tag codes were recorded and entered into an electronic database before sealing the caps. With the inclusion of 18 blank PVC sections (no PIT tags embedded) for quality control purposes, there were a total of 198 PVC sections used in the study. For all testing performed by the authors, readers were checked to ensure that they were fully charged before beginning any phase of testing. For equipment tested by cooperators, it was requested that all readers be fully charged. The PVC sections were used together with different PIT tag readers to determine (1) PIT tag and PIT tag
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TABLE 2.—Descriptions of the 20 passive integrated transponders used in the study. Manufacturer Allflex AVID
BMDS Destron
Texas Instruments Trovan
a
Model
Size (mm)
Frequency (kHz)
FDX-A AVID2323 AVID2123 AVID2103 AVID2023 AVID2011 IMI1000 TX1415BE TX1410BE TX1400ST TX1405L TX1400L TX1400A RI-TRP-REHP RI-TRP-RE2B ID100A ID162A ID100 ID103 ID162
11.5 12 12 14 12 18 11 23 20 11.5 14 12 12 23 32 11.5 11.5 11.5 12 11.5
125 134.2 125 125 125 125 400 134.2 134.2 134.2 125 125 400 134.2 134.2 128 128 128 128 134.2
Code formata Standard ISO Standard Standard Encrypted Encrypted Standard ISO ISO ISO Standard Standard Standard HD HD Standard Standard Standard Standard ISO
ISO ¼ International Organization for Standardization; HD ¼ half duplex.
reader compatibility, (2) transponder interaction, and (3) the maximum read distances associated with compatible PIT tag and PIT tag reader combinations. However, given that the implant medium (i.e., PVC pipe and insulation) could have affected equipment performance, an empirical test was performed to compare the maximum read distances of the PIT tags embedded in sections of PVC pipe with those of tags implanted into the muscular tissue of fish. One of each tag model was injected into striped mullets Mugil cephalus ranging from 200 to 250 mm in total length. Tag placement was intramuscular, ventral to the insertion of the dorsal fin. The read distance test (described later) was performed and the maximum read distance for each tag was recorded.
Compatibility The 198 PVC pipe sections were used for determining transponder–transceiver compatibility. Tag and tag reader combinations were considered compatible if the transceiver (1) detected the transponder and (2) yielded the correct tag code. The correct tag code was defined as the numeric or alphanumeric code supplied with the transponder by the tag manufacturer at the time of purchase. In cases where codes were not supplied by the manufacturer, the correct code was that yielded by readers of the same manufacturer as the transponder. In addition to the transponders, 11 tag readers from three manufacturers (Table 3) were used to determine equipment compatibility. A blind format was used, with the type of tag and its associated code unknown
TABLE 3.—Tag readers evaluated and the component(s) of the study in which they were used. Component abbreviations are as follows: C, compatibility; TI, transponder interaction; and RD, read distance. Manufacturer AVID
Destron
Trovan a
Model
Abbreviated name
Power TracKer II Power TracKer IV Power TracKer V Power TracKer VIII HS5100 400-kHz Paddle Reader HS5900L Mini Portable Reader Ia HS5900L Mini Portable Reader IIa 9250L Pocket Reader FS2001F-ISO LID 500 LID 570
AVID PT II AVID PT IV AVID PT V AVID PT VIII Destron Paddle Reader Destron MPR Destron MPR Destron PR Destron FS2001 Trovan 500 Trovan 570
Study component C, C, TI C, C, C, C, C, C, C, C,
TI, RD TI RD RD TI, RD TI, RD TI, RD TI, RD RD RD
Data from the Destron Model HS5900L transceivers are from two releases of equipment with the same model number. These data were combined to represent the mini portable reader system (Destron MPR) as a whole.
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during the test. Each PVC section was placed next to the antenna of each reader and the code, if detected, was noted. Three attempts were made to read each tag by altering position of tube relative to reader (i.e., turning and rotating). If no code was detected after the third attempt, the tag was considered unreadable in combination with that tag reader. Tags were read in no particular order and each was read twice. All recorded tag codes were verified for accuracy using the electronic database of tag codes. All tags were initially tested at the Bears Bluff National Fish Hatchery. To increase the pool of PIT tag readers available for evaluation, three replicate tags of each tag model were distributed to fisheries offices located in the eastern United States (Table 3). Each office followed the established procedure for reading the tags using their standard tag-reading equipment, and provided manufacturer, model number, serial number, and approximate date of purchase for all equipment tested. Transponder interactions To characterize the influence of tag type in situations where two tags are in close proximity, a series of readings were performed with seven transceiver models (Table 3) and a subset of PVC sections containing PIT tags. A blind format was used, with the type of tag and its associated code unknown during the test. For each reader, nine PVC sections containing tags were randomly selected from the pool of compatible tags and arranged in groups of two. Read attempts were made on each two-tag combination until all 36 combinations were exhausted. All read attempts were performed in the same fashion, so that the two PVC sections were positioned side by side and the tag reader was placed adjacent to them. The reader was activated only after its antenna was equidistant to, and touching, both sections. The code detected by the reader was recorded. A maximum of three attempts were made to read each tag combination, but after a code was detected, read attempts ceased (i.e., only one code was recorded from each two-tag combination). If no code was detected after the third attempt, the two-tag combination was considered unreadable by that tag reader. Read distance Maximum read distance was measured for eight commercially available PIT tag readers (Table 3) and three replicates of each tag model in a blind test format where tag identity was unknown during the test. Read distance was determined using a wooden measuring form (containing no metal parts) calibrated for linear distance to the nearest 1.3 cm. To perform a reading, a tag reader was placed at one end of the form and a PVC
pipe section (reader antenna parallel to the PVC section and tag) containing a PIT tag was placed at the shortest calibrated distance away from the reader (0 cm) on the form. If the tag’s code was detected, the distance between the tag and reader was increased in length by 1.3-cm increments until the reader could no longer detect the tag. Each read attempt was performed in a similar fashion. The largest distance that a tag reader could detect a tag was defined as the maximum read distance, and was recorded as such. A maximum of three attempts were made to read each tag at progressively greater read distances until the tag could no longer be detected. If no code was detected after the third attempt, the tag was considered unreadable in combination with that reader and no read distance was recorded. The maximum read distances recorded for each tag model were combined by tag size and frequency, and subsequently compared among compatible transceivers. We also analyzed the maximum read distances to investigate whether transponder– transceiver combinations originating from the same manufacturer (Destron, AVID, and Trovan; Table 3) yielded greater read distances (i.e., manufacturer fidelity) relative to mixed-manufacturer combinations. Maximum read distance was compared using a Kruskal–Wallis test using Wilcoxon rank scores. A Student’s t-test was performed after analysis of variance (ANOVA) to determine the relationship of each pair of mean maximum read distances among all compatible transponder and transceiver combinations. Bonferroni adjustments were made on multiple comparisons to maintain the experiment-wise alpha level at 0.05. Statistical analyses were performed with JMP statistical software, version 4 (SAS Institute, Cary, North Carolina). Results Compatibility In general, the Trovan 500 and 570 transceivers and the Destron Paddle Reader were compatible with less than 25% of the transponder models tested, while the Destron MPR, AVID PT II, and AVID PT IV readers were compatible with 25–75% of those tested (Table 4). The Destron FS2001, Destron PR reader, and the AVID PT VIII were compatible with greater than 75% of all PIT tag models tested (Table 4). The Destron PR was able to read 16 of the 20 tag models (80%), the most of all readers tested. In fact, the only tag models that were incompatible with this reader were the Texas Instruments half-duplex (N ¼ 2) transponders, which the reader could not detect, and those manufactured by AVID with encrypted codes (N ¼ 2), which the reader could detect, but could not yield a correct code. Interestingly, even though this reader did not yield a
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TABLE 4.—Compatibility of the PIT tagging equipment evaluated in this study. Solid circles indicate compatible transponder– tag reader combinations, open circles noncompatible transponder–tag reader combinations, and asterisks that an incorrect code was displayed. See Tables 2 and 3 for more information on the equipment evaluated. Reader
AVID PT II
AVID PT IV
AVID PT VIII
Destron FS2001
Destron MPR
Destron Paddle Reader
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
Transponder Brand
Model
BMDS Allflex Trovan Trovan Trovan Destron Trovan AVID Destron Trovan AVID Destron AVID AVID Destron AVID Destron Destron Texas Instruments Texas Instruments
IMI1000 FDX-A ID100A ID162A ID100 TX1400ST ID162 AVID2123 TX1400L ID103 AVID2323 TX1400A AVID2023 AVID2103 TX1405L AVID2011 TX1410BE TX1415BE TI23 TI32
Trovan 500
Trovan 570
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
correct code for the AVID encrypted tags, it consistently yielded the same unique code for each individual tag. Both the Destron FS2001 and the AVID PT VIII were compatible with 15 of the 20 tag models (75%), and together with the Destron PR, these three readers were the only ones that consistently detected 134.2kHz ISO-formatted transponders. The two Trovan reader models (LID 500 and 570) could only read some of the 128-kHz-frequency Trovan tags (14% of all tag models), while the Destron Paddle Reader was limited to compatibility with 400-kHz-frequency tags of multiple brands. The only tag reader tested that was able to read the Texas Instruments half-duplex format tags was the Destron FS2001 transceiver. It is important to note, however, that this was possible only after changing the transceiver’s settings to scan for half-duplex tags and that other tag reader models, such as the AVID PT VIII, have the capability to read these tags, but may not have read them in this study because their settings were not adjusted accordingly. Transponder Interactions Based on the observed patterns of tag code detection when two PIT tags were placed next to each other and scanned with a PIT tag reader, tag type appears to influence which of the two codes are detected in some cases. The Destron Model TX1400ST (134.2 kHz) tags, referred to as ‘‘super’’ tags because of their presumed ability to be detected by readers when placed
*
*
Destron PR
*
*
*
*
** **
*
*
*
*
*
*
*
*
*
*
*
* * *
*
*
*
*
* ** *
* * * *
next to other tag types, had a combined detection rate of 78 6 2.0% (mean 6 SE) when coupled with 125-, 128-, 134.2-, and 400-kHz tags. Likewise, the 134.2kHz (non–super-tag) transponders were detected an average of 82 6 1.2% of the time when placed next to 125-, 128-, and 400-kHz tags, but readability of this tag decreased when placed next to the 134.2-kHz super tags. The signals of 125-kHz tags were dominated by 134.2-kHz transponders (both standard and super tags), read the majority of the time when coupled with 400kHz tags, and detected 50% of the time when placed next to 128-kHz tags. On the other hand, the codes of 400-kHz tags did not perform well in the presence of other tags, and were only read by transceivers an average of 13 6 0.6% of the time when placed next to 125-, 128-, and 134.2-kHz tags and super tags. Read Distance The empirical test comparing the maximum read distances of PIT tags embedded in PVC pipe with those implanted into fish revealed no differences (unpublished data). Maximum read distance across all tags and tag readers averaged 9.5 cm (range, 2.0–31.3 cm), and there was a significant (P , 0.0001) difference in maximum read distance among tag reader and tag type combinations (Table 5). Transponder signal strength, as measured by maximum read distance, increased with tag size (P , 0.001). The tag frequency and transceiver model also significantly (P , 0.001) influenced the
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TABLE 5.—Mean maximum readable distances (cm; ranges in parentheses) for transponder–tag reader combinations. Within rows, means without a letter in common are significantly (P , 0.00556) different. Asterisks denote incompatible combinations. Reader Destron Paddle Reader
Destron PR
Trovan 500
Trovan 570
AVID PT II
AVID PT VIII
Destron FS2001
Destron MPR
BMDS IMI1000
*
*
Allflex FDX-A
*
*
14.3 z (0.0–17.6) *
2.5 x (2.5) *
8.5 z (2.5–17.6) 11.8 z (5.1–15.1) *
5.1 zy (5.1) 14.4 z (10.1–17.6) *
*
*
*
*
*
12.7 z (7.6–15.1) *
*
AVID2023
21.7 z (17.6–25.2) 11.9 z (10.1–12.6) *
*
AVID2123
14.4 z (12.6–15.1) *
2.5 y (2.5) *
2.5 yx (2.5) 11.0 z (7.6–12.7) 11.0 y (7.6–12.7) 8.2 y (2.5–12.7) 6.8 y (5.1–7.6) 8.5 z (5.1–7.6) *
4.2 y (2.5–5.1) *
Troven ID100A
2.5 yx (2.5) 12.7 z (10.1–15.1) *
*
*
* *
*
*
Destron TX1405L
*
*
*
*
2.5 z (2.5) 14.8 z (10.1–17.6) *
3.4 z (2.5–5.1) *
AVID2011 Destron TX1410BE
*
*
2.5 z (2.5) 11.4 y (7.6–12.6) 12.6 z (12.6) *
18.6 z (15.1–20.2) 2.5 z (2.5) 12.3 zy (5.1–15.1) *
*
Destron TX1400A
*
*
Destron TX1415BE
*
*
*
*
*
Texas Instruments RI-TRP-REHP
*
*
*
7.6 y (7.6) 2.5 z (2.5) 8.9 x (5.1–12.7) 7.6 z (2.5–12.7) 9.3 y (7.6–12.7) 14.4 y (12.7–15.2) *
*
*
5.1 y (5.1) 5.9 x (5.1–7.6) *
Texas Instruments RI-TRP-RE2B
*
*
*
*
*
*
*
Transponder
Trovan ID162
Trovan ID103 AVID2323
* 10.6 z (5.1–12.6) 11.0 z (10.1–12.6) * *
maximum read distance. Destron readers coupled with Destron tags did not offer significantly (P ¼ 0.0360) greater maximum read distances compared with that of AVID or Trovan tags. AVID readers combined with AVID tags did not provide greater (P ¼ 0.0603) read distances compared with those produced in combination with Destron and Trovan tags. Since Trovan readers were not compatible with any AVID or Destron brand tags, no comparison could be made using the Trovan readers. Discussion With respect to the management of long-lived and interjurisdictional fishery resources, equipment compatibility may be the most important quality of a PIT tag system. These fish often migrate beyond local authority and their lives may span one or more technological advances in the PIT tag industry, thus increasing the probability that multiple tag types are in use simultaneously. The 20 transponder models evaluated in this study represented four tag frequencies (125, 128, 134.2, and 400 kHz), three code formats (ISO, standard, and encrypted), and two code trans-
18.6 z (17.6–20.2) 30.5 z (27.7–32.8) 27.9 (25.2–32.8) 31.3 (25.2–35.3)
*
*
*
3.4 y (2.5–5.1) 5.9 y (5.1–7.6) 3.2 x (2.5–5.1) 4.8 x (2.5–5.1) 5.9 y (5.1–7.6) * 2.5 y (2.5) 5.1 y (5.1) 5.1 z (5.1) 5.9 x (5.1–7.6) *
mission methods (half and full duplex). From the pool of tag readers available for this study, those manufactured by Destron and AVID clearly exhibited the greatest overall compatibility with the tags tested, but within these brands the range of compatibility varied greatly by reader model (range, 14–81%). The Destron MPR and AVID PT II were limited to use with tag frequencies of 125 and 400 kHz, while the Destron Paddle Reader could only read one tag frequency (400 kHz). On the other hand, the Destron FS2001, Destron PR, and AVID PT VIII all exhibited exceptional compatibility (range, 76–81%) with the tags evaluated in this study, and each of these readers were able to read tags of all available frequencies. The poor compatibility associated with the two Trovan transceivers can be attributed to the inability of those readers to detect any frequency other than 128 kHz. If researchers focusing on the same species are using equipment that is not compatible, there is legitimate concern that multiple transponders could unknowingly be implanted into one fish. This could result in the loss of valuable data and equipment functionality. Some patterns of transponder interactions are evident. In
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general, the 125-, 128-, and 134.2-kHz tags do not perform well when placed next to 134.2-kHz ISO tags (both standard and super types). However, even the 134.2-kHz ISO-formatted super tag, marketed to dominate the signal of other tags while transmitting its own, was only effective 78% of the time when read next to 125-, 128-, 134.2-, and 400-kHz tags. The orientation of transponders within the PVC sections was not standardized during construction of the sections (exact position of antenna side of transponder), but may have been a confounding factor in this component of the study. Another important quality of a PIT tag system is the maximum signal strength (read distance) of the transponder–transceiver combination. Equipment will probably perform best if matched to the size of the fish and the environment in which readings will primarily take place. Since maximum read distance generally increases with tag size and frequency (excluding 400kHz tags), larger tags of the 134.2-kHz frequency should generally optimize equipment performance. An added benefit of this finding is that most 134.2-kHz tag models are equipped with ISO-formatted codes, which provide a standard method to decrease the probability of duplicate tag codes. Three of the tag manufacturers whose products were tested in this study offer standard ISO-compatible tags: Destron (three sizes), Trovan (one size), and AVID (one size). However, factors such as fish size and implant location can limit transponder size. Thus, transceiver model selection may allow for the greatest practical increase in maximum read distance. For instance, when paired with the 134.2kHz ISO-formatted tags (N ¼ 4 tag types), the Destron FS2001 transceiver exhibited the greatest read distances (range, 18.6–30.5 cm) compared with all other compatible tag readers tested (range, 4.7–9.3 cm) (Table 5). Additionally, coupling transponders and transceivers produced by the same manufacturer did not appear to offer any measurable advantage in terms of read distance. The International Pacific Halibut Commission has selected an ISO-compatible transponder as their standard transponder (Destron TX1400ST) (Hauser 2003). When this transponder was tested in combination with the Destron FS2001 transceiver and the Allflex-Boulder ISO Compatible RF/ID Portable Reader (not evaluated in our study) on Pacific halibut Hippoglossus stenolepis, there was no significant difference in detection rate between the two models (100% and 96.7% respectively) (Forsburg 2003). However, due to qualitative factors (primarily reported ease of use), the Allflex reader was selected as the standard transceiver coupled with the Destron tag. There were only four instances in which transceivers detected a transponder’s code but displayed it incor-
rectly. All of these involved AVID encrypted transponders that were designed to inhibit the detection of their codes by non-AVID brand transceivers. While the majority of PIT tag readers simply did not detect the AVID-encrypted tags, the Destron PR and MPR transceivers did detect them but displayed incorrect codes. Interestingly, the codes that these tag readers displayed were consistent for each individual encrypted tag. This study shows that the capabilities of PIT tag system equipment are highly variable. A diverse array of instrumentation exists, but choosing the system that will maximize project success, or minimize project failure, can be a difficult task. We present data that provide insight into the benefits and limitations of PIT tag system equipment specific to interjurisdictional fisheries management in use along the east coast of the United States. The information should assist resource managers in making informed decisions regarding the coordinated use of this equipment for their applications and intended purposes. To this end, management agencies should standardize tagging systems and revise their recommendations as new technology becomes available. For example, standardization of transceiver and transponder systems by the International Pacific Halibut Commission and Pacific States Marine Fisheries Commission is an ongoing effort. Since tagging efforts are often associated with numerous variables and diverse goals, we have purposely refrained from making specific equipment recommendations. For example, those working with species of concern (endangered, threatened, or declining populations) may have more conservative requirements than those working with sport or commercial fishes. However, we do recommend the following general guidelines: (1) communication and coordination are vital when planning or managing a PIT tag identification program, particularly those involving interjurisdictional or longlived species; (2) with advances in transceiver technology, simply sharing tag code information is no longer adequate, especially when 134.2-kHz ISO transponders and compatible transceivers provide multiple formats in which to display a tag’s code; (3) a transceiver that is highly compatible (75%) with multiple tag types is desired to reduce the probability of missing a tag in a recaptured fish and subsequently implanting the fish with another tag; (4) the ISOformatted (134.2-kHz) tags are advantageous for use in new tagging programs because the probability of tag code duplication is reduced; (5) the 134.2-kHz ISO tags appear to have greater read distances and show a greater affinity for detection when placed next to another transponder; (6) the use of transponders with encrypted codes for coordinated PIT tagging efforts is
MANAGEMENT BRIEF
less desirable since they are the least compatible with multiple equipment types; and (7) transceivers should be sufficiently portable and able to withstand environmental conditions at the site of use. Specific transponder–transceiver performance information is available from the authors to aid managers in making their future equipment purchase decisions. Acknowledgments Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture or U.S. Fish and Wildlife Service. The authors thank M. Owens of Biomark, Inc. and B. Mason of Electronic Identification Devices, Ltd. for product information and use of tag readers; and K. Ware, R. Crumpton, and S. Hawkins for technical assistance. The authors also thank the study participants, without whom we could not have completed this study: B. Post, J. Mohler, B. Richardson, C. Stence, A. Lazur, D. Fox, G. Murphy, S. Minkkinen, M. Atcheson, T. Savoy, S. Leach, D. Secor, R. Woodland, A. Henderson, G. Kenney, A. Kahnle, H. Macurdy, B. Hallstead, M. Randall, M. Kieffer, and L. Heyward. References Achord, S., G. M. Matthews, O. W. Johnson, and D. M. Marsh. 1996. Use of passive integrated transponder (PIT) tags to monitor migration timing of Snake River Chinook salmon smolts. North American Journal of Fisheries Management 16:302–313. Axel, G. A., E. F. Prentice, and B. P. Sandford. 2005. PIT-tag detection system for large-diameter juvenile fish bypass pipes at Columbia River Basin hydroelectric dams. North American Journal of Fisheries Management 25:646–651. Bell, E., W. G. Duffy, and T. D. Roelofs. 2001. Fidelity and survival of juvenile coho salmon in response to a flood.
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