Migration and Histologic Effects of Visible Implant Elastomer (VIE) and Passive Integrated Transponder (PIT) Tags in the Marine Toad (Rhinella marina)

Passive integrated transponder (PIT) and visible implant elastomer (VIE) tags are commonly used to identify reptiles, amphibians, and fish. Despite reports of good retention rates and little to no negative effect on survival time, migration remains a concern and histologic changes have not been widely evaluated. Fifty-six wild-caught marine toads (Rhinella marina) were marked with a PIT tag in the left caudal thigh and a VIE tag over the right gastrocnemius muscle prior to transport to the North Carolina Zoo. Fourteen toads were then humanely euthanized on day 9, 15, 32, and 62 for postmortem examination and histopathology which were compared to 10 control toads with no tags. All PIT tags were functional and 95% remained at the insertion site with minimal to no histologic changes. Externally, 48% of VIE tags were visible through the skin at the original site of injection under fluorescent or UV light. Upon gross examination of the tissues, VIE tags had an overall retention rate of 62% at the injection site, with similar retention rates across time points. Migrated VIE material was visible grossly and histologically in the kidneys of 98% of toads and along the right leg, proximally and distally, in 25% of toads. VIE material was also found sporadically in mesentery, colon, and free in the coelomic cavity. Histologically, VIE material in the skin was surrounded by minimal to mild granulomatous inflammation while in the kidney it was associated with dilation of the small vessels, edema, and granulomatous nephritis that progressed in severity over time. Based on these findings, the authors recommend the use of PIT tags over VIE tags for identification of adult anurans, when feasible.

Operculum PIT tagging: a viable alternative to avoid human consumption in processed salmon

Background Passive integrated transponder (PIT) tags are commonly used to identify individual fish. However, use of PIT tags in commercial aquaculture research is limited by consumer safety concerns. For farmed fish, it is critical that tags do not end up in the final product. One possibility to enable the use of PIT tags in commercial research is to insert tags into a part of the body that will be separated from the trunk during processing. We compare tag loss, mortality rate and welfare scores between Atlantic salmon post-smolts (n = 798) marked with PIT tags either in the operculum musculature or the abdominal cavity (standard practice) before and after mechanical delousing. Results We found that neither condition factor (K) (range 0.60–1.99) nor tagging location significantly affected tag loss (operculum = 6%, intraperitoneal = 8%, z = 1.46, p = 0.14) or mortality (operculum = 2%, intraperitoneal = 2%, z = 0.55, p = 0.58). However, on average, the fish which died weighed 20% less at the time of handling (271 ± 13 g, K = 1.12 ± 0.02) than those which survived (340 ± 3 g, K = 1.14 ± 0.004), and those which lost tags (291 ± 7 g, K = 1.11 ± 0.02) weighed 15% less than those which retained them (340 ± 3 g, K = 1.14 ± 0.004), irrespective of tagging location or handling treatment. Conclusions Fish tagged in the operculum musculature had comparable rates of mortality and tag loss to the current “best practice” standard of intraperitoneal tagging. We show that placement of PIT tags in operculum musculature is a viable alternative to placement in the peritoneal cavity.

The impact of PIT tags on the growth and survival of pythons is insignificant in randomised controlled trial

Individual identification is fundamental to the study of captive and wild animals but can have adverse impacts if the method of identification is inappropriate for the species or question of interest. We conducted a randomised controlled trial to test whether passive integrated transponder (PIT) tags reduced the growth or survival of pythons. We randomly allocated 200 captive-bred Burmese python (Python bivittatus) hatchlings into two groups, tagged versus untagged. Hatchlings were individually identified using a combination of PIT tags and unique colour patterns, and their mass, snout-vent length (SVL) and body condition measured at 9, 73, 134, 220, 292 and 385 days of age. We recorded the date of all mortalities. Python morphometrics and their rate of change increased or fluctuated non-linearly with age. The impact of PIT tagging on python body mass and body mass growth over the 376 day study period was insignificant. PIT tagging additionally had an insignificant impact on python survival. However, we found minor differences in SVL growth between tagged and untagged pythons. These differences peaked at approximately 0.5 mm/day and appeared to drive similar, but more pronounced, differences between tagged and untagged pythons in their rate of change in body condition; peaking at approximately 3–4 g/day. While we cannot be certain that these small differences are, or are not, biologically meaningful, they nonetheless appear to be short-term and readily resolved. Unsurprisingly, the strongest driver of python growth was their age, with growth rapidly increasing or highest amongst younger snakes for all measures of size. Python sex was associated with their body mass and survival, with higher mass but lower survival amongst females. Python size at hatching did not impact on their growth or survival. Our results confirm that PIT tags are a valuable and effective tool for the identification and tracking of captive pythons, and snakes generally, and meet high safety and animal welfare standards.

Impact of river weirs on bedload dynamics in low to medium energy rivers

<p>Assessing the impact of weirs in low- to medium-energy rivers, especially their influence on the bedload continuity, is an important issue for the understanding and management of river hydrosystems. The implementation of European regulations has for example led to an increasing number of restoration projects involving the total or partial dismantling of weirs. The effect of weirs on sedimentary continuity is beginning to be studied but remains poorly understood. In this study we present the results of monitoring over three hydrological seasons of 900 particles equipped with PIT tags set up around two weirs on the Rognon river (France) and the Amblève river (Belgium). For the two sites studied, and while floods were relatively frequent (max 5 return-interval years for the Rognon River and 2 return-interval years for the Amblève River), nearly 80% of the tagged particles positioned just upstream of the weirs were exported downstream of them during the study period. However, the tagged particles in the control reaches, non-influenced by weirs, travelled distances 2 to 2.5 times greater than the particles injected in the impoundment. Mobilisation rates are also significantly higher in the control reaches. Whereas the size of the mobilised particles (D50, D90) is similar between the impoundment and the control reaches in the Amblève river, mobilised particles are significantly smaller in the impoundment reach in the Rognon river. This data indicates that these weirs can have a significant effect by slowing down the bed load velocity, especially its coarsest part. Nevertheless, in the current weir operating, weirs do not interrupt the bedload continuity. This type of structure does not seem to constitute a real obstacle to sedimentary continuity and the question of their dismantling may be raised in view of the potential impacts they could have on the other components of ecological continuity.</p>

Simultaneous Monitoring of the Same Animals with PIT Tags and Sensor Nodes Causes No System Interference

Recent technological advances have multiplied the variety of biologgers used in wildlife research, particularly with small-bodied animals. Passive integrated transponders (PIT) have been used for decades to log visits of tagged animals at reader-equipped artificial feeders or roost boxes. More recently, novel miniaturized sensor nodes can collect data on social encounters among tagged individuals in any location. Combining these systems allows researchers to gather high-resolution tracking data on certain individuals from their long-term PIT-tagged animal populations. However, there can be a risk of interference among tracking systems. Here we tested whether placing an additional biologging sensor on top of a PIT tag might attenuate the magnetic field reaching the PIT tag and, in turn, hamper reading success of the radio-frequency identification (RFID) reader. We also evaluated data transmission by a digital sensor node in the presence of a magnetic field created by the RFID antenna. The combination of this RFID system and wireless biologging sensors works without error, suggesting that the simultaneous use of PIT tags and other digital biologgers, e.g., miniaturized GPS-loggers, should also work together properly when communication channels do not overlap. The combination of long-term monitoring with PIT tags and short-term tracking with biologging sensor nodes creates exciting new opportunities to gather rich social data when individuals are not present at RFID reader stations.

Systematic review and meta-analysis of PIT tagging effects on mortality and growth of juvenile salmonids

A systematic review and meta-analysis was conducted to evaluate the appropriate tag:fish size ratio when tagging juvenile salmonids (genera Oncorhynchus, Salmo, and Salvelinus). The review yielded 18 publications with 211 control and treatment groups reporting results from laboratory studies on the effects of passive integrated transponder (PIT) tags, plus a small number of additional studies on acoustic transmitters. A meta-analysis of the PIT tagging studies showed significant heterogeneity among studies with respect to mortality. Meta-regression revealed that juvenile salmonid mortality increased curvilinearly with the tag:fish length ratio, indicating that mortality risk is rapidly enhanced as smaller fish or larger tag sizes are used. The tag:fish length ratio effect on daily length or mass gain increased linearly. The results provide an estimate of the effects of the tag:fish length ratio on mortality and growth parameters in juvenile salmonids. Based on this, we suggest that researchers can follow best practices for tagging juvenile salmonids with tags that are not greater than 17.5% of fish total length (TL). This equates a minimum size threshold of 131 mm TL for tagging salmonids with 23-mm PIT tags, and 69 mm TL with 12-mm PIT tags. This information can assist researchers, managers, and welfare agencies striving to use the best possible evidence to make informed decisions regarding fish tagging.

Long-Term Retention of Passive Integrated Transponder Tags Injected into the Pelvic Girdle of Adult Walleye

We assessed long-term retention of passive integrated transponder (PIT) tags injected into the subcutaneous musculature between the pelvic fins of adult Walleye Sander vitreus via collecting fish from natural lakes in northwestern Iowa during April 2015, examining fish for the presence of an existing visual implant tag (used as secondary mark), implanting PIT tags in a representative subsample of previously marked fish, and recapturing fish during subsequent annual surveys. Of the 332 Walleye (range = 444–706 mm; mean total length = 544 mm; standard deviation = 43) PIT tagged in 2015, 87 of 88 (98.9%) recaptured from 1 to 4 y after tagging retained their tag. We captured 23 Walleye more than once (≥ 2 y after tagging) and all Walleye had retained their tag on their second or third recapture. This study and others demonstrate that the pelvic girdle was an effective PIT-tagging location for long-term studies evaluating adult Walleye population dynamics. In addition, the low probability of tags being encountered in fish fillets by anglers makes this a desirable tag location for Walleye studies where Walleye are often targeted for consumption. These studies collectively demonstrate that PIT tags inserted into the pelvic girdle of a range of Walleye sizes yield retention rates suitable for advanced population modeling or stocking evaluations.