External Radio Transmitters Research Articles

First observation of fouling of externally attached radio transmitters in an African river

Fouling of externally attached tags is an important consideration in long-term tagging studies as it may affect fish behaviour and well-being. Two externally attached radio transmitters on African tigerfish Hydrocynus vittatus were covered with short green algae, after the fish were recaptured 49 and 64 days after tagging in the Kavango River, Namibia. This is the first observation of fouling on external radio transmitters from any African river which highlights the importance of conducting studies that evaluate the various health or behavioural effects resulting from tagging.

Chytrid fungus dynamics and infections associated with movement distances in a red‐listed amphibian

AbstractAmphibians are among the most threatened vertebrate taxa due to anthropogenic habitat change and emerging pathogens. The fungus Batrachochytrium dendrobatidis (Bd) may cause trade‐offs between the immune responses and other important functions, such as mobility. The pool frog (Pelophylax lessonae) is red‐listed in Sweden, and an earlier study conducted in our study area did not detect the fungus. In this study, 67 Swedish pool frogs were tested for Bd. Of these, 28 adults were provided with external radio transmitters and tracked during the summer and autumn to compare movement among infected and non‐infected individuals. Additionally, we tested some individuals for Bd twice during the summer to study intra‐seasonal variation in individual infections. Our results suggest that Bd has recently invaded these pool frog populations. During autumn, movement distances of infected pool frogs were shorter compared to uninfected individuals, and summer movements within ponds were reduced by increasing Bd load. We also found that the frogs can clear (or reduce) Bd infection during their active season. The results from this study increase understanding of the implications of Bd infections in an anuran fringe population, as well as in amphibian metapopulations, and can further guide amphibian conservation planning and management.

Implications of the movement behaviour of African tigerfish Hydrocynus vittatus for the design of freshwater protected areas.

African tigerfish Hydrocynus vittatus (n = 35) were tagged with external radio-transmitters in the Kavango River, Namibia, to determine whether freshwater protected areas could be an effective tool for the management and conservation of this species. They were manually tracked in the core study area of 33 km every c. 12 days from July-October 2016 to May 2017 for between 123 to 246 days. In addition, 14 extended surveys were carried out for up to 680 km to determine the total area use of the tagged individuals. Tigerfish displayed at least two behavioural patterns either having high site fidelity with shorter movements or using larger areas with longer movements. Twenty-three (66%) of the tigerfish had high site fidelity using an area of less than 33 km of river, whereas 12 tigerfish (34%) undertook long distance movements of up to 397 km upstream and 116 km downstream from their tagging locations. During the long-distance movements tigerfish crossed the territorial boundaries of Angola, Namibia and Botswana. Of the 35 fish that were monitored, 14 (40%) spent more than 80% of the monitored time in the 33 km study area and 18 (51%) stayed within the study area for at least 50% of the monitored time. These findings suggest that freshwater protected areas may be a useful management tool and we predict that a protected river area of 2-5 km river length could protect 25.9-34.6% of the population for at least 75% of the time whereas protection of 10 km river length could protect at least 50% of tigerfish for at least 75% of the time.

Monitoring Eastern Diamondback Rattlesnakes Using a Novel External Radio-Transmitter Attachment Method

Internal implantation of radio-transmitters is the preferred attachment technique for snakes, but the high costs and invasive nature of the surgery make a functional alternative desirable. Attaching radio-transmitters externally can be a cost-effective alternative to surgical implantation. External transmitter attachment site and methodology depend on the unique morphology of a given study species, making external adherence impractical for most snake species. Rattlesnake rattles are unique morphological features that can serve as an attachment site for external radiotransmitters. From 2011 to present, we have been attaching transmitters to the rattles of Eastern Diamondback Rattlesnakes (Crotalus adamanteus; EDB) using thread and epoxy. We calculated average monitoring duration using radio-telemetry data collected from 49 adult EDBs telemetered from 2014 to 2017 in coastal South Carolina. On average, we monitored EDBs for 189±78 days with 14 EDBs monitored >240 days and 3 EDBs monitored >300 days. External transmitter attachment is a viable alternative to surgical implantation, providing a noninvasive approach to monitoring rattlesnakes.

Evaluation of a waistband for attaching external radiotransmitters to anurans

ABSTRACTRadiotelemetry provides fine‐scale temporal and spatial information about an individual's movements and habitat use; however, its use for monitoring amphibians has been restricted by transmitter mass and lack of suitable attachment techniques. We describe a novel waistband for attaching external radiotransmitters to anurans and evaluate the percentages of resulting abrasions, lacerations, and shed transmitters. We used radiotelemetry to monitor movements and habitat use of wood frogs (Lithobates sylvaticus) in 2006 and 2011–2013 in Maine, USA; American toads (Anaxyrus americanus) in 2012 in North Carolina, USA; and, wood frogs, southern leopard frogs (L. sphenocephalus), and green frogs (L. clamitans) in 2012 in South Carolina, USA. We monitored 172 anurans for 1–365 days (56.4 ± 59.4) in a single year and 1–691 days (60.5 ± 94.1) across years. Our waistband resulted in an injury percentage comparable to 7 alternative anuran waistband attachment techniques; however, 12.5% fewer anurans shed their waistband when attached with our technique. Waistband retention facilitates longer monitoring periods and, thus, provides a greater quantity of data per radiotagged individual. © 2015 The Wildlife Society.

Does Catch‐and‐Release Angling Alter the Behavior and Fate of Adult Atlantic Salmon During Upriver Migration?

AbstractTo reproduce, Atlantic Salmon Salmo salar return to freshwater rivers and migrate upriver to spawning areas. This migration is the basis for recreational fisheries, which for conservation reasons are increasingly characterized by catch‐and‐release angling. The effectiveness of catch and release for Atlantic Salmon conservation is contingent on the ability of individuals to recover from angling, resume migration, and reach spawning grounds at appropriate times. We monitored 27 caught and released Atlantic Salmon in River Gaula in 2013, a prominent and relatively pristine Norwegian river, by affixing external radio transmitters to them. Those fish were compared with a control group of 33 individuals caught and radio‐tagged at sea in bag nets before river entry. Whereas none of the control fish died during the study period, there were three mortalities among the caught‐and‐released fish (11%; significant difference). All mortalities were qualitatively associated with poor angler care, emphasizing the responsibility of anglers in practicing effective catch and release of Atlantic Salmon. Both control and caught and released Atlantic Salmon spent similar time resting below and in transiting a large natural barrier to migration, an 80‐m gorge. The angled and released Atlantic Salmon were distributed in similar locations throughout the river during the spawning season compared with control fish, but those caught and released later in the season appeared to migrate shorter total distances than control fish. Among the caught and released Atlantic Salmon, 17% were recaptured by anglers, which was similar to the rate of recapture of the control fish (21%). Ultimately, individual and population fitness was not likely to be significantly compromised as a result of catch and release because individuals were recorded in spawning areas at appropriate times. Catch and release can therefore be considered a tenable strategy for balancing the costs and benefits associated with the recreational fishery.Received September 26, 2014; accepted December 16, 2014

Spatial Ecology ofScaphiophryne gottlebeiin the Canyons of the Isalo Massif, Madagascar

The Rainbow Frog Scaphiophryne gottlebei lives within the humid canyons that cross the Isalo Massif, central-southern Madagascar. Knowing that a single haplotype dominates the largest part of its distribution range raised questions about the dispersal ability of the species. We affixed external radio transmitters to 36 individuals of S. gottlebei to understand whether the adults of this species actively displaced from the canyon they inhabit. We studied 13 males and 7 females in 2009 and 7 males and 9 females in 2011 over two periods (November-December 2009 and January-February 2011). Study sessions were chosen due to the different meteorological conditions: the first is the beginning of the rainy season, which corresponds to the start of reproduction; and the second being the end of the rainy season, which corresponds to a wetter period during which individuals are more likely to be feeding in order to increase body weight. Our results revealed that there is no significant difference in the activity patterns between sexes and that rain and temperature stimulate the dispersal rate. The distance covered by the individuals did not differ between males and females; the range varied from a few centimeters to approximately 50 m, although two individuals displaced more than 100 m in a single day. These data suggest that individuals of this species are quite phylopatric to the canyons they inhabit. The generalized haplotype sharing observed might then be explained by passive dispersal of larvae and metamorphosed individuals during the intense cyclonic floods.

Spring and Summer Distribution and Habitat Use by Adult Threatened Spotted Gar in Rondeau Bay, Ontario, Using Radiotelemetry

AbstractThe spotted gar Lepisosteus oculatus is designated as threatened in Canada under the federal Species at Risk Act. Identification and protection of critical habitat is an important component of recovering species at risk. To understand the habitat utilization of the adult life stage of the spotted gar in Rondeau Bay, a shallow coastal wetland of Lake Erie, external radio transmitters were surgically attached to 37 specimens in May 2007. These individuals were tracked at 224 discrete locations throughout the spring and summer of 2007. Aquatic macrophytes were present at 201 (90%) of these sites. Habitat and water chemistry data were collected at all tracked locations occupied by spotted gars. On the basis of electivity indices, in spring spotted gars showed a strong preference for shallow (<0.5‐m) and deep (>2.5‐m) waters with pH values <8.5. In summer, strong preference was shown for areas with mixed macrophyte beds. Spotted gars were found to relate to specific depths and cover rather than to shoreline features in Rondeau Bay. The study results are being used by the spotted gar Recovery Team to identify critical habitat in Rondeau Bay. This critical habitat designation will be used to ensure the protection of habitat needed to preserve the species in Canada, in part by curtailing the removal of aquatic vegetation in Rondeau Bay.

Evaluation of the physiology, behaviour, and survival of adult muskellunge ( Esox masquinongy) captured and released by specialized anglers

Angling for muskellunge ( Esox masquinongy) is a specialized endeavor involving species-specific equipment and handling procedures. The latter were developed by anglers with little influence from fisheries managers or the scientific community. Today, release rates approach 100% for specialized anglers; therefore, a formal evaluation of these procedures was warranted. Using two handling treatments – one to mimic current handling procedures with a period of air exposure and another gentler alternative without a period of air exposure – we assessed the physiological and behavioural disturbances as well as mortality associated with the catch-and-release process. Seventy-seven muskellunge were angled and blood sampled during the 2009 and 2010 muskellunge angling seasons. An additional 18 muskellunge were electrofished and immediately blood sampled to obtain baseline physiology data. A subsample ( N = 30, 15 per treatment) of the 77 angled individuals was fitted with external radio transmitters to assess behaviour and survival. Glucose and lactate concentrations were found to be significantly lower for controls, and glucose and potassium concentrations increased significantly with increasing surface water temperatures. No differences in physiology were noted between angling treatments. Muskellunge treated with normal and alternative handling procedures exhibited similar post-release behaviour, and no angling related mortalities were observed across a range of water temperatures (17.5–26.0 °C) This study demonstrates the effectiveness of current handling procedures at minimizing physiological and behavioural disturbances, particularly when compared with a gentler alternative. A fishery in which no angling mortality exists is not possible, but our study provides support for the notion that angling related mortality for muskellunge captured and released by specialized anglers using handling procedures evaluated in this study may indeed be negligible.

Comparing Size, Movement, and Habitat Selection of Wild and Streamside‐Reared Lake Sturgeon

AbstractA streamside rearing facility (SRF) on the Big Manistee River, Michigan, was constructed for the purpose of rearing larval and age‐0 lake sturgeon Acipenser fulvescens. Size, movement, and habitat selection were studied from 2007 to 2008 to determine whether there were differences between age‐0 lake sturgeon reared in the streamside facility and natural cohorts. Lake sturgeon reared streamside showed no significant difference in length from their wild counterparts. Movement patterns were studied by attaching external radio transmitters to 17 age‐0 streamside (198–250 mm total length) and 17 age‐0 wild lake sturgeon (206–262 mm). The average weekly distances traveled by SRF fish ranged from 0.05–2.28 km (of 46 km surveyed) while wild fish traveled 0.04–2.81 km. In the river sections sampled, sand, pebble, and gravel comprised over 92.5% of the encountered substrates and Strauss index values indicated no differences in the presence of wild and SRF sturgeon over these substrates. Age‐0 lake sturgeon were most often found in water 1.7 m deep with a velocity of 0.5 m/s, and no statistically significant differences were observed between wild and SRF sturgeon for either depth or velocity during the study years. By September, streamside‐reared age‐0 lake sturgeon attained a size similar to that of their wild cohorts and exhibited similar movement patterns and substrate association.Received February 8, 2010; accepted January 27, 2011

Technique, Safety, and Efficacy of Intra‐Abdominal Transmitters in Nine‐Banded Armadillos

ABSTRACT The future management of nine‐banded armadillos (Dasypus novemcinctus) requires solid space‐use and activity data, which are currently lacking and which radiotelemetry can provide. External radiotransmitters have not been successful applied with this species. To make recommendations for intra‐abdominal radiotransmitter placement in nine‐banded armadillos, we 1) evaluated 4 different anesthetic protocols for safety, efficiency, and cost‐effectiveness; 2) evaluated a surgical technique for the intra‐abdominal placement of radiotransmitters that addresses problems described in previous studies; and 3) evaluated the physiologic and behavioral effects of such a technique. We captured and surgically implanted 37 nine‐banded armadillos using either butorphanol and isoflurane, ketamine alone, ketamine and xylazine, or a combination of butorphanol, ketamine, and medetomidine for anesthesia. We recovered and necropsied armadillos after the completion of the study. The objective and subjective assessment of butorphanol, ketamine, and medetomidine combination protocol, followed by reversal of the anesthesia with atipamezole, showed that it was the best overall anesthetic protocol for field use, providing both a smooth induction and fast recovery. We evaluated the fate and effects of radiotransmitters on 13 recovered animals at the end of the study and found no adverse effects. We recommend the implantation of radiotransmitters that are allowed to free‐float within the abdominal cavity and specifically emphasize the need for strict aseptic technique. Wildlife managers and wildlife veterinarians aiming to implant nine‐banded armadillos with radiotransmitters will benefit from using the recommended anesthetic protocol and surgical technique in future studies.

The post-release behaviour and fate of tournament-caught smallmouth bass after ‘fizzing’ to alleviate distended swim bladders

In recreational fishing, barotrauma occurs when fish that are angled from deep water are rapidly brought to the surface, causing a number of injuries and physiological alterations associated with gas expansion (such as distended swim bladders) that may impede swimming and prevent the fish from returning to depth. By deflating the swim bladder using a hypodermic needle (a process called “fizzing”) fish typically can return to depth. However, little is known about its consequences and efficacy on wild fish. At a competitive smallmouth bass ( Micropterus dolomieu) angling event on Rainy Lake in northwestern Ontario, we evaluated the effects of post-weigh in fizzing on the behaviour and short-term survival of three treatment groups after release: (i) barotrauma fish without fizzing ( N = 8); (ii) barotrauma fish that were fizzed ( N = 9); (iii) fish without signs of barotrauma that were fizzed ( N = 10) (sham control). Small external radio transmitters were affixed to the fish and tracked for 4 days. Fish were released at a common site and we assessed their dispersion at specific distances from the release site (50, 250, and 2000 m). All fish survived the 4-day monitoring period. No differences were observed in the time it took each group to disperse from the release site. Furthermore, there was no statistical evidence that fizzing influenced mean daily movements relative to controls, though a consistent trend was noted where fish that were fizzed displayed greater movement than non-fizzed fish with distended swim bladders. This study revealed that fizzing by trained experts is not detrimental to barotrauma fish. However, if done improperly there is risk to vital organs suggesting that there is merit in exploring other less invasive approaches to recompressing fish. Because our statistical power was generally low, further research is needed to determine whether fizzing should be encouraged or dissuaded to maintain the welfare status of the fish, decrease sublethal impairments, and reduce mortality.

Effect of habitat fragmentation on spawning migration of brown trout (Salmo truttaL.)

Abstract – Human‐induced habitat alteration is one of the main causes of the decline of freshwater fish populations. The watershed of the River Bidasoa (Spain) is an example of heavily fragmented habitat. The local brown trout (Salmo truttaL.) population is disturbed, with evidence of poor recruitment as well as low adult densities in the main stem. Forty male and female adult migratory trout were tagged with external or internal radio transmitters and released. Fixed stations with data loggers and mobile antennae were used with daily surveys to track fish movements during the migration and spawning period (3 months). Migration distances did not exceed 10 km, and half of the fish never entered a tributary in the study area. Fragmentation because of weirs on the main stem apparently prevented fish from reaching their spawning destination. Fish that entered the tributaries were first confronted with an accessibility problem because of low discharge. However, each fish chose one tributary, without making attempts to run up in other tributaries. Once in the tributary, fish were restrained in their upstream movements by dams. The study area appeared to be isolated from the vast upper part of the watershed. Within the study area, upper parts of tributaries also seemed strongly disconnected from the main stem. This study illustrates the negative impact of river fragmentation onS. truttamigration pattern. Population sustainability can be directly affected through the low availability of spawning grounds for migratory fish. Long‐term effects of fragmentation may cause reproductive isolation within watersheds, which in the case of trout also means isolated phenotypic population units.

Effects of radiotransmitters on the reproductive performance of Cassin’s auklets

We examined whether radiotransmitters adversely affected the reproductive performance of Cassin's auklets (Ptychoramphus aleuticus) breeding on the California Channel Islands during 1999-2001. We attached external radiotransmitters to 1 partner in 108 Cassin's auklet pairs after nest initiation and used 131 unmarked, but handled, pairs as controls. Compared to alpha chicks raised by radiomarked pairs, alpha chicks raised by unmarked pairs had faster mass growth rates (1.95 ± 0.30 g d−1 vs. 3.37 ± 0.53 g d−1, respectively), faster wing growth rates (2.46 ± 0.10 mm d−1 vs. 2.85 ± 0.05 mm d−1), greater peak fledging masses (118.9 ± 3.5 g vs. 148.3 ± 2.4 g), and higher fledging success (61% vs. 90%). Fledging success was reduced more when we radiomarked the male (50% fledged) rather than the female partner (77% fledged). After fledging an alpha chick, unmarked pairs were more likely to initiate a second clutch (radiomarked: 7%; unmarked: 39%) but did not hatch a second egg (radiomarked: 4%; unmarked: 25%) or fledge a second (beta) chick (radiomarked: 4%; unmarked: 18%) significantly more often than radiomarked pairs. We resighted 12 radiomarked individuals nesting during a subsequent breeding season; each bird had shed its transmitter and healed the site of attachment. We suggest caution in using telemetry to evaluate the reproductive performance of alcids, but marking only females may minimize adverse effects.

Effects of Absorbable Suture Strand Diameter on Retention of External Radio Transmitters by Juvenile Lake Sturgeon

Abstract We evaluated the effects of four absorbable suture strand diameters (numbers 3/0, 0, 1, and 2 [from smallest to largest diameter]) on the short-term retention of externally attached dummy radio transmitters by juvenile lake sturgeon Acipenser fulvescens (fork-length range, 257–293 mm; wet-weight range, 100–132 g). Four lake sturgeon were contained in each of 10 aquaria, and one fish in each tank was assigned to each of the four suture treatment groups. Transmitter retention was positively related to suture strand diameter, the mean retention duration for number 2 sutures being nearly twice as long (21 d) as that of number 3/0 sutures (11.8 d). The smallest suture (number 3/0) also exhibited the fewest number of days to transmitter loss (25% loss, 9 d; 50% loss, 11 d; and 75% loss, 14 d). In contrast, the largest suture (number 2) had the greatest number of days to transmitter loss (25% loss, 16 d; 50% loss, 21 d; and 75% loss, 26 d). Based on the diameter of sutures examined in this study, we rec...

Influence of External Transmitter Shape and Size on Tag Retention and Growth of Juvenile Lake Sturgeon

AbstractFew studies have examined the effects of external radio transmitters on small fish. We evaluated the influence of two shapes (cylindrical and compressed) and three sizes (small, medium, and large [approximately 1.25, 2.00, and 6.00% of body weight, respectively]) of dummy transmitters on the tag retention and growth of juvenile lake sturgeon Acipenser fulvescens in an 8‐week laboratory experiment. Thirty‐five lake sturgeon were contained in each of three tanks, with five fish in each tank assigned to each of the six transmitter treatments. The remaining five fish in each tank, which served as the control group, were handled but did not receive a transmitter. A greater number of compressed transmitters were shed than cylindrical transmitters, and more large transmitters were lost than small or medium transmitters. Fish with medium and large transmitters, regardless of shape, exhibited lower growth than fish with small transmitters or the control group from week 2 through the end of the study. Only fish with small transmitters exhibited growth similar to that of the control group. Our results suggest that external radio transmitters should not exceed 1.25% of body weight and should be cylindrical in shape for telemetry studies involving juvenile lake sturgeon.

Externally attached radio transmitters do not affect the parental care behaviour of rock bass

Turning, pectoral fin and caudal fin rates and time spent on the nest of male rock bass Ambloplites rupestris, engaged in parental care, were not affected after the attachment of external radio transmitters. Reproductive success was similar between treatment and control fish. Micro external radio transmitters can be used on small fishes for studying parental care duration and post‐care movement without altering their behaviour.

Torpor in free-ranging tawny frogmouths (Podargus strigoides).

Several small caprimulgiform birds (<80 g) are known to enter torpor, apparently to cope with a fluctuating supply of insect prey. Since the large Australian tawny frogmouth (Podargus strigoides; 381-556 g) is also insectivorous, we investigated its thermoregulatory behaviour and thermal biology to determine whether this species is also heterothermic. In an open woodland at approximately 1,000 m altitude, we equipped eight free-ranging birds with external temperature-sensitive radio transmitters attached to an elastic harness to measure skin temperature (T(skin)). Core body temperature (T(b)) was measured in three of these birds fitted with an additional intraperitoneal transmitter. T(skin) was closely correlated with T(b), although T(skin) was usually several degrees below T(b). During the three coldest months of the year (June-August), shallow torpor with T(b) as low as 29.1 degrees C occurred frequently, whereas during spring and summer, torpor was not recorded. Torpor occurred either during the night and/or during the first half of the day. Night torpor bouts were initiated after a short activity period around dusk and lasted on average for about 7 h. Torpid birds always aroused before sunrise to either commence a second short foraging period or to fly directly to a day roost tree. After birds roosted, T(b) fell again around sunrise, and birds occasionally entered a second dawn torpor bout; however, in most cases, T(b) increased rapidly not long after entry, most likely due to passive heating by the sun. We conclude that despite their large body size and energetically conservative hunting strategy, tawny frogmouths, like several related caprimulgiform species, frequently enter shallow torpor when low T(a) demands high energetic costs for normothermic thermoregulation and likely reduces insect availability.

Prespawning migratory behaviour and spawning success of sea‐ranched Atlantic salmon, Salmo salar L., in the River Gudenaa, Denmark

The migratory behaviour of sea‐ranched Atlantic salmon, Salmo salar L., was analysed by radio‐telemetry in the River Gudenaa, Denmark. The main objectives were to: (1) estimate mortality of returning adults through the fjord; (2) observe rate of progression and migratory pattern in the fjord and river; and (3) record whether spawning occurs in the river. Forty‐two returning salmon (19 males and 23 females of total body length from 60–97 cm) reared and released as smolts, were caught and equipped with external radio transmitters in the outer estuary of the River Gudenaa in 1994 and 1995. Of the tagged salmon, 18 (43%) were caught in the estuary, four (10%) were not recorded after release and 20 (47%) entered the river. The mean rate of progression through the fjord was 7.6 km d−1 (range 1.4–18.2) in 1994 and 5.4 km d−1 (range 1.6–17.1) in 1995. Eleven salmon were alive at the onset of the spawning period. Eight were retrieved dead from the river during or after the spawning period; four with empty gonads assumed to be successful spawners, and four with intact gonads. In 1994, unsuccessful spawners (found dead with intact gonads) entered the river earlier and had a longer total migration distance in the river compared to successful spawners. This suggests that spawning success of sea‐ranched salmon is associated with time of river entry and river migration length.

“Soft” harness for external attachment of large radio transmitters to northern pike ( Esox lucius)

We developed a “soft” harness for dorsally attaching large, external radio transmitters to northern pike ( Esox lucius). The key harness component was a soft, flexible, thick-walled tubing that prevented tissue abrasion by the attachment lines which passed through the tubing. Six field-tagged fish (1.5–7.5 kg) were monitored for 45–115 days before tracking was terminated. Tracking patterns of fish indicated no apparent effect of these large, external transmitters on movement behavior; further, the transmitters did not appear to entangle the fish in vegetation. One fish with its transmitter still secure was recaptured after 54 days, and there was minimal tissue erosion under the transmitter. With minor improvements for the attachment lines and the transmitter saddle, the method is suitable for externally attaching large telemetry transmitters to fish.