Telemetry Tags Research Articles

Development and Characterization of an Antimicrobial Polydopamine Coating for Conservation of Humpback Whales.

Migration patterns of humpback whales have been monitored using 316L stainless steel (SS) satellite telemetry tags. The potential for tissue infection and necrosis is increased if the bacteria, naturally a part of the diverse microbiome on the skin of humpback whales, can adhere to and colonize the surface of the tags. Polydopamine (pDA) has the potential to prevent the adhesion of one of the most prevalent bacterial strains on the surface of the skin of cetaceans (Psychrobacter) through the release of hydrogen peroxide. The release of hydrogen peroxide from the pDA coatings (40–100 μM) has the ability to induce a bacteriostatic response in E. coli, a commonly used bacteria strain in antimicrobial studies and potentially P. cryohalolentis, a common humpback associated bacteria. The H2O2 dose required to induce bacteriostatic conditions in E. coli is approximately 60 μM and in P. cryohalolentis is 100 μM. Bacterial adhesion on the surface of pDA coated SS coupons was measured first using E. coli. The coating successfully prevented adhesion of E. coli on the surface of SS coupons under certain conditions (60% reduction, p < 0.05) but the same was not seen with P. cryohalolentis. When coating conditions were altered (an increase in pH and temperature) the adhesion of P. cryohalolentis was reduced (80% reduction, p < 0.001). Overall, the pDA coatings have the capacity to generate varying amounts of hydrogen peroxide by altering the coating conditions and have the ability to reduce bacterial adhesion on the surface of satellite telemetry tags, and therefore the potential to increase tag functional service lifetime.

Utilizing accelerometer telemetry tags to compare red snapper (Lutjanus campechanus [Poey, 1860]) behavior on artificial and natural reefs

Artificial reefs have been shown to support important reef fishes such as red snapper (Lutjanus campechanus [Poey, 1860]), however, few studies have compared fish behavior on artificial and natural habitats. We examined activity levels and behavioral patterns of red snapper over natural reefs, oil platforms and submerged ships. Telemetry tags (Sonotronics model MTT) that transmitted tri-axial acceleration range, with average depth or average temperature were developed specifically to monitor red snapper and tested in captive fish. Wild red snapper were surgically implanted at depth and monitored for 16 months over artificial and natural reefs. Overall dynamic body acceleration (ODBA) as the sum of x, y and z acceleration range (0–0.398 g along each axis) was used to estimate activity levels of red snapper at each reef. Measurements of red snapper indicated that season, diel period, temperature time blocks and reef type had significant effects on ODBA and depth use. Red snapper were more active during the summer, at night, and during a period of rapid temperature increase. Red snapper were also generally more active and stayed at shallower depths on ships. The increases in activity reported here may be attributed to differing feeding or spawning behaviors on certain reefs. These results suggest that environmental factors such as temperature and diel period heavily influence red snapper and that they behave differently on specific habitat types at certain times. Future efforts to examine the ecological performance of red snapper across reef types should therefore carefully take environmental influences into account.

Frequent encounters with the seafloor increase right whales’ risk of entanglement in fishing groundlines

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 39:235-246 (2019) - DOI: https://doi.org/10.3354/esr00963 ESR Special: Marine vertebrate bycatch: problems and solutions Frequent encounters with the seafloor increase right whales’ risk of entanglement in fishing groundlines Philip K. Hamilton*, Scott D. Kraus Anderson Cabot Center for Ocean Life, New England Aquarium, Central Wharf, Boston, MA 02110, USA *Corresponding author: phamiltn@neaq.org ABSTRACT: North Atlantic right whales Eubalaena glacialis utilize the entire water column and are frequently entangled in ropes from fishing gear. Data from telemetry tags have shown that right whales can swim/feed at or near the seafloor. Because those data are limited, some uncertainty remains regarding the frequency of dives to the seafloor and thus the likelihood of right whale encounters with fishing ropes there. The North Atlantic right whale photo-identification catalog was used to determine the number of sightings of right whales with seafloor sediment on their bodies and the relative frequency and geographic location of those seafloor encounters. Between 1980 and 2016, there were 2053 detections of right whales with ‘mud’ on their bodies, which represents 2.9% of all sightings (n = 70593), or 58.2% of all cataloged whales (n = 730). Although muddy right whales were found throughout their range and in all months, 92.7% of all detections occurred in the Bay of Fundy in the summer where there was an average annual detection rate of 7.3%, with a maximum of 26% of sightings in 2010. Mud was found on whales of all age classes including calves of the year, and equally among males and females. These seafloor encounters suggest that any rope resting on, or floating above, the seafloor could pose an entanglement hazard. The use of sinking groundlines likely reduces the risk of entanglements for whales swimming near the seafloor, but may not eliminate the risk for whales making contact with the sediment. KEY WORDS: Right whale · Seafloor sediment · Mud · Bay of Fundy · Entanglement · Eubalaena glacialis Full text in pdf format PreviousNextCite this article as: Hamilton PK, Kraus SD (2019) Frequent encounters with the seafloor increase right whales’ risk of entanglement in fishing groundlines. Endang Species Res 39:235-246. https://doi.org/10.3354/esr00963 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 39. Online publication date: July 25, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Assessing Solar Power for Globally Migrating Marine and Submarine Systems

Remote marine sensing systems, such as autonomous underwater vehicles or telemetry tags, can be limited in data collection and deployment duration due to the finite energy of the onboard battery. With these technologies migrating vast distances over long-term deployments, maintaining high data resolution is difficult and often yields nonideal data sets. Furthermore, electronics systems used in telemetry tags are often potted in epoxy, which makes replacing or recharging the battery impractical. The implementation of solar energy harvesting on these technologies could increase the fidelity of collected data and/or tag longevity. This paper presents an assessment model that estimates the energy output of a stationary or migrating solar cell above or below the ocean's surface. The theory and assumptions behind the model are explained, including a review of established concepts for the purpose of consolidation and variable consistency. The model is then compared to benchmark data for verification. Finally, a preliminary analysis is conducted on the previously collected time, depth, and global location data from a northern elephant seal deployment to demonstrate the resulting model outputs and how they can be used for analysis in future works.

Evaluation of Tag Retention, Healing, Growth, and Behavior in Age‐0 Muskellunge Following Acoustic Transmitter Implantation

AbstractThe development of small acoustic transmitters has enabled researchers to monitor earlier life stages and smaller fish species than was previously possible. The underlying assumptions of any telemetry study are minimal tag loss and negligible effects on the behavior, survival, and growth of tagged individuals. To that end, tag retention, healing, survival, specific growth rates, and behavior were evaluated for 96 age‐0 MuskellungeEsox masquinongy(TL[mean ± SD] = 205 ± 10 mm) from three treatment groups. Tagged fish were compared to untagged controls and sham fish (fish that had undergone anesthesia and laparotomy but not transmitter implantation). Thirty‐two fish (tagged group) were implanted with one of the smallest commercially available acoustic transmitters (Juvenile Salmon Acoustic Telemetry tag; 12.0 × 5.3 × 3.7 mm, 0.217 g in air, &gt;120‐d tag life) and monitored in a 4‐month, overwinter tank experiment. Tricaine methanesulfonate was used for anesthesia, incisions were closed with a synthetic absorbable monofilament, and all surgeries were conducted by a single trained researcher. All tags were retained throughout the experiment; surgical wounds healed within 30 d, 32% of sutures were retained at 120 d postsurgery, and survival did not differ between treatments. No biologically significant effects of tagging on mean relative growth rates (percent change in weight/d) were observed among the three groups (tagged, untagged, and sham fish) at 4 months postprocessing. The reaction of tagged fish to a moving object within 15 minutes after tagging was slower than the reaction at 7 d postsurgery, reiterating the importance of testing appropriate sedation methods prior to releasing fish in field studies. Results validate the utility of surgical implantation of small acoustic transmitters in juvenile Muskellunge for future studies, although immobilization methods for early life stages require further study.

Assessing Acoustic Tagging Effects on Survival, Growth, and Swimming Ability of Juvenile Lake Sturgeon

AbstractAcoustic telemetry is used to quantify fish movement, ecology, and habitat use and can contribute to assessing the success of species supplementation. In this field, a better understanding of the effects of tag burden (or the impact of an acoustic telemetry tag, which is related to the ratio of tag weight to body weight) is critical to ensure postrelease monitoring. Research on the effects of acoustic tag burden on imperiled fishes at different ontogenic stages, such as juvenile Lake Sturgeon Acipenser fulvescens, is limited. Our study provides key information for the selection of the largest acoustic tag with the greatest battery life possible (taking into account tag burden) to monitor the release success and movements of juvenile Lake Sturgeon stocked for reintroduction. We characterized tag burden effects by examining survival, TL, weight, Fulton's condition factor, and swim performance of individuals. We examined four groups of fish: control (anesthetized and no acoustic tag inserted; n = 24), sham control (anesthetized with incision sutured but no acoustic tag inserted; n = 24), Vemco V8 acoustic tag (2.0 g in air; n = 24), and Vemco V9 tag (4.4 g in air; n = 24). Acoustic tags were inserted into anesthetized fish, and the incision was sutured; tag burden (mean ± SE) ranged from 2.2 ± 0.06% to 4.6 ± 0.10% of total body weight. Results showed that the two tag burden treatments had no significant effects on growth or survival (compared to both control groups) across a 114‐d study period and that critical swim speed at 12–20 d postsurgery was not significantly impacted by increasing tag burden. Because neither of the acoustic tag sizes had significant deleterious effects on the metrics studied, we recommend using a larger V9 tag (i.e., the most powerful tag with the longest battery life) for postrelease monitoring of reintroduced juvenile Lake Sturgeon.

Estimating population abundance at a site in the open ocean: combining information from conventional and telemetry tags with application to gray triggerfish (Balistes capriscus)

Estimates of animal abundance are widely used to support conservation and resource management. For populations in open systems, abundance estimates from tagging data can be highly uncertain or biased. Here, we develop a novel approach to estimate abundance of an open population by pairing two models, each utilizing distinct tagging data. Using data from telemetry tags, we infer movement rates to and from the study site with a Markovian model allowing for an environmental effect. Then, using data from conventional passive tags, we apply a Lincoln–Petersen abundance estimator modified to account for mortality and movement. After developing the model within a Bayesian framework, we demonstrate its application to data on gray triggerfish (Balistes capriscus) tagged in the Atlantic Ocean off North Carolina, USA. For this open population, we estimate site abundance to be ∼1000 fish (∼2000 fish·km–2) and additionally find evidence for an effect of hurricanes on movement. The general approach may be useful for fisheries, wildlife, and other ecological studies utilizing multiple tag types, particularly for estimating abundance of an open population.

Vertical Habitat Use by Adult Walleyes Conflicts with Expectations from Fishery‐Independent Surveys

AbstractStock assessments of Walleyes Sander vitreus in Lake Erie rely on a combination of suspended and bottom overnight gill‐net surveys to provide population and demographic information. However, the assumption that Walleyes undertake diel vertical migrations and become available to the suspended gill nets at night has never been validated. To understand how vertical habitat use affects the availability of Walleyes to fishery‐independent surveys, we compared individual behaviors observed by means of acoustic depth telemetry tags (20 individuals; 2013–2016) with catches in paired suspended and bottom gill‐net sets (273 paired sets; 2013–2016) used by management agencies. In contrast to our expectations and observations in other lakes, the mean depths for Walleyes most often occurred in the lower one‐half to one‐third of the water column, and at lake depths &lt;25 m the fish tended to be close to the bottom. The relationship between fish and lake depth was dependent on year and season. At lake depths &gt;15 m, Walleyes were found at shallower depths during stratified periods (i.e., summer) than during unstratified periods (autumn). They were also found at shallower depths in 2015 and 2016 than in 2013 and 2014. In paired autumn gill‐net surveys, (1) the overall proportion of Walleye catch was nearly equal in suspended and bottom gill nets and (2) the proportion of the catch in suspended gill nets declined with fish length. The pattern of decline was dependent on how deep the suspended net was fished and the year in which the data were collected. These results provide evidence that the suspended gill‐net surveys currently being used to assess Walleye demographics in Lake Erie are biased toward the capture small Walleyes, while bottom nets are biased toward the capture of large ones. Future telemetry investigations will be needed to understand whether these biases reflect differences in the depth of habitat between small and large Walleyes.

Post‐release dispersal and spawning movements of a translocated lake sturgeon (Acipenser fulvescens, Rafinesque 1817) population in the Mattagami River, Ontario

Species translocations are increasingly being used as a management tool to mitigate population losses due to such factors as habitat degradation and fragmentation, but post-introduction follow-up is relatively sparse. Post-translocation telemetry can assess success by identifying activity, emigrations, survival, habitat usage, and reproductive events, aiding in the continued management of translocated populations and informing future efforts. This study assessed movement of translocated adult lake sturgeon (Acipenser fulvescens) immediately post-release and a decade later, and tested for associations between environmental variables and spawning movements. Prior to their translocation in 2002, 13 of 51 adult lake sturgeon were surgically implanted with radio telemetry tags and tracked for 1 year. In 2011 and 2013, eight additional adults were captured within the reintroduction site and implanted with radio-tags. Six of the 13 sturgeon tagged in 2002 dispersed downstream over a dam during the early post-release period. In spring 2014, tagged adults were tracked to the spillway at the release area's inflow, and spawning was confirmed by larval captures. Movement data for tagged adults differed between the two tracking periods, showing marked differences in behaviour over time. Water velocity was correlated with upstream and downstream spawning movements, with water temperature also correlated with downstream movement. Research regarding post-translocation movement and dispersal provides insight on behavioural responses following translocation, and may improve outcomes by informing future efforts.

Tag retention and survival of juvenile bighead carp implanted with a dummy acoustic tag at three temperatures

Bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix (together, the bigheaded carps) are invasive fishes in North America that have resulted in substantial negative effects on native fish communities and aquatic ecosystems. Movement and behavior of adult bigheaded carps has been studied previously using telemetry, while similar studies with juvenile bigheaded carps have yet to be attempted. Recent technological advances in telemetry transmitters has increased the availability of tags sufficiently small enough to implant in juvenile carps. However, the effects of surgical implantation of telemetry tags on juvenile bigheaded carps have not been evaluated. We determined tag retention and survival associated with surgical implantation of acoustic telemetry tags into juvenile bighead carp (range 128–152 mm total length) at three temperatures (13, 18, and 23°C). In addition, we assessed the effect of surgically implanted transmitters on the fitness, defined as changes in weight or critical swimming speed, of carp implanted with transmitters. Survival was high among tagged fish (85%) with 47% of tags retained at the conclusion of the 45‐day study. No substantial decline in fitness of the fish was observed in tagged fish compared to untagged fish.

Long-term implantation of acoustic transmitters induces chronic inflammatory cytokine expression in adult rainbow trout (Oncorhynchus mykiss)

Telemetry transmitters are frequently used in studies of wild fish migration and behavior. Although the effects of surgically implanted transmitters on survival, tag retention, healing and growth have been studied, there has been little research regarding the potential immune response induced by these transmitters. In the current study, mature rainbow trout received either surgical implantation of an acoustic transmitter or a sham surgical procedure. These fish were then sampled over a 10-week period so that pro-inflammatory cytokine expression in the spleen, peritoneal cavity lymphocytes and muscle at the surgical site could be analyzed. There were no significant differences in transcript expression for the spleen and muscle tissue between fish that had a transmitter and those that received the surgical procedure alone. However, transmitter presence significantly increased the expression of IL-6, IL-1β and TNFα in the peritoneal cells at 10 weeks indicating that tagged fish may be coping with chronic inflammation. Furthermore, tagged male fish had a higher inflammatory response in 10-week peritoneal lavage samples when compared to their tagged mature female counterparts, providing some evidence that mature female rainbow trout may have suppressed immune function when sexually mature. Externally, fish appeared to heal at similar rates regardless of the presence or absence of the transmitter, but the tag itself was prone to encapsulation and adhesion to the body wall and/or surgical site. This suggests that fish tagged with large intraperitoneal implants may not behave similarly to their wild counterparts. This research could aid in the development of improved telemetry tags that are more biocompatible, economical and better able to track fish behavior/movement.

Evaluation of a field protocol for internally-tagging fish predators using difficult-to-tag ictalurid catfish as examples

Tagging protocols that result in high tag retention will benefit fisheries professionals who use telemetry data. Ictalurid catfish historically have had very poor telemetry tag retention. Here, we use these difficult-to-tag taxa to address two research objectives. First, we evaluated our field-based internal tagging methodology by quantifying six tag retention metrics using data from 48 acoustically-tagged blue catfish (Ictalurus furcatus) released into Milford Reservoir, KS, USA. Second, to better understand the results of this field evaluation, we evaluated tag retention and survival in the hatchery for the closely-related channel catfish (I. punctatus). Field and hatchery studies provided complementary information. Eighty percent of tagged blue catfish were detected at the end of our 5-mo field study (1,139,402 = total detections; 24,243 = average detections per fish). A 13-week hatchery evaluation of our field methodology also had high tag retention (100%). Hatchery treatments that used a lateral-ventral incision had higher tag retention and survival than those treatments that included a mid-ventral incision. Time invested in training, protocol refinement, and field organization were also important. Furthermore, monitoring the surgical history and recovery of individual fish allowed us to correct problems before mortality occurred. Because a need exists for a range of internal tagging methodologies that are effective on an assortment of fish species tagged under a variety of circumstances, our high tag retention methodology may be useful to the expanding research community that studies native and non-native catfish, as well as, other telemetry researchers who seek beneficial refinements to their tagging protocols.

The Salton Sea: Critical Migratory Stopover Habitat for Caspian Terns (Hydroprogne caspia) in the North American Pacific Flyway

For migratory waterbirds, the availability and quality of suitable stopover habitat can affect body condition and demographic parameters throughout the annual cycle. This study investigates the importance of the Salton Sea, a large saline lake located in the southwestern United States near the USA-Mexico border, for migrating Caspian Terns (Hydroprogne caspia) fitted with long-duration satellite telemetry tags in the northwest contiguous USA. During fall migration, 100% (n = 25) in 2014 and 98% (n = 63) in 2015 of all tagged individuals were tracked to the Salton Sea, with median durations of stay lasting 36 and 25 days, respectively. Use of the Salton Sea during subsequent spring migrations was less consistent than in fall, but still substantial, with 91% (n = 23) and 68% (n = 53) of all birds conducting brief stops there during 2015 and 2016, respectively. The future of the Salton Sea as suitable habitat for fish and piscivorous birds is uncertain due to rising salinity levels caused by reduced input flows. It is also uncertain if other wetlands in the region can serve as replacement habitat for Caspian Terns and other migratory piscivorous species should the Salton Sea cease to provide fish prey.

Tag retention and mortality of adult Atlantic salmon Salmo salar gastrically tagged with different sized telemetry transmitters.

A batch of 1 sea winter pre-spawning adult Salmo salar from the Bush river in Northern Ireland, U.K., were gastrically tagged with large (13 mm diameter) and small (9mm diameter) dummy acoustic telemetry tags alongside untagged control fish. Survival differed between control and tagged fish and the estimated probability of survival by the end of the study for control fish with no tag was 0·94, small tags was 0·90 and large tags was 0·72. Tag loss through regurgitation was slightly higher for fish tagged with larger tags than for fish tagged with smaller tags and the estimated probability of tag loss for fish with a small tag was 0·10 and for large tags was 0·14.

Telemetry tags increase the costs of swimming in northern fur seals, Callorhinus ursinus

AbstractAnimal‐borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers (&lt;1% of animals’ mass and front profile) on the swimming speeds and energy expenditure of four female northern fur seals (Callorhinus ursinus) while swimming at depth. Swim speeds and rates of oxygen consumption were measured as the trained fur seals repeatedly swam an underwater circuit, with or without the tags. We found the placement of either tested tag significantly affected both the behavior and energetics of the fur seals in our study. Diving metabolic rate increased an average of 8.1%–12.3% (depending on tag type) and swim speed decreased an average of 3.0%–6.0% when wearing the tags. The combined changes in velocities and metabolic rates resulted in a 12.0%–19.0% increase in the total energy required by the fur seals to swim a set distance. The demonstrated effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer‐term impacts on the studied animals.

Seals and shipping: quantifying population risk and individual exposure to vessel noise

Summary Vessels can have acute and chronic impacts on marine species. The rate of increase in commercial shipping is accelerating, and there is a need to quantify and potentially manage the risk of these impacts. Usage maps characterising densities of grey and harbour seals and ships around the British Isles were used to produce risk maps of seal co‐occurrence with shipping traffic. Acoustic exposure to individual harbour seals was modelled in a study area using contemporaneous movement data from 28 animals fitted with UHF global positioning satellite telemetry tags and automatic identification system data from all ships during 2014 and 2015. Data from four acoustic recorders were used to validate sound exposure predictions. Across the British Isles, rates of co‐occurrence were highest within 50 km of the coast, close to seal haul‐outs. Areas identified with high risk of exposure included 11 Special Areas of Conservation (SAC; from a possible 25). Risk to harbour seal populations was highest, affecting half of all SACs associated with the species. Predicted cumulative sound exposure level, cSELs(Mpw), over all seals was 176·8 dB re 1 μPa2 s (95% CI 163·3–190·4), ranging from 170·2 dB re 1μPa2 s (95% CI 168·4–171·9) to 189·3 dB re 1 μPa2 s (95% CI 172·6–206·0) for individuals. This represented an increase in 28·3 dB re 1 μPa2 s over measured ambient noise. For 20 of 28 animals in the study, 95% CI for cSELs(Mpw) had upper bounds above levels known to induce temporary threshold shift. Predictions of broadband received sound pressure levels were underestimated on average by 0·7 dB re 1 μPa (±3·3). Synthesis and applications. We present a framework to allow shipping noise, an important marine anthropogenic stressor, to be explicitly incorporated into spatial planning. Potentially sensitive areas are identified through quantifying risk to marine species of exposure to shipping traffic, and individual noise exposure is predicted with associated uncertainty in an area with varying rates of co‐occurrence. The detailed approach taken here facilitates spatial planning with regard to underwater noise within areas protected through the Habitats Directive, and could be used to provide evidence for further designations. This framework may have utility in assessing whether underwater noise levels are at Good Environmental Status under the Marine Strategy Framework Directive.

Accounting for false mortality in telemetry tag applications

Deaths of animals in the wild are rarely observed directly, which often limits understanding of survival rates. Telemetry transmitters offer field ecologists the opportunity to observe mortality events in cases as the absence of animal movement. When observations of mortality are based on factors such as the absence of animal movement, live individuals can be mistaken for dead, resulting in biased estimates of survival. Additionally, tag failure or emigration might also influence estimates of survival in telemetry studies. Failing to account for mis-classification, tag failure, and emigration rates can result in overestimates of mortality rates by up two-fold, even when the data are corrected for obviously mistaken entries. We use a multi-state capture–recapture model with a misclassification parameter in estimating both the rate of permanent emigration and/or tag failure and the rate at which individuals are mistakenly identified as dead. We use this method on an annual telemetry survey of three species of native fish in the Murray river, Australia: Murray cod (Maccullochella peelii), trout cod (Maccullochella macquariensis) and golden perch (Macquaria ambigua). Evidence for higher mortality rates in the first year post-implantation occurred for Murray cod and golden perch, which is likely an effect of tagging and/or the transmitter, or transmitters shedding. Using simulations, we confirm that our model approach is robust to a broad range of misclassification and transmitter failure rates. With these simulations we also demonstrate that misclassification models that do not account for emigration will likely be erroneous if live and dead animals have different probabilities of detection. These findings will have a broad interest to ecologists wishing to account for multiple sources of misclassification error in capture-mark-recapture studies, with the caveat that the specifics of the approach are dependent on species, transmitter types and other aspects of experimental design which may or may not be amenable to the misclassification framework.

First documented large-scale horizontal movements of individual Arctic cod (Boreogadus saida)

Arctic cod (Boreogadus saida) are a key component of the Arctic marine ecosystem. Understanding their movements and distribution is important for predicting future trends in response to climate change. It was commonly assumed that Arctic cod move horizontally throughout the Arctic, but this was so far unproven. In July 2012, 85 Arctic cod were implanted with acoustic transmitters at Resolute Bay, Nunavut, Canada. Five (5.9%) were subsequently detected ∼192 km due east along the Barrow Strait, between 67 and 215 days after last detection in Resolute Bay (mean ± SE = 161.4 ± 26.7 days). Minimum transition rates ranged between 0.89 and 2.87 km·day−1 (mean ± SE = 1.4 ± 0.4 km·day−1). A combination of factors, most notably sea ice extent, make it highly improbable that the detections were representative of predated or scavenged Arctic cod. This represents the first confirmed account of large-scale horizontal movements by this or any Arctic forage fish species. With continuing miniaturization of acoustic telemetry tags, increasing battery life, and expanded receiver coverage, it will be possible to gain a more comprehensive understanding of Arctic cod movements.

Lake trout (Salvelinus namaycush) spawning site use in Lake Champlain

Abstract The decline of lake trout ( Salvelinus namaycush ) populations in the Laurentian Great Lakes stimulated research on restoration, addressing many knowledge gaps of lake trout behavior and ecology. However, studies focused on lake trout spawning behavior are relatively recent, and little is known about sex-specific differences in spawning site use. To test several hypotheses about spawning movements, we surgically implanted acoustic telemetry tags in 45 male and 48 female lake trout and tracked their movements within and among three spawning seasons and eight spawning sites up to 56 km apart in Lake Champlain. Both sexes traveled similar distances throughout the lake and visited a similar number of sites during the spawning season. Males spent more days during the spawning season on a spawning site, were more likely to return to the same preferred site each year, spent more time per day on a site, and tended to stay closer to site-center than females. Twenty of 86 fish (23%) preferred a site in their tagging year other than the site at which they were tagged, so the assumption that a tagging site is the spawning site should be treated with caution. Only 61 to 74% of lake trout returned to the same site in a second year (repeat homing). A high incidence of straying (non-homing) may facilitate colonization of invaded lakes and man-made spawning reefs.

Comparative thermal biology and depth distribution of largemouth bass (Micropterus salmoides) and northern pike (Esox lucius) in an urban harbour of the Laurentian Great Lakes

Understanding how individuals are distributed in space and time, as well as how they interact with dynamic environmental conditions, represent fundamental knowledge gaps for many fish species. Using acoustic telemetry tags, we monitored the temperatures and depths used by northern pike (Esox lucius L., 1758) and largemouth bass (Micropterus salmoides (Lacepède, 1802)) in Toronto Harbour (Lake Ontario). Northern pike and largemouth bass had similar thermal experiences throughout the year, except during summer, when northern pike were observed in cooler waters than largemouth bass. Both species used different depths throughout the year, with northern pike occupying deeper depths. Statistical modelling indicated that depth usage was influenced by all variables (season, species, and body size) and interactions between them, whereas thermal preferences were influenced by the main effects and interactions between species:season and species : body size. Both species were observed at temperatures warmer than those in the vicinity of nearby telemetry stations, but as station temperatures exceeded 20 °C, northern pike moved into cooler water, indicating active thermoregulation. These data will be useful for refining our understanding of the spatial ecology of fish and for informing fisheries and habitat management in this and other urban harbours of the Laurentian Great Lakes.