Monitoring partially marked populations using camera and telemetry data.

Long-term monitoring is an important component of effective wildlife conservation. However, many methods for estimating density are too costly or difficult to implement over large spatial and temporal extents. Recently developed spatial mark-resight (SMR) models are increasingly being applied as a cost-effective method to estimate density when data include detections of both marked and unmarked individuals. We developed a generalized SMR model that can accommodate long-term camera data and auxiliary telemetry data for improved spatiotemporal inference in monitoring efforts. The model can be applied in two stages, with detection parameters estimated in the first stage using telemetry data and camera detections of instrumented individuals. Density is estimated in the second stage using camera data, with all individuals treated as unmarked. Serial correlation in detection and density parameters is accounted for using time-series models. The two-stage approach reduces computational demands and facilitates the application to large data sets from long-term monitoring initiatives. We applied the model to 3 years (2015-2017) of white-tailed deer (Odocoileus virginianus) data collected in three study areas of the Big Cypress Basin, Florida, USA. In total, 59 females marked with ear tags and fitted with GPS-telemetry collars were detected along with unmarked females on 180 remote cameras. Most of the temporal variation in density was driven by seasonal fluctuations, but one study area exhibited a slight population decline during the monitoring period. Modern technologies such as camera traps provide novel possibilities for long-term monitoring, but the resulting massive data sets, which are subject to unique sources of observation error, have posed analytical challenges. The two-stage spatial mark-resight framework provides a solution with lower computational demands than joint SMR models, allowing for easier implementation in practice. In addition, after detection parameters have been estimated, the model may be used to estimate density even if no synchronous auxiliary information on marked individuals is available, which is often the case in long-term monitoring.

Application of machine learning to identify predators of stocked fish in Lake Ontario: using acoustic telemetry predation tags to inform management.

Understanding predator-prey interactions and food web dynamics is important for ecosystem-based management in aquatic environments, as they experience increasing rates of human-induced changes, such as the addition and removal of fishes. To quantify the post-stocking survival and predation of a prey fish in Lake Ontario, 48 bloater Coregonus hoyi were tagged with acoustic telemetry predation tags and were tracked on an array of 105 acoustic receivers from November 2018 to June 2019. Putative predators of tagged bloater were identified by comparing movement patterns of six species of salmonids (i.e., predators) in Lake Ontario with the post-predated movements of bloater (i.e., prey) using a random forests algorithm, a type of supervised machine learning. A total of 25 bloater (53% of all detected) were consumed by predators on average (± S.D.) 3.1 ± 2.1 days after release. Post-predation detections of predators occurred for an average (± S.D.) of 78.9 ± 76.9 days, providing sufficient detection data to classify movement patterns. Tagged lake trout Salvelinus namaycush provided the most reliable classification from behavioural predictor variables (89% success rate) and was identified as the main consumer of bloater (consumed 50%). Movement networks between predicted and tagged lake trout were significantly correlated over a 6 month period, supporting the classification of lake trout as a common bloater predator. This study demonstrated the ability of supervised learning techniques to provide greater insight into the fate of stocked fishes and predator-prey dynamics, and this technique is widely applicable to inform future stocking and other management efforts.

Medical-Grade ECG Sensor for Long-Term Monitoring.

The recent trend in electrocardiogram (ECG) device development is towards wireless body sensors applied for patient monitoring. The ultimate goal is to develop a multi-functional body sensor that will provide synchronized vital bio-signs of the monitored user. In this paper, we present an ECG sensor for long-term monitoring, which measures the surface potential difference between proximal electrodes near the heart, called differential ECG lead or differential lead, in short. The sensor has been certified as a class IIa medical device and is available on the market under the trademark Savvy ECG. An improvement from the user's perspective-immediate access to the measured data-is also implemented into the design. With appropriate placement of the device on the chest, a very clear distinction of all electrocardiographic waves can be achieved, allowing for ECG recording of high quality, sufficient for medical analysis. Experimental results that elucidate the measurements from a differential lead regarding sensors' position, the impact of artifacts, and potential diagnostic value, are shown. We demonstrate the sensors' potential by presenting results from its various areas of application: medicine, sports, veterinary, and some new fields of investigation, like hearth rate variability biofeedback assessment and biometric authentication.

Long-term retention of dummy acoustic transmitters in adult brown trout.

A group of 36 1+ age class Salmo trutta were surgically implanted with dummy acoustic tags and monitored for 370 days. In total 13 tags were expelled throughout the experiment with an overall tag loss rate of c. 0.035 tags per day. Fish length was the only explanatory variable which had a significant association with subsequent tag expulsion. The estimated probability of retaining a tag for a year for a fish of length 32 cm was 0.76, 34 cm was 0.60 and 36 cm was 0.38. The long-term tag loss patterns were examined and discussed.

Migration patterns of a potamodromous piscivore, asp (Leuciscus aspius), in a river-lake system.

Potamodromous fishes require safe migration routes between spawning, feeding and wintering habitats to complete their life cycle. As knowledge on asp migrations is restricted, this work investigated the movements of adult asp tagged with acoustic transmitters for 3 years in the large Peipsi-Emajõgi-Võrtsjärv lake-river system, Estonia, which is free of migration barriers. Asp showed complex migration patterns, moving between and within different waterbodies (lakes, river, tributaries) in all seasons, but with a tendency to repeat habitat use patterns between years. Lakes were mainly used for feeding during spring and summer (after spawning 65% of the fish migrated to Lake Peipsi), and more so by large fish. The majority (80-96%) of the fish spent the winter in the rivers, mostly close to their subsequent spawning area. Spawning areas were in swift-flowing waters in tributaries and the main river. The results indicate that asp may benefit from an extensive and diverse complex of habitats, and any migration barrier during any season may restrict the natural habitat use by asp. Maintenance and restoration of habitat heterogeneity and connectivity is critical to protect behaviourally diverse fish populations and increase resilience in rivers negatively impacted by various human activities.

Predicting the factors influencing the inter- and intraspecific survival rates of riverine fishes implanted with acoustic transmitters.

Biotelemetry is a central tool for fisheries management, with the implantation of transmitters into animals requiring refined surgical techniques that maximize retention rates and fish welfare. Even following successful surgery, long-term post-release survival rates can vary considerably, although knowledge is limited for many species. The aim here was to investigate the post-tagging survival rates in the wild of two lowland river fish species, common bream Abramis brama and northern pike Esox lucius, following their intra-peritoneal double-tagging with acoustic transmitters and passive integrated transponder (PIT) tags. Survival over a 2-year period was assessed using acoustic transmitter data in Cox proportional hazards models. Post-tagging survival rates were lowest in the reproductive periods of both species, but in bream, fish tagged just prior to spawning actually had the highest subsequent survival rates. Pike survival was influenced by sex, with males generally surviving longer than females. PIT tag detections at fixed stations identified bream that remained active, despite loss of an acoustic transmitter signal. In these instances, loss of the acoustic signal occurred up to 215 days post-tagging and only during late spring or summer, indicating a role of elevated temperature, while PIT detections occurred between 18 and 359 days after the final acoustic detections. Biotelemetry studies must thus always consider the date of tagging as a fundamental component of study designs to avoid tagged fish having premature end points within telemetry studies.

ANESTHESIA AND SURGERY PROTOCOLS FOR INTRA-ABDOMINAL TRANSMITTER PLACEMENT IN FOUR SPECIES OF WILD ARMADILLO.

The anatomy and physiology of armadillos make anesthetic procedures and the placement of telemetry devices challenging. From June 2011 to November 2019, a total of 73 free-living armadillos were captured and anesthetized in the Pantanal, Brazil. Giant (Priodontes maximus), six-banded (Euphractus sexcinctus), southern naked-tailed (Cabassous unicinctus), and nine-banded (Dasypus novemcinctus) armadillos were divided into two groups. In group 1, 30 armadillos were anesthetized for collection of biological samples, body measurements, and placement of a microchip tag. Anesthetic combination BDM was applied: butorphanol tartrate, detomidine hydrochloride, and midazolam hydrochloride, each at 0.1 mg/kg. In group 2, 43 armadillos received ketamine hydrochloride at 10 mg/kg 20 min after BDM injection, and intra-abdominal radio transmitters were surgically implanted. The transmitter was inserted freely into the abdominal cavity. Vital signs were monitored during anesthesia every 10 min and varied within species and between groups. Rectal temperature varied from 33.1 ± 1.36 to 35.34 ± 1.21°C, heart rate (beats/min) from 19 ± 2.14 to 84.71 ± 9.25, respiratory rate (breaths/min) from 11 ± 4.16 to 31 ± 2.82, and oxygen saturation values (SPO2%) from 84.17% ± 2.39 to 98% ± 1.20. Both groups received the antagonist combination NYF: naloxone hydrochloride (0.02 mg/kg), yohimbine hydrochloride (0.125 mg/kg), and flumazenil (0.01 mg/kg). Recovery varied according to intravenous or intramuscular injection from 2 ± 4 to 8.08 ± 2.93 min respectively. BDM protocol was considered satisfactory and provided enough time to complete the procedures (60 ± 85 to 133.20 ± 9.12 min) according to the species and group. Ketamine added to the BDM provided enough time and a surgical plane of anesthesia (97 ± 22 to 137 ± 39.5 min). The surgical procedure technique chosen did not appear to have a negative impact on armadillos studied. Implantable transmitters provide a cost-effective method for long-term monitoring of wild individuals.

Using on-board sound recordings to infer behaviour of free-moving wild animals.

Technological advances in the last 20 years have enabled researchers to develop increasingly sophisticated miniature devices (tags) that record an animal's behaviour not from an observational, external viewpoint, but directly on the animals themselves. So far, behavioural research with these tags has mostly been conducted using movement or acceleration data. But on-board audio recordings have become more and more common following pioneering work in marine mammal research. The first questions that come to mind when recording sound on-board animals concern their vocal behaviour. When are they calling? How do they adjust their behaviour? What acoustic parameters do they change and how? However, other topics like foraging behaviour, social interactions or environmental acoustics can now be addressed as well and offer detailed insight into the animals' daily life. In this Review, we discuss the possibilities, advantages and limitations of on-board acoustic recordings. We focus primarily on bats as their active-sensing, echolocating lifestyle allows many approaches to a multi-faceted acoustic assessment of their behaviour. The general ideas and concepts, however, are applicable to many animals and hopefully will demonstrate the versatility of on-board acoustic recordings and stimulate new research.

Respiratory sinus arrhythmia is a major component of heart rate variability in undisturbed, remotely monitored rattlesnakes, Crotalus durissus.

ECG recordings were obtained using an implanted telemetry device from the South American rattlesnake, Crotalus durissus, held under stable conditions without restraining cables or interaction with researchers. Mean heart rate (fH) recovered rapidly (<24 h) from anaesthesia and operative procedures. This preceded a more gradual development of heart rate variability (HRV), with instantaneous fH increasing during each lung ventilation cycle. Atropine injection increased mean fH and abolished HRV. Complete autonomic blockade revealed a cholinergic tonus on the heart of 55% and an adrenergic tonus of 37%. Power spectral analysis of HRV identified a peak at the same frequency as ventilation. This correlation was sustained after temperature changes and it was more evident, marked by a more prominent power spectrum peak, when ventilation is less episodic. This HRV component is homologous to that observed in mammals, termed respiratory sinus arrhythmia (RSA). Evidence for instantaneous control of fH indicated rapid conduction of activity in the cardiac efferent nervous supply, as supported by the description of myelinated fibres in the cardiac vagus. Establishment of HRV 10 days after surgical intervention seems a reliable indicator of the re-establishment of control of integrative functions by the autonomic nervous system. We suggest that this criterion could be applied to other animals exposed to natural or imposed trauma, thus improving protocols involving animal handling, including veterinarian procedures.

Genetics and telemetry indicate unexpected movements among structured populations for Brachyplatystoma platynemum in the Amazon.

The genetic analysis of Brachyplatystoma platynemum individuals sampled from the lower Madeira River reinforces the existence of two structured populations in the Amazon Basin (Madeira and Amazon populations). However, the recapture of an individual from the Amazon population in the Solimões River, which was telemetry-tagged in the Madeira River after the damming, indicates that fish from the Amazon population move between the two river systems. This has not yet been observed, however, in the Madeira River population, which is currently divided and isolated in the lower and upper Madeira River by the construction of two dams.

INTRANASAL ADMINISTRATION OF MIDAZOLAM HYDROCHLORIDE IMPROVES SURVIVAL IN FEMALE SURF SCOTERS (MELANITTA PERSPICILLATA) SURGICALLY IMPLANTED WITH INTRACOELOMIC TRANSMITTERS.

The intracoelomic implantation of satellite transmitters is associated with lower survival in surf scoters (Melanitta perspicillata) compared with other species of diving ducks, potentially due to physiologic alterations following physical exertion and stress caused by handling and confinement. The effect of intranasal administration of midazolam hydrochloride on survival of surf scoters surgically implanted with intracelomic transmitters was evaluated. Shortly after their capture in Forestville (QC, Canada) in the fall of 2013, 26 randomly selected adult female surf scoters were administered midazolam hydrochloride (4.6-5.9 mg/kg) intranasally. The same volume of saline (1 mL) was given to another 26 adult female surf scoters as a control group. All birds were surgically implanted with an intracoelomic transmitter equipped with a percutaneous antenna. Transmitters were programmed to transmit 2 hr each day for 30 days after implantation, and mortality was estimated for each group using the telemetry data. The association between the administration of midazolam and survival was assessed while controlling for other factors such as body mass, transmitter-mass-to-body-mass ratio, hematocrit, total solids, and duration of surgery, anesthesia, and confinement. The odds of presumed death in the saline group were 5.3 times higher than in the midazolam group (95% confidence interval: 1.7, 19.0; P = 0.004). The presumed mortality at 30 days for the midazolam group (23%) was lower than for the saline group (61%). No other variable was significantly associated with survival. These results suggest that sedation with midazolam shortly after capture increased the postsurgical survival of female surf scoters surgically implanted with intracoelomic transmitters.

Genetic determination of migration strategies in large soaring birds: evidence from hybrid eagles.

The relative contributions of genetic and social factors in shaping the living world are a crucial question in ecology. The annual migration of birds to their wintering grounds and back provides significant knowledge in this field of research. Migratory movements are predominantly genetically determined in passerine birds, while in large soaring birds, it is presumed that social (cultural) factors play the largest role. In this study, we show that genetic factors in soaring birds are more important than previously assumed. We used global positioning system (GPS)-telemetry to compare the autumn journeys and wintering ranges of two closely related large raptorial bird species, the greater spotted eagle Clanga clanga and the lesser spotted eagle Clanga pomarina, and hybrids between them. The timing of migration in hybrids was similar to that of one parental species, but the wintering distributions and home range sizes were similar to those of the other. Tracking data were supported by habitat suitability modelling, based on GPS fixes and ring recoveries. These results suggest a strong genetic influence on migration strategy via a trait-dependent dominance effect, although we cannot rule out the contribution of social interactions.

Divergent migration within lake sturgeon (Acipenser fulvescens) populations: Multiple distinct patterns exist across an unrestricted migration corridor.

Population structure, distribution, abundance and dispersal arguably underpin the entire field of animal ecology, with consequences for regional species persistence, and provision of ecosystem services. Divergent migration behaviours among individuals or among populations are an important aspect of the ecology of highly mobile animals, allowing populations to exploit spatially or temporally distributed food and space resources. This study investigated the spatial ecology of lake sturgeon (Acipenser fulvescens) within the barrier free Huron-Erie Corridor (HEC), which connects Lake Huron and Lake Erie of the North American Laurentian Great Lakes. Over 6 years (2011-2016), movements of 268 lake sturgeon in the HEC were continuously monitored across the Great Lakes using acoustic telemetry (10 years battery life acoustic transmitters). Five distinct migration behaviours were identified with hierarchical cluster analysis, based on the phenology and duration of river and lake use. Lake sturgeon in the HEC were found to contain a high level of intraspecific divergent migration, including partial migration with the existence of residents. Specific behaviours included year-round river residency and multiple lake-migrant behaviours that involved movements between lakes and rivers. Over 85% of individuals were assigned to migration behaviours as movements were consistently repeated over the study, which suggested migration behaviours were consistent and persistent in lake sturgeon. Differential use of specific rivers or lakes by acoustic-tagged lake sturgeon further subdivided individuals into 14 "contingents" (spatiotemporally segregated subgroups). Contingents associated with one river (Detroit or St. Clair) were rarely detected in the other river, which confirmed that lake sturgeon in the Detroit and St. Clair represent two semi-independent populations that could require separate management consideration for their conservation. The distribution of migration behaviours did not vary between populations, sexes, body size or among release locations, which indicated that intrapopulation variability in migratory behaviour is a general feature of the spatial ecology of lake sturgeon in unfragmented landscapes.

Satellite telemetry tracks flyways of Asian Openbill storks in relation to H5N1 avian influenza spread and ecological change.

BACKGROUND: Asian Openbills, Anastomus oscitans, have long been known to migrate from South to Southeast Asia for breeding and nesting. In Thailand, the first outbreak of H5N1 highly pathogenic avian influenza (HPAI) infection in the Openbills coincided with the outbreak in the poultry. Therefore, the flyways of Asian Openbills was determined to study their role in the spread of H5N1 HPAI virus to poultry and wild birds, and also within their flocks. RESULTS: Flyways of 5 Openbills from 3 colonies were monitored using Argos satellite transmitters with positioning by Google Earth Programme between 2007 and 2013. None of the Openbills tagged with satellite telemeters moved outside of Thailand. Their home ranges or movement areas varied from 1.6 to 23,608 km2 per month (95% utility distribution). There was no positive result of the viral infection from oral and cloacal swabs of the Openbills and wild birds living in the vicinity by viral isolation and genome detection during 2007 to 2010 whereas the specific antibody was not detected on both Openbills and wild birds by using microneutralization assay after 2008. The movement of these Openbills did not correlate with H5N1 HPAI outbreaks in domestic poultry but correlated with rice crop rotation and populations of the apple snails which are their preferred food. Viral spread within the flocks of Openbills was not detected. CONCLUSIONS: This study showed that Openbills played no role in the spread of H5N1 HPAI virus, which was probably due to the very low prevalence of the virus during the monitoring period. This study revealed the ecological factors that control the life cycle of Asian Openbills.

Body temperature of bitches in the first week after parturition measured by ingestible loggers.

The objective of this study was to identify the physiological ranges of body temperature of bitches in the first 7 days after parturition by measurement with ingestible temperature loggers. Twenty bitches swallowed one ingestible temperature logger daily. Bitches were defined to be healthy by spontaneous parturition and leucocyte concentration. Mean core body temperatures of eight healthy bitches were (Mean ± SD) 38.8°C ± 0.40 on day 0 p.p., 38.9°C ± 0.47 on day 1 p.p., 38.9°C ± 0.35 on day 2 p.p. 38.7°C ± 0.31 on day 3 p.p., respectively. In the following days, the three remaining healthy bitches showed mean core body temperatures (Mean ± SD) of 38.8°C ± 0.30 on day 4 p.p., 38.6°C ± 0.35 on day 5 p.p., 38.5°C ± 0.27 on day 6 p.p. and 38.4°C ± 0.34 on day 7 p.p., respectively. Three out of the eight healthy bitches showed temperatures ≥39.5°C. Bitches with leucocytosis showed significant higher mean core body temperatures (39.0°C ± 0.49) than healthy bitches (38.8°C ± 0.39) during the first 3 days after parturition (p < 0.01). We conclude that the physiological ranges of body temperature of healthy bitches in the first days after parturition do not differ from those of healthy dogs in general, while the appearance of short episodes of febrile temperatures seems to be physiological. Puerperal bitches with leucocytosis show higher body temperatures increased by only 0.2°C.

A Physiological Signature of the Cost of Reproduction Associated with Parental Care.

Costs of reproduction are an integral and long-standing component of life-history theory, but we still know relatively little about the specific physiological mechanisms underlying these trade-offs. We experimentally manipulated workload during parental care in female European starlings (Sturnus vulgaris) using attachment of radios and/or wing clipping and assessed measures of workload, current breeding productivity, future fecundity, and survival (local return rate) in relation to treatment. Females with wing clipping and radio attachment paid a clear cost of reproduction compared with all other treatment groups: they had lower future fecundity and lower return rates despite having lower current breeding productivity. We then measured 13 physiological traits, including measures of aerobic/metabolic capacity, oxidative stress and muscle damage, intermediary metabolism and energy supply, and immune function. Our results show that the cost of reproduction in females with wing clipping and radio attachment was associated with lower oxygen-carrying capacity (lower hematocrit and hemoglobin levels), lower energy reserves (plasma nonesterified fatty acid and triglyceride levels), decreased immune function (lower haptoglobin levels), and elevated levels of oxidative stress (higher levels of dROMs [reactive oxygen metabolites] and lower levels of the endogenous antioxidant uric acid). Our study provides evidence that costs of reproduction involve a widespread decline in physiological function across multiple physiological systems consistent with long-standing ideas of cumulative "wear and tear" and allostatic load.

Fast-slow life history is correlated with individual differences in movements and prey selection in an aquatic predator in the wild.

Fast and slow life histories are proposed to covary with consistent individual differences in behaviour, but little is known whether it holds in the wild, where individuals experience natural fluctuations of the environment. We investigated whether individual differences in behaviour, such as movement traits and prey selection, are linked to variation in life-history traits in Eurasian perch (Perca fluviatilis) in the wild. Using high-resolution acoustic telemetry, we collected the positional data of fish in a whole natural lake and estimated individual movement traits by fitting a two-state correlated random walk model. Prey selection was inferred from stable isotope analysis using scale samples. Life-history traits were estimated by fitting a biphasic growth model to an individual growth trajectory back-calculated from scale samples. Life-history traits were correlated with behavioural traits such as movements and prey selection. Individuals with higher reproductive effort were found to switch more frequently between active and inactive modes and show greater reliance on prey from pelagic pathways (indicated by lower δ13 C). Further, individuals with faster juvenile growth were found to stay active for a longer time during the adult stage. Our results demonstrate the link between individual behavioural differences and fast-slow life-history traits under ecologically relevant conditions.

Intraperitoneal implantation of life-long telemetry transmitters in three rehabilitated harbor seal pups.

BACKGROUND: Pinnipeds, including many phocid species of concern, are inaccessible and difficult to monitor for extended periods using conventional, externally attached telemetry devices that are shed during the annual molt. Archival satellite transmitters were implanted intraperitoneally into three stranded Pacific harbor seal pups (Phoca vitulina richardii) that completed rehabilitation, to evaluate the viability of this surgical technique for the deployment of life long telemetry devices in phocids. The life history transmitters record information throughout the life of the host and transmit data to orbiting satellites after extrusion following death. RESULTS: Surgeries were performed under general anesthesia and a single transmitter was inserted into the ventrocaudal abdominal cavity via a 7-8 cm incision along the ventral midline between the umbilicus and pubic symphysis or preputial opening in each animal. Surgeries lasted from 45 to 51 min, and anesthesic times ranged from 55 to 79 min. All animals recovered well, were released into dry holding pens overnight, and were given access to water the following day. All three animals exhibited an expected inflammatory response, with acute phase responses lasting approximately three to four weeks. All three animals were tracked via externally attached satellite transmitters after release at 58 to 78 days following surgery, and minimum post-release survival was confirmed through continued movement data received over 278 to 289 days. CONCLUSION: The initial findings of low morbidity and zero mortality encountered during captive observation and post-release tracking periods support the viability of this surgical technique for the implantation of long-term telemetry devices in phocids.

Effect of weight and frontal area of external telemetry packages on the kinematics, activity levels and swimming performance of small-bodied sharks.

This study sought to observe the effects of submerged weight and frontal cross-sectional area of external telemetry packages on the kinematics, activity levels and swimming performance of small-bodied juvenile sharks, using lemon sharks Negaprion brevirostris (60-80 cm total length, LT ) as a model species. Juveniles were observed free-swimming in a mesocosm untagged and with small and large external accelerometer packages that increased frontal cross-sectional area of the animals and their submerged weight. Despite adhering to widely used standards for tag mass, the presence of an external telemetry package altered swimming kinematics, activity levels and swimming performance of juvenile N. brevirostris relative to untagged individuals, suggesting that tag mass is not a suitable standalone metric of device suitability. Changes in swimming performance could not be detected from tail-beat frequency, which suggests that tail-beat frequency is an unsuitable standalone metric of swimming performance for small N. brevirostris. Lastly, sharks experienced treatment-specific changes in activity level and swimming kinematics from morning to afternoon observation. Therefore, the presence of external telemetry packages altered the kinematics, activity levels and swimming performance of small young-of-the-year N. brevirostris and these data may therefore be relevant to other similar-sized juveniles of other shark species.

Behaviour of growth hormone transgenic coho salmon Oncorhynchus kisutch in marine mesocosms assessed by acoustic tag telemetry.

Underwater acoustic tag telemetry was used to assess behavioural differences between juvenile wild-type (i.e. non-transgenic, NT) and growth hormone (GH) transgenic (T) coho salmon Oncorhynchus kisutch in a contained simulated ocean environment. T O. kisutch were found across days to maintain higher baseline swimming speeds than NT O. kisutch and differences in response to feeding were detected between T and NT genotypes. This is the first study to assess behaviour of GH transgenic salmonids in a marine environment and has relevance for assessing whether behavioural effects of GH overexpression seen in freshwater environments can be extrapolated to oceanic phases of the life cycle.