Simultaneous biologging of heart rate and acceleration, and their relationships with energy expenditure in free-swimming sockeye salmon (Oncorhynchus nerka)

Swimming at Increasing Speeds in Steady and Unsteady Flows of Atlantic Salmon Salmo salar: Oxygen Consumption, Locomotory Behaviour and Overall Dynamic Body Acceleration

The swimming performance of cultured finfish species is typically studied under steady flow conditions. However, flow conditions are mostly unsteady, for instance, as experienced in sea pens in exposed sea areas. Using a Loligo swim tunnel, we investigated the effects of swimming in steady and unsteady flows at increasing swimming speeds on post-smolt Atlantic salmon. Oxygen consumption (MO2), locomotory behaviour, and overall dynamic body acceleration (ODBA), as determined with implanted acoustic sensor tags, were compared between both flow conditions. Results were obtained for mean swimming speeds of 0.2 to 0.8 m.s-1 under both flow conditions. Sensor tags that were implanted in the abdominal cavity had no significant effects on MO2 and locomotory parameters. The MO2 of fish swimming in unsteady flows was significantly higher (15-53%) than when swimming in steady flows (p < 0.05). Significant interaction effects of ODBA with flow conditions and swimming speed were found. ODBA was strongly and positively correlated with swimming speed and MO2 in unsteady flow (R2 = 0.94 and R2 = 0.93, respectively) and in steady flow (R2 = 0.91 and R2 = 0.82, respectively). ODBA predicts MO2 well over the investigated range of swimming speeds in both flow conditions. In an unsteady flow condition, ODBA increased twice as fast with MO2 compared with steady flow conditions (p < 0.05). From these results, we can conclude that (1) swimming in unsteady flow is energetically more costly for post-smolt Atlantic salmon than swimming in steady flow, as indicated by higher MO2, and (2) ODBA can be used to estimate the oxygen consumption of post-smolt Atlantic salmon in unsteady flow in swim tunnels.

Heart Rate and Acceleration Dynamics during Swim-Fitness and Stress Challenge Tests in Yellowtail Kingfish (Seriola lalandi)

The yellowtail kingfish is a highly active and fast-growing marine fish with promising potential for aquaculture. In this study, essential insights were gained into the energy economy of this species by heart rate and acceleration logging during a swim-fitness test and a subsequent stress challenge test. Oxygen consumption values of the 600-800 g fish, when swimming in the range of 0.2 up to 1 m·s-1, were high-between 550 and 800 mg·kg-1·h-1-and the heart rate values-up to 228 bpm-were even among the highest ever measured for fishes. When swimming at these increasing speeds, their heart rate increased from 126 up to 162 bpm, and acceleration increased from 11 up to 26 milli-g. When exposed to four sequential steps of increasing stress load, the decreasing peaks of acceleration (baseline values of 12 to peaks of 26, 19 and 15 milli-g) indicated anticipatory behavior, but the heart rate increases (110 up to 138-144 bpm) remained similar. During the fourth step, when fish were also chased, peaking values of 186 bpm and 44 milli-g were measured. Oxygen consumption and heart rate increased with swimming speed and was well reflected by increases in tail beat and head width frequencies. Only when swimming steadily near the optimal swimming speed were these parameters strongly correlated.

Metabolic constraints and individual variation shape the trade-off between physiological recovery and anti-predator responses in adult sockeye salmon

Metabolic scope represents the aerobic energy budget available to an organism to perform non-maintenance activities (e.g., escape a predator, recover from a fisheries interaction, compete for a mate). Conflicting energetic requirements can give rise to ecologically relevant metabolic trade-offs when energy budgeting is constrained. The objective of this study was to investigate how aerobic energy is utilized when individual sockeye salmon (Oncorhynchus nerka) are exposed to multiple acute stressors. To indirectly assess metabolic changes in free-swimming individuals, salmon were implanted with heart rate biologgers. The animals were then exercised to exhaustion or briefly handled as a control, and allowed to recover from this stressor for 48 h. During the first 2 h of the recovery period, individual salmon were exposed to 90 ml of conspecific alarm cues or water as a control. Heart rate was recorded throughout the recovery period. Recovery effort and time was higher in exercised fish, relative to control fish, whereas exposure to an alarm cue had no effect on either of these metrics. Individual routine heart rate was negatively correlated with recovery time and effort. Together, these findings suggest that metabolic energy allocation towards exercise recovery (i.e., an acute stressor; handling, chase, etc.) trumps anti-predator responses in salmon, although individual variation may mediate this effect at the population level.

Effect of flowing water on the pharmacokinetic properties of norfloxacin in channel catfish ( Ictalurus punctatus ) after single‐dose oral administration

BACKGROUND

The recirculating aquaculture system (RAS) is a widely used, water-saving and efficient aquaculture model. However, bacterial diseases are common in farmed fish reared at high densities. Although antibiotics effectively treat these diseases, developing efficient methods to increase drug clearance in fish and decrease the concentrations of antibiotic residues in aquatic products is essential.

OBJECTIVES

This study evaluates the effect of flowing water in the RAS on norfloxacin (NOR) pharmacokinetics in channel catfish (Ictalurus punctatus).

METHODS

Channel catfish were randomly divided into the control group (RAS group) and the experimental group (flow-through aquaculture system group) (120 individuals/group). A NOR dose of 20 mg/kg was then orally administered to the fish. Plasma, muscle, liver and kidney samples were collected up to 168 h after treatment. NOR concentrations were measured using liquid chromatography-mass spectrometry, and pharmacokinetic parameters were calculated using a non-compartmental method.

RESULTS

Flowing water had a significant effect on the plasma pharmacokinetics and tissue distribution of NOR, increasing NOR clearance in the kidney, muscle and plasma. The time to maximum concentration of NOR was shorter in the plasma and longer in the kidney and liver. Moreover, flowing water increased the maximum concentration of NOR in the kidney, muscle and plasma and decreased the area under the concentration-time curve from time 0 to the last measurable concentration in the liver and plasma. Flowing water decreased the withdrawal period in muscle from 10 to 6 days.

CONCLUSIONS

These results indicate that flowing water can potentially increase NOR clearance in channel catfish.

Investigating the physiological response and antibody concentration of gilthead sea bream (Sparus aurata) following Vibrio anguillarum vaccination depending on the stress coping style

Stress coping styles (SCSs) are defined as coherent sets of individual physiological and behavioral differences in stress response consistent across time and context and are described in a wide range of taxa, including fishes. These differences in behavior and physiology are of great interest because they may have direct implications on animal health, welfare, and performance in farming systems, including aquaculture. In this study, the physiological responses of sea bream (Sparus aurata) from different SCSs following Vibrio anguillarum vaccination were monitored. Fish were first screened either bold or shy (proxy of proactive and reactive SCSs, respectively) using group risk-taking tests and were then injected with a vaccine against V. anguillarum. Following vaccination, the fish were implanted with an accelerometer tag to monitor their swimming activity (proxy of energy expenditure), and blood sampling was carried out to measure health and welfare parameters (e.g., cortisol, glucose, hemoglobin) and aspecific immunity (e.g., protease, total proteins). In addition, blood was also collected at three different sampling times to screen antibody levels and, thus, to evaluate the efficiency of the vaccine. Following vaccination, bold fish displayed lower swimming activity values, indicative of lower energy expenditure, and also displayed higher levels of hematocrit, total proteins, and lysozyme in the plasma than the shy ones, which could be indicative of better health/welfare status and greater aspecific immunity. Finally, the V. anguillarum vaccination appeared to be more efficient in bold fish since the number of total antibodies was found higher than in shy fish 1 month after vaccination. Such results could help improve both health/welfare and productivity of farmed sea breams by selecting more robust fish, better adapted to farming conditions.

Empirical Evidence for Energy Efficiency Using Intermittent Gliding Flight in Northern Bald Ibises

Birds face exceptionally high energy demands during their flight. One visible feature of some species is alternating between flapping and gliding, which should allow them to save energy. To date, there is no empirical evidence of an energetic benefit to this. To understand the physiology behind the strategy, we equipped hand-raised Northern Bald Ibises (Geronticus eremita) with data loggers during human-guided migration. We monitored the position of the birds, wingbeats, overall dynamic body acceleration (ODBA), and heart rates as a proxy for energy expenditure. The energy expenditure was significantly affected by the length of flapping and gliding bouts. A pronounced decrease in heart rate was measured after already 1 s of gliding. Additionally, the heart rate at flapping bouts up to 30 s increased steadily but stabilized thereafter. The gilding proportion during intermittent flight affected the energy saving compared to continuous flapping. At a gliding proportion of about 20%, we measured a maximum of 11% saving based on heart rate measurement. At higher gliding proportions, the additional energy saving was negligible. Furthermore, as during flight, not all energy is used for mechanical work, we found a greater decrease rate of ODBA at different gliding proportions compared to heart rate. Nevertheless, the combination of the two methods is essential to determine birds’ movement and energy expenditure. This study provides empirical evidence that intermittent flight is energetically beneficial and can reduce the high costs of flights.

Exploring relationships between oxygen consumption and biologger-derived estimates of heart rate in two warmwater piscivores

Estimating metabolic rate in wild, free-swimming fish is inherently challenging. Here, we explored using surgically implanted heart rate biologgers to estimate metabolic rate in two warmwater piscivores, bowfin Amia calva (Linneaus 1766) and largemouth bass Micropterus salmoides (Lacepède 1802). Fish were surgically implanted with heart rate loggers, allowed to recover for 24 h, exposed to a netting and air exposure challenge, and then placed into respirometry chambers so that oxygen consumption rate (Ṁ_O2 ) could be measured in parallel to heart rate (f_H ) for a minimum of 20 h (ca. 20 estimates of Ṁ_O2 ). Heart rate across the duration of the experiment (at 19°C) was significantly higher in largemouth bass (mean ± s.d., 45 ± 14 beats min^-1 , range 18-86) than in bowfin (27 ± 9 bpm, range 16-98). Standard metabolic rate was also higher in largemouth bass (1.06 ± 0.19 mg O₂  kg^-1  min^-1 , range 0.46-1.36) than in bowfin (0.89 ± 0.17 mg O₂  kg^-1  min^-1 , range 0.61-1.28). There were weak relationships between f_H and Ṁ_O2 , with heart rate predicting 28% of the variation in oxygen consumption in bowfin and 23% in largemouth bass. The shape of the relationship differed somewhat between the two species, which is perhaps unsurprising given their profound differences in physiology and life history, illustrating the need to carry out species-specific validations. Both species showed some potential for a role of f_H in efforts to estimate field metabolic rates, although further validation experiments with a wider range of conditions (e.g., digestive states, swimming activity) would likely help improve the strength of the Ṁ_O2 -f_H relationship for use in field applications.

Moving average and standard deviation thresholding (MAST): a novel algorithm for accurate R-wave detection in the murine electrocardiogram

Advances in implantable radio-telemetry or diverse biologging devices capable of acquiring high-resolution ambulatory electrocardiogram (ECG) or heart rate recordings facilitate comparative physiological investigations by enabling detailed analysis of cardiopulmonary phenotypes and responses in vivo. Two priorities guiding the meaningful adoption of such technologies are: (1) automation, to streamline and standardize large dataset analysis, and (2) flexibility in quality-control. The latter is especially relevant when considering the tendency of some fully automated software solutions to significantly underestimate heart rate when raw signals contain high-amplitude noise. We present herein moving average and standard deviation thresholding (MAST), a novel, open-access algorithm developed to perform automated, accurate, and noise-robust single-channel R-wave detection from ECG obtained in chronically instrumented mice. MAST additionally and automatically excludes and annotates segments where R-wave detection is not possible due to artefact levels exceeding signal levels. Customizable settings (e.g. window width of moving average) allow for MAST to be scaled for use in non-murine species. Two expert reviewers compared MAST's performance (true/false positive and false negative detections) with that of a commercial ECG analysis program. Both approaches were applied blindly to the same random selection of 270 3-min ECG recordings from a dataset containing varying amounts of signal artefact. MAST exhibited roughly one quarter the error rate of the commercial software and accurately detected R-waves with greater consistency and virtually no false positives (sensitivity, Se: 98.48% ± 4.32% vs. 94.59% ± 17.52%, positive predictivity, +P: 99.99% ± 0.06% vs. 99.57% ± 3.91%, P < 0.001 and P = 0.0274 respectively, Wilcoxon signed rank; values are mean ± SD). Our novel, open-access approach for automated single-channel R-wave detection enables investigators to study murine heart rate indices with greater accuracy and less effort. It also provides a foundational code for translation to other mammals, ectothermic vertebrates, and birds.

An exposé of Frappellian Motion

Contrary to the well-recognised role of an abstract in helping to summarise the main points of the following article, this abstract takes its influence from Peter B. Frappell ('Frapps') and, therefore, is distracted from its key purpose. While the abstract was supposed to discuss the serious phenomenon of 'Frappellian Motion' (FM), someone just passed along some gossip that is heaps more exciting, so "let's go grab a beer and I'll talk at you".

Atlantic Salmon (Salmo salar) Cage-Site Distribution, Behavior, and Physiology During a Newfoundland Heat Wave

Background: Climate change is leading to increased water temperatures and reduced oxygen levels at sea-cage sites, and this is a challenge that the Atlantic salmon aquaculture industry must adapt to it if it needs to grow sustainably. However, to do this, the industry must better understand how sea-cage conditions influence the physiology and behavior of the fish.

Method: We fitted ~2.5 kg Atlantic salmon on the south coast of Newfoundland with Star-Oddi milli-HRT ACT and Milli-TD data loggers (data storage tags, DSTs) in the summer of 2019 that allowed us to simultaneously record the fish's 3D acceleration (i.e., activity/behavior), electrocardiograms (and thus, heart rate and heart rate variability), depth, and temperature from early July to mid-October.

Results: Over the course of the summer/fall, surface water temperatures went from ~10–12 to 18–19.5°C, and then fell to 8°C. The data provide valuable information on how cage-site conditions affected the salmon and their determining factors. For example, although the fish typically selected a temperature of 14–18°C when available (i.e., this is their preferred temperature in culture), and thus were found deeper in the cage as surface water temperatures peaked, they continued to use the full range of depths available during the warmest part of the summer. The depth occupied by the fish and heart rate were greater during the day, but the latter effect was not temperature-related. Finally, while the fish generally swam at 0.4–1.0 body lengths per second (25–60 cm s⁻¹), their activity and the proportion of time spent using non-steady swimming (i.e., burst-and-coast swimming) increased when feeding was stopped at high temperatures.

Conclusion: Data storage tags that record multiple parameters are an effective tool to understand how cage-site conditions and management influence salmon (fish) behavior, physiology, and welfare in culture, and can even be used to provide fine-scale mapping of environmental conditions. The data collected here, and that in recent publications, strongly suggest that pathogen (biotic) challenges in combination with high temperatures, not high temperatures + moderate hypoxia (~70% air saturation) by themselves, are the biggest climate-related challenge facing the salmon aquaculture industry outside of Tasmania.

Editorial: Untangling the oxygen transport cascade: a tribute to Peter Frappell (Frapps)

This collection of research articles was put together in honour of respiratory physiologist Professor Peter Frappell's (Frapps's) academic achievements. It encompasses various topics relating to the oxygen transport cascade, which was central to Frapps' career as a comparative physiologist. This issue highlights the diversity and outreach of his influence on the field and his pioneering spirit; promoting novel perspectives, methodologies and research techniques. This issue also demonstrates how Frapps' knowledge and scientific findings answered some of the fundamental questions within the field of respiratory physiology while creating and fostering a rather unique work atmosphere in the laboratories he led. We thank Frapps for the contributions he has made and the friendships he has nurtured over his career. Cheers, Frapps - we love you mate!

Animal tag technology keeps coming of age: an engineering perspective

Animal-borne tags (biologgers) have now become extremely sophisticated, recording data from multiple sensors at high frequencies for long periods and, as such, have become a powerful tool for behavioural ecologists and physiologists studying wild animals. But the design and implementation of these tags is not trivial because engineers have to maximize performance and ability to function under onerous conditions while minimizing tag mass and volume (footprint) to maximize the wellbeing of the animal carriers. We present some of the major issues faced by tag engineers and show how tag designers must accept compromises while maintaining systems that can answer the questions being posed. We also argue that basic understanding of engineering issues in tag design by biologists will help feedback to engineers to better tag construction but also reduce the likelihood that tag-deploying biologists will misunderstand their own results. Finally, we suggest that proper consideration of conventional technology together with new approaches will lead to further step changes in our understanding of wild-animal biology using smart tags. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.

Cardiac and behavioural responses to hypoxia and warming in free-swimming gilthead seabream, Sparus aurata

Gilthead seabream were equipped with intraperitoneal biologging tags to investigate cardiac responses to hypoxia and warming, comparing when fish were either swimming freely in a tank with conspecifics or confined to individual respirometers. After tag implantation under anaesthesia, heart rate (fH) required 60 h to recover to a stable value in a holding tank. Subsequently, when undisturbed under control conditions (normoxia, 21°C), mean fH was always significantly lower in the tank than in the respirometers. In progressive hypoxia (100% to 15% oxygen saturation), mean fH in the tank was significantly lower than in the respirometers at oxygen levels down to 40%, with significant bradycardia in both holding conditions below this level. Simultaneous logging of tri-axial body acceleration revealed that spontaneous activity, inferred as the variance of external acceleration (VARm), was low and invariant in hypoxia. Warming (21 to 31°C) caused progressive tachycardia with no differences in fH between holding conditions. Mean VARm was, however, significantly higher in the tank during warming, with a positive relationship between VARm and fH across all temperatures. Therefore, spontaneous activity contributed to raising fH of fish in the tank during warming. Mean fH in respirometers had a highly significant linear relationship with mean rates of oxygen uptake, considering data from hypoxia and warming together. The high fH of confined seabream indicates that respirometry techniques may bias estimates of metabolic traits in some fishes, and that biologging on free-swimming fish will provide more reliable insight into cardiac and behavioural responses to environmental stressors by fish in their natural environment.

Determining the Effects of Environmental Events on Cultured Atlantic Salmon Behaviour Using 3-Dimensional Acoustic Telemetry

The health and welfare of farmed fish are highly dependent on environmental conditions. Under suboptimal conditions, the negative impact on welfare can cause changes in fish behaviour. Acoustic tags can provide high resolution and high frequency data to monitor fish positioning within the cage, which can be used to infer swimming behaviour. In this study, implanted acoustic tags were used to monitor the three-dimensional positioning of Atlantic salmon (Salmo salar) at a commercial farm in Nova Scotia, Canada. The one-month study period allowed the characterisation of background behaviour and changes in behaviour in relation to different environmental conditions, namely, water characteristics in terms of dissolved oxygen and temperature caused by the fall overturn, storm conditions, and feeding activity. The three-dimensional position of 15 fish was recorded using high temporal resolution (3 s). Fish movement was characterised by calculating four fish variables: distance from the centre of the cage [m], depth [m], velocity [ms−1], and turning angle [°]. The population swam in a counterclockwise swimming direction around 4 ± 2 m depth at an average speed of 0.61 ± 0.38 ms−1. After the fall overturn, the population moved significantly towards cage centre while decreasing velocity, and non-significant differences in depth and turning angle were observed. During feeding periods, a significant increase in depth and velocity, as well as a reduction in turning angle were observed. The storm event did not cause any significant change in the four fish variables. While some of the behavioural changes were difficult to assess with respect to causation, the high resolution, high frequency data provide unique detailed positioning information to further our understanding of the swimming behaviour of farmed fish.

Swimming Activity of Gilthead Seabream (Sparus aurata) in Swim-Tunnels: Accelerations, Oxygen Consumption and Body Motion

Acoustic transmitters equipped with accelerometer sensors are considered a useful tool to study swimming activity, including energetics and movement patterns, of fish species in aquaculture and in nature. However, given the novelty of this technique, further laboratory-derived calibrations are needed to assess the characteristics and settings of accelerometer acoustic transmitters for different species and specific environmental conditions. In this study, we compared accelerometer acoustic transmitter outputs with swimming performance and body motion of gilthead seabream (Sparus aurata L.) in swim-tunnels at different flow speeds, which allowed us to characterize the swimming activity of this fish species of high aquaculture interest. Tag implantation in the abdominal cavity had no significant effects on swimming performance and body motion parameters. Accelerations, cost of transport and variations on head orientation (angle with respect to flow direction) were negatively related to flow speed in the tunnel, whereas oxygen consumption and frequencies of tail-beat and head movements increased with flow speed. These results show that accelerometer acoustic transmitters mainly recorded deviations from sustained swimming in the tunnel, due to spontaneous and explorative swimming at the lowest speeds or intermittent burst and coast actions to cope with water flow. In conclusion, accelerometer acoustic transmitters applied in this study provided a proxy for unsustained swimming activity, but did not contemplate the high-energy cost spent by gilthead seabream on sustained swimming, and therefore, it did not provide a proxy for general activity. Despite this limitation, accelerometer acoustic transmitters provide valuable insight in swim patterns and therefore may be a good strategy for advancing our understanding of fish swimming behavior in aquaculture, allowing for rapid detection of changes in species-specific behavioral patterns considered indicators of fish welfare status, and assisting in the refinement of best management practices.

Too big to study? The biologging approach to understanding the behavioural energetics of ocean giants

Wild animals are under selective pressure to optimise energy budgets; therefore, quantifying energy expenditure, intake and allocation to specific activities is important if we are to understand how animals survive in their environment. One approach toward estimating energy budgets has involved measuring oxygen consumption rates under controlled conditions and constructing allometric relationships across species. However, studying 'giant' marine vertebrates (e.g. pelagic sharks, whales) in this way is logistically difficult or impossible. An alternative approach involves the use of increasingly sophisticated electronic tags that have allowed recordings of behaviour, internal states and the surrounding environment of marine animals. This Review outlines how we could study the energy expenditure and intake of free-living ocean giants using this 'biologging' technology. There are kinematic, physiological and theoretical approaches for estimating energy expenditure, each of which has merits and limitations. Importantly, tag-derived energy proxies can hardly be validated against oxygen consumption rates for giant species. The proxies are thus qualitative, rather than quantitative, estimates of energy expenditure, and have more limited utilities. Despite this limitation, these proxies allow us to study the energetics of ocean giants in their behavioural context, providing insight into how these animals optimise their energy budgets under natural conditions. We also outline how information on energy intake and foraging behaviour can be gained from tag data. These methods are becoming increasingly important owing to the natural and anthropogenic environmental changes faced by ocean giants that can alter their energy budgets, fitness and, ultimately, population sizes.

Bio-sensing technologies in aquaculture: how remote monitoring can bring us closer to our farm animals

Farmed aquatic animals represent an increasingly important source of food for a growing human population. However, the aquaculture industry faces several challenges with regard to producing a profitable, ethical and environmentally sustainable product, which are exacerbated by the ongoing intensification of operations and increasingly extreme and unpredictable climate conditions. Fortunately, bio-sensors capable of measuring a range of environmental, behavioural and physiological variables (e.g. temperature, dissolved gases, depth, acceleration, ventilation, heart rate, blood flow, glucose and l-lactic acid) represent exciting and innovative tools for assessing the health and welfare of farmed animals in aquaculture. Here, we illustrate how these state-of-the-art technologies can provide unique insights into variables pertaining to the inner workings of the animal to elucidate animal-environment interactions throughout the production cycle, as well as to provide insights on how farmed animals perceive and respond to environmental and anthropogenic perturbations. Using examples based on current challenges (i.e. sub-optimal feeding strategies, sub-optimal animal welfare and environmental changes), we discuss how bio-sensors can contribute towards optimizing the growth, health and welfare of farmed animals under dynamically changing on-farm conditions. While bio-sensors currently represent tools that are primarily used for research, the continuing development and refinement of these technologies may eventually allow farmers to use real-time environmental and physiological data from their stock as 'early warning systems' and/or for refining day-to-day operations to ethically and sustainably optimize production. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.

Field assessments of heart rate dynamics during spawning migration of wild and hatchery-reared Chinook salmon

During spawning, adult Pacific salmonids (Oncorhynchus spp.) complete challenging upriver migrations during which energy and oxygen delivery must be partitioned into activities such as locomotion, maturation and spawning behaviours under the constraints of an individual's cardiac capacity. To advance our understanding of cardiac function in free-swimming fishes, we implanted migrating adult Chinook salmon (Oncorhynchus tshawytscha) collected near the mouth of the Sydenham River, Ontario, with heart rate (f_H) biologgers that recorded f_H every 3 min until these semelparous fish expired on spawning grounds several days later. Fundamental aspects of cardiac function were quantified, including resting, routine and maximum f_H, as well as scope for f_H (maximum-resting f_H). Predictors of f_H were explored using generalized least-squares regression, including water temperature, discharge, fish size and fish origin (wild versus hatchery). Heart rate was positively correlated with water temperature, which aligned closely with daily and seasonal shifts. Wild fish had slower resting heart rates than hatchery fish, which led to significantly higher scope for f_H. Our findings suggest that wild salmon may have better cardiac capacity during migration than hatchery fish, potentially promoting migration success in wild fish. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.

Heart rates of Atlantic salmon Salmo salar during a critical swim speed test and subsequent recovery

In this study, heart rate (HR) bio-loggers were implanted in the abdominal cavity of 12 post-smolt Atlantic salmon Salmo salar weighing 1024 ± 31 g and acclimated to 12°C sea water. One week after the surgical procedure, a critical swim speed (U_crit ) test was performed on tagged and untagged conspecifics, whereafter tagged fish were maintained in their holding tanks for another week. The U_crit was statistically similar between tagged and untagged fish (2.67 ± 0.04 and 2.74 ± 0.05 body lengths s^-1 , respectively) showing that the bio-logger did not compromise the swimming performance. In the pre-swim week, a diurnal cycle was apparent with HR peaking at 65 beats min^-1 during the day and approaching 40 beats min^-1 at night. In the U_crit test, HR increased approximately exponentially with swimming speed until a plateau was reached at the final speed before fatigue with a maximum of 85.2 ± 0.7 beats min^-1 . During subsequent recovery tagged fish could be divided into a surviving group (N = 8) and a moribund group (N = 4). In surviving fish HR had fully recovered to pre-swim levels after 24 h, including reestablishment of a diurnal HR cycle. In moribund fish HR never recovered and remained elevated at c. 80 beats min^-1 for 4 days, whereafter they started dying. We did not identify a proximal cause of death in moribund fish, but possible explanations are discussed. Tail beat frequency (TBF) was also measured and showed a more consistent response to increased swimming speeds. As such, when exploring correlations between HR, TBF and metabolic rates at different swimming speeds, TBF provides better predictions. On the contrary, HR measurements in free swimming fish over extended periods of time are useful for other purposes such as assessing the accumulative burden of various stressors and recovery trajectories from exhaustive exercise.

Implantation, orientation and validation of a commercially produced heart-rate logger for use in a perciform teleost fish

Quantifying how the heart rate of ectothermic organisms responds to environmental conditions (e.g. water temperature) is important information to quantify their sensitivity to environmental change. Heart rate studies have typically been conducted in lab environments where fish are confined. However, commercially available implantable heart rate biologgers provide the opportunity to study free-swimming fish. Our study aimed to determine the applicability of an implantable device, typically used on fusiform-shaped fish (e.g. salmonids), for a perciform fish where morphology and anatomy prevent ventral incisions normally used on fusiform-shaped fish. We found that ventrolateral incisions allowed placement near the heart, but efficacy of the loggers was sensitive to their orientation and the positioning of the electrodes. Electrocardiogram detection, signal strength and subsequent heart rate readings were strongly influenced by logger orientation with a significant effect on the quality and quantity of heart rate recordings. We provide details on the surgical procedures and orientation to guide future heart rate biologger studies on perciform-shaped fish.

Effects of prophylactic antibiotic-treatment on post-surgical recovery following intraperitoneal bio-logger implantation in rainbow trout

Bio-logging devices can provide unique insights on the life of freely moving animals. However, implanting these devices often requires invasive surgery that causes stress and physiological side-effects. While certain medications in connection to surgeries have therapeutic capacity, others may have aversive effects. Here, we hypothesized that the commonly prescribed prophylactic treatment with enrofloxacin would increase the physiological recovery rate and reduce the presence of systemic inflammation following the intraperitoneal implantation of a heart rate bio-logger in rainbow trout (Oncorhynchus mykiss). To assess post-surgical recovery, heart rate was recorded for 21 days in trout with or without enrofloxacin treatment. Contrary to our hypothesis, treated trout exhibited a prolonged recovery time and elevated resting heart rates during the first week of post-surgical recovery compared to untreated trout. In addition, an upregulated mRNA expression of TNFα in treated trout indicate a possible inflammatory response 21 days post-surgery. Interestingly, the experience level of the surgeon was observed to have a long-lasting impact on heart rate. In conclusion, our study showed no favorable effects of enrofloxacin treatment. Our findings highlight the importance of adequate post-surgical recovery times and surgical training with regards to improving the welfare of experimental animals and reliability of research outcomes.

Cardiac Performance of Free-Swimming Wild Sockeye Salmon during the Reproductive Period

Researchers have surmised that the ability to obtain dominance during reproduction is related to an individual’s ability to better sequester the energy required for reproductive behaviors and develop secondary sexual characteristics, presumably through enhanced physiological performance. However, studies testing this idea are limited. Using sockeye salmon (Oncorhynchus nerka), we explored the relationship between heart rate and dominance behavior during spawning. We predicted that an individual’s reproductive status and energy requirements associated with dominance can be assessed by relating routine heart rate to changes in spawning status over time (i.e., shifts among aggregation, subordinance, and dominance). Thus, we used routine heart rate as a proxy of relative energy expenditure. Heart rate increased with temperature, as expected, and was higher during the day than at night, a known diel pattern that became less pronounced as the spawning period progressed. Routine heart rate did not differ between sexes and average heart rate of the population did not differ among reproductive behaviors. At the individual level, heart rate did not change as behavior shifted from one state to another (e.g., dominance versus aggregation). No other trends existed between routine heart rate and sex, secondary sexual characteristics, survival duration or spawning success (for females only). Therefore, while our study revealed the complexity of the relationships between cardiac performance and reproductive behaviors in wild fish and demonstrated the importance of considering environmental factors when exploring individual heart rate, we found no support for heart rate being related to specific spawning behavioral status or secondary sexual characteristics.

Analysing tropical elasmobranch blood samples in the field: blood stability during storage and validation of the HemoCue® haemoglobin analyser

Blood samples collected from wild-caught fishes can provide important information regarding the effects of capture (and thus post-release survival) as well as other stressors. Unfortunately, blood samples often cannot be analysed immediately upon sampling, and blood parameters (e.g. blood oxygen levels and acid-base parameters) are known to change with storage duration due to the metabolic activity of the red blood cells. We obtained blood samples from both untreated and stressed individuals of both blacktip reef shark (Carcharhinus melanopterus) and sicklefin lemon shark (Negaprion acutidens) to determine the effects of storage duration on blood pH, haematocrit and haemoglobin concentration ([Hb]). We found no significant effects after storage on ice for up to 180 minutes. Moreover, to validate the usability of a HemoCue haemoglobin analyser (a point-of-care device), we compared data from this device to [Hb] determined using the cyanomethaemoglobin method with blood samples from 10 individuals from each of the aforementioned species as well as epaulette shark (Hemiscyllium ocellatum). Values from the HemoCue consistently overestimated [Hb], and we therefore developed the necessary correction equations. The correction equations were not statistically different among the three elasmobranch species within the biologically relevant range but did differ from published corrections developed using blood from temperate teleost fishes. Although the HemoCue is useful in field situations, development of species-specific calibration equations may be necessary to ensure the reliability of inter-species comparisons of blood [Hb]. Together, these data should increase confidence in haematological stress indicators in elasmobranch fishes, measurements of which are critical for understanding the impact of anthropogenic stressors on these ecologically important species.

Behavioral and physiological responses to stocking density in sea bream (Sparus aurata): Do coping styles matter?

Stocking density is considered a stress factor for fish and is therefore one of the numerous concerns about fish welfare in an aquaculture context. Stress coping styles (SCS) are defined as a coherent set of individual physiological and behavioral differences in stress responses that are consistent across time and context and appear to be promising for improving fish welfare in aquaculture. The aim of the present study was to describe the physiological and zootechnical performances of gilthead sea bream (Sparus aurata) at different stocking densities (low density, LD: 15 kg/m³ and high density, HD: 30 kg/m³), depending on individual SCS. To do so, the fish SCS were first screened by measuring boldness (prior to the experiment). Three consecutive samplings were performed over the experiment to measure several blood parameters, including hematocrit (Hct), red blood cell count (RBCC), hemoglobin (Hb), cortisol, adrenalin, noradrenalin, glucose, lactate, and lysozyme, to infer the consequence of the SCS profile on the welfare condition in response to stocking density. Finally, swimming activity was recorded in a subsample of individuals (9 BOLD and 9 SHY individuals per density), and BOLD individuals displayed higher swimming activity than SHY ones at HD, while the opposite pattern was observed at LD. According to principal component analysis, physiological parameters are linked to the SCS profile, mostly at the beginning of the experiment, while density effects on physiology remain during the entire experiment duration. In conclusion, regarding all the variables observed, fish SCS appeared to be promising criteria to select the most adaptive individuals relating to rearing conditions and therefore improve welfare.

Ultra-Low Power Sensor Devices for Monitoring Physical Activity and Respiratory Frequency in Farmed Fish

Integration of technological solutions aims to improve accuracy, precision and repeatability in farming operations, and biosensor devices are increasingly used for understanding basic biology during livestock production. The aim of this study was to design and validate a miniaturized tri-axial accelerometer for non-invasive monitoring of farmed fish with re-programmable schedule protocols. The current device (AE-FishBIT v.1s) is a small (14 mm × 7 mm × 7 mm), stand-alone system with a total mass of 600 mg, which allows monitoring animals from 30 to 35 g onwards. The device was attached to the operculum of gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax) juveniles for monitoring their physical activity by measurements of movement accelerations in x- and y-axes, while records of operculum beats (z-axis) served as a measurement of respiratory frequency. Data post-processing of exercised fish in swimming test chambers revealed an exponential increase of fish accelerations with the increase of fish speed from 1 body-length to 4 body-lengths per second, while a close relationship between oxygen consumption (MO₂) and opercular frequency was consistently found. Preliminary tests in free-swimming fish kept in rearing tanks also showed that device data recording was able to detect changes in daily fish activity. The usefulness of low computational load for data pre-processing with on-board algorithms was verified from low to submaximal exercise, increasing this procedure the autonomy of the system up to 6 h of data recording with different programmable schedules. Visual observations regarding tissue damage, feeding behavior and circulating levels of stress markers (cortisol, glucose, and lactate) did not reveal at short term a negative impact of device tagging. Reduced plasma levels of triglycerides revealed a transient inhibition of feed intake in small fish (sea bream 50-90 g, sea bass 100-200 g), but this disturbance was not detected in larger fish. All this considered together is the proof of concept that miniaturized devices are suitable for non-invasive and reliable metabolic phenotyping of farmed fish to improve their overall performance and welfare. Further work is underway for improving the attachment procedure and the full device packaging.

Examples of Weak, If Not Absent, Form-Function Relations in the Vertebrate Heart

That form and function are related is a maxim of anatomy and physiology. Yet, form-function relations can be difficult to prove. Human subjects with excessive trabeculated myocardium in the left ventricle, for example, are diagnosed with non-compaction cardiomyopathy, but the extent of trabeculations may be without relation to ejection fraction. Rather than rejecting a relation between form and function, we may ask whether the salient function is assessed. Is there a relation to electrical propagation, mean arterial blood pressure, or propensity to form blood clots? In addition, how should the extent of trabeculated muscle be assessed? While reviewing literature on trabeculated muscle, we applied Tinbergen's four types of causation-how does it work, why does it work, how is it made, and why did it evolve-to better parse what is meant by form and function. The paper is structured around cases that highlight advantages and pitfalls of applying Tinbergen's questions. It further uses the evolution of lunglessness in amphibians to argue that lung reduction impacts on chamber septation and it considers the evolution of an arterial outflow in fishes to argue that reductions in energy consumption may drive structural changes with little consequences to function. Concerning trabeculations, we argue they relate to pumping function in the embryo in the few weeks before the onset of coronary circulation. In human fetal and postnatal stages, a spectrum of trabeculated-to-compact myocardium makes no difference to cardiac function and in this period, form and function may appear unrelated.

The role of physiological traits in assortment among and within fish shoals

Individuals of gregarious species often group with conspecifics to which they are phenotypically similar. This among-group assortment has been studied for body size, sex and relatedness. However, the role of physiological traits has been largely overlooked. Here, we discuss mechanisms by which physiological traits—particularly those related to metabolism and locomotor performance—may result in phenotypic assortment not only among but also within animal groups. At the among-group level, varying combinations of passive assortment, active assortment, phenotypic plasticity and selective mortality may generate phenotypic differences among groups. Even within groups, however, individual variation in energy requirements, aerobic and anaerobic capacity, neurological lateralization and tolerance to environmental stressors are likely to produce differences in the spatial location of individuals or associations between group-mates with specific physiological phenotypes. Owing to the greater availability of empirical research, we focus on groups of fishes (i.e. shoals and schools). Increased knowledge of physiological mechanisms influencing among- and within-group assortment will enhance our understanding of fundamental concepts regarding optimal group size, predator avoidance, group cohesion, information transfer, life-history strategies and the evolutionary effects of group membership. In a broader perspective, predicting animal responses to environmental change will be impossible without a comprehensive understanding of the physiological basis of the formation and functioning of animal social groups.

This article is part of the themed issue ‘Physiological determinants of social behaviour in animals’.

Does the Treadmill Support Valid Energetics Estimates of Field Locomotion?

SYNOPSIS

Quantifying animal energy expenditure during locomotion in the field is generally based either on treadmill measurements or on estimates derived from a measured proxy. Two common proxies are heart rate (ƒH) and dynamic body acceleration (accelerometry). Both ƒH and accelerometry have been calibrated extensively under laboratory conditions, which typically involve prompting the animal to locomote on a treadmill at different speeds while simultaneously recording its rate of oxygen uptake (V̇o2) and the proxy. Field estimates of V̇o2 during locomotion obtained directly from treadmill running or from treadmill-calibrated proxies make assumptions about similarities between running in the field and in the laboratory. The present study investigated these assumptions, focusing on humans as a tractable species. First we investigated experimentally if and how the rate of energy expenditure during treadmill locomotion differs to that during field locomotion at the same speeds, with participants walking and running on a treadmill, on tarmac, and on grass, while wearing a mobile respirometry system. V̇o2 was substantially higher during locomotion in both of the field conditions compared with on a level treadmill: 9.1% on tarmac and 17.7% on grass. Second, we included these data in a meta-analysis of previous, related studies. The results were influenced by the studies excluded due to particulars of the experiment design, suggesting that participant age, the surface type, and the degree of turning during field locomotion may influence by how much treadmill and field locomotion V̇o2 differ. Third, based on our experiments described earlier, we investigated the accuracy of treadmill-calibrated accelerometry and ƒH for estimating V̇o2 in the field. The mean algebraic estimate errors varied between 10% and 35%, with the ƒH associated errors being larger than those derived from accelerometry. The mean algebraic errors were all underestimates of field V̇o2, by around 10% for fH and varying between 0% and 15% for accelerometry. Researchers should question and consider how accurately a treadmill-derived proxy calibration of V̇o2 will estimate V̇o2 during terrestrial locomotion in free-living animals.

Bio-logging, new technologies to study conservation physiology on the move: a case study on annual survival of Himalayan vultures

Bio-logging, the on-animal deployment of miniaturised electronic data recorders, allows for the study of location, body position, and physiology of individuals throughout their ontogeny. For terrestrial animals, 1 Hz GPS-position, 3D-body acceleration, and ambient temperature provide standard data to link to the physiology of life histories. Environmental context is added at ever finer scales using remote sensing earth observation data. Here we showcase the use of such bio-logging approaches in a conservation physiology study on endangered Himalayan vultures (Gyps himalayensis). We determine environmental, behavioural, and physiological causes of survival in immature birds that roam from wintering sites in India, Bhutan, and Nepal towards summer areas in Tibet and Mongolia. Five of 18 immature griffons died during one year. Individuals that died had failed to migrate sufficiently far northward (>1500 km) in spring. Individuals likely died if they flew against headwinds from the north or were less able to find thermal updrafts. Surviving individuals migrated to cold and dry areas with low population density. We highlight flight experience, long distance movements, and remote places with low human population as factors critical for the survival of Himalayan vultures. High-resolution bio-logging studies can advance conservation management by pinpointing where and why migratory animals have problems and die.

Managing consequences of climate-driven species redistribution requires integration of ecology, conservation and social science

Climate change is driving a pervasive global redistribution of the planet's species. Species redistribution poses new questions for the study of ecosystems, conservation science and human societies that require a coordinated and integrated approach. Here we review recent progress, key gaps and strategic directions in this nascent research area, emphasising emerging themes in species redistribution biology, the importance of understanding underlying drivers and the need to anticipate novel outcomes of changes in species ranges. We highlight that species redistribution has manifest implications across multiple temporal and spatial scales and from genes to ecosystems. Understanding range shifts from ecological, physiological, genetic and biogeographical perspectives is essential for informing changing paradigms in conservation science and for designing conservation strategies that incorporate changing population connectivity and advance adaptation to climate change. Species redistributions present challenges for human well-being, environmental management and sustainable development. By synthesising recent approaches, theories and tools, our review establishes an interdisciplinary foundation for the development of future research on species redistribution. Specifically, we demonstrate how ecological, conservation and social research on species redistribution can best be achieved by working across disciplinary boundaries to develop and implement solutions to climate change challenges. Future studies should therefore integrate existing and complementary scientific frameworks while incorporating social science and human-centred approaches. Finally, we emphasise that the best science will not be useful unless more scientists engage with managers, policy makers and the public to develop responsible and socially acceptable options for the global challenges arising from species redistributions.

Identification of animal movement patterns using tri-axial magnetometry

BACKGROUND

Accelerometers are powerful sensors in many bio-logging devices, and are increasingly allowing researchers to investigate the performance, behaviour, energy expenditure and even state, of free-living animals. Another sensor commonly used in animal-attached loggers is the magnetometer, which has been primarily used in dead-reckoning or inertial measurement tags, but little outside that. We examine the potential of magnetometers for helping elucidate the behaviour of animals in a manner analogous to, but very different from, accelerometers. The particular responses of magnetometers to movement means that there are instances when they can resolve behaviours that are not easily perceived using accelerometers.

METHODS

We calibrated the tri-axial magnetometer to rotations in each axis of movement and constructed 3-dimensional plots to inspect these stylised movements. Using the tri-axial data of Daily Diary tags, attached to individuals of number of animal species as they perform different behaviours, we used these 3-d plots to develop a framework with which tri-axial magnetometry data can be examined and introduce metrics that should help quantify movement and behaviour..

RESULTS

Tri-axial magnetometry data reveal patterns in movement at various scales of rotation that are not always evident in acceleration data. Some of these patterns may be obscure until visualised in 3D space as tri-axial spherical plots (m-spheres). A tag-fitted animal that rotates in heading while adopting a constant body attitude produces a ring of data around the pole of the m-sphere that we define as its Normal Operational Plane (NOP). Data that do not lie on this ring are created by postural rotations of the animal as it pitches and/or rolls. Consequently, stereotyped behaviours appear as specific trajectories on the sphere (m-prints), reflecting conserved sequences of postural changes (and/or angular velocities), which result from the precise relationship between body attitude and heading. This novel approach shows promise for helping researchers to identify and quantify behaviours in terms of animal body posture, including heading.

CONCLUSION

Magnetometer-based techniques and metrics can enhance our capacity to identify and examine animal behaviour, either as a technique used alone, or one that is complementary to tri-axial accelerometry.

Determining forward speed from accelerometer jiggle in aquatic environments

How fast animals move is critical to understanding their energetic requirements, locomotor capacity, and foraging performance, yet current methods for measuring speed via animal-attached devices are not universally applicable. Here we present and evaluate a new method that relates forward speed to the stochastic motion of biologging devices since tag jiggle, the amplitude of the tag vibrations as measured by high sample rate accelerometers, increases exponentially with increasing speed. We successfully tested this method in a flow tank using two types of biologging devices and tested the method in situ on wild cetaceans spanning ∼3 to &gt;20 m in length using two types of suction cup-attached and two types of dart-attached tag. This technique provides some advantages over other approaches for determining speed as it is device-orientation independent and relies only on a pressure sensor and a high sample rate accelerometer, sensors that are nearly universal across biologging device types.

The influence of water temperature on sockeye salmon heart rate recovery following simulated fisheries interactions

Selective harvest policies have been implemented in North America to enhance the conservation of Pacific salmon (Oncorhynchus spp.) stocks, which has led to an increase in the capture and release of fish by all fishing sectors. Despite the immediate survival benefits, catch-and-release results in capture stress, particularly at high water temperatures, and this can result in delayed post-release mortality minutes to days later. The objective of this study was to evaluate how different water temperatures influenced heart rate disturbance and recovery of wild sockeye salmon (Oncorhynchus nerka) following fisheries interactions (i.e. exhaustive exercise). Heart rate loggers were implanted into Fraser River sockeye salmon prior to simulated catch-and-release events conducted at three water temperatures (16°C, 19°C and 21°C). The fisheries simulation involved chasing logger-implanted fish in tanks for 3 min, followed by a 1 min air exposure. Neither resting nor routine heart rate differed among temperature treatments. In response to the fisheries simulation, peak heart rate increased with temperature (16°C = 91.3 ± 1.3 beats min^-1; 19°C = 104.9 ± 2.0 beats min^-1 and 21°C = 117 ± 1.3 beats min^-1). Factorial heart rate and scope for heart rate were highest at 21°C and lowest at 16°C, but did not differ between 19°C and 21°C. Temperature affected the initial rate of cardiac recovery but not the overall duration (~10 h) such that the rate of energy expenditure during recovery increased with temperature. These findings support the notion that in the face of climate change, efforts to reduce stress at warmer temperatures will be necessary if catch-and-release practices are to be an effective conservation strategy.

Correlations of metabolic rate and body acceleration in three species of coastal sharks under contrasting temperature regimes

The ability to produce estimates of the metabolic rate of free-ranging animals is fundamental to the study of their ecology. However, measuring the energy expenditure of animals in the field has proved difficult, especially for aquatic taxa. Accelerometry presents a means of translating metabolic rates measured in the laboratory to individuals studied in the field, pending appropriate laboratory calibrations. Such calibrations have only been performed on a few fish species to date, and only one where the effects of temperature were accounted for. Here, we present calibrations between activity, measured as overall dynamic body acceleration (ODBA), and metabolic rate, measured through respirometry, for nurse sharks (Ginglymostoma cirratum), lemon sharks (Negaprion brevirostris) and blacktip sharks (Carcharhinus limbatus). Calibrations were made at a range of volitional swimming speeds and experimental temperatures. Linear mixed models were used to determine a predictive equation for metabolic rate based on measured ODBA values, with the optimal model using ODBA in combination with activity state and temperature to predict metabolic rate in lemon and nurse sharks, and ODBA and temperature to predict metabolic rate in blacktip sharks. This study lays the groundwork for calculating the metabolic rate of these species in the wild using acceleration data.

Conservation physiology of marine fishes: state of the art and prospects for policy

The state of the art of research on the environmental physiology of marine fishes is reviewed from the perspective of how it can contribute to conservation of biodiversity and fishery resources. A major constraint to application of physiological knowledge for conservation of marine fishes is the limited knowledge base; international collaboration is needed to study the environmental physiology of a wider range of species. Multifactorial field and laboratory studies on biomarkers hold promise to relate ecophysiology directly to habitat quality and population status. The 'Fry paradigm' could have broad applications for conservation physiology research if it provides a universal mechanism to link physiological function with ecological performance and population dynamics of fishes, through effects of abiotic conditions on aerobic metabolic scope. The available data indicate, however, that the paradigm is not universal, so further research is required on a wide diversity of species. Fish physiologists should interact closely with researchers developing ecological models, in order to investigate how integrating physiological information improves confidence in projecting effects of global change; for example, with mechanistic models that define habitat suitability based upon potential for aerobic scope or outputs of a dynamic energy budget. One major challenge to upscaling from physiology of individuals to the level of species and communities is incorporating intraspecific variation, which could be a crucial component of species' resilience to global change. Understanding what fishes do in the wild is also a challenge, but techniques of biotelemetry and biologging are providing novel information towards effective conservation. Overall, fish physiologists must strive to render research outputs more applicable to management and decision-making. There are various potential avenues for information flow, in the shorter term directly through biomarker studies and in the longer term by collaborating with modellers and fishery biologists.

A perspective on physiological studies supporting the provision of scientific advice for the management of Fraser River sockeye salmon (Oncorhynchus nerka)

The inability of physiologists to effect change in fisheries management has been the source of frustration for many decades. Close collaboration between fisheries managers and researchers has afforded our interdisciplinary team an unusual opportunity to evaluate the emerging impact that physiology can have in providing relevant and credible scientific advice to assist in management decisions. We categorize the quality of scientific advice given to management into five levels based on the type of scientific activity and resulting advice (notions, observations, descriptions, predictions and prescriptions). We argue that, ideally, both managers and researchers have concomitant but separate responsibilities for increasing the level of scientific advice provided. The responsibility of managers involves clear communication of management objectives to researchers, including exact descriptions of knowledge needs and researchable problems. The role of the researcher is to provide scientific advice based on the current state of scientific information and the level of integration with management. The examples of scientific advice discussed herein relate to physiological research on the impact of high discharge and water temperature, pathogens, sex and fisheries interactions on in-river migration success of adult Fraser River sockeye salmon (Oncorhynchus nerka) and the increased understanding and quality of scientific advice that emerges. We submit that success in increasing the quality of scientific advice is a function of political motivation linked to funding, legal clarity in management objectives, collaborative structures in government and academia, personal relationships, access to interdisciplinary experts and scientific peer acceptance. The major challenges with advancing scientific advice include uncertainty in results, lack of integration with management needs and institutional caution in adopting new research. We hope that conservation physiologists can learn from our experiences of providing scientific advice to management to increase the potential for this growing field of research to have a positive influence on resource management.

Remote bioenergetics measurements in wild fish: Opportunities and challenges

The generalized energy budget for fish (i.e., Energy Consumed=Metabolism+Waste+Growth) is as relevant today as when it was first proposed decades ago and serves as a foundational concept in fish biology. Yet, generating accurate measurements of components of the bioenergetics equation in wild fish is a major challenge. How often does a fish eat and what does it consume? How much energy is expended on locomotion? How do human-induced stressors influence energy acquisition and expenditure? Generating answers to these questions is important to fisheries management and to our understanding of adaptation and evolutionary processes. The advent of electronic tags (transmitters and data loggers) has provided biologists with improved opportunities to understand bioenergetics in wild fish. Here, we review the growing diversity of electronic tags with a focus on sensor-equipped devices that are commercially available (e.g., heart rate/electrocardiogram, electromyogram, acceleration, image capture). Next, we discuss each component of the bioenergetics model, recognizing that most research to date has focused on quantifying the activity component of metabolism, and identify ways in which the other, less studied components (e.g., consumption, specific dynamic action component of metabolism, somatic growth, reproductive investment, waste) could be estimated remotely. We conclude with a critical but forward-looking appraisal of the opportunities and challenges in using existing and emerging electronic sensor-tags for the study of fish energetics in the wild. Electronic tagging has become a central and widespread tool in fish ecology and fisheries management; the growing and increasingly affordable toolbox of sensor tags will ensure this trend continues, which will lead to major advances in our understanding of fish biology over the coming decades.

Measuring abnormal movements in free-swimming fish with accelerometers: implications for quantifying tag and parasite load

Animal-borne data loggers allow movement, associated behaviours and energy expenditure in fish to be quantified without direct observations. As with any tagging, tags that are attached externally may adversely affect fish behaviour, swimming efficiency and survival. We report on free-swimming wild Atlantic cod (Gadus morhua) held in a large mesocosm that exhibited distinctly aberrant rotational swimming (scouring) when externally tagged with accelerometer data loggers. To quantify the phenomenon, the cod were tagged with two sizes of loggers (18 and 6 g; <2% body mass) that measured tri-axial acceleration at 50 Hz. An automated algorithm, based on body angular rotation, was designed to extract the scouring movements from the acceleration signal (98% accuracy). The algorithm also identified the frequency pattern and associated energy expenditure of scouring in relation to tag load (% body weight). The average per cent time spent scouring (5%) was independent of tag load. The vector of the dynamic body acceleration (VeDBA), used as a proxy for energy expenditure, increased with tag load (r(2)=0.51), and suggests that fish with large tags spent more energy when scouring than fish with small tags. The information allowed us to determine potential detrimental effects of an external tag on fish behaviour and how these effects may be mitigated by tag size. The algorithm can potentially identify similar rotational movements associated with spawning, courtship, feeding and parasite-load shedding in the wild. The results infer a more careful interpretation of data derived from external tags and the careful consideration of tag type, drag, buoyancy and placement, as well as animal buoyancy and species.

Measurement and relevance of maximum metabolic rate in fishes

Maximum (aerobic) metabolic rate (MMR) is defined here as the maximum rate of oxygen consumption (M˙O2max ) that a fish can achieve at a given temperature under any ecologically relevant circumstance. Different techniques exist for eliciting MMR of fishes, of which swim-flume respirometry (critical swimming speed tests and burst-swimming protocols) and exhaustive chases are the most common. Available data suggest that the most suitable method for eliciting MMR varies with species and ecotype, and depends on the propensity of the fish to sustain swimming for extended durations as well as its capacity to simultaneously exercise and digest food. MMR varies substantially (>10 fold) between species with different lifestyles (i.e. interspecific variation), and to a lesser extent (<three-fold) between individuals of the same species (i.e. intraspecific variation). MMR often changes allometrically with body size and is modulated by several environmental factors, including temperature and oxygen availability. Due to the significance of MMR in determining aerobic scope, interest in measuring this trait has spread across disciplines in attempts to predict effects of climate change on fish populations. Here, various techniques used to elicit and measure MMR in different fish species with contrasting lifestyles are outlined and the relevance of MMR to the ecology, fitness and climate change resilience of fishes is discussed.

Recent advances in telemetry for estimating the energy metabolism of wild fishes

Metabolic rate is a critical factor in animal biology and ecology, providing an objective measure that can be used in attributing a cost to different activities and to assessing what animals do against some optimal behaviour. Ideally, metabolic rate would be estimated directly by measuring heat output but, until recently, this has not been easily tractable with fishes so instead metabolic rate is usually estimated using indirect methods. In the laboratory, oxygen consumption rate is the indirect method most frequently used for estimating metabolic rate, but technical requirements preclude the measurement of either heat output or oxygen consumption rate in free-ranging fishes. There are other field methods for estimating metabolic rate that can be used with mammals and birds but, again, these cannot be used with fishes. Here, the use of electronic devices that record body acceleration in three dimensions (accelerometry) is considered. Accelerometry is a comparatively new telemetric method for assessing energy metabolism in animals. Correlations between dynamic body acceleration (DBA) and oxygen consumption rate demonstrate that this will be a useful proxy for estimating activity-specific energy expenditure from fishes in mesocosm or field studies over extended periods where other methods (e.g. oxygen consumption rate) are not feasible. DBA therefore has potential as a valuable tool for attributing cost to different activities. This could help in gaining a full picture of how fishes make energy-based trade-offs between different levels of activity when faced with conflicting or competing demands arising from increased and combined environmental stressors.

Accelerometer-derived activity correlates with volitional swimming speed in lake sturgeon (Acipenser fulvescens)

Quantifying fine-scale locomotor behaviours associated with different activities is challenging for free-swimming fish. Biologging and biotelemetry tools can help address this problem. An open channel flume was used to generate volitional swimming speed (Us) estimates of cultured lake sturgeon (Acipenser fulvescens Rafinesque, 1817) and these were paired with simultaneously recorded accelerometer-derived metrics of activity obtained from three types of data-storage tags. This study examined whether a predictive relationship could be established between four different activity metrics (tail-beat frequency (TBF), tail-beat acceleration amplitude (TBAA), overall dynamic body acceleration (ODBA), and vectorial dynamic body acceleration (VeDBA)) and the swimming speed of A. fulvescens. Volitional Us of sturgeon ranged from 0.48 to 2.70 m·s−1 (0.51–3.18 body lengths (BL)·s−1). Swimming speed increased linearly with all accelerometer-derived metrics, and when all tag types were combined, Us increased 0.46 BL·s−1 for every 1 Hz increase in TBF, and 0.94, 0.61, and 0.94 BL·s−1 for every 1g increase in TBAA, ODBA, and VeDBA, respectively. Predictive relationships varied among tag types and tag-specific parameter estimates of Us are presented for all metrics. This use of acceleration data-storage tags demonstrated their applicability for the field quantification of sturgeon swimming speed.

Fishing for Effective Conservation: Context and Biotic Variation are Keys to Understanding the Survival of Pacific Salmon after Catch-and-Release

Acute stressors are commonly experienced by wild animals but their effects on fitness rarely are studied in the natural environment. Billions of fish are captured and released annually around the globe across all fishing sectors (e.g., recreational, commercial, subsistence). Whatever the motivation, release often occurs under the assumption of post-release survival. Yet, capture by fisheries (hereafter "fisheries-capture") is likely the most severe acute stressor experienced in the animal's lifetime, which makes the problem of physiological recovery and survival of relevance to biology and conservation. Indeed, fisheries managers require accurate estimates of mortality to better account for total mortality from fishing, while fishers desire guidance on strategies for reducing mortality and maintaining the welfare of released fish, to maximize current and future opportunities for fishing. In partnership with stakeholders, our team has extensively studied the effects of catch-and-release on Pacific salmon in both marine and freshwater environments, using biotelemetry and physiological assessments in a combined laboratory-based and field-based approach. The emergent theme is that post-release rates of mortality are consistently context-specific and can be affected by a suite of interacting biotic and abiotic factors. The fishing gear used, location of a fishery, water temperature, and handling techniques employed by fishers each can dramatically affect survival of the salmon they release. Variation among individuals, co-migrating populations, and between sexes all seem to play a role in the response of fish to capture and in their subsequent survival, potentially driven by pre-capture pathogen-load, maturation states, and inter-individual variation in responsiveness to stress. Although some of these findings are fascinating from a biological perspective, they all create unresolved challenges for managers. We summarize our findings by highlighting the patterns that have emerged most consistently, and point to areas of uncertainty that require further research.