Great leaps forward in scientific understanding are often spurred by innovations in technology. The explosion of miniature sensors that are driving the boom in consumer electronics, such as smart phones, gaming platforms, and wearable fitness devices, are now becoming available to ecologists for remotely monitoring the activities of wild animals. While half a century ago researchers were attaching balloons to the backs of seals to measure their movement, today ecologists have access to an arsenal of sensors that can continuously measure most aspects of an animal's state (e.g., location, behavior, caloric expenditure, interactions with other animals) and external environment (e.g., temperature, salinity, depth). This technology is advancing our ability to study animal ecology by allowing researchers to (1) answer questions about the physiology, behavior, and ecology of wild animals in situ that would have previously been limited to tests on model organisms in highly controlled settings, (2) study cryptic or wide-ranging animals that have previously evaded investigation, and (3) develop and test entirely new theories. Here we explore how ecologists are using these tools to answer new questions about the physiological performance, energetics, foraging, migration, habitat selection, and sociality of wild animals, as well as collect data on the environments in which they live.

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/14-1401.1

The golden age of bio‐logging: how animal‐borne sensors are advancing the frontiers of ecology

Spatial behaviour of fishes in fresh and brackish water ranges in temporal scales between localized diel movements, often associated with foraging and predator evasion, to seasonal or life-cycle related events involving movements between freshwater habitats or freshwater and marine biotopes. Recent technological advances have resulted in dramatic improvements in the range of techniques available for the study of spatial behaviour of freshwater fishes in the natural environment, and broadly may be divided into two categories: capture dependent and capture independent. The former incorporates those methods that rely on sampling marked fish (mark–recapture) or unmarked fish (density estimates, catch per unit effort) over defined scales of time and space in order to derive information on distribution and movement. Captured fish may also be tagged with transmitters that radiate energy, enabling the fish to be tracked and/or environmental data to be gathered. Biochemical analysis of samples from fish, requiring non-destructive sampling (genetic analysis and scale microchemistry) or destructive sampling (otolith microchemistry) may also provide information on migration and ontogenetic processes. Capture independent techniques include visual observation and video techniques, hydroacoustics and automated fish counting. Catch per unit effort and mark–recapture techniques are most efficient where long-term fishery or monitoring studies are in place and data on crude spatial and temporal scales are acceptable. They also have the advantages of low technical requirements and low equipment costs. Where specific management or ecological questions are pertinent, recapture independent techniques may be more appropriate. Telemetric methods can provide high resolution information at the individual level, while hydroacoustics is increasingly providing information at the population level in large lake and river environments. Biochemical methods are becoming increasingly useful in determining the extent of population segregation, where DNA analysis is used, and in the study of migration and ontogenetic changes in behaviour, where otolith microchemistry and stable isotope analysis is used.

Methods for studying spatial behaviour of freshwater fishes in the natural environment

Freshwater fish move vertically and horizontally through the aquatic landscape for a variety of reasons, such as to find and exploit patchy resources or to locate essential habitats (e.g., for spawning). Inherent challenges exist with the assessment of fish populations because they are moving targets. We submit that quantifying and describing the spatial ecology of fish and their habitat is an important component of freshwater fishery assessment and management. With a growing number of tools available for studying the spatial ecology of fishes (e.g., telemetry, population genetics, hydroacoustics, otolith microchemistry, stable isotope analysis), new knowledge can now be generated and incorporated into biological assessment and fishery management. For example, knowing when, where, and how to deploy assessment gears is essential to inform, refine, or calibrate assessment protocols. Such information is also useful for quantifying or avoiding bycatch of imperiled species. Knowledge of habitat connectivity and usage can identify critically important migration corridors and habitats and can be used to improve our understanding of variables that influence spatial structuring of fish populations. Similarly, demographic processes are partly driven by the behavior of fish and mediated by environmental drivers. Information on these processes is critical to the development and application of realistic population dynamics models. Collectively, biological assessment, when informed by knowledge of spatial ecology, can provide managers with the ability to understand how and when fish and their habitats may be exposed to different threats. Naturally, this knowledge helps to better evaluate or develop strategies to protect the long-term viability of fishery production. Failure to understand the spatial ecology of fishes and to incorporate spatiotemporal data can bias population assessments and forecasts and potentially lead to ineffective or counterproductive management actions.

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A moving target—incorporating knowledge of the spatial ecology of fish into the assessment and management of freshwater fish populations

1. This review examines the physical habitat and ecology of glacial rivers which have been relatively unstudied compared with rivers originating from other sources.

2. Typical glacial rivers have summer temperatures below 10°C, a single seasonal peak in discharge, which in the Northern Hemisphere typically occurs in July, a diel fluctuation in flow which usually peaks in late afternoon, and turbidity levels in summer that exceed 30 NTU. These variables contrast with those in snowmelt/rainfall streams, particularly in summer, and make conditions more extreme for the biota.

3. Where maximum temperatures are 2°C benthic invertebrate communities are dominated by Diamcsa (Chironomidae). Downstream, temperatures increase, channels become more stable and valley floors become older. Orthocladiinae (Chironomidae), Simuliidae, Baetidae, Nemouridae and Chloroperlidae become characteristic members of the invertebrate community.

4. Fauna may be displaced, or at least colonization delayed, by channel instability; the variable age structure of the valley floor will influence the faunal gradient, which may also be reset by the effects of tributaries, lakes and valley confinement.

5. We propose a qualitative model that outlines zoobenthic community gradients determined by two principal variables, water temperature and channel stability, as a function of distance downstream, or time since deglaciation.

Glacial rivers: physical habitat and ecology

There is increasing interest in documenting and explaining the existence of marked intraspecific variation in metabolic rate in animals, with fishes providing some of the best-studied examples. After accounting for variation due to other factors, there can typically be a two to three-fold variation among individual fishes for both standard and maximum metabolic rate (SMR and MMR). This variation is reasonably consistent over time (provided that conditions remain stable), and its underlying causes may be influenced by both genes and developmental conditions. In this paper, current knowledge of the extent and causes of individual variation in SMR, MMR and aerobic scope (AS), collectively its metabolic phenotype, is reviewed and potential links among metabolism, behaviour and performance are described. Intraspecific variation in metabolism has been found to be related to other traits: fishes with a relatively high SMR tend to be more dominant and grow faster in high food environments, but may lose their advantage and are more prone to risk-taking when conditions deteriorate. In contrast to the wide body of research examining links between SMR and behavioural traits, very little work has been directed towards understanding the ecological consequences of individual variation in MMR and AS. Although AS can differ among populations of the same species in response to performance demands, virtually nothing is known about the effects of AS on individual behaviours such as those associated with foraging or predator avoidance. Further, while factors such as food availability, temperature, hypoxia and the fish's social environment are known to alter resting and MMRs in fishes, there is a paucity of studies examining how these effects vary among individuals, and how this variation relates to behaviour. Given the observed links between metabolism and measures of performance, understanding the metabolic responses of individuals to changing environments will be a key area for future research because the environment will have a strong influence on which animals survive predation, become dominant and ultimately have the highest reproductive success. Although current evidence suggests that variation in SMR may be maintained within populations via context-dependent fitness benefits, it is suggested that a more integrative approach is now required to fully understand how the environment can modulate individual performance via effects on metabolic phenotypes encompassing SMR, MMR and AS.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/jfb.12699

Does individual variation in metabolic phenotype predict fish behaviour and performance

Considerable technical developments over the past half century have enabled widespread application of electronic tags to the study of animals in the wild, including in freshwater environments. We review the constraints associated with freshwater telemetry and biologging and the technical developments relevant to their use. Technical constraints for tracking animals are often influenced by the characteristics of the animals being studied and the environment they inhabit. Collectively, they influence which and how technologies can be used and their relative effectiveness. Although radio telemetry has historically been the most commonly used technology in freshwater, passive integrated transponder (PIT) technology, acoustic telemetry and biologgers are becoming more popular. Most telemetry studies have focused on fish, although an increasing number have focused on other taxa, such as turtles, crustaceans and molluscs. Key technical developments for freshwater systems include: miniaturization of tags for tracking small-size life stages and species, fixed stations and coded tags for tracking large samples of animals over long distances and large temporal scales, inexpensive PIT systems that enable mass tagging to yield population- and community-level relevant sample sizes, incorporation of sensors into electronic tags, validation of tag attachment procedures with a focus on maintaining animal welfare, incorporation of different techniques (for example, genetics, stable isotopes) and peripheral technologies (for example, geographic information systems, hydroacoustics), development of novel analytical techniques, and extensive international collaboration. Innovations are still needed in tag miniaturization, data analysis and visualization, and in tracking animals over larger spatial scales (for example, pelagic areas of lakes) and in challenging environments (for example, large dynamic floodplain systems, under ice). There seems to be a particular need for adapting various global positioning system and satellite tagging approaches to freshwater. Electronic tagging provides a mechanism to collect detailed information from imperilled animals and species that have no direct economic value. Current and future advances will continue to improve our knowledge of the natural history of aquatic animals and ecological processes in freshwater ecosystems while facilitating evidence-based resource management and conservation.

/pdf/tracking-animals-in-freshwater-with-electronic-tags-past-1f25e70juo.pdf

Tracking animals in freshwater with electronic tags: past, present and future

Radio telemetry was used to determine the distribution of sockeye salmon Oncorhynchus nerka returning to spawn in the glacial Taku River in 1984 and 1986, and to locate and characterize spawning areas used by this species. During the study, 253 sockeye salmon were tracked as they moved upriver; 204 of these were followed to spawning areas. Only 37% of the 204 fish traveled to areas associated with lakes; the remaining 63% returned to “riverine” areas – river areas without lakes (42% to the Taku River main stem, 17% to the Nakina River, and 4% to other rivers). Sockeye salmon spawning in riverine areas used a variety of habitat types, including main-river channels, side channels, tributary streams, and upland sloughs. Most (55%) of the radio-tagged fish that returned to the Taku River main stem were tracked to side-channel spawning areas. Half of the 471 adult sockeye salmon sampled in main-stem spawning areas had migrated to sea as juveniles before their first winter. This study showed that many ...

http://dnr.alaska.gov/mlw/mining/largemine/tulsequah/pdf3/taku7.pdf

Riverine Spawning by Sockeye Salmon in the Taku River, Alaska and British Columbia

A remote tracking system with a satellite uplink was used to study the movements of adult Chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch in the large, isolated Taku River in Alaska and British Columbia. Salmon were tagged with pulse-coded radio transmitters; 10 codes identified individual fish on each of 52 frequencies. Remote tracking stations automatically collected, processed, and transferred telemetry data via a computer-controlled receiver. A satellite uplink was used to retrieve the data for within-season analysis. Three hundred six Chinook salmon were tracked upriver in 1990 and 351 coho salmon in 1992. Coho salmon could not have been tracked with conventional methods due to the inclement fall weather and mountainous terrain typical of this area. The stations recorded 98–100% of the radio-tagged fish that moved past. Tracking success was much higher than in previous studies in which fish were tracked exclusively from aircraft. The remote tracking system is an effective ...

A Remote Satellite‐Linked Tracking System for Studying Pacific Salmon with Radio Telemetry

Autonomous underwater vehicles (AUV’s) are increasingly used to collect physical, chemical, and biological information in the marine environment. Recent efforts include merging AUV technology with acoustic telemetry to provide information on the distribution and movements of marine fish. We compared surface vessel and AUV tracking capabilities under rigorous conditions in coastal waters near Juneau, Alaska. Tracking surveys were conducted with a REMUS 100 AUV equipped with an integrated acoustic receiver and hydrophone. The AUV was programmed to navigate along predetermined routes to detect both reference transmitters at 20–500 m depths and tagged fish and crabs in situ. Comparable boat surveys were also conducted. Transmitter depth had a major impact on tracking performance. The AUV was equally effective or better than the boat at detecting reference transmitters in shallow water, and significantly better for transmitters at deeper depths. Similar results were observed for tagged animals. Red king crab, Paralithodes camtschaticus, at moderate depths were recorded by both tracking methods, while only the AUV detected Sablefish, Anoplopoma fimbria, at depths exceeding 500 m. Strong currents and deep depths caused problems with AUV navigation, position estimation, and operational performance, but reflect problems encountered by other AUV applications that will likely diminish with future advances, enhanced methods, and increased use.

/pdf/comparing-autonomous-underwater-vehicle-auv-and-vessel-based-46hj2qb1bg.pdf

Comparing autonomous underwater vehicle (AUV) and vessel-based tracking performance for locating acoustically tagged fish

Chemical and hydrological AUV sensors (e.g. C, T, 02, CDOM, Chlorophyll a) collect information about water in contact with or in close proximity to the vehicle. Sonar (e.g. ADCF, side scan, dual beam, and multibeam) collect data about features distant on the scale of tens of meters away and linked to coordinates. In contrast, acoustic tags implanted in fishes or other marine fauna can be detected at distances greater than a kilometer away, which brings special considerations to data treatment and merging. In the case of telemetry systems that log sound pressure levels, relative signal strength can be used to produce proximity maps using regression. For systems with invariant signal timing, a synthetic aperture engine can calculate location of the tag if a suitable AUV path produces a good aperture. In the common case where both of these conditions are lacking, the tag position must be assigned to a place along the vehicle's path. The use of tags that broadcast information from their own sensors (e.g. pressure, temperature) can help resolve both the position and environment of the distant tag. An empirically-fashioned hierarchical decision matrix based on numerous AUV-fish telemetry missions in shallow and deep (<3m to 600m) water assists in mission planning, data processing, and displaying AUV-collected data about telemetered fauna and their environment.

John H. Eiler

Papers

Tracking animals in freshwater with electronic tags: past, present and future

Riverine Spawning by Sockeye Salmon in the Taku River, Alaska and British Columbia

A Remote Satellite‐Linked Tracking System for Studying Pacific Salmon with Radio Telemetry

Comparing autonomous underwater vehicle (AUV) and vessel-based tracking performance for locating acoustically tagged fish

Collecting, interpreting, and merging fish telemetry data from an AUV: Remote sensing from an already remote platform