Acoustic Telemetry Data Research Articles

Novel deep-water spawning patterns of bonefish (Albula vulpes), a shallow water fish

Coastal marine fishes that form spawning aggregations most commonly exhibit a two-point movement pattern, with locations separated by migration: home range to spawning aggregation site and return to home range. However, the bonefish, Albula vulpes, partakes in a unique three-point spawning migration. Bonefish migrate up to 80 km from shallow water home flats to form nearshore pre-spawning aggregations (PSA) before moving offshore to spawn. Although these broad patterns have previously been documented, details of the offshore spawning-associated diving behavior have yet to be rigorously examined. Using active acoustic telemetry and sonar data in 2019 in Abaco, The Bahamas, we provide a complete account of bonefish offshore spawning movements and novel deep diving behavior to 137.9 m. Bonefish were continuously observed at depths ≥ 100 m for 2 h; a time period that included multiple depth changes and culminated in a spawning ascent to 67.3 m at 0.57 m s−1. These new data on bonefish offshore movements and deep dives, coupled with CTD data, suggest that bonefish actively spawn at pycnoclines and thermoclines. Two previous tracking attempts (2013, 2018) at this location reflect spatiotemporal plasticity in spawning, a behavior counter to other aggregation forming fishes. This is the first detailed documentation of such deep spawning for a shallow water coastal fish species. The ecological motivation for diving to the deepest depths remains speculative. Future work must examine the dynamic relationship between bonefish diving behavior, spawning site selection, and oceanographic features.

Actel: Standardised analysis of acoustic telemetry data from animals moving through receiver arrays

Abstract Acoustic telemetry data often contain erroneous detections, which need to be addressed before further analysis. It is important that this process is systematic, standardised and reproducible. The r package actel provides a systematic conditional pipeline to filter and analyse acoustic telemetry data in a reproducible fashion, for animals moving between receiver arrays. actel outputs a standardised report containing the main results and the steps taken by the user, in addition to summary information for each animal and other content such as efficiency estimations for each receiver array. actel improves the reproducibility of the acoustic data filtering and analysis, and simplifies the integration of acoustic data sets originating from different studies (in time and/or in space).

Estimating marine protected area network benefits for reef sharks

Abstract Animal movement has direct applications in spatial management and conservation planning, yet it is rarely taken into account for the design of natural protected areas. For instance, reef shark species are thought to benefit from marine protected area networks, even though their movement behaviour remains poorly characterized. Poor understanding of species' movements implies that the benefits of MPA networks for species' populations are still widely unknown. To understand the consequences of movement behaviour for protection, we modelled movements of three reef shark species' (Carcharhinus albimarginatus, C. amblyrhynchos and C. leucas) with distinct levels of reef association using real passive‐acoustic telemetry data. The model simulates if individuals are protected or unprotected by their movements in a system of reef patches in a network of MPAs. Model parameters that control individuals' movements were estimated from acoustic telemetry data. To estimate benefits for species we monitored longevity and time spent in protected habitats across all scenarios of reef protection, fishing intensity (11 values for each) and protection of high or low suitability reefs (a reef‐dependent factor that attracts sharks to reside in it) for populations of 1,000 individuals per species. The time individuals spent in protected reefs increased linearly with protection until it levelled off after 50%–80% of reefs protected (78% C. amblyrhynchos, 72% C. albimarginatus and 52% C. leucas, at 100% protection). Individuals' life span decreased exponentially with fishing intensity. Reef protection only mildly counteracted life span lost to fishing. Protecting highly suitable reefs increased time spent in protected reefs, optimal protection was reached at a lower number of reefs protected, and life expectancy was higher with protection of highly suitable reefs. Synthesis and applications. Our framework can be applied to many studies using passive‐acoustic telemetry to track animal movements. Protected area networks benefit species highly attached to protected sites. To increase benefits of marine protected area networks for all species (with low and high degrees of reef attachment) we need to understand the use of reef‐adjacent areas, dispersal routes and characterize reef suitability for multiple species.

Inferring individual fate from aquatic acoustic telemetry data

Abstract Acoustic telemetry has become a popular means of obtaining individual behavioural data from a wide array of species in marine and freshwater systems. Fate information is crucial to understand important aspects of population dynamics such as mortality, predation or dispersal rates. Here we present a method to infer individual fate from acoustic telemetry arrays of receivers with overlapping detection ranges. Our method depends exclusively on information on animal movements and the characteristics and configuration of the telemetry equipment. By answering a limited number of simple questions, our method identifies six different fates: tagging mortality, natural mortality, fishing mortality, predation, dispersal and survival. Applying the method to a cod telemetry dataset, we were able to determine the fate of 97% of the individuals. We validate the results using several external sources of information, such as recaptures from fishers and control fish with known fate. The method is readily applicable to a wide array of species with minimal adjustments, expanding the range of hypotheses that can be tested using telemetry data.

Movement-assisted localization from acoustic telemetry data

BackgroundAcoustic telemetry technologies are being increasingly deployed to study a variety of aquatic taxa including fishes, reptiles, and marine mammals. Large cooperative telemetry networks produce vast quantities of data useful in the study of movement, resource selection and species distribution. Efficient use of acoustic telemetry data requires estimation of acoustic source locations from detections at receivers (i.e., “localization”). Multiple processes provide information for localization estimation including detection/non-detection data at receivers, information on signal rate, and an underlying movement model describing how individuals move and utilize space. Frequently, however, localization methods only integrate a subset of these processes and do not utilize the full spatial encounter history information available from receiver arrays.MethodsIn this paper we draw analogies between the challenges of acoustic telemetry localization and newly developed methods of spatial capture-recapture (SCR). We develop a framework for localization that integrates explicit sub-models for movement, signal (or cue) rate, and detection probability, based on acoustic telemetry spatial encounter history data. This method, which we call movement-assisted localization, makes efficient use of the full encounter history data available from acoustic receiver arrays, provides localizations with fewer than three detections, and even allows for predictions to be made of the position of an individual when it was not detected at all. We demonstrate these concepts by developing generalizable Bayesian formulations of the SCR movement-assisted localization model to address study-specific challenges common in acoustic telemetry studies.ResultsSimulation studies show that movement-assisted localization models improve point-wise RMSE of localization estimates by >50% and greatly increased the precision of estimated trajectories compared to localization using only the detection history of a given signal. Additionally, integrating a signal rate sub-model reduced biases in the estimation of movement, signal rate, and detection parameters observed in independent localization models.ConclusionsMovement-assisted localization provides a flexible framework to maximize the use of acoustic telemetry data. Conceptualizing localization within an SCR framework allows extensions to a variety of data collection protocols, improves the efficiency of studies interested in movement, resource selection, and space-use, and provides a unifying framework for modeling acoustic data.

Quantifying and reducing epistemic uncertainty of passive acoustic telemetry data from longitudinal aquatic systems

Passive acoustic telemetry data are used to study animal movement in aquatic environments, but tools to process the data are limited. In areas that are too large to be fully covered by the limited detection ranges of receivers or acoustic listening stations, researchers generally assume that animals are residing in an area when they are detected frequently at specific receivers. There is, however, no consensus on how this area and frequency should be spatially and temporally defined respectively, thereby introducing some unaccounted uncertainty of this residency-at-receivers. In longitudinal aquatic systems such as rivers or estuaries, strategically placed receivers are often used as gates or curtains through which tagged animals have to pass. Rather than being a proxy for the time spent near receivers, the detections can serve as boundary conditions to delineate the durations that animals spent between receivers (i.e. residency-between-receivers). As such, providing a spatial and temporal context to the detections and enabling the quantification of epistemic uncertainty. To assess the usefulness of this approach, we analyzed telemetry data for migrating eel in a longitudinal estuarine acoustic tracking network of 21 gates. Results revealed a logarithmic relationship between epistemic uncertainty and gate network resolution, which indicates that transferring information from the spatial to the temporal level has a positive effect on the epistemic uncertainty. The poor correlation between the at-receivers and the between-receivers approach indicates that the latter, although less precise, may be more accurate. It should be noted that the suggested approach assumes that the gates of receivers are perfect detectors. If tagged animals are able to pass these gates undetected the uncertainty will actually be higher than assumed. Our approach is therefore less suited for large open areas such as lagoons or seas where gates with high detection probabilities are logistically challenging. This approach allows the quantification and reduction of epistemic uncertainty by providing a spatiotemporal context to the detections. Since establishing and maintaining passive telemetry networks is generally expensive and the results these networks generate are often used in decision making, an assessment of the network quality and data uncertainty is vital.

Detecting commonality in multidimensional fish movement histories using sequence analysis

BackgroundAcoustic telemetry, for tracking fish movement histories, is multidimensional capturing both spatial and temporal domains. Oftentimes, analyses of such data are limited to a single domain, one domain nested within the other, or ad hoc approaches that simultaneously consider both domains. Sequence analysis, on the other hand, offers a repeatable statistical framework that uses a sequence alignment algorithm to calculate pairwise dissimilarities among individual movement histories and then hierarchical agglomerative clustering to identify groups of fish with similar movement histories. The objective of this paper is to explore how acoustic telemetry data can be fit to this statistical framework and used to identify commonalities in the movement histories of acoustic-tagged sea lamprey during upstream migration through the St. Clair-Detroit River System.ResultsFive significant clusters were identified among individual fish. Clusters represented differences in timing of movements (short vs long duration in the Detroit R. and Lake St. Clair); extent of upstream migration (ceased migration in Lake St. Clair, lower St. Clair R., or upper St. Clair R.), and occurrence of fallback (return to Lake St. Clair after ceasing migration in the St. Clair R.). Inferences about sea lamprey distribution and behavior from these results were similar to those reached in a previous analysis using ad-hoc analysis methods.ConclusionsThe repeatable statistical framework outlined here can be used to group sea lamprey movement histories based on shared sequence characteristics (i.e., chronological order of “states” occupied). Further, this framework is flexible and allows researchers to define a priori the movement aspect (e.g., order, timing, duration) that is important for identifying both common or previously undetected movement histories. As such, we do not view sequence analysis as a panacea but as a useful complement to other modelling approaches (i.e., exploratory tool for informing hypothesis development) or a stand-alone semi-quantitative method for generating a simplified, temporally and spatially structured view of complex acoustic telemetry data and hypothesis testing when observed patterns warrant further investigation.

RAD-Seq Analysis and in situ Monitoring of Nassau Grouper Reveal Fine-Scale Population Structure and Origins of Aggregating Fish

Nassau grouper (Epinephelus striatus) Bloch, 1792 are globally critically endangered and an important fishery species in The Commonwealth of The Bahamas (hereafter The Bahamas) and parts of the Caribbean, with an urgent need for better management and conservation. Here, we adopted a combined approach, integrating restriction-site-associated DNA sequencing (RAD-seq) and acoustic telemetry to establish country-wide demographic structure, diversity and connectivity, and the origins of Nassau grouper using an active fish spawning aggregation (FSA) in the central Bahamas. RAD-seq analysis of 94 Nassau grouper sampled from nine locations in The Bahamas generated a working dataset of 13,241 single nucleotide polymorphisms. Similar levels of genetic diversity were found among sampled locations. Evidence of population sub-structuring across The Bahamas was demonstrated and supported by discriminate analysis of principal components (DAPCs) along with analyses of molecular variance (AMOVAs). Associated acoustic telemetry data indicated Nassau grouper tagged at an active FSA in the central Bahamas during the 2016-2017 spawning season migrated to the Exumas at the conclusion of the spawning period. Telemetry data suggest the likely origins of five individuals, which travelled one-way distances of up to 176 km from the FSA in the central Bahamas to two sites within a no-take marine protected area (MPA). Analyses of high-resolution SNP markers (including candidate loci under selection) illustrated patterns of spatial structure and genetic connectivity not reflected by telemetry data alone. Nassau grouper from Exuma and Long Island appear to have genetic signatures that differ from other islands and from the Hail Mary FSA. Collectively, these findings provide novel information on the intraspecific population dynamics of Nassau grouper within The Bahamian archipelago and within an active FSA.

Combining Models of the Critical Streakline and the Cross-Sectional Distribution of Juvenile Salmon to Predict Fish Routing at River Junctions

Because fish that enter the interior Delta have poorer survival than those emigrating via the Sacramento River, understanding the mechanisms that drive entrainment rates at side channel junctions is critically important for the management of imperiled juvenile salmon. Here, we implement a previously proposed process-based conceptual model to study entrainment rates based on three linked elements: the entrainment zone, critical streakline, and cross-sectional distribution of fish. The critical streakline is the location along a channel cross-section immediately upstream of a junction that forms the spatial divide between parcels of water that enter a side channel or remain in the main channel. The critical streakline therefore divides the main channel into entrainment zones within which fish would likely enter each channel. Combined with information about the cross-sectional distribution of fish upstream of a junction, this conceptual model provides a means to predict fish entrainment into each channel. To apply this conceptual model, we combined statistical models of the critical streakline, the cross-sectional distribution of acoustic tagged juvenile Chinook salmon, and their probability of entrainment into Georgiana Slough. We fit joint beta regression and logistic regression models to acoustic telemetry data gathered in 2011 and 2012 to estimate the cross-sectional distribution of fish upstream of the junction, and to estimate the probability of entrainment for fish on either side of the critical streakline. We show that entrainment rates can be predicted by understanding how the combination of critical streakline position and cross-sectional distribution of fish co-vary as a function of environmental covariates. By integrating over individual positions and entrainment fates to arrive at population-level entrain probability in relation to environmental covariates, our model offers managers a simple but powerful tool to evaluate how alternative actions affect migrating fish.

Revealing migration and reproductive habitat of invasive fish under an active population suppression program

AbstractEndemic species face a variety of threats including predation from non‐native invaders. In some cases, however, invasive species can be managed by directly suppressing populations, and tracking technologies that allow researchers to identify movement patterns and aggregations representative of the population can facilitate suppression activities. In Yellowstone Lake (Yellowstone National Park, Wyoming), invasive lake trout (Salvelinus namaycush) have been the target of a population suppression program for over two decades. For this form of management, the reproductive period is particularly important because fish migrate to and from spawning grounds. From 2011 to 2014, adult lake trout (n = 317) in Yellowstone Lake were tracked using acoustic biotelemetry. After controlling for spatial and temporal dependency in the data, total abundance of unique individuals was estimated where migratory trajectories occurred at confirmed spawning sites. Aggregations and migratory trajectories were further estimated at locations where spawning had not previously been observed. Across years, the greatest number of individuals was observed along a migration corridor in the southwestern area of the lake. Novel strategies for analyzing acoustic telemetry data provided insights into the behavior of an invasive fish species. By betraying the positions of conspecifics, tagged fish revealed potentially important reproductive habitats and migration corridors that warranted further investigation as possible sites for population suppression.

Relating survival of fall-run Chinook Salmon through the San Joaquin Delta to river flow

Survival of juvenile fall-run Chinook Salmon Oncorhynchus tshawytscha from the San Joaquin River (SJR) during their migration through the Sacramento-San Joaquin Delta of California has been low in recent years, and there is uncertainty about the role of river flow on survival. Five years (2010–2014) of acoustic telemetry data from juvenile hatchery-reared salmon offer spatially detailed survival information through this region. Multinomial regression and generalized linear models were used to relate survival to river flow in the SJR and its distributary, Old River (OR), on various spatial and temporal scales. Higher survival to Delta exit (rkm 77 from Golden Gate Bridge) was associated with higher root mean square of OR flow in the strongly tidal interior Delta (rkm 123; P < 0.0001), but not with higher SJR flow either entering the Delta from upstream (rkm 196; P = 0.2795) or measured in the Delta near the riverine/tidal interface (rkm 150; P = 0.3845). Survival in the upstream, more riverine region of the Delta was positively associated with SJR flow measured at rkm 150 and average net flow in the interior Delta (P ≤ 0.0001 for each), suggesting different mechanisms driving survival in the upstream versus downstream reaches of the Delta. The spatial complexity of the survival-flow relationship suggests that efforts to maximize total Delta survival should focus on a sequence of smaller regions, tailoring management strategies to each region rather than a single strategy for the Delta as a whole. Highly variable environmental conditions in this region combined with very low survival require more data to fully address the complex survival-flow relationship, both more years of data on various spatial scales and larger sample sizes of acoustic-tagged fish.

Behaviour of endangered European eels in proximity to a dam during downstream migration: Novel insights using high accuracy 3D acoustic telemetry

AbstractRiver infrastructures such as weirs, hydropower stations or water reservoirs represent obstructions to migration for diadromous fish. Knowledge of accurate behaviour of fish in front of such structures is required to protect migrants from hazardous areas, guide them towards safe passage or adapt structure to improve the escapement. We developed and made available a method to process acoustic telemetry data based on Time Difference Of Arrival analysis to accurately locate tagged fish. Improved accuracy allows the detection of escape routes and description of dam‐crossing tactics. Sixteen tagged eels were tracked with high accuracy (1–2 m) and ~1 location min−1 frequency during their exploration period on reaching the dam. Two migration routes (spillways and bottom compensation flow pipe) were used by 77% and 23% of eels respectively. Spillways were the preferred route, but a median of 16 days were required to pass the dam versus 1.1 days via the compensation pipe. A minimal water crest of 40 cm was required for passage via spillways. Eels passing through the compensation pipe were exclusively nocturnal and mainly explored the bottom of the dam. Eels passing through spillways explored the whole dam area by night and day, and were not attracted to the compensation pipe entrance. With global warming, more frequent drought periods are expected, potentially leading to decreased opportunities for eels to migrate across safer dams by spillways. To conserve this endangered species, dam management strategies that account for expected hydrologic conditions and distinct exploration behaviours are needed.

Estimating spatial–temporal differences in Chinook salmon outmigration survival with habitat- and predation-related covariates

Low survival rates of Chinook salmon (Oncorhynchus tshawytscha) smolts in California’s Central Valley have been attributed to multiple biological and physical factors, but it is not clear which factors have the largest impact. We used 5 years of acoustic telemetry data for 1709 late-fall Chinook salmon smolts to evaluate the effect of habitat- and predation-related covariates on outmigration survival through the Sacramento River. Using a Cormack–Jolly–Seber mark–recapture model, we estimated survival rates both as a function of covariates (covariate model) and as a function of river location and release year (spatial–temporal model). Our covariate model was overwhelmingly supported as the preferred model based on model selection criteria, suggesting the covariates adequately replicated spatial and temporal patterns in smolt survival. The covariates in the selected model included individual fish covariates, habitat-specific covariates, and temporally variable physical conditions. The most important covariate affecting salmon survival was flow. We describe the importance of these parameters in the context of juvenile salmon predation risk and suggest that additional research on predator distribution and density could improve model estimates.

Going Downriver: Patterns and Cues in Hurricane-Driven Movements of Common Snook in a Subtropical Coastal River

Extreme climate events such as hurricanes can influence the movement and distribution of fish and other aquatic vertebrates. However, our understanding of the scale of movement responses and how they vary across taxa and ecosystems remains incomplete. In this study, we used acoustic telemetry data to investigate the movement patterns of common snook (Centropomus undecimalis) in the Florida Coastal Everglades during Hurricane Irma, which made landfall on the southwest Florida coast as a Category 3 storm on 10 September 2017 after passing in close proximity to our study site. We hypothesized that the hurricane resulted in shifts in distribution and that these movements may have been driven by environmental cues stemming from changes in barometric pressure associated with hurricane conditions, fluctuations in water levels (stage) characterizing altered riverine conditions, or a combination of both hurricane and riverine drivers. The data revealed large-scale movements of common snook in the time period surrounding hurricane passage, with 73% of fish detected moving from the upper river into downriver habitats, and some individuals potentially exiting the river. Furthermore, regression model selection indicated that these movements were correlated to both hurricane and riverine conditions, showing increased common snook movement at higher river stage and lower barometric pressure, and stage explaining a larger proportion of model deviance. Animal movement has widespread and diverse ecological implications, and by better understanding the factors that drive movement, we may anticipate how future extreme climate events could affect fish populations in impact-prone regions.

Modelling the three‐dimensional space use of aquatic animals combining topography and Eulerian telemetry data

Abstract Passive acoustic telemetry provides the opportunity to monitor and contextualize the movements of diverse aquatic animals. Despite depth being an essential dimension along which many processes are organized, the Eulerian structure of the acoustic telemetry data (movements perceived from fixed locations) and the consequences of sound propagation in water hinders the incorporation of the vertical dimension into animal’s space use analyses. Here, we propose a new data‐driven quantitative method to estimate 3D space use from telemetry networks. The methodology is based on simulating large numbers of stochastic synthetic paths, accommodating the detection probability around receivers and the depth information from transmitters and integrating the local topography. The methodological protocol is explained in detail and tested with acoustic telemetry data from the common dentex Dentex dentex in a Mediterranean marine protected area. We present 3D space use estimations for the tagged individuals and compare them with other 3D and 2D estimations derived with existing probabilistic methods. 3D space use estimations that incorporate topography provided a more comprehensive view of the movement ecology of tracked individuals, with relevant pieces being missed by 2D representations. Our method generated realistic representations of the actual spatial co‐occurrence of individuals, including the spatio‐temporal identification of relevant aggregation areas.

Overwinter thermal habitat use in lakes by anadromous Arctic char

Anadromous Arctic char (Salvelinus alpinus) migrate back to fresh water in late summer to spawn and (or) overwinter. Upon freshwater entry, feeding is reduced or absent, and movement activity is restricted. While the physiological responses to low temperatures (e.g., growth, metabolism) are understood, specifics of the use of thermal habitat for overwintering remains poorly characterized. This study used acoustic and archival telemetry data from two lakes in southern Labrador, Canada, to study thermal habitat use during the ice-covered period. Results showed that lake-dwelling anadromous Arctic char predominantly occupied a narrow range of temperatures (0.5–2 °C) and used cooler temperatures available within the middle and upper water column. Use of the selected temperatures is likely a strategy that lowers metabolic costs and minimizes energy expenditure, preserving stored lipids for overwinter survival and the energetic costs of preparation for seaward migration. As Arctic char are visual feeders, use of the upper water column is also thought to aid foraging efficiency by increasing the likelihood of prey capture.

Comparing catch rate, conventional tagging, and acoustic telemetry data for understanding the migration patterns of coastal fishes

While acoustic telemetry (AT) has become the dominant technique for understanding patterns of fish migration, catch rate (CR) and conventional tagging (CT) techniques still play a major role, particularly in developing countries. Understanding the potential biases of each technique is important for fish migration research. We compared these techniques for understanding the migration patterns of two coastal fishery species (Argyrosomus coronus and Lichia amia) in southern Angola. Seasonal fluctuations in the catchability of A. coronus led to incorrect conclusions about migration patterns using CR and CT and we recognised “cryptic residency” during the austral summer. This was attributed to a fine-scale offshore movement that was detected using AT. The AT data provided evidence for partial migration in L. amia, and while supported by the CR and CT data, these did not provide direct evidence for this intraspecific behavioural diversity. Range test results indicated that the optimal placement of nearshore AT receivers is essential, especially when migratory routes proceed along noisy, nearshore pathways. These limitations should be addressed during the design phase of fish migration experiments.

Variation in DNA methylation is associated with migratory phenotypes of lake sturgeon Acipenser fulvescens in the St. Clair River, MI, USA.

Lake sturgeon Acipenser fulvescens populations show a variety of movement patterns that are poorly understood. To compare two migratory phenotypes of A. fulvescens in the St. Clair River, MI, USA, multiple data types were analysed. Individual fish were classified into migratory phenotypes based on acoustic telemetry data collected 2012-2015. Acipenser fulvescens consistently showed movement from the St. Clair River upriver into Lake Huron or downriver into Lake St. Clair. The two migratory phenotypes were then compared for differences in morphometrics, genetics and epigenetics. Morphological differences based on linear measurements were not detected between phenotypes. Microsatellite data from 11 loci suggested one population with no genetic differentiation between migratory phenotypes. Our epigenetic results indicated that the migratory phenotypes are differentially methylated (P < 0.05), thus epigenetics may be associated with migratory differences in A. fulvescens. Only one restriction site was identified to be driving the differential methylation (P < 0.05). While little evidence at neutral loci occurred for genetic differentiation of A. fulvescens, DNA methylation may play a role in the observed movement pattern variation. When combined with microsatellite and morphometric analyses, our results suggested that different migratory patterns may reflect phenotypic plasticity, allowing A. fulvescens to acclimate to short-term environmental variability. Without an integrated approach, the role of epigenetics in the migratory phenotype of A. fulvescens may have been overlooked. Further characterization of migratory phenotypes could be important for management to conserve behavioural variation across the distribution of A. fulvescens and for design of stocking guidelines.

A spatial point process model to estimate individual centres of activity from passive acoustic telemetry data

Abstract Failure to account for time‐varying detection ranges when inferring space use of marine species from passive acoustic telemetry data can bias estimates and result in erroneous biological conclusions. This potential source of bias is widely acknowledged but often ignored in practice due to a lack of available statistical methods. Here, we describe and apply a spatial point process model for estimating individual centres of activity (COAs) from acoustic telemetry data that can be modified to account for both receiver‐ and time‐specific detection probabilities. We use simulation testing to evaluate the suitability of the proposed models for estimating COAs and compare their performance to that of the popular mean‐weighted COA method for a variety of scenarios. We illustrate how the approach can be applied to correct for variable detection ranges by integrating data from moored test tags and demonstrate how accounting for time‐varying detection probabilities can impact space use estimates by fitting the model to data collected from a black sea bass (Centropristis striata) on a receiver array off the east coast of the United States. The proposed model reduced bias in COA estimates, particularly when tagged individuals occurred along the periphery of the receiver array. The test tag‐integrated model largely corrected the bias associated with receiver‐ and time‐specific detection probabilities. When applied to the black sea bass detection data, the model revealed fine‐scale movements not apparent when detection ranges were assumed constant. Spatial management practices for coastal marine species are often based on trends in space use inferred from passive acoustic telemetry data, which can be misinterpreted when factors influencing detection ranges are not accounted for. Our approach provides a general framework for estimating individual COAs that can be modified on a study‐specific basis to ensure resulting patterns of space use reflect a species’ movements and behaviour, rather than variation in receiver detection ranges.

Performance and reliability of active acoustic biotelemetry to best track marine pelagic species in temperate coastal waters

Acoustic tracking is a commonly used method to study the movement ecology of marine species. The characteristics of the data collected are not simply functions of the location of the tagged animal as they are also influenced by the method of data collection and its sampling frequency. In particular, since the data are acoustically driven, the significance of any result hinges not only on the accuracy of the equipment but also on the reliability of the information received. While passive acoustic telemetry requires an evaluation of the detection efficiency of receivers moored in different habitats (or sites) to obtain reliable data, active acoustic telemetry requires more field-related information on how to best track tagged animals without impacting on their natural behaviour. This study aimed to evaluate the reliability of active acoustic telemetry data in a temperate coastal environment. This was achieved by conducting a series of field experiments to assess (i) the use of signal strength-to-infer distance to the tracked animal under different tracking conditions, (ii) what signal strength threshold can be used to obtain reliable bio-telemetered data, (iii) whether the behaviour of a tracked animal would be a main concern in terms of data reliability, and (iv) the best filtering option to reduce the data to be analysed. The findings yielded a signal strength-to-distance relationship to improve the accuracy of the positional fixes of actively tracked animals, which can be used as a practical reference for future tracking studies on pelagic species in temperate coastal environments.