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Testing the VEMCO Positioning System: Spatial distribution of the probability of location and the positioning error in a reservoir
Abstract and Figures
Background
Recent improvements in fixed acoustic monitoring receivers allow the tracking of individual aquatic animals over long periods of time with regular fine-scale positions. The VEMCO Positioning System (VPS) is now widely used, but various methodological issues remain to be clarified. The aim of this study was to analyze the spatial distribution of the probability of location and the positioning error over the entire surface of a hydropower reservoir, prior to analyzing fish behavior.
Findings: Filtering the data set by the horizontal position error (HPE) significantly reduced the positioning error. Retaining only the positions with an HPE less than 15 retained 79% of VPS positions and decreased the positioning error by 33% (mean = 3.3 m, SD = 3.3 m). A higher probability of location was observed inside than outside the receiver array (44% and 36%, respectively). Moreover, the positioning error significantly differed inside (n = 243, mean = 2.4 m, SD = 2.1 m) and outside (n = 253, mean = 4.2 m, SD = 4.0 m) the receiver array (P < 0.001). Finally, the lowest positioning errors were detected in the area with the highest receiver density.
Conclusions
The VPS measures fish positioning in a reservoir, under suitable conditions, with satisfactory accuracy. We showed that the probability of location and the positioning error differed spatially in accordance with previous results in other conditions. Consequently, these analyses are recommended as a prerequisite to further spatial analyses using VPS-derived data.
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... VPS calculates one basic position for every possible group of three receivers that detected a given transmission, which is then combined to calculate a synthesized position [182]. Positional error is expressed as Horizontal Position Error (HPE), a relative unitless estimate of error sensitivity used to retain the highest quality estimated positions [62,167], which is not comparable across studies because calibration is specific to each study [182]. Higher HPE means a calculated position is more sensitive to measurement errors, hence, a lower HPE is preferred [162,182]. ...
... The accuracy estimation of calculated positions requires stationary transmitters at known locations to compare with [182]. Even though high-resolution of positions are obtained with systems like VPS or PinPoint, the data may still need to be filtered before analyzing it as suggested by some authors (e.g., [130,167]. For example, filtering VPS data by the HPE can greatly reduce the positioning error in the data set [130,167]. ...
... Even though high-resolution of positions are obtained with systems like VPS or PinPoint, the data may still need to be filtered before analyzing it as suggested by some authors (e.g., [130,167]. For example, filtering VPS data by the HPE can greatly reduce the positioning error in the data set [130,167]. ...
Acoustic telemetry has helped overcome many of the challenges faced when studying the movement ecology of aquatic species, allowing to obtain unprecedented amounts of data. This has made it into one of the most widely used methods nowadays. Many ways to analyse acoustic telemetry data have been made available and deciding on how to analyse the data requires considering the type of research objectives, relevant properties of the data (e.g., resolution, study design, equipment), habits of the study species, researcher experience, among others. To ease this decision process, here we showcase (1) some of the methods used to estimate pseudo-positions and positions from raw acoustic telemetry data, (2) methods to estimate residency and (3) methods to estimate two-dimensional home and occurrence range using geometric or hull-based methods and density-distribution methods, a network-based approach, and three-dimensional methods. We provide examples of some of these were tested using a sample of real data. With this we intend to provide the necessary background for the selection of the method(s) that better fit specific research objectives when using acoustic telemetry.
... Best practice is to tow a transmitter whose position is continuously recorded by dGPS through the array, and then to compare the dGPS positions with those estimated by the positioning algorithm (e.g. Aspillaga, Arlinghaus, Martorell-Barceló, Follana-Berná, et al., 2021;Baktoft et al., 2015;Baktoft et al., 2017;Leander et al., 2020;Roy et al., 2014). Ideally, the test should be performed at different depths and across different habitats, representing what is expected from the targeted species (e.g. ...
... Importantly, and especially for species known to prefer nearshore habitats, it is recommended to perform tests inside and outside the array, as performances can vary between both (e.g. Roy et al., 2014). The speed and turning angles of the towed tags should also be in agreement with the movement characteristics of the targeted species. ...
Geolocating aquatic animals with acoustic tags has been ongoing for decades, relying on the detection of acoustic signals at multiple receivers with known positions to calculate a 2D or 3D position, and ultimately recreate the path of an aquatic animal from detections at fixed stations.
This method of underwater geolocation is evolving with new software and hardware options available to help investigators design studies and calculate positions using solvers based predominantly on time‐difference‐of‐arrival and time‐of‐arrival.
We provide an overview of the considerations necessary to implement positioning in aquatic acoustic telemetry studies, including how to design arrays of receivers, test performance, synchronize receiver clocks and calculate positions from the detection data. We additionally present some common positioning algorithms, including both the free open‐source solvers and the ‘black‐box’ methods provided by some manufacturers for calculating positions.
This paper is the first to provide a comprehensive overview of methods and considerations for designing and implementing better positioning studies that will support users, and encourage further knowledge advances in aquatic systems.
... density) and surrounding environment (e.g. water velocity) can affect both detection efficiency (resulting in tracks with irregular time interval) and positional error in an array (Bergé et al. 2012, Roy et al. 2014). Assessments of positional error were performed using HPE, which is a relative and unitless estimate of error potential for a calculated position. ...
... Prior analysis of the VPS determined an HPE value of 16 to be the optimal threshold for positional accuracy without reducing too much of the dataset via filtering (Golder Associates Ltd 2015). This value lies within the typical 10 to 20 HPE threshold range of other VPS studies (Roy et al. 2014). Positions with HPE >16 were considered inaccurate and excluded from the final dataset. ...
Acoustic telemetry allows for fine-scale, or positional, tracking of fish in localised environments, and advancement in analytical techniques allows for quantifiable patterns in fish movement and behaviour. White sturgeon Acipenser transmontanus in the regulated Upper Columbia River are listed as endangered in Canada due to their considerable decline over the last century. An
improved understanding of where, when, and why white sturgeon move in relation to river regulation is important for species recovery. A VEMCO Positioning System was used to collect the positions of white sturgeon in critical habitats immediately downstream of a dam on the Upper Columbia River over a 1 yr period. We applied hidden Markov models and generalised linear mixed models to (1) identify ecologically meaningful movement behaviours within the positions dataset; and (2) investigate the relationships between movement behaviour and biological (sex) and environmental (e.g. discharge, temperature, habitat) factors. Two behaviour states were identified: ‘residential’, characterised by short movements with less frequent turns, and ‘exploratory’, characterised by longer movements with more frequent turns. Water temperature largely influenced the mean weekly probability of a behaviour state, while discharge influenced the spatial distribution of movement behaviours. Changes in movement patterns were also apparent across seasons, with a higher occurrence of residential behaviour in the winter and spring and exploratory behaviour in the summer and fall. Results will help inform species recovery measures, such as overall flow management and optimization of operations to reduce impacts of river regulation.
... The data for triangulated positioning of the fish locations were derived from tag signal detections using Fathom Position software (Innovasea Systems Inc.). Fish positions with horizontal position error greater than 15 were filtered from the original data set (i.e., 4%) to reduce precision error (Roy et al. 2014). In addition, some fish were filtered from the data set and analyses based on the following criteria: (1) lacking position data for two or more daily periods, (2) confirmed to have emigrated due to detections on the receiver gate beyond the study area inlet, and (3) presumed to have shed their transmitter and/or died as determined via trajectory analysis (McLean and Skowron Volponi 2018). ...
Objective
The removal of invasive Silver Carp Hypophthalmichthys molitrix is a primary control action in North America. Strong avoidance responses to underwater sound and electricity have been shown to facilitate herding and mass removal of these fish. We conducted a telemetry study on a closed population of Silver Carp (i.e., 10 telemetered fish) to assess fine‐scale movement responses to herding stimuli.
Methods
Two herding boats traveled along bank‐to‐bank transects through the study area (longitudinal progression rate = 0.37 m/s) emitting sound and electricity (“combination technique”) or no added stimuli (“control”).
Result
The combination technique was most effective in terms of increasing fish presence (2.2 × the control) in the refuge zones when herding had concluded and effective range (i.e., fish reaction distance; 1.6 × the control) relative to the herding boats. The median (~1 m/s) and maximum (~2 m/s) swimming velocity was relatively stable across fixed effects, except for the negative influence of water depth on maximum velocity. Water depth also exhibited a negative effect on fish reaction distance.
Conclusion
Our results suggest that the effective range of the combination technique was conservatively 200 m (~20 dB re 1 μPa > ambient level) when accounting for water depth in the study area. Herding deployments <1 m/s (longitudinal progression) could control fish passing and maintain fish movements toward an intended location. The information provided herein can serve to assist planning, designing, and applying herding efforts to manage, control, and remove these invasive fish.
... Acoustic telemetry is a powerful method for quantifying the movement of marine organisms and has been broadly applied in fisheries research [2,3,14]. Recently, hyperbolic positioning systems have allowed researchers to track animals at increasingly fine spatiotemporal scales (e.g., metres and minutes; see Hyperbolic positioning for technical details; [15][16][17]). In addition, accelerometry has enabled detailed insight into the behavioural structure of animal movement [18,19]. ...
Background
Effective fisheries management of mobile species relies on robust knowledge of animal behaviour and habitat-use. Indices of behaviour can be useful for interpreting catch-per-unit-effort data which acts as a proxy for relative abundance. Information about habitat-use can inform stocking release strategies or the design of marine protected areas. The Giant Mud Crab (Scylla serrata; Family: Portunidae) is a swimming estuarine crab that supports significant fisheries harvest throughout the Indo-West Pacific, but little is known about the fine-scale movement and behaviour of this species.
Methods
We tagged 18 adult Giant Mud Crab with accelerometer-equipped acoustic tags to track their fine-scale movement using a hyperbolic positioning system, alongside high temporal resolution environmental data (e.g., water temperature), in a temperate south-east Australian estuary. A hidden Markov model was used to classify movement (i.e., step length, turning angle) and acceleration data into discrete behaviours, while also considering the possibility of individual variation in behavioural dynamics. We then investigated the influence of environmental covariates on these behaviours based on previously published observations.
Results
We fitted a model with two well-distinguished behavioural states describing periods of inactivity and foraging, and found no evidence of individual variation in behavioural dynamics. Inactive periods were most common (79% of time), and foraging was most likely during low, incoming tides; while inactivity was more likely as the high tide receded. Model selection removed time (hour) of day and water temperature (°C) as covariates, suggesting that they do not influence Giant Mud Crab behavioural dynamics at the temporal scale investigated.
Conclusions
Our study is the first to quantitatively link fine-scale movement and behaviour of Giant Mud Crab to environmental variation. Our results suggest Giant Mud Crab are a predominantly sessile species, and support their status as an opportunistic scavenger. We demonstrate a relationship between the tidal cycle and foraging that is likely to minimize predation risk while maximizing energetic efficiency. These results may explain why tidal covariates influence catch rates in swimming crabs, and provide a foundation for standardisation and interpretation of catch-per-unit-effort data—a commonly used metric in fisheries science.
... Outside the grid, our system is slightly limited with a median error of 10.97 m compared to the median error of 4.12 m with the VPS-VR2W (Innovasea, Boston, MA, USA), corresponding to a 6.85 m difference in positioning error. Nonetheless, it is still demonstrating encouraging performances, with an average positioning difference of 2.13 m compared to the VPS-VR2W, whose results are from [16]. ...
Recent acoustic telemetry positioning systems are able to reconstruct the positions and trajectories of organisms at a scale of a few centimeters to a few meters. However, they present several logistical constraints including receiver maintenance, calibration procedures and limited access to real-time data. We present here a novel, easy-to-deploy, energy self-sufficient underwater positioning system based on the time difference of arrival (TDOA) algorithm and the Global System for Mobile (GSM) communication technology, capable of locating tagged marine organisms in real time. We provide an illustration of the application of this system with empirical examples using continuous and coded tags in fish and benthic invertebrates. In situ experimental tests of the operational system demonstrated similar performances to currently available acoustic positioning systems, with a global positioning error of 7.13 ± 5.80 m (mean ± SD) and one-third of the pings can be localized within 278 m of the farthest buoy. Despite some required improvements, this prototype is designed to be autonomous and can be deployed from the surface in various environments (rivers, lakes, and oceans). It was proven to be useful to monitor a wide variety of species (benthic and pelagic) in real time. Its real-time property can be used to rapidly detect system failure, optimize deployment design, or for ecological or conservation applications.
Many fish species depend on migration for various parts of their life cycle. Well‐known examples include diadromous fish such as salmon and eels that need both fresh water and salt water to complete their life cycle. Migration also occurs within species that depend only on fresh water. In recent decades, anthropogenic pressures on freshwater systems have increased greatly, and have resulted, among other effects, in drastic habitat fragmentation. Fishways have been developed to mitigate the resulting habitat fragmentation, but these are not always effective. To improve fishway efficiency, the variety of navigation cues used by fish must be better understood: fish use a multitude of sensory inputs ranging from flow variables to olfactory cues. The reaction of a fish is highly dependent on the intensity of the cue, the fish species involved, and individual traits. Recently developed monitoring technologies allow us to gain insights into different combinations of environmental and physiological conditions. By combining fish behavioural models with environmental models, interactions among these components can be investigated. Several methods can be used to analyse fish migration, with state‐space models, hidden Markov models, and individual‐based models potentially being the most relevant since they can use individual data and can tie them to explicit spatial locations within the considered system. The aim of this review is to analyse the navigational cues used by fish and the models that can be applied to gather knowledge on these processes. Such knowledge could greatly improve the design and operation of fishways for a wider range of fish species and conditions.
To understand the behavior of the large yellow croaker ( Larimichthys crocea ) in a pen aquaculture setting, three individuals in each of two experimental groups were telemetered in meter scale by four cable-synchronized hydrophones. The ultrasound pinger system was applied to track the motion of six L. crocea for 24 h using two fixation methods, i.e., implanting tags in the abdomen (the in vivo implantation group) and hanging tags on the dorsal fin (the dorsal fin suspension group). Pingers repeated unique 62.5 kHz coded signals at 5 s intervals along with a pressure signal. The results showed that fish tagged with internal pingers took approximately 3 h longer than externally tagged fish to stabilize in their behavior, as measured by depth utilization; the horizontal movements of the test fish were mostly found outside of the fence, where the test fish performed round-trip swimming, with the least probability of appearing near the production platform and more frequent activities in the feeding areas.
We proposed a simple hyperbolic positioning method that does not require solving simultaneous quadratic equations. Moreover, we introduced the mathematical concept of a “pencil” into analytical calculations in the hyperbolic positioning method for a better understanding. In many recent studies using positioning biotelemetry, the specific procedure for intersection calculation of hyperbolas has rarely been described. This might be one of two major obstacles, with the other being clock synchronisation among receivers, for positioning biotelemetry users, including potential users. We focus only on the intersection calculation in this paper. Therefore, we propose a novel method and introduce the mathematical concept into analytical calculations. The computing performances of the novel method, an analytical method applying the concept of a pencil, and an approximating method using the Newton-Raphson method were compared regarding positioning correctness, accuracy, and calculation speed. In the novel method, hyperbolas were represented using the parameter θ , which was treated as a discrete variant. The finer the tick-width of the parameter θ , the more accurate was its positioning, but it took slightly longer to calculate. By setting the tick-width to 0.01°, a simulated trajectory was correctly and accurately localised, as in the analytical method which always correctly returned the accurate solution. The approximating method has a major limitation concerning correctness. It returns a single solution regardless of two intersections of hyperbolas; however, the positioning is accurate when the hyperbolas intersect at a single point. This study approached one major difficulty in positioning biotelemetry and will help biotelemetry users overcome this drawback with a simple and intuitive understanding of hyperbolic positioning.
Acoustic telemetry systems are an increasingly common way to examine the movement and behaviour of marine organisms. However, there has been little published on the methodological and analytical work associated with this technology. We tested transmitters of differing power outputs simultaneously in several trials, some lasting ~50 days, to examine the effects of power output and environmental factors (water movement, temperature, lunar cycle and time of day). There were considerable and volatile changes in detections throughout all trials. Increased water movement and temperature significantly reduced detection rates, whereas daytime and full-moon periods had significantly higher detection rates. All nine transmitters (from seven transmitter types tested) showed a sigmoidal trend between detection frequency and distance. Higher-powered transmitters had a prolonged detection distance with near-maximal detections, whereas lower-powered transmitters showed an almost immediate decline. Variation of detection frequency, transmitter type and the modelled relationship between distance and detection frequency were incorporated into a positioning trial which resulted in markedly improved position estimates over previous techniques.
We examined movement tracks of ultrasonic-tagged juvenile Chinook salmon (Oncorhynchus tshawyscha) smolts at the juncture of two migratory pathways. This migratory juncture occurs where the Delta Cross Channel splits from the Sacramento River in California’s Sacramento–San Joaquin Delta. Smolt tracks were analyzed to compare the importance of river flow and individual parameters in migratory route selection. The two routes differ significantly in smolt survival probabilities (Perry et al. N Am J Fish Manag 30:142–156, 2010), thus a clearer understanding of the variables contributing to route selection will be valuable for management of this declining species. A comparison of the two migratory groups showed that fish remaining within the Sacramento River: 1) Encountered the migratory juncture when river water velocities were much higher than those in the Delta Cross Channel (p < 0.0001), 2) showed more direct swimming paths (p = 0.03) and 3) migrated at higher speeds (p = 0.04). Logistic regression models showed that the ratio of mean water velocity between the two routes was a much stronger predictor of ultimate route selection than any other variable tested. However, parameters for both the lateral position of smolts within the river and smolt size added predictive power to the final model. Our results suggest that river flow remains the most important variable for predicting smolt migration route, but note that knowledge of individual smolt attributes and movement patterns can increase our predictive ability.
Atlantic cod Gadus morhua exhibit multiyear homing to discrete spawning grounds, where they aggregate in dense schools. Within an aggregation, a series of complex mating behaviors takes place before mate selection and successful spawning. Disruption of these behaviors has been suggested as a cause of diminished reproductive success and poor recruitment in some stocks. An area known to support a spawning aggregation in Massachusetts Bay was closed to both commercial and recreational fishing for the months of May and June 2009. During the closure period, 10 Atlantic cod were captured, tagged with acoustic transmitters, and released back to the aggregation. Four stationary acoustic receivers were deployed in the area to record transmissions from the tagged fish. Overlapping detection ranges of the receivers allowed for the reconstruction of fine‐scale movements of the tagged fish over several days. The tagged cod showed a consistent pattern of aggregation prior to the fishery, characterized by limited movement and similar space use. With the opening of the fishery, the aggregation behavior was disrupted, resulting in increased horizontal and vertical movements and dissimilar space use among individuals. Half of the tagged fish appeared to have been caught in gill nets within 9 h of the opening, while the remainder left the area within 18 h. Even though the receivers were maintained for 9 d after the opening, none of the tagged fish that left the area returned. These results indicate that the spawning aggregation was completely dispersed by the onset of the fishery. Managers hoping to protect spawning aggregations should be aware that the effects of fishing on a spawning aggregation go beyond the removals from the spawning stock.
Received May 3, 2011; accepted October 13, 2011
We attached sonic transmitters to, and tracked, 40 giant Pacific octopuses (Enteroctopus dofleini) ranging from < 1 to 21 kg in size in south-central Alaska using near-continuous tracking by fixed-array receivers and intermittent tracking with a mobile receiver. We documented area use, daily activity patterns, spatial scale of movements and whether these differed by octopus size, and whether octopuses actively selected habitats. Near-continuous fixed tracking provided positions about every 4 min over a limited area, while intermittent mobile tracking provided positions every 1–6 h but over open and larger areas. Mantle-mounted transmitters on modified Peterson disks had > 83% retention to the end of a tracking period (range < 1 day [before animal left the study area] to at least 88 days post-release), an improvement over published studies. Octopuses were found to be stationary or hiding 94% of the time. Otherwise, octopuses were active throughout the day but more so from midnight to 0500. During low tides, movements were restricted for animals in intertidal habitats but not for those deeper. Maximum movement distance from release was 4.8 km (by a 16.5 kg female). Minimum convex polygon area use averaged 4,300 m2 for the smallest animals to an average over 50,000 m2 for the largest during 2 to 20 days of tracking, substantially larger than previously reported. Larger octopuses moved further and used greater area than smaller animals, but differences between sexes were not significant.
The development of miniature acoustic transmitters and economical, robust automated receivers has enabled researchers to study the movement patterns and survival of teleosts in estuarine and ocean environments, including many species and age-classes that were previously considered too small for implantation. During 2001–2003, we optimized a receiver mooring system to minimize gear and data loss in areas where current action or wave action and acoustic noise are high. In addition, we conducted extensive tests to determine (1) the performance of a transmitter and receiver (Vemco, Ltd.) that are widely used, particularly in North America and Europe and (2) the optimal placement of receivers for recording the passage of fish past a point in a linear-flow environment. Our results suggest that in most locations the mooring system performs well with little loss of data; however, boat traffic remains a concern due to entanglement with the mooring system. We also found that the reception efficiency of the receivers depends largely on the method and location of deployment. In many cases, we observed a range of 0–100% reception efficiency (the percentage of known transmissions that are detected while the receiver is within range of the transmitter) when using a conventional method of mooring. The efficiency was improved by removal of the mounting bar and obstructions from the mooring line.