Environmental factors influence the detection probability in acoustic telemetry in a marine environment : results from a new setup

Acoustic telemetry is a commonly applied method to investigate the ecology of marine animals and provides a scientific basis for management and conservation. Crucial insight in animal behaviour and ecosystem functioning and dynamics is gained through acoustic receiver networks that are established in many different environments around the globe. The main limitation to this technique is the ability of the receivers to detect the signals from tagged animals present in the nearby area. To interpret acoustic data correctly, understanding influencing factors on the detection probability is critical. Therefore, range test studies are an essential part of acoustic telemetry research. Here, we investigated whether specific environmental factors (i.e. wind, currents, waves, background noise, receiver tilt and azimuth) influence the receiver detection probability for a permanent acoustic receiver network in Belgium. Noise and wind speed in relation to distance, the interaction of receiver tilt and azimuth and current speed were the most influential variables affecting the detection probability in this environment. The study indicated that there is high detection probability up to a distance of circa 200 m. A new setup, making use of features that render valuable information for data analysis and interpretation, was tested and revealed general applicability

The need for aquatic tracking networks : the Permanent Belgian Acoustic Receiver Network

Abstract Aquatic biotelemetry techniques have proven to be valuable tools to generate knowledge on species behaviour, gather oceanographic data and help in assessing effects from anthropogenic disturbances. These data types support international policies and directives, needed for species and habitat conservation. As aquatic systems are highly interconnected and cross administrative borders, optimal data gathering should be organized on a large scale. This need triggered the development of regional, national and international aquatic animal tracking network initiatives around the globe. In Belgium, a national acoustic receiver network for fish tracking, called the Permanent Belgian Acoustic Receiver Network, was set up in 2014 with different research institutes collaborating. It is a permanent network with 160 acoustic receivers and since the start, over 800 animals from 16 different fish species have been tagged and generated more than 17 million detections so far. To handle all the (meta)data generated, a data management platform was built. The central database stores all the data and has an interactive web interface that allows the users to upload, manage and explore (meta)data. In addition, the database is linked to an R-shiny application to allow the user to visualize and download the detection data. The permanent tracking network is not only a collaborative platform for exchange of data, analysis tools, devices and knowledge. It also creates opportunities to perform feasibility studies and Ph.D. studies in a cost-efficient way. The Belgian tracking network is a first step towards a Pan-European aquatic tracking network

Transcending boundaries in fish movement ecology through the European Tracking Network

6th International Conference on Fish Telemetry, Sète (France), 11-16 June 2023In the marine realm, few barriers exist to limit the extent of animal migrations. As a result, mobile marine animals can occupy vast home ranges and undertake migrations that span across entire ocean basins. These large-scale movements can in turn, complicate both research and management occurring at local or regional scales. Advances in aquatic telemetry are continuing to allow researchers to monitor marine animal movements across greater distances and with increasing resolutions. However, for acoustic telemetry studies that typically use an array of fixed receivers to detect presence of tagged animals moving within a defined region, the spatial scale of acquired movement data is often restricted to regions delimited by invisible geographic or jurisdictional boundaries. To overcome this limitation, acoustic telemetry networks such as the European Tracking Network have been established to facilitate collaboration among movement ecologists and to house archives of detection data for more efficient data sharing. By combining the detections of individual tagged animals recorded across multiple discrete arrays, the extent of monitoring can be greatly expanded to reflect more ecologically-relevant spatial and temporal scales. To exemplify the benefit of the acoustic telemetry networks for large-scale collaboration and fundamental research on migratory fish, we have compiled examples of movement trajectories collected by an international group of researchers using multiple acoustic arrays and spanning national or international boundaries. From basin-wide migrations to cross-continental displacements, this diverse dataset demonstrates how connectivity between acoustic telemetry arrays and research institutes can lead to novel insights in movement ecology for a range of fish speciesN

Herrie onder water : Hoe geluid het gedrag van kabeljauw beïnvloedt

Er worden steeds meer aanwijzingen gevonden dat vissen worden beïnvloed door geluid van menselijke activiteiten op zee. De gevolgen hiervan voor populaties op lange termijn zijn nog onduidelijk, zo ook voor de Noordzeekabeljauw. Gecombineerd onderzoek geeft een eerste beeld van de mogelijke effecten vanseismisch onderzoek op het gedrag van deze vis

Archival data series and acoustic detections of acoustic data storage tags in the southern North Sea

Acoustic data storage tag (ADST) data, providing acoustic detections and archival depth and temperature series for Dicentrarchus labrax, Gadus morhua and Mustelus asterias.Acoustic data storage tag (ADST) data and metadata of 109 Dicentrarchus labrax, 15 Gadus morhua and 30 Mustelus asterias, tagged in the southern North Sea. Data include archival temperature and depth histories, acoustic detections and reconstructed trajectories. Metadata regard the tagged animals, the tags and the acoustic receiver deployments

Evaluating Acoustic Positional Telemetry designs for research on Atlantic cod around wind turbines

Evaluation of receiver contribution to the performance of two Acoustic Positional Telemetry (APT) designs for research on Atlantic cod with seasonally high site fidelity around offshore wind turbines

Evaluating receiver contributions to acoustic positional telemetry : a case study on Atlantic cod around wind turbines in the North Sea

Background: The effect of individual acoustic receiver contributions to animal positioning is a crucial aspect for the correct interpretation of acoustic positional telemetry (APT). Here, we evaluated the contribution of each receiver within two APT designs to the number of tag signals detected and the position accuracy of free-ranging Atlantic cod, through data exclusion of single receivers from the analysis. The two APTs were deployed around offshore (ca 50 km) wind turbines at which 27 individual cod were tagged. Results: We found that the exclusion of data from an APT receiver that was positioned within the movement area of the individual fish reduced the number of tag signals detected and the position accuracy of the set-up the most. Excluding the data from a single receiver caused a maximum of 34% positions lost per fish and a maximum increase in core area of 97.8%. Single-receiver data exclusion also caused a potentially large bias in the reconstruction of swimming tracks. By contrast, exclusion of a receiver that was deployed within 50 m from a turbine actually improved fish position accuracy, probably because the turbine can cause signal interference as a reflective barrier. Conclusions: We recommend that an exploratory small-scale study like the one presented here be conducted before embarking on a larger-scale APT study. By excluding the data of single receivers from the positioning analysis, we were able to explore the suitability of a receiver set-up for the movement patterns of our target species. Furthermore, when a receiver is lost from an APT during deployment, the data should be treated with care as our results show that changes in triangulation outcome can lead to considerable differences in swimming tracks and home range estimates.</p

Atlantic cod acoustic telemetry dataset used to assess impact of a multi-day full-scale seismic survey experiment on the behaviour of free-ranging cod at a wind farm

Effects of a full-scale seismic survey experiment on the movement behaviour of Atlantic cod

Effects of a seismic survey on movement of free-ranging Atlantic cod

Geophysical exploration of the seabed is typically done through seismic surveys, using airgun arrays that produce intense, low-frequency-sound pulses1 that can be heard over hundreds of square kilometers, 24/7.2,3 Little is known about the effects of these sounds on free-ranging fish behavior.4–6 Effects reported range from subtle individual change in activity and swimming depth for captive fish7,8 to potential avoidance9 and changes in swimming velocity and diurnal activity patterns for free-swimming animals.10 However, the extent and duration of behavioral responses to seismic surveys remain largely unexplored for most fish species.4 In this study, we investigated the effect of a full-scale seismic survey on the movement behavior of free-swimming Atlantic cod (Gadus morhua). We found that cod did not leave the detection area more than expected during the experimental survey but that they left more quickly from 2 days to 2 weeks after the survey. Furthermore, during the exposure, cod decreased their activity, with time spent being “locally active” (moving small distances, showing high body acceleration) becoming shorter, and time spent being “inactive” (moving small distances, having low body acceleration) becoming longer. Additionally, diurnal activity cycles were disrupted with lower locally active peaks at dusk and dawn, periods when cod are known to actively feed.11,12 The combined effects of delayed deterrence and activity disruption indicate the potential for seismic surveys to affect energy budgets and to ultimately lead to population-level consequences.13 van der Knaap et al. show that exposure to a seismic survey caused delayed deterrence of free-ranging Atlantic cod. During sound exposure, cod became less active at dusk and dawn, interrupting their diurnal activity cycle. These effects indicate the potential for anthropogenic noise to affect energy budgets and to have population-level consequences.</p