Acoustic telemetry has long been an effective tool for monitoring the occurrence and behaviors of marine organisms, enabling researchers to address previously unreachable questions regarding fine-scale movement patterns and species interactions. The development and implementation of fine-scale positioning systems (FSPS) has significantly expanded the capacity of acoustic telemetry techniques in recent years. FSPS leverage the time difference of arrival (TDOA) derived from acoustic transmissions at multiple receivers to accurately position tagged animals in space and time.
While FSPS have shown promise in a variety of marine environments, their effective implementation across expansive, dynamic temperate ecosystems poses unique challenges. Factors such as turbidity, tidal regimes, temperature fluctuations, and human activities can impact the performance of acoustic telemetry arrays, potentially reducing detection efficiency and increasing positioning error. Further, the diversity of species life-history strategies associated with temperate assemblages may differentially influence FSPS array performance.
Here, we present the results of an FSPS deployed around a subsea power cable associated with the Ørsted South Fork Wind Farm off the coast of New York. Our goal was to validate the array’s ability to determine fine-scale behaviors across a diverse array of temperate fishes, including highly mobile sharks and rays, as well as more resident species like flounders and skates. Specifically, we examined how positioning error varied in relation to environmental variables, fish movement rates, transmitter power, and after losing 25% of the receivers over the 16-month deployment period.
Our findings suggest that the FSPS can effectively monitor fine-scale behaviors across a wide range of temperate marine fishes, with many species exhibiting both high residency and distinct movement patterns within the array. While we observed some spatial variation in positioning error, with boundary receivers exhibiting higher error, the central portion of the array maintained consistently low horizontal positioning error (HPE) and root-mean-square error (RMSE) despite substantial receiver losses. Generalized linear models revealed that environmental factors like temperature, noise, tilt, and depth were significant predictors of positioning error, though they explained only a small portion of the total variance.
Importantly, we found that higher transmitter power (158 dB) led to larger and more variable HPE values compared to lower power transmitters (146–147 dB). This suggests that the use of lower power tags may be optimal for fine-scale behavioral monitoring, especially for resident species that display high movement tortuosity. Overall, our results demonstrate the broad utility of FSPS for studying the impacts of offshore marine developments on temperate fish assemblages, while also highlighting key considerations for effective array design and deployment in these dynamic environments.
Acoustic Telemetry and Fine-Scale Positioning Systems
Acoustic telemetry has long been a valuable tool for monitoring the occurrence and behaviors of marine organisms, enabling researchers to track the movements of individual animals over broad spatial and temporal scales. In recent years, the development and implementation of fine-scale positioning systems (FSPS) has significantly expanded the capacity of acoustic telemetry techniques. FSPS leverage the time difference of arrival (TDOA) derived from acoustic transmissions at multiple receivers to accurately position tagged animals in space and time, allowing researchers to address previously unreachable questions regarding fine-scale movement patterns and species interactions.
Despite the potential of FSPS, their effective implementation across expansive, dynamic temperate marine environments poses unique challenges. Factors such as turbidity, tidal regimes, temperature fluctuations, and human activities can impact the performance of acoustic telemetry arrays, potentially reducing detection efficiency and increasing positioning error. Furthermore, the diversity of species life-history strategies associated with temperate assemblages may differentially influence FSPS array performance.
Evaluating FSPS Performance in a Temperate Marine Environment
In this study, we present the results of an FSPS deployed around a subsea power cable associated with the Ørsted South Fork Wind Farm off the coast of New York. Our primary goal was to validate the array’s ability to determine fine-scale behaviors across a diverse array of temperate fishes, including highly mobile sharks and rays, as well as more resident species like flounders and skates.
Over a 16-month deployment period, we tracked 260 individuals spanning 17 species within the FSPS, obtaining a total of 53,744 unique positions. The greatest number of individuals were detected for Atlantic sturgeon (n = 120), striped bass (n = 33), and clearnose skate (n = 29), while the highest number of unique positions were estimated for little skate (n = 15,186), summer flounder (n = 13,304), and clearnose skate (n = 10,306).
Analyses of positioning error, as measured by horizontal positioning error (HPE) and root-mean-square error (RMSE), revealed that the FSPS was effective in monitoring fine-scale behaviors across this diverse temperate fish assemblage. While we observed some spatial variation in error, with boundary receivers exhibiting higher HPE and RMSE, the central portion of the array maintained consistently low positioning error despite substantial receiver losses (25%) over the deployment period.
Generalized linear models indicated that environmental factors like temperature, noise, tilt, and depth were significant predictors of positioning error, though they explained only a small portion of the total variance. Importantly, we found that higher transmitter power (158 dB) led to larger and more variable HPE values compared to lower power transmitters (146–147 dB), suggesting that the use of lower power tags may be optimal for fine-scale behavioral monitoring, especially for resident species that display high movement tortuosity.
Implications for Monitoring Offshore Marine Developments
Our results demonstrate the broad utility of FSPS for studying the impacts of offshore marine developments, such as wind farms, on temperate fish assemblages. The ability to accurately track fine-scale behaviors across a diverse array of species, including those that may serve as sentinels for assessing potential impacts, is critical for informing effective management and mitigation strategies.
Moreover, the performance of the FSPS in this dynamic temperate environment, even after substantial receiver losses, highlights the potential of these systems to provide robust, long-term monitoring data to support the responsible development of offshore renewable energy infrastructure. By coupling FSPS with other survey techniques, such as environmental DNA and fisheries-independent monitoring, researchers and resource managers can gain a more comprehensive understanding of the ecological impacts associated with various phases of offshore development.
As global efforts to combat climate change drive the rapid expansion of offshore renewable energy, the insights provided by this study underscore the importance of fine-scale animal movement monitoring in informing the sustainable management of marine environments. The European Future Energy Forum will continue to play a crucial role in advancing these efforts, fostering collaborations between researchers, industry leaders, and policymakers to ensure the responsible development of offshore renewable energy solutions.