Hydroacoustic Monitoring of Fish Populations

Hydroacoustic monitoring employs active sonar technologies to assess fish populations in freshwater and marine environments. By emitting high-frequency sound pulses and analysing returning echoes, researchers can estimate fish density, biomass and size distribution without physical capture. Multi-frequency and wideband systems enhance species discrimination by exploiting differences in swim-bladder resonance and body composition, while upward-looking and downward-looking transducer configurations facilitate the survey of surface and pelagic layers. Integration with geographic information systems and statistical models elucidates the influence of environmental drivers on spatial and temporal patterns. Autonomous platforms such as uncrewed surface vehicles extend the spatial and temporal reach of surveys, offering continuous data collection under varying conditions. These advances underpin ecosystem-based management, inform marine protected area design and support sustainable fisheries by providing non-invasive, high-resolution insights into fish community dynamics on a global scale.

Research from Nature Portfolio

Recent studies have exploited high-resolution wideband hydroacoustics to differentiate between species based on their spectral backscatter signatures. In controlled mesocosm experiments, spectral data combined with machine learning algorithms have yielded classification accuracies exceeding seventy per cent for similar-sized swim-bladdered fish, pointing to the potential for non-invasive, species-specific monitoring at scale. Elsewhere, real-time hydroacoustic surveys paired with spatial modelling and geographic information systems have revealed pronounced diel shifts in fish distributions within reservoirs, demonstrating aggregation in deep central zones during daylight and dispersal to near-shore slopes at night. These approaches have begun to elucidate fine-scale habitat preferences and movement patterns that underpin ecosystem dynamics.

Hydroacoustic Monitoring of Fish Populations publication trend

The graph below shows the total number of articles in hydroacoustic monitoring of fish populations across all publications each year (not limited to Nature Index journals).

Technical terms

Hydroacoustic monitoring: The use of underwater sound pulses to detect, count and characterise fish populations.

Echosounder: An instrument that emits acoustic pulses and records returning echoes to measure backscatter from aquatic organisms.

Backscatter: The portion of an emitted acoustic signal that is reflected back towards the transducer by fish or other targets.

Target strength: A logarithmic measure of the intensity of acoustic backscatter from an individual fish, used to estimate size and biomass.

Echogram: A visual record of acoustic backscatter returns displayed as a function of time (or distance) and depth.

Wideband hydroacoustics: The collection of acoustic data across a broad frequency range to capture detailed spectral signatures of fish.

References

1. Fishery Resource Evaluation with Hydroacoustic and Remote Sensing in Yangjiang Coastal Waters in Summer. Remote Sensing (2023).
2. Differentiation of two swim bladdered fish species using next generation wideband hydroacoustics. Scientific Reports (2021).
3. A novel upward-looking hydroacoustic method for improving pelagic fish surveys. Scientific Reports (2017).
4. Real-time distribution of pelagic fish: combining hydroacoustics, GIS and spatial modelling at a fine spatial scale. Scientific Reports (2018).
5. Long-term measurements of fish backscatter from Saildrone unmanned surface vehicles and comparison with observations from a noise-reduced research vessel. ICES Journal of Marine Science (2019).
6. Uncrewed surface vehicle (USV) survey of walleye pollock, Gadus chalcogrammus, in response to the cancellation of ship-based surveys. ICES Journal of Marine Science (2021).
7. Comparisons of day-time and night-time hydroacoustic surveys in temperate lakes. Aquatic Living Resources (2020).
8. Hydroacoustics as a tool to examine the effects of Marine Protected Areas and habitat type on marine fish communities. Scientific Reports (2018).