Acoustic Methods in Fish Population Assessment

Acoustic methods have become indispensable in estimating fish abundance, distribution and behaviour at scales ranging from localised stocks to basin-wide assessments. By emitting sound pulses into the water column and measuring the returning echoes, researchers quantify the density and size structure of fish populations while minimising ecological impact. Key approaches include single-beam and split-beam echosounders for echo integration and target strength measurements, and multifrequency systems that exploit frequency-dependent scattering to distinguish taxa. Advances in backscattering models allow theoretical prediction of reflectivity based on swimbladder morphology, enhancing species discrimination. Integration with visual observations and autonomous platforms extends habitat mapping and behavioural studies into previously inaccessible regions. Recent developments also harness machine-learning techniques to automate data annotation and classification, improving processing speed and consistency. Together, these tools underpin fisheries management, marine spatial planning and conservation, offering cost-effective, non-invasive means to monitor global fish stocks and inform policy.

Research from Nature Portfolio

Recent studies have advanced theoretical and applied aspects of acoustic surveys. One investigation employed X-ray tomography of swimbladders combined with a Kirchhoff Ray Mode model to derive target strength (TS) for Mediterranean pelagic species, revealing frequency- and tilt-dependent backscatter that aligned closely with ex situ measurements. This work broadens species-specific TS databases, facilitating more accurate abundance estimates in data-poor regions. Another study integrated multifrequency acoustics with underwater video to map tropical reef fish assemblages around an oceanic island. By classifying echoes into assemblages and correlating distributions with shelf topography and productivity gradients, the authors provided the first biomass estimate for a key triggerfish and elucidated the spatial dynamics of the island mass effect, yielding insights for marine spatial planning.

Acoustic Methods in Fish Population Assessment publication trend

The graph below shows the total number of articles in acoustic methods in fish population assessment across all publications each year (not limited to Nature Index journals).

Technical terms

Acoustic backscatter: sound energy reflected by a target, used to infer abundance and distribution.

Target Strength (TS): a logarithmic measure of the reflectivity of an individual fish or aggregation.

Echosounder: a sonar instrument that emits acoustic pulses and records returning echoes to assess underwater biomass.

Backscattering model: a computational tool predicting TS from biological and physical parameters such as swimbladder shape and sound frequency.

Acoustic target classification (ATC): the process of assigning acoustic echoes to species or groups, often using statistical or machine-learning methods.

References

1. Application of an analytical approach to characterize the target strength of ancillary pelagic fish species. Scientific Reports (2023).
2. Comprehensive spatial distribution of tropical fish assemblages from multifrequency acoustics and video fulfils the island mass effect framework. Scientific Reports (2022).
3. Self-supervised feature learning for acoustic data analysis. Ecological Informatics (2024).
4. Automated classification of schools of the silver cyprinid Rastrineobola argentea in Lake Victoria acoustic survey data using random forests. ICES Journal of Marine Science (2020).
5. Impacts of Morphological Characteristics on Target Strength of Chub Mackerel (Scomber japonicus) in the Northwest Pacific Ocean. Frontiers in Marine Science (2022).