Quantifying the interplay between environmental and social effects on aggregated-fish dynamics

TL;DR

This study combines acoustic tracking and modeling to quantify how social interactions and external stimuli influence fish aggregation patterns in natural, heterogeneous environments.

Contribution

It introduces a novel field-based modeling approach that integrates experimental data to distinguish social and external effects on fish dynamics.

Findings

Social interactions significantly influence fish aggregation structure.

External stimuli like floating objects attract fish and shape their spatial distribution.

The model accurately reproduces observed fish movement patterns around stimuli.

Abstract

Demonstrating and quantifying the respective roles of social interactions and external stimuli governing fish dynamics is key to understanding fish spatial distribution. If seminal studies have contributed to our understanding of fish spatial organization in schools, little experimental information is available on fish in their natural environment, where aggregations often occur in the presence of spatial heterogeneities. Here, we applied novel modeling approaches coupled to accurate acoustic tracking for studying the dynamics of a group of gregarious fish in a heterogeneous environment. To this purpose, we acoustically tracked with submeter resolution the positions of twelve small pelagic fish (Selar crumenophthalmus) in the presence of an anchored floating object, constituting a point of attraction for several fish species. We constructed a field-based model for aggregated-fish dynamics, deriving effective interactions for both social and external stimuli from experiments. We tuned the model parameters that best fit the experimental data and quantified the importance of social interactions in the aggregation, providing an explanation for the spatial structure of fish aggregations found around floating objects. Our results can be generalized to other gregarious species and contexts as long as it is possible to observe the fine-scale movements of a subset of individuals.