High-Throughput Tracking of Social Networks in Marine Fish Populations

Eneko Aspillaga,Margarida Barcelo-Serra,Martina Martorell-Barceló,Josep Alós,Robert Arlinghaus

doi:10.3389/fmars.2021.688010

Abstract

Despite their potential to generate high-quality positioning data, the use of high-resolution acoustic telemetry systems (HRATS) has been neglected in coastal marine areas due to the limitations that these environments pose to the transmission of acoustic signals. In this work, we applied a HRATS and social network analysis (SNA) to study the social interactions of the pearly razorfish (Xyrichtys novacula), a small coastal wrasse, in a Mediterranean marine reserve. Our analysis was based on proximity measures estimated from high-resolution trajectories from 232 individuals tracked during 55 days within a marine protected area. Associations were defined as the proportion of 5-min intervals in which two individuals were observed within 1 m from each other, and social networks were generated for the overall tracking period and for each particular day. The obtained network parameters were contrasted against 1,000 null association models obtained by randomly redistributing individual trajectories within the study area. The obtained networks showed a harem-like social structure, with agonistic behavior between males and larger association indices between individuals of different sex. Occasionally, sporadic associations of large groups of females were observed conducting excursions along the study area. By providing a comprehensive view of the organizational structure of the pearly razorfish, our study demonstrates the potential of HRATS to efficiently produce high-throughput tracking data from large numbers of individuals and of proper null social model formulation to reconstruct the social networks in wild-living marine fish populations. The combination of HRATS and SNA represents a powerful tool to study key ecological processes regarding the social interactions of individuals, including social dynamics, collective movements, and the response to environmental perturbations.

Highlights

The complex social interactions that occur within populations and communities are a fundamental aspect in ecological research aimed at understanding the functioning of ecosystems and their resilience to external perturbations (Tylianakis et al, 2008; Ings et al, 2009)
The objective of our study was to test the performance of highresolution acoustic telemetry systems (HRATS) and Social Network Analysis (SNA) characterizing the social structure of a freeliving fish population in a marine environment, using the pearly razorfish (Xyrichtys novacula, Labridae) as a study species
The average weight of MM and MF associations were significantly smaller and larger, respectively, than the average weights obtained from random networks (p < 0.001), indicating an active avoidance of males toward other males and an association preference between males and females

Summary

Introduction

The complex social interactions that occur within populations and communities are a fundamental aspect in ecological research aimed at understanding the functioning of ecosystems and their resilience to external perturbations (Tylianakis et al, 2008; Ings et al, 2009). The popularization of miniaturized GPS and other tracking devices has dramatically increased our ability to monitor the movements of terrestrial animals (Rutz et al, 2012; Kays et al, 2015), providing precise positioning data that allows interaction networks to be derived from the spatial proximity of individuals (Whitehead, 2008; Farine, 2015). Recent analysis tools, such as the utilization of random null models to infer the significance of the obtained network (Farine, 2017; Davis et al, 2018; Pasquaretta et al, 2021), provide analytical methods to obtain robust estimations of the observed social structures (Spiegel et al, 2016)

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