Network analysis of intra- and interspecific freshwater fish interactions using year-around tracking

Abstract

A long-term, yet detailed view into the social patterns of aquatic animals has been elusive. With advances in reality mining tracking technologies, a proximity-based social network (PBSN) can capture detailed spatio-temporal underwater interactions. We collected and analysed a large dataset of 108 freshwater fish from four species, tracked every few seconds over 1 year in their natural environment. We calculated the clustering coefficient of minute-by-minute PBSNs to measure social interactions, which can happen among fish sharing resources or habitat preferences (positive/neutral interactions) or in predator and prey during foraging interactions (agonistic interactions). A statistically significant coefficient compared to an equivalent random network suggests interactions, while a significant aggregated clustering across PBSNs indicates prolonged, purposeful social behaviour. Carp ( Cyprinus carpio ) displayed within- and among-species interactions, especially during the day and in the winter, while tench ( Tinca tinca ) and catfish ( Silurus glanis ) were solitary. Perch ( Perca fluviatilis ) did not exhibit significant social behaviour (except in autumn) despite being usually described as a predator using social facilitation to increase prey intake. Our work illustrates how methods for building a PBSN can affect the network's structure and highlights challenges (e.g. missing signals, different burst frequencies) in deriving a PBSN from reality mining technologies.

Social networks and the conservation of fish

“…To accomplish this, the appropriate study systems need careful selection. We suggest that a reasonable starting point would be to work with existing infrastructure that tracks species of limited movement (e.g., reef fish; 21 ) or that move in enclosed (e.g., lakes 61 ) or semi-enclosed areas (e.g., fjords; 53 ) where social interactions can be tracked continuously for long periods. Much of such infrastructure is already in place with a spatial resolution that is sufficient to infer social interactions.…”

Overwintering aggregation patterns of a freshwater giant

“…For example, shy individuals could be more likely to cooperate whereas bold ones could act more independently (Krause et al, 2008;Conrad et al, 2011). Based on the calculation of a proximity index, Vanovac et al (2021) concluded that cat sh do not display within-species interactions whereas common carp do, especially in winter. We may however question the sensitivity of this index to the sample size of sh.…”

“…Brevé et al (2014) also observed an aggregation of cat sh adults in a river section underneath boats, but just once. Yet, in a small shallow eutrophic lake, Vanovac et al (2021) found that while common carp were aggregating during winter, a stocked population of European cat sh was not. European cat sh are reported to be solitary foragers (Carol et al, 2007), that preferentially feed at night.…”

“…starvation, thermal stress, but this has rarely been studied (Thayer et al, 2017). In freshwater systems, these wintering aggregations have long been described in common carp Cyprinus carpio (Johnsen & Hasler, 1977;Pitcher, 1998;Penne & Pierce, 2008;Bajer et al, 2011;Vanovac et al, 2021) and more recently in another large and long-lived species, the lake sturgeon Acipenser fulvescens, the largest freshwater sh in North America (Thayer et al, 2017). Winter aggregations also occur in centrarchid shes during the light phase of the day (Suski & Ridgway, 2009).…”

Overwintering aggregation patterns of European catfish Silurus glanis

“…starvation, thermal stress, but this has rarely been studied [ 59 ]. In freshwater systems, these wintering aggregations have long been described in common carp Cyprinus carpio [ 3 , 29 , 46 , 48 , 65 ] and more recently in another large and long-lived species, the lake sturgeon Acipenser fulvescens , the largest freshwater fish in North America [ 59 ]. Winter aggregations also occur in centrarchid fishes during the light phase of the day [ 58 ].…”