A methodological framework for characterizing fish swimming and escapement behaviors in trawls

Type Article
Date 2020-12
Language English
Author(s) Robert Marianne1, Cortay Aurore1, Morfin Marie1, Simon Julien1, Morandeau Fabien1, Deneubourg Jean Louis2, Vincent Benoit1
Affiliation(s) 1 : Ifremer, LTBH (Laboratory of Fisheries Technology and Biology), Lorient, France.
2 : Center for Nonlinear Phenomena and Complex Systems, Université libre de Bruxelles, Bruxelles, Belgium.
Source Plos One (1932-6203) (Public Library of Science (PLoS)), 2020-12 , Vol. 15 , N. 12 , P. e0243311 (17p.)
DOI 10.1371/journal.pone.0243311

Knowledge about fish behavior is crucial to be able to influence the capture process and catch species composition. The rapid expansion of the use of underwater cameras has facilitated unprecedented opportunities for studying the behavior of species interacting with fishing gears in their natural environment. This technological advance would greatly benefit from the parallel development of dedicated methodologies accounting for right-censored observations and variable observation periods between individuals related to instrumental, environmental and behavioral events. In this paper we proposed a methodological framework, based on a parametric Weibull mixture model, to describe the process of escapement attempts through time, test effects of covariates and estimate the probability that a fish will attempt to escape. We additionally proposed to better examine the escapement process at the individual level with regard to the temporal dynamics of escapement over time. Our approach was used to analyze gadoids swimming and escapement behaviors collected using a video set up in front of a selective device known to improve selectivity on gadoids in the extension of a bottom trawl. Comparison of the fit of models indicates that i) the instantaneous rate of escape attempts is constant over time and that the escapement process can be modelled using an exponential law; ii) the mean time before attempting to escape increases with the increasing number of attempts; iii) more than 80% of the gadoids attempted to escape through the selective device; and iv) the estimated probability of success was around 15%. Effects of covariates on the probability of success were investigated using binomial regression but none of them were significant. The data set collected is insufficient to make general statements, and further observations are required to properly investigate the effect of intrinsic and extrinsic factors governing gadoids behavior in trawls. This methodology could be used to better characterize the underlying behavioral process of fish in other parts of a bottom trawl or in relation to other fishing gears.

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Publisher's official version 17 1 MB Open access
S1 Fig. Time budget comparison between the two video recordings. 52 KB Open access
S2 Fig. Comparison of escapement attempt location between the two video recordings. 45 KB Open access
S3 Fig. Number of gadoids observed in the field of view per second in video 1(a) and video 2(b). 37 KB Open access
S1 File. 38 KB Open access
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