Using automated video analysis to study fish escapement through escape panels in active fishing gears: Application to the effect of net colour

Type Article
Date 2020-06
Language English
Author(s) Simon Julien1, Kopp DorotheeORCID1, Larnaud Pascal1, Vacherot Jean-Philippe1, Morandeau Fabien1, Lavialle Gael2, Morfin MarieORCID1
Affiliation(s) 1 : IFREMER, Laboratoire de Technologie et Biologie Halieutique, 8 rue François Toullec, F-56100, Lorient, France
2 : COBRENORD, Organisation de Producteurs, Terre-plein du port, 22410, Saint-Quay-Portrieux, France
Source Marine Policy (0308-597X) (Elsevier BV), 2020-06 , Vol. 116 , P. 103785 (10p.)
DOI 10.1016/j.marpol.2019.103785
WOS© Times Cited 5
Keyword(s) Trawl selectivity, Fish behaviour, Underwater videos, Computer vision, Object detection, Object tracking

Quantification of the escapement rate of unwanted fish through a selective device is usually based on catch comparison. This study proposes a new, time efficient method to automatically compare two selective devices by automated counting of fish escapements through each selective device based on video sequences. First, sea trials were conducted to record video sequences of fish escaping a white and black square mesh panel. Then, all of the underwater sequences were automatically analysed by a computer vision software for automated object detection and tracking. Finally, the algorithm was assessed using 150 min of video sequences analysed by humans. We observed that the variability in escapements rate between all the observers on reference video sequences could reach 5%. As the difference in escapements rate between the algorithm and the observers was lower than the variability between observers, the automated approach was validated. The software detected a significant difference in fish escapement rate according to the net colour in the camera field of view: 60% of all fish escaped through the white panel. Our results suggest that net colour influences the escape rates of fish. The colour of the selective device should therefore be investigated further with the aim of increasing their efficiency. Further development of the software could be done to identify species and size of the fish and assess the effectiveness of a selective device by species and size.

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Simon Julien, Kopp Dorothee, Larnaud Pascal, Vacherot Jean-Philippe, Morandeau Fabien, Lavialle Gael, Morfin Marie (2020). Using automated video analysis to study fish escapement through escape panels in active fishing gears: Application to the effect of net colour. Marine Policy, 116, 103785 (10p.). Publisher's official version : , Open Access version :