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Pré-Publication, Document De Travail (Working Paper) Année : 2023

Quantifying the impact of habitat modifications on species behavior and mortality: case-study on floating objects and tropical tuna

Résumé

Ecosystems and biodiversity across the world are being altered by human activities. Habitat modification and degradation is among the most important drivers of biodiversity loss. These modifications can have an impact on species behavior, which can in turn impact their mortality. With around 5 million tons fished yearly, tuna species represent more than 7 % of global marine fish capture, of which two third are captured by purse seine vessels. Because several pelagic fish species, such as tuna, associate with floating objects, fishers have started deploying their own floating objects – Drifting Fish Aggregating Devices (DFADs) – in the early 1990s to increase tuna catchability. Since then, the massive deployment of DFADs has modified tuna habitat, by increasing the density of floating objects, with potential consequences on tuna associative behavior. This use of DFADs by purse seine fisheries is a major concern and it offers an important case study to assess the impact of habitat modifications on species behavior and mortality. In this study we use an individual-based model, based on a correlated random walk calibrated on passive acoustic tagging data, to determine a general relationship between DFAD density and the time tuna spend between two associations with a DFAD. Using this general relationship and fisheries data in the Indian Ocean, we predict that the increase of floating object density, due to DFAD use, strongly increases the percentage of time tuna spend associated, which directly impacts tuna availability to fishers and fishing mortality. This modification of tuna associative behavior could also have indirect impacts on their fitness, by retaining tuna in areas detrimental to them or disrupting schooling behavior. Hence, there is an urgent need to further investigate DFAD impacts on tuna behavior, in particular taking social behavior into account, and to continue regulation efforts on DFAD use and deployments.
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Dates et versions

hal-04094705 , version 1 (11-05-2023)
hal-04094705 , version 2 (20-07-2023)
hal-04094705 , version 3 (20-12-2023)

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  • HAL Id : hal-04094705 , version 1

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Amaël Dupaix, Laurent Dagorn, Jean-Louis Deneubourg, Manuela Capello. Quantifying the impact of habitat modifications on species behavior and mortality: case-study on floating objects and tropical tuna. 2023. ⟨hal-04094705v1⟩
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