First look at the distribution of deactivated dFADs used by the French Indian Ocean tropical tuna purse-seine fishery

Abstract

The presence of abandoned, lost or otherwise discarded fishing gears, including drifting fish aggregating devices (dFADs), in marine ecosystems poses significant ecological and socioeconomic concerns. The estimation of the number of dFADs in the marine environment is challenging due to the loss of tracking information when dFAD tracking buoys are remotely deactivated. For the first time, a data set of dFADs buoy positions, including those that had previously been remotely deactivated, has been made available for the period July-August 2020. Data from this period provide valuable insights into the life expectancy, spatial distribution, and status of deactivated dFAD buoys, enabling a more accurate assessment of dFAD presence and impacts. Deactivated buoys represented a 17.2% increase in the total number of tracked objects, and we estimate the in-water half-life of deactivated dFAD tracking buoys to be 101 days. Including deactivated buoys increases the number of strandings during the SP by 23.7%. Nevertheless, the representativity of these results is unknown given the limited spatio-temporal and numerical extent of our data, highlighting the importance of availability of comprehensive data on dFADs to effectively estimate their total numbers and mitigate their environmental impacts.