Impact of IUU Fishing on Leatherback Turtle Population Dynamics in French Guiana

In partnership with CNRS, TOTM contributes to a scientific study led by Damien Chevallier and Manon Niviere that aims to quantify the impact of illegal, unreported and unregulated (IUU) fishing on the population dynamics of the leatherback turtle (Dermochelys coriacea) in French Guiana.

French Guiana is one of the world’s main nesting sites for this species, which is listed as Vulnerable globally by the IUCN and Critically Endangered at the regional scale of the western Atlantic. Despite this major ecological importance, the local population is undergoing a rapid collapse: the number of nests fell from more than 5,000 in 2009 to only 17 in 2025, reflecting a drastic decline in the number of breeding females. Results from previous studies indicate that mortality at sea is now the main limiting factor for the population. In particular, accidental capture in IUU fisheries represents a critical pressure on adult females, whose survival directly determines population renewal.

This decline is occurring in a context of documented growth in illegal fishing pressure in French Guianese waters over the last decade, increasing the risk of interactions with marine turtles. Combined analysis of telemetry data and fishing activity highlights a strong spatial and temporal overlap between essential marine habitats used by turtles and zones of intense IUU fishing, particularly within the three high-risk interaction areas identified in transboundary waters west of French Guiana. Beyond documenting the problem, the project provides robust indicators to guide public action, including identification of priority surveillance areas, support for targeted deployment of enforcement resources at sea, and contributions to the design of management measures at regional scale. It also strengthens the capacity of local stakeholders to integrate scientific data into conservation strategies.

By improving understanding of the mechanisms behind the decline and identifying high-risk zones, this study will provide an operational lever for strengthening anti-IUU fishing policies and supporting the long-term conservation of one of the last major leatherback turtle populations in the Atlantic.