Indirect assessment of sea turtle bycatch in waters adjacent to the Yucatán peninsula, Mexico

Supervisor: Eduardo Amir Cuevas Flores (Dep. Sea Turtle Conservation, Pronatura Peninsula, Yucatan, Mexico)
Current endangered conservation status of sea turtles has encouraged the increase of research and mitigation plans focused on the hazards provoking population declines and their habitats degradation. Due to their complex life history, fisheries bycatch represent one threat of the most concern around the world, becoming characterisation of fisheries dynamics essential for implementing any mitigation strategy for sea turtle conservation. Enhancing in developing countries the expansion of small-scale fisheries because of its crucial role in generation of employment and livelihood, its data are under-reported in the case of existing. Additionally to this lack of information is the absence of agreement in terms of globalisation of the fishing fleet descriptive parameters, and the difficulties in terms of interpretation of results with such slanted and subjective records. Compilation of data with the purpose of an accurate description of artisanal fisheries at Chiquila (Mexico), was carried out through the performance of 956 in person harbour semi-structured surveys from June 2012 to May 2013. Descriptive, inferential and spatial statistical analyses were carried out. Fishing activity on the area was mainly characterised by its variability, as most of the artisanal fisheries; showing fluctuations in terms of temporal and spatial display of different fishing gears. Gillnets and artisanal longlines were found out to be the most dangerous in the zone in terms of sea turtle bycatch, which promoted the focusing of analysis on those two devices. Differences between the two fishing gears in terms of disposal and bycatch activities that were characterised with the help of three basic parameters: fishing effort (FE), bycatch per unit effort (BPUE) and frequency of fishing travels; were confirmed. Following evaluations based on their behaviour along the year, presented dissimilarities between the fishing gears as well, in both temporal and spatial analyses. Corroboration of the correlation between FE and BPUE and suggestion of complementing parameters in this kind of studies were performed too. Finally, identification of bycatch hotspots due to overlap situations between the fishing habits and sea turtles aggregation spots in the area were displayed, based on results obtained in other sections. This research’s goal was to provide information about the dynamics of the area of study in order to further implementations of management programmes in such a rich environment as Yum Balam Protected Area, together with the establishment of a baseline descriptive parameters set that might facilitate and accelerate the creation of global fishing and bycatch databases and studies.

Keywords: Bycatch rates, fisheries bycatch, fishing effort, gillnet, longline, marine turtles, small-scale fisheries.