PhD position: The importance of the twilight zone for endangered oceanic filter-feeding elasmobranchs – Deadline 03 July 2023

Summary of the work plan

Oceanic predators spend most of their lives in the marine equivalent of a desert, where epipelagic resources are scarce and patchily distributed. It has been proposed that the large fish biomass of the Ocean’s twilight zone (mesopelagic) might be an essential food resource for these species. Yet, we still do not know to what extent oceanic predators may rely on mesopelagic prey, especially filter-feeding elasmobranchs which little interest has been given regarding this subject. The ocean’s twilight zone is currently facing three eminent threats: 1) the world’s growing population is raising issues of food security, increasing the pressure to exploit mesopelagic resources; 2) the advent of sea-floor mining may release waste into this region; and, 3) climate change is affecting the ocean’s biochemistry and biogeography. Our understanding of how these changes may affect the higher trophic levels is hindered by the paucity of information on the mesopelagic biome and on the feeding ecology of many oceanic predators.

This PhD project proposes to evaluate the importance of mesopelagic resources oceanic elasmobranchs in the Atlantic ocean, in particular the endangered and least known filter-feeder species (whale shark, devil rays), using a multidisciplinary/multiscale approach. Both species have been labelled as planktivorous surface dwellers but recent studies have described recurrent feeding events on small pelagic fishes and frequent deep dives reaching far beyond the twilight zone, suggesting that they may be more reliant on mesopelagic resources than previously thought. The PhD project will benefit from unique high-resolution biologging and satellite-tracking/Argos-linked datasets. The project is expected to contribute to the development of new animal-borne technology (mini-sonar and low-light camera), with the potential to provide a denser low-cost/low-effort sampling of the tridimensional open ocean, and to the improvement/validation of SEAPODYM’s zooplankton and micronekton spatiotemporal predictions, which were already successfully used to model the possible impacts of climate change in tuna.

The project’s final results will contribute to the state of the art concerning the ecology of oceanic filter-feeding elasmobranchs and provide crucial insights into the importance of mesopelagic resources for the preservation of biodiversity at higher trophic levels, supporting science-based conservation and management decisions in the context of the large-scale exploitation of a potentially essential feeding habitat for the Atlantic’s megafauna (i.e., twilight zone), and under the current climate change scenario. Specifically, it will contribute to work packages 1 (Ecosystem Integrated Assessment), 3 (pelagic mapping), 5 (trend analyses/state drivers), 6 (ecosystem modelling/dynamics) and (risk assessment) of the EC HORISON 2020/EUROPE projects Mission Atlantic (2020-2025; www.missionatlantic.eu), and build on MEESO Project (www.meeso.org) and OceanICU with the support of those international consortia.

Candidate Profile

The candidate will be selected based on his/her CV, LoS and accompanying documentation,  and evaluated taking in consideration :

• background knowledge of open ocean megafauna and ecosystems, especially elasmobranchs
• experience dealing with large datasets of data (remote sensing, tracking fisheries, etc.)
• experience with animal movement analysis techniques, on both spatial and temporal scales, and from different sources (acoustic, data storage, satellite)
• advanced skills in R and GIS software.
• experience in tagging and tracking of large marine animals, mostly elasmobranchs
• ability to work abroad in remote locations, in dynamic team’s environments, and independently

Name(s) of supervisor(s)

• Supervisor: Jorge Fontes, IMAR/University of the Azores, Portugal
• Co-Supervisor:  Pedro Afonso, IMAR/University of the Azores, Portugal
• Co-Supervisor:  Camrin Braun, Woods Hole Oceanographic Institution (US)
• Co-Supervisor:  Patrick Lehodey, CLS/Mercator, France

Name(s) of host institution(s)

The research will be conducted at the Institute of Marine Sciences – OKEANOS of the University of the Azores, in cooperation with the co-supervisors research groups.

Identification of PhD program (at the Portuguese University)

PhD in Marine Sciences – University of the Azores (link).

Notice of the Call ( English version)