Rays for days

  • Rays & Skates
  • Long-term
  • Current
Years funded
  • since 2021
  • Conservation
  • Research

The lagoon of St Joseph Atoll provides a home for three ray species. Juvenile mangrove whiptail (Urogymnus granulatus), porcupine (U. asperrimus) and feathertail (Pastinachus ater) rays all inhabit the shallow waters around the atoll’s various islands. We tag these rays with small electronic (PIT) tags that become their ID numbers. We also measure them and take a tissue sample. As time goes by and we recapture individuals, we can learn about how many of them use the lagoon, where they go and how quickly they grow. All this is important information that helps us to understand how these rays use the site. We collect data for this project every month.

About the project leader

Since its inception in 2012, the SOSF-DRC has been managed and run by different people in various capacities. Lab managers, research officers and research assistants have been integral to the daily operations of the centre over these years and our long-term projects have been handed on from past to present management.

Currently the SOSF-DRC is run by Dr Robert Bullock and Henriette Grimmel in a joint-management capacity.

The following is a history of past management staff:

  • Dr Rainer von Brandis (scientific director) 2006/2012–2016, previously did his PhD on D’Arros and managed the research lab for the previous owners of the island
  • Chris Boyes...
Project details

Ray population monitoring

Key objective

The key objective of this project is to develop an understanding of the ecology and population dynamics of the different ray species that use the St Joseph lagoon. We are looking specifically at the abundance of juvenile rays using the site, which areas of habitat are important to different ray species, and how they use the site to support their fitness and survival.

Why is this important

All three of the ray species using St Joseph Atoll are currently threatened with extinction and yet little is known about their behaviour and habitat use at the juvenile stage. This project should improve understanding of how rays use key refuge sites such as St Joseph, as well as which key habitat features are important to them. Data such as these are critical in defining conservation measures for threatened species and helping to mitigate population declines.


Rays are a group of elasmobranch fishes related to sharks. Despite being more numerous, they receive comparatively little attention and, to date, research into rays lags behind that into sharks. Rays are key predators in the ecosystems they inhabit and many species, including those inhabiting St Joseph Atoll, are at risk of extinction. Effective conservation for rays requires accurate information about their ecology, habitat use and behaviour. Understanding the juvenile life stages is particularly important for ensuring the stability of populations into the future. Mark-recapture studies are a popular means of estimating population sizes and survival rates and, more recently, the use of unmanned aerial vehicles has been adopted as a way to estimate the abundance of rays using particular sites, as well as how they move around different areas and habitats.

Aims & objectives

The key objective of this project is met by several specific study objectives:

– To mark and recapture juvenile rays of all three species, collecting tissue samples and data on their size and sex.

– To develop a drone survey protocol to estimate ray abundance, distribution and movements within the study site.

– To map each species’ core areas of use and investigate which habitat features and/or environmental conditions correlate with this.