Halfway between Cape Town in South Africa and the southern tip of South America lies Tristan da Cunha, UK Overseas Territory (UKOT) and the world’s most remote inhabited island. With a population of just under 250 residents, it’s marine and terrestrial habitats are rich in biodiversity, including endemic species and critical bird nesting sites, and the island’s primary export is the Tristan Rock Lobster (Crawfish). The Tristan Rock Lobster preys on abundant sea urchins, which in turn rely on the natural red turf algae, a delicate balance which sustains biodiversity and the fishing industry.
In 2006 an oil rig washed up on the island, introducing new and invasive marine species, among them the Silver Porgy fish (also known as Sea Bream or Black Tail). This successful invasive fish is thought to feed on red algae turf, competing with the native sea urchins, and threatening the primary food for the lobsters. The predators have even been observed eating a juvenile lobster, so TDC’s Fisheries Department is worried for the local fishing industry as well as the wider biodiversity of the islands.
Through our work with the UKOTS we were able to step in and offer help to grow knowledge about the threat of these invasive fish to TDC island life, introducing Dr Kristan Metcalfe from the University of Exeter to James Glass, Director of TDC Fisheries, and funding a doctoral study to assess the impact on TDC’s marine life.
James Glass said “the issue of invasive species is a real concern for us, and it’s a great asset to have a doctoral candidate with full time focus and the strength of Exeter University and Cefas behind them to help us better understand what’s happening in our waters”.
The doctoral student Becca Nicholls is on the case, and after receiving extensive specialised training here in the UK, she has now completed her first field season on the island, collecting underwater video and laying the ground work for the fish surveys, stable isotope and genetic studies that she will use to understand food web and biodiversity shifts where the invasives have taken hold. Becca is currently planning for her next five-month stint on the remote island, taking advantage of the “summer season” in the South Atlantic to maximise her data collection.
Becca said “The Tristan da Cunha Ecosystem is amazing, with so much still to discover. I am thrilled to contribute both ecological insights and to support the fisheries department to monitor and manage their resources. This project is everything I could have hoped for in a PhD and it is a privilege to be a part of something so impactful.”
Becca’s doctoral study is supported by a supervisory team from both the University of Exeter and the Centre for Environment, Fisheries and Aquaculture Science (Cefas), drawing in premier UK expertise and building on the wider legacy of Cefas’s past and ongoing initiatives.
Exeter’s Dr Metcalfe said “Becca has embraced this challenging and unique project with energy and intelligence. It’s great to see our marine ecology students working on issues with relevance to real world problems, and to be working with the Tristan da Cunha Fisheries Department is an opportunity like no other and will be a great boost to Becca’s qualification and experience.”
The Fishmongers’ Company’s Fisheries Charitable Trust provides funding for a range of applied doctoral, master and internship projects in line with the wider work of the Trust through the Targeted Academic Sponsorship Programme.
© The Fishmongers’ Company 2025
