Combined technologies identify abundance of species

Spotted rays were among fish found by the research team. Image: University of Sussex

A new study has identified 81 different marine species along coastlines in southern England, including the critically endangered European eel.

The study, by the University of Sussex, shows how using a combination of two biomonitoring tools, baited remote underwater video (BRUV) and environmental DNA (eDNA), can help better understand the aquatic biodiversity.

In March 2021, a bylaw came into effect prohibiting trawling in over 300 square kilometres of local coastline in the county of Sussex.

Over the last three years, the university research team has conducted an in-depth study to monitor underwater habitats along the Sussex coast and identify species. Across 28 survey sites, the team recorded 81 different marine species living in the waters along this stretch of coastline.

Fish including black sea bream, Atlantic mackerel and tub gurnard fish were detected, as well as spotted rays, tope sharks and the rare European eel. Both the tope sharks and European eels are of high conservation concern.

"People will be surprised to learn how diverse this area of UK coastline is.”

Alice Clark, University of Sussex

The data collected forms part of PhD candidate Alice Clark’s research into the recovery of biodiversity in Sussex Bay.

She said, “Coastal ecosystems suffer from a range of stressors including overfishing, habitat degradation, pollution and climate change, all of which can lead to population decline and a loss of diversity in species.

"Through this analysis, we have been able to discover so many different species in our waters, and I think people will be surprised to learn just how diverse this area of the UK coastline is.”

The study has monitored underwater habitats along the Sussex coast. Image: Ben Collins, Unsplash

The research has provided a monitoring baseline of marine life diversity. Using both BRUV and eDNA monitoring will allow the team to document ecosystem changes, following the banning of trawling in the area, with the hope of seeing signs of recovery over time.

Professor Mika Peck, project co-lead, said, “There is the urgent need to address destructive fishing practices globally, the seminal trawler ban by Sussex IFCA in 2021 being a leading example.

“Our team at Sussex are providing the critical evidence to understand ecosystem recovery upon removing human pressures, such as trawling, using emerging technologies such as eDNA.”

BRUV imaging is an increasingly common and effective tool for monitoring underwater and allows researchers to learn more about the traits and behaviours of marine life through video footage.

The eDNA technique is used to identify DNA found in the environment and can help to detect rare species. The team found that three times as many species were detected using eDNA sampling compared to video surveys alone.

Combining BRUV and eDNA methods can inform how future monitoring programmes are conducted around the globe, says the researchers.

This study was funded by the SoCoBio DTP, Blue Marine Foundation, Sussex Wildlife Trust and NatureMetrics.