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• Could fish DNA in seawater revolutionise marine conservation? New ÃûæÂÖ±²¥ research puts it to the test.
• Scientists uncover strengths (and limits) of a non-invasive way to track marine life in Sussex Bay.
• Environmental DNA detects three times more species than traditional underwater video surveys.

Can we count fish without even seeing them? from the ÃûæÂÖ±²¥ explores how well environmental DNA (eDNA) works in monitoring marine life in dynamic coastal environments.

, led by PhD candidate Alice J. Clark, Dr. Valentina Scarponi and Prof. Mika Peck, focuses on Sussex Bay. It investigates whether eDNA metabarcoding — a method that collects genetic material shed by organisms into water — can be used to estimate marine species abundance and richness in tidal waters.

eDNA is found in traces such as scales, skin cells, faeces, mucous and other excretions. The team compared results from eDNA sampling with those from Baited Remote Underwater Video (BRUV) surveys. The findings showed limited overlap: while BRUV recorded fewer species overall, tidal movement may also have influenced the eDNA readings.

PhD candidate Alice J. Clark said:

“Assessing the abundance and distribution of fish species is crucial for informing sustainable fishing practices and developing effective conservation management plans. However, counting animals underwater, where you can’t see them, is quite challenging, especially without disturbing marine life or damaging ecosystems.

“Our study found that while eDNA metabarcoding may not be the most accurate method for estimating species numbers in tidal environments, it does reinforce that eDNA is an effective tool for species monitoring. Other methods, such as BRUVs, may be better for counting fish numbers.

Furthermore, eDNA is non-invasive and time-effective, and can actually be more affordable than others when taking into account the number of species it detects and its range, and detects up to three times the number of species detecting using BRUVs alone.”

In a previous study in April 2024, the team identified 81 different marine species along the Sussex coast using a combination of BRUV and eDNA, including the tope shark, tub gurnard and the critically endangered European eel.

was supported by the South Coast Biosciences Doctoral Training Partnership (SoCoBio DTP), funded by the Biotechnology and Biological Sciences Research Council (BBSRC). Additional funding was provided by the Blue Marine Foundation (via GreenTheUK), NatureMetrics, the Sussex Wildlife Trust (via the Pebble Trust) and the Sussex Sustainability Research Programme.

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