eDNA analysis of the Floating Harbour

Bristol Avon Rivers Trust have worked in partnership with Bristol City Council to carry out a pilot environmental DNA (eDNA) analysis of individual species and communities of fish by sampling the water at 10 sites across Bristol’s Floating Harbour and the River Avon during February, June, and July 2022. One of the sampling points was the entrance to Bathurst Basin.

Sources of eDNA include secreted faeces, mucous, gametes, shed skin, scales, hair and carcasses. It provides a cost effective and reliable technique to determine the fish species present in the water and their spatial and temporal distribution.

The findings of the analysis are remarkable. In addition to familiar fish, like the European bass caught in Bathurst Basin and shown in our image, there is eDNA present of species of particular note due to their designated threatened status:

  • European eel,  critically endangered on the International Union for Conservation of Nature (IUCN) Red List;
  • Eurasian carp, vulnerable on the IUCN Red List. This is technically an invasive species introduced to the UK in the Middle Ages.
  • Atlantic mackerel;
  • Common sole;
  • Atlantic salmon, vulnerable on the IUCN list;
  • Sea lamprey.

On the European eel the report writes:

“It is encouraging to find the critically endangered European eel so well present at the majority of sampling sites, including in relatively high abundance in the Floating Harbour and the Feeder Canal. This critically endangered species faces an extremely high risk of extinction in the wild and effort should be made to ensure that it can thrive in our waterways.”

The report concludes on  challenging note:

“However, in its current degraded state, the harbour is not fulfilling its potential in supporting aquatic or terrestrial wildlife. Much more action is needed to improve water quality as well as increasing biodiversity through improving and increasing areas of habitat.”


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