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A “diadromous” fish species is a species that divides its lifecycle between freshwater and the sea. Such species are under threat from a range of factors, including overfishing, damage to their freshwater habitats, ocean warming and shifts in ocean currents.

Twaite shad at St Mullins

Cultural significance

Many diadromous fish species have a special status in the culture and traditions of communities along the western seaboard of Europe and in many of the large European rivers. Some have been an important source of food and their movement from the sea to rivers in springtime has been widely celebrated by annual festivals over the centuries.

Raising awareness and ecological services

The aim of the DiadES project is to raise awareness of and assess the ecological services provided by a wide range of diadromous fish species, for example, as sources of food, leisure, recreation and commerce. To do this, we focus on the twaite shad and on a lesser-known species, the thin-lipped mullet. The twaite shad is a source of high angling activity every May at St. Mullins on the River Barrow (Co. Wexford), and Inland Fisheries Ireland joins with other partners in trying to put facts and figures together on the ‘value’ of this fishing activity.

Picking our study location

Inland Fisheries Ireland has nominated Waterford Harbour as its ‘demonstration site’ and has nominated the twaite shad and the thin-lipped mullet as its two key fish species within Waterford Harbour and its Three Sisters river complex, the Barrow, Nore and Suir rivers. We will undertake fish community studies in these waters with an emphasis on learning more about twaite shad and thin-lipped mullet.

Suir at Kilsheelan

Modern techniques

Inland Fisheries Ireland and its various international project partners are also interested in the distribution (geographic spread) and status of the species in the open sea and will carry out sampling in the open sea using a special environmental DNA (eDNA) technique. This method involves collecting water samples from the sea that contain fragments of DNA released or shed by an organism. This material remains in the water for a period of time and is incredibly useful for analysis as it doesn’t require catching or damaging live fish using conventional methods.

Anglers with DiadES hats on

Collaborating with commercial fishers and other state bodies

We will also be looking for information on both species by checking discarded fish data from commercial landings and from surveys done by other marine state fisheries bodies, the Marine Institute, an Bord Iascaigh Mhara (BIM) and the Sea Fisheries Protection Agency (SFPA).

If you would like to contribute, please take 10 minutes to fill out our survey.

This is an EU-funded INTERREG Atlantic Area project with a number of European partners (DiadES). These are based in, France (National Research Institute of Science and Technology for Environment and Agriculture & Muséum National D’Histoire naturelle), Portugal (Aquamuseu do Rio Minho, Cerveira Vila das Artes, MARE, Técnico Lisboa & Universidade de Évora), Spain (Universidade de Santiago de Compostela & AZTI-Tecnalia), UK (The Centre for Environment, Fisheries and Aquaculture Science & University of Plymouth).