New research indicates pike fish species in Irish waters have changed their diet

Pike species in Irish waters may have changed their diet preferences according to a new report launched today by Inland Fisheries Ireland.  The report, entitled ‘Pike (Esox Lucius) in Ireland. Developing knowledge and tools to support policy and management’ looks at new research carried out on Lough Conn, County Mayo and Lough Derravaragh, County Westmeath in 2016 and provides an insight into the dietary habits of pike.

Previous dietary research carried out in the 1960s and 1970s in Lough Derravaragh and Lough Sheelin (located across Westmeath, Meath and Cavan) indicated that pike preferred to eat brown trout and perch. However, this latest research reveals that pike appear to have changed their prey preference and now predominately eat roach. Researchers in Scotland and England have also found similar changes in pike diet occurring in Loch Lomond (Scotland) and Lake Windermere (England). It is thought the changes in diet are due to the invasion of roach in these waters.

The research examines whether pike and brown trout can co-exist in the same habitat. Using statistical models, it found that pike and brown trout could live together within relatively large deep lakes with strong stream connectivity however in small, low-complex systems pike introductions could potentially have a devastating impact on resident brown trout populations.

The practice of pike removal and the impact it has on brown trout stocks is also examined.  The findings suggest that pike removal may only be effective in protecting brown trout populations in systems where trout are the only available prey but may have little effect in systems where other prey, such as roach, is available.

CEO of Inland Fisheries Ireland, Dr Ciaran Byrne, said: “This research was initiated to answer some on-going questions relating to the dietary preference of pike and the pike-brown trout interactions in lakes across Ireland. Previous studies in this area were carried out more than 50 years ago which is a long time within our changing lake systems.

“This research is important as it gives an insight into the behaviour of the pike species and provides updated information around their relationship with brown trout. The changing food web and altered preferences of predators in the water systems highlights the need for continued monitoring and updated data to inform effective management strategies.

“This research will now be considered alongside the many historic, socio economic and management factors which all inform fisheries management and development work. Inland Fisheries Ireland uses the best available scientific information to underpin management decision making and advice.”

To view a full copy of the report, visit


About Inland Fisheries Ireland

Inland Fisheries Ireland is a statutory body operating under the aegis of the Department of Communications, Climate Action and Environment (DCCAE) and was established under the Fisheries Act on 1st July 2010. Its principal function is the protection and conservation of the inland fisheries resource. Inland Fisheries Ireland promotes supports, facilitates and advises the Minister on the conservation, protection, management, development and improvement of inland fisheries, including sea angling. Inland Fisheries Ireland also develops policy and national strategies relating to inland fisheries and sea angling and advises the Minister on same.

About this research

This research was carried out by scientists working across the National Research programmes at Inland Fisheries Ireland. Assistance was also provided by staff from the organisation’s operations division.

About Pike

Pike have a torpedo shaped body with a shovel like snout combined with a large mouth with many sharp teeth. They are piscivorous, meaning that they are fish-eating. They are a green olive colour with mottled lighter patches and a single dorsal fin is set far back over the anal fin. They can grow to around 27kg in weight and live for up to 15 years.


Pike are found in lowland lakes and rivers, migrating within freshwater only. They can be found from France to Siberia and as far south as Northern Italy but not found in Northern Scotland.  They are present in many medium and large Irish watercourses.


About Brown Trout

Brown trout are very variable in appearance, depending on their habitat and food. Brown trout usually have a pale belly with greenish grey/olive brown/golden flanks and a darker back with a reddish-brown/orange adipose fin. Brown trout are pigmented with spots, mostly blackish but sometimes with reddish spots.  Lake trout can live up to 12-15 years of age and river trout live to around 8 years.

Brown trout are native to the river basins of Europe and North Africa draining into the Black Sea, Mediterranean Sea, Northeast Atlantic, North Sea, Baltic Sea, and White Sea. They are the most widespread fish in Ireland and are found in practically every river, stream and lake in the country.

About Roach

Roach have silver coloured sides, sometime with a bronze lustre. They are blue on their back with a brownish red dorsal fin and red pelvic, anal and tailfin. They have 40-46 scales running laterally cross their body. Their dorsal fin is noticeably large and they have a short anal fin.

Roach occur on the bottom or midwaters of a water body, migrating within freshwater. They live to around 12 years of age and inhabit lowland lakes, ponds and rivers of moderate flow. They are considered an invasive species in Ireland and are found in many major river systems here and in Europe.

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