Researchers studying Loughs Derravaragh and Sheelin and Mayo’s Lough Conn have announced that they suspect pike may have stopped preying on trout and salmon in locations where there is roach available.
The findings represent good news for the angling sector, as it will improve the already-high standing of the two lakes as wild trout fisheries, Dr Cathal Gallagher, head of Research and Development at Inland Fisheries Ireland, told the Westmeath Examiner this week.
“There’s been a change in the fish species present, particularly with the introduction of roach,” said Dr Gallagher, explaining the reason for the 2016 research project, the findings of which have just been published in a report entitled ‘Pike (Esox Lucius) in Ireland. Developing knowledge and tools to support policy and management’.
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, a fish introduced to Ireland in the late 1800s that has come more to prominence since the 1960s/1970s.
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 examined 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.
Dr Ciaran Byrne, CEO of Inland Fisheries Ireland, said the research was important as it gives an insight into the behaviour of the pike species and provides updated information around their relationship with brown trout.
“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.”
Dr Byrne said 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, socioeconomic 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.”
Dr Byrne and Dr Gallagher said that there are 15 wild trout lakes and Inland Fisheries Ireland manages seven of these, including Loughs Derravaragh and Sheelin, and the findings will assist in the management of those lakes.
There is no longer trout stocking going on, as the lakes are being carefully maintained as wild trout fisheries, and according to the two men, Ireland’s wild trout fisheries are among the best in the world.
From an economic point of view, they are also a valuable resource, and angling is worth an estimated €140m to the economy.
• To view a full copy of the report, visit fisheriesireland.ie/pikeresearch.