Introduction of pike main factor in Owenriff decline of brown trout and salmon, survey shows

Inland Fisheries Ireland this week announced the publication of its Owenriff Fish Stock Survey 2017 and also its Owenriff Fish Population Rehabilitation Plan 2018 in which declining fish stocks have been identified and a project outlined to promote the recovery of the brown trout and salmon populations in both lakes and rivers and to prevent further decline in the catchment.

Critically, the Fish Stock Survey - which was conducted in the summer of 2017 and forms the basis for the Rehabilitation Plan – deduces that the introduction of pike into the catchment has been the significant factor in the declining fish stocks.

It states: ‘As there are little or no major anthropogenic pressures in the catchment to cause the decline in fish stocks, it is reasonable to infer that the introduction of pike and their subsequent range expansion in the Owenriff catchment (with impacts of competition for food and space and predation on resident and migratory fish ) is the main factor causing the decline of brown trout and salmon in the Owenriff catchment. Research from Europe and North America supports this finding.’

(‘Anthropogenic pressures’ include human-induced factors such as urban growth, deleterious discharges, farming activities and introduction of alien species. )

Although pike were captured for the first time by Inland Fisheries Ireland (IFI ) staff in 2009 in two lakes in the catchment (Loughs Bofin and Agraffard ) and efforts were made by IFI staff to remove the pike from the system, they did not show up in two catchment-wide surveys in 1997 and 2007 and were only officially recorded in a survey for the first time in 2015.

However, this new report states: ‘Results from the 2017 survey suggest that pike are present all over the Owenriff catchment, in areas where they can freely gain access and in some areas where they cannot naturally gain access.’

Welcoming the publication of the two reports, Minister Sean Kyne TD said they have acted swiftly since the interim results of this survey became known.

“In late January, I announced that Inland Fisheries Ireland is to commence fish stock management operations on the Owenriff catchment to protect and restore trout stocks which have been impacted by recent introductions of pike to the catchment. The consequences of not taking wider remedial action on the basis of these survey results would lead to further decline in ecological biodiversity in the catchment, so I very much welcome the publication by IFI of the Owenriff Fish Population Rehabilitation Plan 2018,” he said.

He csaid that the purpose of the plan is to develop a fisheries rehabilitation project that can be undertaken on the catchment to promote the recovery of the brown trout (both resident and migratory Corrib ) and salmon populations in both lakes and rivers.

“It will take time and will be costly, but we are already underway with this very constructive and positive roadmap. With stock management actions having already commenced, the success of the broader rehabilitation project will depend on applying the correct tools to rehabilitate the brown trout and salmon populations in the Owenriff catchment,” he said, adding that these will include fisheries enhancement works in selected sub-catchments to favour brown trout and salmon; genetic restoration; removing the problem (pike control ); reducing anthropogenic impacts in the catchment; public awareness (especially in relation to the impacts of the introductions of species not indigenous to an area ); interagency coordination; climate change mitigation; and any other necessary measures.

The Owenriff catchment is located on the north-western end of the Lough Corrib catchment and the main Owenriff River drains into Lough Corrib Upper downstream of Oughterard, Co. Galway. The Lough Corrib catchment, itself, is the largest and most important wild salmonid catchment in Ireland and Lough Corrib is considered the premier wild brown trout fishery in Ireland.

The two documents are available at this link: http://www.fisheriesireland.ie/Press-releases/owenriff-fish-stock-survey-and-rehabilitation-plan-published-by-inland-fisheries-ireland.html

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