What is the Owenriff Project?
IFI is aware that the ecology of many Irish freshwaters has shown major changes over the last four decades due to various anthropogenic pressures. IFI is the statutory body charged with the conservation of fish in these systems, and must stay informed on the status of fish stocks in all major fisheries. A fish population survey using standardised protocols is accepted best practice for this kind of assessment.
The Owenriff sub-catchment, located in the north-western side of the Lough Corrib catchment provides important spawning and nursery areas for both salmon and brown trout. It also supports a population of the endangered freshwater pearl mussel (Margaratifera margaratifera). The lower part of the Owenriff River is regarded as a good salmon river. Resident brown trout in the catchment are relatively small in the lakes in the upper catchment. Large adult brown trout from Lough Corrib migrate to the Owenriff river in late summer in advance of spawning during the winter time. .
A recent catchment wide survey of the fish stocks at selected sites across the Owenriff sub-catchment and surveys of two lakes (Loughh Bofin and Agraffard) identified that there has been a decline in the rivers and lakes of the sub-catchment in recent years. As there are little or no anthropogenic pressures in the catchment the survey report concluded that it is reasonable to infer that the introduction of pike is the main factor causing the decline of brown trout and salmon in the Owenriff catchment (IFI, 2018). pdf Owenriff Fish Survey Report 2017 (5.09 MB)
Pike were officially captured in the catchment for the first time in 2009 and subsequent pike removal operations revealed that both juvenile and adults were present inferring that a breeding population had become established within the system sometime prior to that date. Anecdotal reports suggest that pike were present in some lakes in the catchment in the 1990s, but this was never confirmed by IFI staff. The natural waterfall at Oughterard on the main channel of the Owenriff is probably too steep to allow natural colonisation of pike from Lough Corrib. This suggests relatively recent introduction of the species by humans. Pike are likely to compete with trout for invertebrate prey when introduced to a new area, and may exert some direct predation pressure on smaller trout. It is possible that the introduction of pike to the Owenriff system has resulted in negative impacts on salmonids. Roach, a fish species known to be invasive in certain situations has also been introduced into the catchment.
A rehabilitation plan for the fish stocks in the Owenriff catchment has been designed specifically for the Owenriff sub-catchment and includes numerous remedial measures. The purpose of the Owenriff rehabilitation plan is to develop a series of projects that can be undertaken to promote the recovery of the brown trout (both resident and migratory Corrib) and salmon populations in both lakes and rivers and to prevent further decline. pdf Owenriff Rehabilitation Plan 2018 (7.24 MB)
The case for implementing a fisheries rehabilitation plan to protect the biodiversity and prevent further decline of the fish stocks in the Owenriff sub-catchment is endorsed by EU and national legislation and international guidelines, i.e. EU Water Framework Directive, EU Habitats Directive, Water Policy Regulations (S.I. 722 of 2003) and the guidance from the Food and Agriculture Organization (FAO) of the United Nations.
What is proposed for the Owenriff rehabilitation plan?
The restoration plan has eight components (1) fisheries enhancement, (2) genetic restoration of the brown trout population, (3) removing or controlling the problem (4) mitigation of impacts on the river channel, (5) public awareness, (6) interagency coordination, (7) climate change and (8) other measures are recommended for consideration.
How will the effectiveness of the plan be monitored?
Monitoring and evaluation of rehabilitation works is essential for determining the effectiveness of measures aimed at improving habitat and increasing fish numbers and condition. It also allows the success of a programme to be assessed. The fish populations of the Owenriff will be closely monitored using standardised surveys throughout the rehabilitation project. The purpose of standardised fish population surveys is to obtain a representative sample of the fish assemblage in a system. This information allows comparison of fish densities across years and among systems. Fish populations can be robustly monitored to inform appropriate management measures. Surveys during and after the restoration project will investigate whether/how fish populations may be responding to remedial measures.
Rivers in the Owenriff will be sampled by electric-fishing. This is an established technique used by fishery biologists all over the world for sampling fish in freshwaters and is generally the most non-destructive, effective and cost efficient means of sampling freshwater fish, particularly in rivers. Standard methods have been developed by IFI in compliance with EU standards for fish stock assessment in rivers. Selected Owenriff lakes will be sampled using a combination of survey gill nets and fyke nets, also in accordance with relevant EU standards for fish stock assessment. Other trend monitoring methods are also being considered.
A more detailed catchment wide assessment of the fish stocks will be undertaken during 2018. Approximately 50 sites on the main Owenriff river and its tributaries and four lakes will be surveyed. Habitat mapping will also be undertaken to identify potential pike spawning and nursery areas. Further work will be undertaken once the baseline surveys are complete.
Who will be involved in the work?
The project will be led by IFI, who have broad expertise in fisheries surveys and in rehabilitation works in freshwater systems. The intention is to work closely with local stakeholders and other state agencies.
To find out more information on where we monitor, how we monitor and to access results and reports from recent surveys, visit the WFD project website www.wfdfish.ie