Brown Trout Genetics and Fisheries Management in Ireland

The remarkable variation in appearance, behaviour, ecology and life history displayed by the brown trout is linked to enormous diversity in this species’ genetic make-up. Due to the great importance of trout genetic diversity for both management and conservation of this key angling species, IFI have commissioned several population genetics studies of brown trout in major lake and river catchments that contain important trout fisheries to understand more about this species.

In general, these studies have aimed to investigate the genetic diversity of trout stocks in each of these catchments, to assess the contribution of genetic subpopulations from rivers to the adult stock of each fishery, and to establish whether habitat degradation, interbreeding with stocked trout from hatcheries, fish kills or problems with water quality have affected the genetic structuring of trout populations.

These studies began in 2006 with a collaborative investigation of the trout subpopulations in Lough Corrib’s inflowing rivers reported by Massa-Gallucci et al. (2010) in “Patterns of genetic structuring in a brown trout (Salmo trutta L.) metapopulation” (Cons. Gens. 11:1689 1699). This research was followed by a study of the Lough Mask catchment that was conducted in collaboration with local angling clubs.

Brown Trout Genetics and the EREP

Subsequent IFI-sponsored studies have largely followed this approach exploring the relationship between adult stocks in major lake and river trout fisheries exploited by anglers and the river subpopulations from which this stock is recruited. By 2011, two more genetics research programmes were completed as part of the Environmental River Enhancement Programme (EREP): a comparison of the Boyne and Suir catchments, and a study of the Lough Ennell catchment. A study of brown trout genetics in Lough Sheelin and its tributaries has also commenced.

In the context of the EREP, these genetic studies specifically aimed to clarify the extent of human impacts, especially arterial drainage, on wild brown trout populations and to provide catchment-specific information that is invaluable for the management of these trout fisheries. The studies addressed the following questions:

Whether major arterial drainage schemes from the 1950s onwards have changed the genetic diversity of trout populations.
Whether some genetic subpopulations in tributaries within each catchment are more important for the recruitment of adult fish to the fisheries’ trout stock.
Whether genetic information on the importance of individual tributaries as nursery habitat can be used to develop habitat enhancement programmes.
Whether fish stocking programmes using farmed fish have changed the genetic structure of wild brown trout fisheries.

Summary information and analysis of these studies can also be found in the following EREP reports:
Boyne, Suir, Ennell: EREP Annual Report 2011
Sheelin: EREP Annual Report 2013

Studies in Progress & Publications for Download

More studies of brown trout genetics in catchments around Ireland are in progress:

The Dodder, Liffey & Tolka river catchments
The Moy catchment, including Loughs Conn and Cullin
Lough Sheelin and its tributaries
The mid-Shannon catchments around Lough Ree
Further analysis of the Corrib system

Technical reports on completed projects and interim reports on current projects are available via the links below:

Final Technical Reports:

IFI Interim Reports:

These reports can also be accessed for your catchment of interest by clicking on the map below:

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