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Transitional Waters

Fish Stock Survey of Lettercraffroe Lough, August, 2022

Lettercraffroe Lough is located 6km south-west of Oughterard, Co. Galway on a tributary of the Owenriff River which flows through the town and into Lough Corrib (Plate 1.1, Figure 1.1). It has a surface area of 82ha, a mean depth of 2.86m and a maximum depth of 17.9m (WRFB, 2006). The lake is categorised as typology class 2 (as designated by the EPA for the purposes of the Water Framework Directive), i.e., shallow (<4m), greater than 50ha and low alkalinity (<20mg/l CaCO3). Lettercraffroe Lough is an excellent example of a lowland oligotrophic lake, an Annex 1 habitat.

Lettercraffroe Lough is situated within the Connemara Bog Complex, a large Special Area of Conservation (SAC) site that encompasses a wide range of habitats, including extensive tracts of blanket bog, heath, woodland, lakes, rivers and streams. The Connemara Bog Complex is underlain by various Galway granites, with small areas along the northern boundary made up of schist and gneiss (NPWS, 2015).

The main perceived threats within the SAC are peat cutting, overgrazing and afforestation. Forestry affects habitat uniformity, lake and river catchments, nesting and feeding habitats for animals, and landscape integrity (NPWS, 2015). The western and southern shores of the lake are heavily forested and there have previously been problems with phosphorus loading in the lake, which reached critical levels in the summer of 2004 (FIE, 2010). Subsequent water samples indicated that phosphorus levels were decreasing in the lake (Coillte, pers. comm.). A tree felling plan was due to take place during 2010, along the streams and in areas surrounding the lake. However, due to issues regarding pearl mussels in the catchment, this plan was revisited and a new forestry management plan was developed (Coillte, 2010). Conifers will be felled and they will not be replaced in areas along the streams or between the access road and the lake. It is hoped that these efforts will lead to the creation of an extensive buffer zone surrounding the lake.

The lake has been surveyed on five occasions since 2007 (2007, 2010, 2013, 2016 and 2019) (Kelly and Connor, 2007 and Kelly et al., 2011, 2014, 2017 and Corcoran et al., 2020). In previous surveys roach (Rutilus rutilus) were found to be the dominant species present in the lake. Brown trout (Salmo salar), European eel (Anguilla anguilla) and three-spined stickleback (Gasterosteus aculeatus) were also recorded.

This report summarises the results of the 2022 fish stock survey carried out on the lake using Inland Fisheries Ireland’s fish in lakes monitoring protocol. The protocol is WFD compliant and provides insight into fish stock status in the lake.

Topics: Lake Surveys 2022 , |