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Transitional Waters

Fish Stock Survey of Ross Lake, September 2022

Ross Lake is situated in the Corrib catchment, located approximately 1km south-east of Rosscahill and 3km north-west of Moycullen, Co. Galway in a chain of lakes entering Lough Corrib at Moycullen Bay (Plate 1.1, Figure 1.1). It has a surface area of 139ha, a mean depth of >4m, a maximum depth of 14m and is categorised as typology class 12 (as designated by the EPA for the purposes of the Water Framework Directive), i.e., deep (>4m), greater than 50ha and high alkalinity (>100mg/l CaCO3).

The presence of zebra mussels (Dreissena polymorpha) was confirmed in Ross Lake in May 2007 (IFI, pers. comm.). Ross Lake and the surrounding woodlands have been designated as a Special Area of Conservation (SAC) for containing a hard water lake, a habitat listed on Annex I of the EU Habitats Directive (Council Directive 92/43/EEC) (NPWS, 2013). The SAC also contains a breeding colony of the lesser horseshoe bat (Rhinolophus hipposideros), a species listed on Annex II of the same Directive.

The woodlands and lakeside vegetation on the site provide foraging habitat within a small radius of the roost site (NPWS, 2013). The underlying geology of the area is limestone, with the main habitat in the SAC being Ross Lake, which has a limestone bed covered by deposits of precipitated marl and a shoreline of marl encrusted limestone boulders. The lake supports communities of Chara pedunculata and Chara curta, both of which are characteristic of marl lakes. The rocky limestone shore supports mostly fen-type vegetation characterised by Black Bog-rush (Schoenus nigricans). The site also contains otter (Lutra lutra), a species listed on Annex II of the EU Habitats Directive, and a small colony of common gull (Larus canus). The main land uses within the site are angling, commercial forestry, and grazing of the woodland and wetland areas (NPWS, 2013).

Historically (i.e., prior to 1850’s) Ross Lake supported a population of brown trout. Went (1957) reports that stocks in this relatively small lake were impacted by the pike originating from the resident population in Lough Corrib, which were able to colonise the lake via a newly open canal.

Along with other lakes in the Moycullen area, Ross Lake was developed as a coarse fishery with permanent stands located at several locations on the western shore of the lake. It was noted for stocks of roach (Rutilus rutilus), bream (Abramis brama), roach x bream hybrids (Rutilus rutilus x Abramis brama), perch (Perca fluviatilis) and pike (Esox lucius) (Gough, 1989).

Ross Lake has been surveyed on four occasions since 2007 (2007, 2020, 2013 and 2016 (Kelly and Connor, 2007 and Kelly et al., 2011, 2014 and 2017). During the previous surveys, perch and roach were the dominant species present in the lake. Roach x bream hybrids, bream, eels (Anguilla anguilla) and pike were also captured.

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 , |