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Fish Stock Survey of Lough Carra, July 2022

Lough Carra is situated in County Mayo and forms the most northerly part of the Great Western Lakes
system of Loughs Corrib, Mask and Carra (Plate 1.1, Figure 1.1). The lake is located approximately 5km north of Ballinrobe, Co. Mayo.

Lough Carra is the largest marl lake in Ireland, with a surface area of approximately 1600ha (NPWS, 2015; Irvine et al., 2003). It is a hard water lake which acquires most of its water via the feeder streams that flow in at various points around its perimeter (Huxley and Huxley, 2009). Much of the lake is shallow with a mean depth of approximately 1.8m; however, there are sections of the lake where depths reach over 19m (Huxley and Huxley, 2009). Lough Carra is well known for its green/blue colour which is due to the formation of calcareous encrustations (NPWS, 2015). The lake contains well developed stonewort communities with Chara curta, C. desmacantha, C. rudis and C. contraria also recorded (NPWS, 2015).

The lake is categorised as typology class 10 (as designated by the EPA for the purposes of the Water Framework Directive (WFD)), i.e., shallow (<4m), greater than 50ha and highly alkaline (>100mg/l

The average size of the brown trout (Salmo trutta) taken from Lough Carra is greater than any of the other western lakes and the lake has previously produced a specimen of 8.2kg (O’ Reilly, 2007). Lough Carra is believed to be one of the few remaining wild brown trout calcareous lakes within the EU (Irvine et al., 2003). During the 1990s fishery rehabilitation and enhancement works were undertaken in Lough Carra’s spawning streams by Inland Fisheries Ireland (IFI) (previously the Central and Regional Fisheries Boards) and this led to increased recruitment of juvenile brown trout to the lake (O’ Grady,

The lake was surveyed eight times from 1978 to 2009 as part of IFI’s brown trout research programme using seven-panel benthic braided survey gill nets. Brown trout, perch (Perca fluviatilis) and pike (Esox
) were recorded on all of those sampling occasions. The most recent results (March 2009) using that survey method suggested that the lake supported an excellent and healthy stock of brown trout (IFI, 2009). The lake has also been surveyed on four occasions since 2009, (2009, 2012, 2015 and 2019) (Kelly et al., 2010, 2013, 2016 and Corcoran et al., 2020).

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 also provides insight into fish stock status in the lake.

Topics: Lake Surveys 2022 , |