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Transitional Waters

Fish Stock Survey of Lough Conn, September 2022

Lough Conn is located in the Moy catchment in north County Mayo (Plate 1.1, Figure 1.1). The lake is connected to its immediate neighbour to the south, Lough Cullin, by a narrow channel that passes under a regional road at Pontoon village (Figure 1.1). The River Deel flows into Lough Conn and exits Lough Cullin at its southern end near Foxford, just before joining the River Moy which discharges into the Atlantic at Killala Bay. The lake has a surface area of 4,704ha and a maximum depth of 37.9m.

The lake is categorised as typology class 12 (as designated by the EPA for the Water Framework Directive), i.e., deep (mean depth >4m), greater than 50ha and high alkalinity (>100 mg/l CaCO3). Lough Conn is part of a Special Protection Area (SPA) (Site code: 004228) under the E.U. Birds Directive. The SPA is of special conservation interest for the following species: Greenland White-fronted Goose (Anser albifrons), Tufted Duck (Aythya fuligula), Common Scoter (Melanitta nigra) and Common Gull (Larus canus). The E.U. Birds Directive pays particular attention to wetlands and, as these form part of this SPA; the site, and its associated water birds, are of special conservation interest (NPWS, 2014). Lough Conn’s reputation as a fine brown trout (Salmo trutta) and salmon (Salmo salar) fishery goes back to the very beginning of angling in the west of Ireland (O’ Reilly, 1998). The main run of spring salmon enters Lough Conn from the end of March and continues right through to April. The grilse run begins in May and continues into July (IFI, 2016).

The lake was surveyed by Inland Fisheries Ireland (IFI) on eight occasions between 1978 and 2013 (1978, 1984, 1990, 1994, 1998, 2001, 2005 and 2013) as part of a brown trout fish stock assessment programme (O’ Grady and Delanty, 2001; Delanty and O’Grady, 2014). The lake was also surveyed in 2016 as part of the Water Framework Directive (WFD) surveillance programme (Kelly et al., 2017). Brown trout, rudd (Scardinius erythrophthalmus), roach (Rutilus rutilus), perch (Perca fluviatilis), European eel (Anguilla anguilla) and pike (Esox lucius) were captured in the surveys. Historically the lake held a population of Arctic char (Salvelinus alpinus); however, they have been extinct for some time. Following the apparent collapse of the Arctic char population, IFI surveyed the spawning areas where Arctic char, if present, would be congregating to spawn during the Arctic char spawning seasons of 1991 to 1994. Three Arctic char were captured in the 1991 sampling, one fish in 1992 and none thereafter in 1993 or 1994. An examination of pike stomachs from fish captured in various parts of Lough Conn, throughout the 1990s, found no Arctic char (Igoe, et al., 2000). It is therefore reasonable to assume that Arctic char had become extinct in Lough Conn by the mid-1990s.

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 , |