Long-Term Recruitment Patterns of 0+ Brown Trout in the River Maine, Northern Ireland

Lough Neagh is the largest freshwater lake in the UK and Ireland (392 km2) and has a stock of lake migrating brown trout which recruit/spawn in the influent tributaries and mature in the lake. Potamodromous trout are exploited commercially in Lough Neagh with total landings ranging from c. 0.3 to 29.4 tons year−1 between 2001 and 2020. The recruitment of 0+ trout has been assessed annually on the River Maine, a large tributary of Lough Neagh, across an extensive and consistent network of Semi-Quantitative electric fishing sites between 2002 and 2020. The annual trout recruitment index for the River Maine was analysed against a range of potential explanatory variables including estimates of adult trout migration into the river, the commercial landings from the lake, electric fishing indices of Atlantic salmon (Salmo salar L.) recruitment and various discharge metrics. A stock–recruitment relationship was evident between the run of adult trout measured through the River Maine fish counter and subsequent 0+ recruitment measured in the following year.