Incidence of escaped farmed salmon, Salmo salar L., in commercial salmon catches and fresh water in Northern Ireland

TLDR: External morphological characteristics were used to identify escaped farmed Atlantic salmon, Salmo salar L., in a coastal salmon fishery in County Antrim, Northern Ireland during four fishing seasons and at an adjacent freshwater location during a 5-year period to show correlation between presence in the marine fishery and in fresh water.

Abstract: External morphological characteristics were used to identify escaped farmed Atlantic salmon, Salmo salar L., in a coastal salmon fishery in County Antrim, Northern Ireland during four fishing seasons and at an adjacent freshwater location (R. Bush) during a 5-year period. Out of a total of 36 326 adult salmon examined in the fishery, 883 (2.4%) were identified as having escaped from sea cages. Annual average values ranged from 0.26% to 4.04% of the fish caught. Occurrence of escapees entering an adult trap in fresh water averaged 0.88%, with a range of 0.13–2.62%, depending on year. No correlation between presence in the marine fishery and in fresh water was evident, the latter year-round figures probably being more indicative of presence of escapees in spawning stocks. Entry to fresh water was significantly later on average for escaped farmed salmon, compared with wild salmon.