Unprecedented widespread occurrence of Pink Salmon Oncorhynchus gorbuscha in Ireland in 2017.

The occurrence of non-native pink salmon Oncorhynchus gorbuscha in multiple river systems in Ireland in 2017 was unprecedented and reflected similar concurrent events observed in other countries in the North Atlantic region. Thirty-six fish were captured in a total of 11 river systems located in the south-west, west and north-west of Ireland in the period June to September 2017. The biological characteristics of sampled specimens are described and the potential for establishment in Ireland are considered.

Migration and survival of Atlantic salmon Salmo salar smolts in a large natural lake.

An investigation with acoustic telemetry of the passage of Salmo salar smolts through a large natural lake found heavy mortality occurred at the river-to-lake confluences (mean 31.2% km-1 ), but was lower in the main body of the lake (mean 2.4% km-1 ). Predation was a significant pressure on emigrating smolts as tagged pike Esox lucius aggregated at river-to-lake confluences during the peak of the smolt run. Tagged smolts mainly emmigrated into the lake in the late evening after dusk, possibly as a predator-avoidance behaviour.