Ecology and economics of fish kills: mortality and recovery of brown trout (Salmo truttaL.) and Atlantic salmon (Salmo salarL.) in an Irish river

There is a small international scientific literature, principally from North America, on recovery of fish communities following substantial fish kill events and a smaller literature on monetary assessment of losses in such events. A chemical discharge led to over 90% loss of brown trout (Salmo truttaL.) and Atlantic salmon (Salmosalar L.) age classes in 31km of the River Boyne catchment, a major Irish salmon-producing and angling fishery in July 1997. Subsequent investigations permitted a novel study that examined both the changes in the fish community composition over time and also a monetary assessment of losses. The population structure and density of 1+ and older brown trout took four to five years to recover. The population of 1+ salmon increased substantially during the recovery period, to levels threefold higher than those recorded prior to the pollution event. Financial loss assessment was examined through ‘replacement cost’ and through consequential loss models. An examination of the monetary modelling, in the light of the fish community recovery, showed there was an ecological justification for the potential loss model used. This approach to appraisal of loss is considered to have an international relevance, in the context of ecosystem processes and the ‘polluter pays’ principle.