Abstract of PhD Thesis

Characterisation of Arctic char spawning grounds and the vulnerability of ova to environmental change

Jonathan Low, University College Cork(2011)

The Arctic char (Salvelinus alpinus) is at the southern margin of its natural distribution in Ireland. Although the country has lost approximately one third of its documented char populations, the mechanisms involved remain largely unresolved.

Following the precise determination of spawning sites in four lakes of differing productivity, experiments were conducted to explore spawning requirements, and threats affecting the early life stages.

The threat of increasing winter temperatures was highly evident, as mean temperatures in the spawning substrata during the incubation period were at the level above which mortality has been shown to greatly increase. The brown trout (Salmo trutta) which co-occurs with all Irish char populations was found to predate strongly on Arctic char eggs, with individual trout capable of ingesting the entire egg output of a single Arctic char female. Predation levels appeared to be greater in enriched lakes due to an increase in trout abundance and size.