changes when they are as far south as Ireland, where they are at the southern edge of their species range. The greatest threats to their survival in Ireland are introduced fish species, eutrophication, acidification and climate change. The rate of extinction of entire populations in Ireland has increased in recent decades. The Killarney shad (or goureen) (Alosa fallax killarnensis) is a land-locked lake-dwelling subspecies of twaite shad, a mostly marine species. It is unique to the Lakes of Killarney. It is rarely seen because it feeds mainly on plankton and thus is rarely caught by fishers. It is listed in the Irish "Red Data Book" of threatened species. It is listed in Annex II of the EU Habitats Directive. Invertebrates Several unusual invertebrate species can be found in the Killarney valley. Some of these species, including the northern emerald dragonfly (Somatochlora arctica) and several caddisfly and stonefly species are usually found much further north in Europe. They are thought to be relict species that were left behind in Killarney after the last retreat of ice. The northern or moorland emerald dragonfly, the rarest Irish dragonfly, is confined to the park. It breeds in shallow pools in bogs. The oak woods in the remote Glaism na Marbh valley are a stronghold for Formica lugubris Zett., a wood ant species that is rare both in the Killarney woods and in Ireland as a whole. The Kerry Slug (Geomalacus maculosus) is a hiberno-lusitanean species. It emerges in Killarney's frequent wet weather to graze on lichens on rocks and tree trunks. It is reputedly the only slug capable of rolling itself into a ball. It is on both Annex II and Annex IV of the EU Habitats Directive. Conservation threats The park has a number of conservation and management challenges. One of these is the park's proximity to Killarney town, one of Ireland's best known tourist destinations. Killarney has hundreds of thousands of visitors every year. Most of these visitors spend time in the park. Careful management is needed to ensure minimal conflict between conservation and recreation. The past introduction of several exotic species to the park is an additional human influence on the area. These species have damaged the natural ecosystems of Killarney. The most notable of these species are the common rhododendron (Rhododendron ponticum), which has infested large areas of the National Park, and sika deer, which overgraze the woodland floor and