ABSTRACT
A good grasp of the environmental drivers for population success is particularly pertinent for two quite opposing reasons when considering crayfi sh. For the purpose of conserving particular crayfi sh species, then a clear understanding of environmental tolerances and thresholds is important when defi ning habitat requirements and implementing management strategies for maintaining crayfi sh habitat of suitable quality to best promote sustainable populations. Our understanding of the environmental factors that may limit their distribution, particularly beyond the very local scales often studied, is still often inadequate (Dyer et al. 2013). This would be particularly relevant in the case of ‘ark site’ selection, a key component of the crayfi sh conservation strategy being implemented within Europe (Schulz et al. 2002), since ark sites are typically a last ditch attempt to save a population by translocating it away from perceived threats. An ark site must represent ‘the ideal’, the optimal suite of environmental parameters in which to preserve and hopefully propagate population numbers to potentially use for recolonization of former sites when appropriate. In contrast, understanding when and under what environmental conditions populations of crayfi sh falter or fail might reveal chinks in the armour of particularly pernicious crayfi sh that are gaining repute as invasive species. Exploiting such chinks could be an avenue toward control measures for some of those species introduced either intentionally or accidentally into water bodies where they are now wreaking considerable ecological and economic damage.
