Background to crayfish monitoring
Our knowledge of crayfish taxonomy and distribution is steadily improving; we now know that there are around 650 species of freshwater crayfish in many different habitats, although the ecological roles of most have not been studied or understood and only about 15 of these (less than 3%) are commercially exploited. The main commercial species are examined in Holdich (2002a) and all the European native species and their genetic variation are documented in Souty-Grosset et al. (2006). However, with such knowledge comes an awareness of possible differences in ecology, and indeed vulnerability, between related stocks.
Many crayfish species whose ecology has been studied are shown to play important roles in their ecosystems (Chapter 3). The community in which crayfish operate is modified and regulated by these keystone species, with a potential increase in biodiversity through food-web control. Management-led conservation needs the support of directed research. This should include evaluation of the current status and trends of freshwater biodiversity and of the drivers of change in fresh waters, including climate change and invasive species, and their impacts on freshwater biodiversity.