Grayling population of national importance: core areas

The data on grayling populations of national importance includes three subproducts; the core zones layer includes the areas of particular importance for grayling populations, based on biological and/or ecomorphological characteristics at fisheries. The core data come from the atlas of fish and cyclostome distribution in Switzerland (Pedroli et al. 1991), cantonal catch statistics and information from the cantonal management of fisheries.