Aquatic Fish Irreplaceability - ACE [ds2753]

Aquatic Fish Irreplaceability, Areas of Conservation Emphasis (ACE), version 3.0.

Aquatic Irreplaceability is a measure of the uniqueness of habitat areas for aquatic species in the landscape, and is one measurement used to describe the distribution of overall species biodiversity in California for the California Department of Fish and Wildlife’s (CDFW) Areas of Conservation Emphasis Project (ACE). Other measures of aquatic species biodiversity included in the ACE aquatic biodiversity summary are aquatic native species richness and aquatic rare species richness.

Here, aquatic irreplaceability represents the relative importance of each watershed based on the uniqueness of habitat areas present for rare and endemic aquatic species. Watersheds with high irreplaceability contain species or habitat conditions that occur in few places in the landscape. These areas may be of high conservation value due to their unique contribution to biodiversity. The data provides, 1) the irreplaceability weight, based on the rarity-weighted index (RWI), which weights the species count by the extent of the distribution for each species, so watersheds providing habitat for narrowly distributed species are given a higher score, and 2) a count of the total number of endemic species per taxonomic group in each watershed based on documented species occurrence information for aquatic reptiles and amphibians. Areas with a high RWI support rare species with few documented occurrences; these areas would be expected to support unique habitats or suites of species that are limited in distribution. The data can be used to identify areas of high irreplaceability. Users can view a list of species that contribute to the biodiversity summary for each watershed.