Conservation status of the idle crayfish Austropotamobius bihariensis Pârvulescu, 2019

Knowledge about the conservation status of a species is crucial for its protection in the long run. It provides insights into the geographic range, population size and trend, which are useful in management activities towards safeguarding the future of a species. The idle crayfish, Austropotamobius bihariensis, is a recently described crayfish species that has not yet undergone a full conservation assessment. Here, we present our extensive 13-year study that aimed to fill this gap by investigating and monitoring the species' entire geographic occurrence range and quantifying its subpopulations. Although it is an endemic crayfish located in the Apuseni Mountains (Romania), its range and population is stable. The observed relative abundance is highly unbalanced within subpopulations, with 71% falling below ten individuals per 100 m river stretch. We documented four extinct subpopulations (ca. 16%), whereas more than half of the subpopulations being in a size-decreasing trend. Since no invasive crayfish were detected in (or very close to) its distribution area, the idle crayfish can still be considered safe against invasions. However, based on our findings and following the IUCN Red List Guidelines, we concluded that idle crayfish's most appropriate conservation status is Endangered. IUCN ratification is required for increased significance. [Display omitted] •The species range spans over 3352 sq. km, in the upper sectors of the Criș, Barcău and Arieș rivers from Apuseni Mountains.•Stable population with highly fragmented clusters of subpopulations and decreasing overall trend in their relative abundance.•Highest mitochondrial haplotype diversity per river basin is in Criș Negru and Criș Alb, whereas Arieș has a unique haplotype.•The appropriate conservation status for idle crayfish Austropotamobius bihariensis Pârvulescu, (2019) is Endangered.