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[Display omitted] • Non-invasive environmental DNA (eDNA) metabarcoding can be used to describe fish communities. • Temperature, water age and trophic status influenced eDNA-based fish distribution in heterogeneous reservoirs. • eDNA records can be used to model the ecological requirements of fish species. Biomonitoring of complex heterogeneous environments is highly challenging. Fish in deep water bodies occupy different habitats, so a combination of survey methods has traditionally been used. Environmental DNA (eDNA) metabarcoding is a novel monitoring tool that can overcome spatial heterogeneity in a highly sensitive and entirely non-invasive manner. However, taxon detection probability is dependent on environmental variables. In this study, three reservoirs were sampled in two seasons using a spatiotemporally distributed sampling design covering major environmental gradients. In all sampling campaigns, 31 fish taxa were detected. Data reliability was supported by tight positive correlations between individual taxon scores derived from gillnet sampling and eDNA site occupancy. Analyses confirmed anticipated trends, such as the highest number of taxa in the largest water body, and more taxa in inflows and littoral regions compared to open water. The most important factors for fish distribution were temperature, water age and trophic status (expressed as total Chlorophyll a concentration) of water bodies. Taxon detection reflected ecological niches of individual species, e.g. warm water wels catfish (Silurus glanis) and cold water salmonids. This study provides further evidence that eDNA metabarcoding is a suitable alternative or complement to conventional fish sampling in reservoirs. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) metabarcoding can identify terrestrial taxa utilising aquatic habitats alongside aquatic communities, but terrestrial species' eDNA dynamics are understudied. We evaluated eDNA metabarcoding for monitoring semi-aquatic and terrestrial mammals, specifically nine species of conservation or management concern, and examined spatiotemporal variation in mammal eDNA signals. We hypothesised eDNA signals would be stronger for semi-aquatic than terrestrial mammals, and at sites where individuals exhibited behaviours. In captivity, we sampled waterbodies at points where behaviours were observed ('directed' sampling) and at equidistant intervals along the shoreline ('stratified' sampling). We surveyed natural ponds (N = 6) where focal species were present using stratified water sampling, camera traps, and field signs. eDNA samples were metabarcoded using vertebrate-specific primers. All focal species were detected in captivity. eDNA signal strength did not differ between directed and stratified samples across or within species, between semi-aquatic or terrestrial species, or according to behaviours. eDNA was evenly distributed in artificial waterbodies, but unevenly distributed in natural ponds. Survey methods deployed at natural ponds shared three species detections. Metabarcoding missed badger and red fox recorded by cameras and field signs, but detected small mammals these tools overlooked, e.g. water vole. Terrestrial mammal eDNA signals were weaker and detected less frequently than semi-aquatic mammal eDNA signals. eDNA metabarcoding could enhance mammal monitoring through large-scale, multi-species distribution assessment for priority and difficult to survey species, and provide early indication of range expansions or contractions. However, eDNA surveys need high spatiotemporal resolution and metabarcoding biases require further investigation before routine implementation. [ABSTRACT FROM AUTHOR]