Search

Pitfall trapping is widely used to estimate population density in carabid beetle communities, but overestimates densities of large bodied species relative to smaller ones because large species move more around. The aim of the study was to test whether abundance estimates from hand collection (collection without area fixing and washing of the substratum) is less subject to such body size-related bias. This was addressed by comparing slopes of size-abundance relationships using data from hand collection with slopes estimated from pitfall trapping data. The material consisted of 246 carabid species and more than 63,000 individuals sampled in 11 habitat types. For epigean carnivores, size-abundance slopes based on hand collection data were significantly more negative than those based on pitfall trapping. This shows that population density estimates from hand collection is less subject to the size-related bias associated with pitfall trapping for this group. Hand collection slopes for epigean carnivores were also similar to slopes found using quadrate sampling in a habitat type where this method had been performed. They were also not different from the theoretical value of −0.75 predicted from the energetic equivalence rule in 5 of the 11 habitat types sampled. This suggests that epigean carnivore population density estimates from hand collection may indeed be unbiased regarding body size in many habitat types. Further studies are needed to clarify how extensively this applies. The analyses also show that hand collection underestimates densities of fossorial carnivores regardless of habitat type and overestimates densities of large bodied epigean carnivores in habitat types where large hiding objects are abundant. For phytophages, no significant differences were found between the performance of hand collection and pitfall trapping. [ABSTRACT FROM AUTHOR]

• Combining eDNA and trawl data increases the detected biodiversity. • Good reference databases are of vital importance for correct taxonomic classification. • We advocate that a combined sampling effort is a good strategy for future monitoring of biodiversity in the Arctic including the Barents Sea. Managing natural resources in a sustainable manner requires understanding the complexity of ecosystems and the species that are associated with the different parts of the ecosystem. Much of this knowledge is derived from traditional sampling methods (e.g., different types of trawls). The analysis of environmental DNA (eDNA) can provide increased knowledge, complementary to the traditional methods. In the present pilot study, we sampled eDNA from two geographical areas, north and west of Svalbard (NWS) and in the southwestern Barents Sea (SWBS). The combination of trawling, visual identification of mammals and eDNA collection facilitated a robust analysis of fish and marine mammal diversity and species composition. Through 12S MiFish metabarcoding of the eDNA samples, we found that incorporating eDNA data provided an additional level of information on both the diversity of fish and marine mammals in the study areas. By adding eDNA data to the trawl data, we found that richness increased from 32 to 49 fish taxa. Significant differences in diversity and composition of the fish communities were detected by eDNA between the two study areas. Considering degradation and dilution factors it is postulated that the results represent resident species to the Barents Sea and that long -transported DNA from other areas are less likely. [ABSTRACT FROM AUTHOR]