Accurate data characterizing species distribution and abundance are critical for conservation and management of aquatic resources. Inventory methods, such as gillnet surveys, are widely used to estimate distribution and abundance of fish. However, gillnet surveys can be costly in terms of material and human resources, may cause unwanted mortality in the fish communities being studied, and is subject to size and species selection bias. Detecting allochthonous DNA released by species in their environment (i.e., environmental DNA, hereafter eDNA) could be used as a noninvasive and less costly alternative. In this study, we directly compare eDNA metabarcoding and gillnets for monitoring freshwater fish communities in terms of species richness and relative species abundance. Metabarcoding was performed with the 12S Mifish primers. We also used species‐specific quantitative PCR (qPCR) for the most abundant species, the walleye (Sander vitreus), to compare estimated relative abundance with metabarcoding and gillnet captures. Water sample collection, prior to gillnet assessment, was performed on 17 sites in the hydroelectric impoundment of the Rupert River (James Bay, Canada), comparing two water filtration methods. After controlling for amplification biases and repeatability, we show that fish communities’ complexity is better represented using eDNA metabarcoding than previously recorded gillnet data and that metabarcoding read count correlates with qPCR (r = 0.78, p < .001) in reflecting walleye abundance. Finally, based on partial redundancy analysis, we identified alpha chlorophyll, pH, and dissolved oxygen as environmental variable candidates that may influence differences in fish relative abundance between metabarcoding and gillnets. Altogether, our study demonstrates that the proposed eDNA metabarcoding method can be used as an efficient alternative or complementary technique adapted to the biomonitoring of the fish communities in boreal aquatic ecosystems.

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Invasive non-native species (INNS) are recognized as a major threat to island biodiversity, ecosystems, and economies globally. Preventing high-risk INNS from being introduced is the most cost-effective way to avoid their adverse impacts. We applied a horizon scanning approach to identify potentially INNS in the United Kingdom Overseas Territories (OTs), ranging from Antarctica to the Caribbean, and from the Pacific to the Atlantic. High-risk species were identified according to their potential for arrival, establishment, and likely impacts on biodiversity and ecosystem function, economies, and human health. Across OTs, 231 taxa were included on high-risk lists. The highest ranking species were the Asian green mussel (Perna viridis), little fire ant (Wasmannia auropunctata), brown rat (Rattus norvegicus), and mesquite tree (Prosopis juliflora). Shipping containers were identified as the introduction pathway associated with the most species. The shared high-risk species and pathways identified provide a guide for other remote islands and archipelagos to focus ongoing biosecurity and surveillance aimed at preventing future incursions.

Cyclura lewisi is an endangered rock iguana endemic to the island of Grand Cayman. Like many other animals, C. lewisi increasingly depends on modified landscapes for its survival. The remaining natural population is too small and fragmented to yield information on the natural history and population biology of this species. Therefore, we studied habitat use in a population of captive-bred, released iguanas in a botanic park. Compositional analysis was used to examine habitat selection and use by iguanas at two scales: selection of home range within the landscape and selection of locations within home ranges. At both scales and for all time periods examined, iguanas preferred modified habitat to natural habitat. Subhabitats were examined only at the scale of selection within the landscape, for which iguanas showed preference in some but not all time periods. Iguanas used artificial retreats more often than natural retreats and commonly occupied retreats in modified areas. Many female iguanas nested in artificial sites within the park. The use of modified habitats and artificial retreats and nests by reintroduced C. lewisi is encouraging, because this and other species of Cyclura may depend on these resources for future survival.