Abstract
Introductions of non-native fish have the potential to cause substantial economic and ecological losses. In the western United States, non-native brook trout (Salvelinus fontinalis) are widely established and pose a threat to the persistence of bull trout (Salvelinus confluentus), a native char listed as threatened under the US Endangered Species Act, due to competition and hybridization. With brook trout identified as a factor limiting the recovery of ESA-listed bull trout in the Malheur Watershed of eastern Oregon, managers are pursuing brook trout eradication efforts. Key to the eradication efforts is reliable monitoring to ensure success. Traditional monitoring practices have included mechanical sampling methods such as seining, netting, and electrofishing, all of which are labor intensive and limited in reliability. Environmental DNA (eDNA) is genetic material naturally shed by organisms that can be found in bulk environmental samples without isolating individual organisms. Sampling for eDNA can often be done with less time and expense than traditional methods, making it ideal for effectiveness monitoring following fish eradication efforts. This study placed a single fish in a live-car where the species was not otherwise present and used eDNA sampling to infer the likelihood of detection downstream. Results suggest that a single fish can be detected reliably up to 500 m downstream when multiple samples are taken. This eDNA sampling method provides managers with the ability to conduct eradication effectiveness monitoring reliably and rapidly and may also be used to detect new fish invasions as well as rare or cryptic species.
Highlights
Introductions of non-native fish have the potential to cause substantial economic and ecological losses
DNA is genetic material naturally shed by organisms that can be found in bulk environmental samples without isolating individual organisms
All templates derived from known brook trout fin clips were detected with the brook trout species quantitative polymerase chain reaction (qPCR) assay developed for a mitochondria cytochrome b gene locus (Table 1)
Summary
Introductions of non-native fish have the potential to cause substantial economic and ecological losses. Sampling for eDNA can often be done with less time and expense than traditional methods, making it ideal for effectiveness monitoring following fish eradication efforts. Results suggest that a single fish can be detected reliably up to 500 m downstream when multiple samples are taken This eDNA sampling method provides managers with the ability to conduct eradication effectiveness monitoring reliably and rapidly and may be used to detect new fish invasions as well as rare or cryptic species. Germane to the present study, introduced and invasive brook trout pose a threat to the persistence of bull trout (Salvelinus confluentus), a char native to northwestern North America, in their southern range due to competition (Gunckel 2001), overlapping spawning times, and the ability to produce viable hybrids (DeHaan et al 2010). In portions of its range, the development and implementation of a comprehensive brook trout eradication and control strategy was listed in the 2015 US Fish and Wildlife Bull Trout Recovery Plan as ‘an action that must be taken to prevent extinction or prevent the species from declining irreversibly in the foreseeable future’ (US Fish and Wildlife Service 2015)
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