Environmental DNA as a non-invasive sampling tool to detect the spawning distribution of European anadromous shads (Alosa spp.)

Antognazza, Caterina, Britton, Robert, Potter, Caitlin, Franklin, Elizabeth, Hardouin, Emilie, Gutmann Roberts, Catherine, Aprahamian, Miran and Andreou, Demetra (2021) Environmental DNA as a non-invasive sampling tool to detect the spawning distribution of European anadromous shads (Alosa spp.).

1. The shads Alosa alosa and Alosa fallax (Alosa spp.) have high conservation designations in Europe due to the vulnerability of their populations to human disturbances. In particular, river impoundments block their upstream migration, preventing access to spawning areas. Knowledge on the spatial extent of their spawning is important for informing conservation and river management plans. 2. Determining the spatial extent of Alosa spp. spawning is challenging. They enter rivers over a two to three-month period and the species potentially migrate different distances upstream. Capture and handling can be problematic and spawning events generally occur at night. Thus, assessing their spatial extent of spawning could utilise non-invasive sampling tools, such as environmental DNA (eDNA). 3. An eDNA assay for Alosa spp. was successfully developed, based on the Cytochrome c Oxidase Subunit I gene segment and quantitative polymerase 82 chain reaction (qPCR). Application in spring 2017 to the River Teme (River Severn catchment, Western England) revealed high sensitivity in both laboratory and field trials. Field data indicated spawning between May and June, with migrants mainly restricted to areas downstream of the final impoundment. 4. eDNA can thus be utilised as a non-invasive sampling tool to determine the freshwater distribution of these fishes in Europe, enhancing their conservation at local and regional scales.