Environmental Influences On The Juvenile Migration Of The Threatened Amphidromous Australian Grayling (Prototroctes Maraena)

Many diadromous species are threatened globally. Management actions to conserve these species need to be based on a quantitative understanding of their life history requirements. The transition between marine and freshwater habitats is a critical component of the life cycle of diadromous fishes, but is poorly understood for many species. We investigated recruitment patterns of juvenile Australian grayling (Prototroctes maraena), a nationally threatened amphidromous fish, entering freshwater environments in four streams in south-east Australia across 3 years (2016-18). Migration occurred from September to December, with peak abundances between late October and early November (mid-austral spring). Catches were also related to mean daily discharge in the preceding 7 days, with highest catches at intermediate flows (similar to 100-150 ML day(-1)). Our results can inform management actions, such as environmental flows, for attracting and facilitating the movement of juvenile Australian grayling into freshwater from marine nursery areas.