Fish Movement Behaviour in Dryland Riverscapes: Acoustic Tagging to Identify Response to Flow

In many dryland rivers, fishes are confined to isolated waterholes for much of the year. It is only during the short-duration flow events that typify the hydrology of these systems, that they are able to move between waterholes, explore their home range and select optimum local habitats. Because most of the river channel will dry following such events, there is a strong survival imperative for selection of refuge waterholes. Modifications to both flow regime and hydrological connectivity have the potential to reduce movement opportunities.

Four fish species were tagged (Vemco V7 acoustic tags) and monitored in the Moonie River (Queensland, Australia) with a network of receiver stations to identify: which flow events trigger fish movement between waterholes; differences in response due to species, sex and size; refuge preferences; the effect of barriers (weirs and road crossings).

The majority of individuals of all species moved during events, but the response was species-specific. In general, there was no clear upstream or downstream preference and most utilised a reach of up to 20 km, though some individuals ranged over more than 70 km in only several days. Timing of flow appears to be more important than magnitude, as most movement occurred in response to the first post-winter flow event independent of its magnitude and duration. Many of the fish that moved returned to their starting waterhole either by the end of an event, or on subsequent events, suggesting ability to home and a preference for more permanent refuge pools.

Findings highlight that fish in these systems utilise networks of waterholes and that management should aim to maintain movement opportunities at large spatial scales to preserve population resilience.