Weeta Weir

A barrier to fish passage on the Namoi River

Removed weir

Free passage for fish is now possible

Fishways

Allow fish to move upstream past a weir

Poorly functioning road crossing

Inadequate pipes prevent fish passage

Improved fish passage

Box culverts reduce water velocities and increase light availability

Auto-tidal floodgate

Opens and closes a smaller gate with each tidal cycle to provide fish passage

Improving fish passage

All Australian native fish need to migrate or move within a waterway as part of their life cycle: to access new habitats, avoid predators, find food or to breed. Some species may only move tens of metres, others migrate over thousands of kilometres.

A well connected waterway is therefore important for our native fish to be able survive.

Instream structures such as weirs, roads and floodgates have the potential to stop fish from being able to move within a waterway, potentially leading to increased predation risk, disease transfer and in extreme cases, localised extinctions as fish accumulate below a barrier or are unable to access breeding habitats.

By addressing fish passage at these structures, we are providing the best opportunity for fish to move within a waterway, to access food, find shelter and breed.

In 2002 the installation of and operation of Instream structures and other mechanisms that alter natural flow regimes of rivers and streams was listed as a Key Threatening Process under the NSW Fisheries Management Act 1994.

Since that time actions to reduce or eliminate the impacts of instream structures have been a focus for DPIRD Fisheries across NSW. Some include:

Assessing and mitigating the impacts of new structures
Removing redundant structures that are no longer used
Constructing fishways at major barriers to provide fish passage
Partnering with researchers to improve our understanding of fish swimming abilities and improve structure designs
Ensuring road crossing designs are fish friendly
Managing structures to lessen their impacts (e.g. opening gates at certain times of the year)
Constructing fish friendly screens to reduce the impact of irrigation offtakes
Constructing multi-level off takes and/or mixed devices to reduce the impact of cold water pollution
Allocating environmental flows to promote migration
Managing water delivery to mimic natural flows.