This project investigated barriers to fish migration in rivers in the Darling region of the Basin, and has provided an assessment of the composition and migratory requirements of the fish fauna in the Northern Basin. The work included an analysis of available options for fish passage, as well as justification for the preferred options in terms of the ecological, hydraulic and technical design constraints associated with each weir.
Spanning river systems in both New South Wales and Queensland, 12 high priority sites were identified, together with concept designs and investment costs to fix the top five priority barriers to fish passage. These weirs were chosen because of their anticipated high benefit/cost ratio.
The project identified that there are two feasible approaches to rehabilitating fish passage in the northern Basin:
- provide fish passage at the top 11 priority structures to reinstate 2,086 km of river channel. The total cost was estimated at $14.56 m; or,
- provide a strategic, holistic, program re-establishing broad-scale river connectivity of over 3,242 km. The total cost was estimated to be approximately $70 m.
The key features that make a fish passage program feasible in this area are:
- the main-stem barriers are not numerous (42 for a broad-scale program reinstating over 3,200 km of river).
- most of the barriers are low-level weirs between 1.5 m and 4.5 m high, with the exception of only eight structures.
- most of the sites are relatively easy to work with.
Implications for native fish
The project has provided a clear direction for strategic improvement of fish passage in the Darling system to reduce fragmentation of fish populations. Fishway concepts were specifically designed to suit the fish assemblage and semi-arid ecology of the northern Basin, and considered the feasibility of construction, materials, regional context, maintenance and ownership.
Nichols S, Berghuis A, Lay C, Mallen-Cooper M. (2011). Fishway Options for Weirs of the Northern Murray-Darling Basin. Report prepared for the Murray-Darling Basin Authority. 92pp.
Baumgartner, L. J., Reynoldson, N. & Gilligan, D. M. (2006). Mortality of larval Murray cod (Maccullochella peelii) and Golden perch (Macquaria ambigua) associated with passage through two types of low-head weirs. Marine and Freshwater Research 57, 187-191.
Bell, M. C. & DeLacey, A. C. (1972). A compendium on the survival of fish passing through spillways and conduits. Portland, Oregon: US Army Corps of Engineers, North Pacific Division.
Larinier, M. & Travade, F. (2002). Downstream Migration: Problems and Facilities. Bull. Fr. Pece. Piscic. 364, 181-207.
Marttin, F. & De Graaf, G. J. (2002). The effect of a sluice gate and its mode of operation on mortality of drifting fish larvae in Bangladesh. Fisheries Management and Ecology 9, 123-125.
O’Connor, J. P., O’Mahony, D. J. & O’Mahony, J. M. (2004). Downstream migration of adult Murray-Darling fish species. Downstream Movement of Fish in the Murray-Darling Basin (Lintermans, M. & Phillips, B. eds.) Canberra: Murray Darling Basin Commission.