Indicator: IW-25 Number and extent of re-snagging programs
The Fisheries Management Act 1994, through the Fish Habitat Protection Plan No 1, requires public authorities, including local government and state authorities, to "notify the Minister of any proposal to remove or relocate snags whether they propose to undertake the work or to authorise it".
NSW Fisheries Policy and Guidelines for Aquatic Habitat Management and Fish Conservation (1999) states in relation to snags that:
- snags should be retained to the greatest extent possible
- snag removal for purely aesthetic purposes should not be supported
- NSW Fisheries will not support snag management proposals aimed at improving navigability for individuals. Proposals aimed at maintaining navigability of rivers with a long history of boating use may be supported, provided threatened species would not be adversely affected
- NSW Fisheries will not support snag removal proposals aimed at increasing flood immunity
- NSW Fisheries supports snag management programs that are part of an overall strategy to stabilise and rehabilitate degraded streams, providing that there are minimal levels of disturbance.
Source: NSW Fisheries 2001, Snags (large woody debris) (DF97) - September 2001, viewed 14 Nov 2005, http://www.fisheries.nsw.gov.au/aquatic_habitats/aquatic_habitats/snags
Fourteen sites on the River Murray have been resnagged with the addition of over 300 large river redgum snags. The resnagging used a scientific approach, which allowed the testing of different snag locations and configurations. Structured monitoring showed the same number of native fish species used the sites as in areas of naturally occurring snags. Murray cod, trout cod and golden perch used the snags but carp did not.
Source: Murray Darling Basin Ministerial Council 2003, Native Fish Strategy for the Murray-Darling Basin 2003-2013, Murray Darling Basin Commission, viewed 14 Nov 2005, http://www.mdbc.gov.au/NFS.
In NSW at least, there seems to be wide acceptance that re-snagging of streams is beneficial and efforts are underway to reintroduce snags. Data have not been found for other jurisdictions.
The extent of re-snagging programs in other jurisdictions, and in NSW other than on the Murray, is unknown.
Areas containing snags have a high diversity of river biota. They provide habitat for many plants and animals, from the microscopic bacteria, fungi and algae, through to large native fish and platypus. Snags that stick out of the water provide roosting places for birds and other animals such as turtles. They are sources of food for invertebrates and trap leaves and other organic matter, which are also sources of food. Snags provide breeding sites. Snags can reduce the effects of flooding.
De-snagging in the past has been carried out for ‘river improvement’. Restoring snags are now being considered as part of river restoration projects. Number and extent of resnagging programs would be indicative of improvements in the management of inland waters.
Other indicators for this issue:
- IW-13 Catchment sediment load
- IW-18 Exceedance of suspended solids water quality triggers
- IW-24 Extent of sedimentation (incl sand slugs)
- IW-30 Macroinvertebrate condition