Snags have been identified as being critical for shelter and as spawning sites for native fish, and are one of the few hard substrates available for biofilm growth supporting aquatic invertebrates in lowland rivers flowing through alluvial flood plains. Snags are important as sites for biofilm growth and for shelter and feeding of aquatic invertebrates in both lowland and upland rivers/streams.
In Australia the role of snags has been largely ignored until recently and more than one million snags have been removed from the Murray-Darling basin. Large tracts of the lowland reaches of the Murray-Darling system are now devoid of the snags that native fish like Murray Cod require for shelter and breeding. The damage this snag removal has caused has not been systematically assessed.