The Hawkesbury Nepean is the longest coastal catchment in NSW. The Hawkesbury river flows 470 kilometres (from south of Goulburn near Lake Bathurst to Broken Bay), draining 21,400 square kilometres, or 2.14 million hectares, of land.
The aquatic biodiversity of this region was assessed as part of the project looking at barriers to fish passage. The report provides a listing of the fish species found in the region.
More research is being done into the fish communities and fish habitats within the region. Reports on fish communities in the Nepean River (2007) and changes in the fish habitats in the downstream reaches of the Hawkesbury-Nepean system over the last 60 years (2007) are available.
Fish communities in the Hawkesbury-Nepean River were studied to find out if different species of fish were found on river banks with different types of vegetation. Two categories of vegetation were considered - well-vegetated banks supporting complex flora dominated by trees and shrubs, and grassed banks that have been colonised by grasses after the historical removal of the natural trees and shrubs vegetation. The fish communities differed among different parts of the river, in different seasons, and between river bank types. Habitats adjacent to grassed banks supported 211% more individuals and 29% more fish species than well-vegetated banks. Three small species of fish, firetail gudgeons, flathead gudgeons and empire gudgeons occurred in greater abundances adjacent to grassed banks, but freshwater mullet were 73% less abundant near grassed banks than beside well-vegetated banks. It is thought that the observed differences in the distributions of fish species are primarily related to the greater density of aquatic macrophytes near grassed banks. It is suggested that to attain an appropriate level of habitat complexity to support fish communities, current large declines in macrophytes in the lower reaches of the river system needs to be reversed. Management of riparian vegetation should therefore contain a component of macrophyte management at a local scale.
For the full article see: Growns, I. , Gehrke, P.C., Astles, K.L. and Pollard, D.A., 2003. A comparison of fish assemblages associated with different riparian vegetation types in the Hawkesbury-Nepean River system. Fisheries Management and Ecology 10(4): 209-220.
There is now a complete coverage for the 154 NSW estuaries which contain one or more of the important estuarine habitats such as seagrass, mangrove and saltmarsh. These maps will provide coastal Local Land Services and Local, State and Australian Governments with information to support natural resource condition targets and to monitor the effectiveness of management actions against those targets.
More information about Key Fish Habitat mapping.
Fish movement within this region can be restricted by in-stream structures. Reports are available on reducing the impact of weirs and of road crossings.
The aquatic habitat of the Hawkesbury Nepean has a specific protection plan. This is a document under the Fisheries Management Act.
There are several NSW DPI projects aimed at rehabilitating aquatic habitat within this region. NSW has partnered with Oceanwatch Australia for the Tide-to-Table project.
Of the pests that occur within the region, there are two for which specific control plans have been developed: salvinia and alligator weed.