The diversity of fauna and wildlife throughout this area  is unusual for South Australia. The freshwater river and national park being so close to the sea provides an environment for a large mix of animals, birdlife and plants.There are several walks through the Onkaparinga River National Park and these are signposted at the swing bridge entrance to the park.

The Bird Sanctuary on River Road has a pedestrian walk through bushland and across wooden broadwalks and feeds back along the river to the car parking area and cycle track. A walk around Old Noarlunga , following the river , takes you past tall cliffs with nesting falcons through reeded pools with cormorants fishing. The river changes from fresh water to salt as you travel toward the sea , and the fauna and birds change with this water change.Fishing is good for Pelicans and the wider pools between the bridges provide an ideal area to get a feed.

History :-The lower reaches of the Onkaparinga River were inhabited by the Kaurna Aboriginal people, and the name of the river is taken from the Kaurna name meaning “women’s river”. European settlement and farming in the district began about 1840 leading to the rapid displacement of the Aboriginal inhabitants. Noarlunga (now Old Noarlunga) was the business centre with farm produce being transported 10 km down river to Port Noarlunga.The Onkaparinga River National Park (1544 ha)features rounded ridge tops, steep gorge slopes and the narrow river valley of the Onkaparinga Gorge. Here the Onkaparinga River’s rocky and tumbling course connects the townships of Clarendon and Old Noarlunga.In the gentle estuarine environment of the Onkaparinga Recreation Park (284 ha), the now quietened river spills on the plains, providing views of meandering riverbanks, wetland ponds and flood plains.At the western end of the estuary between the scenic Port Noarlunga cliffs, sand dunes, beachand reef, the river water completes the journey to the sea. From the rugged gorge to the river plains, the parks provide a natural corridor for wildlife.

The early custodians :- Prior to and during European settlement these parks and river system were undoubtedly important to the Kaurna (‘Gar-na’) people. Kaurna people still have strong ties to this area through cultural practices and religious beliefs. Many local place names such as ‘Onkaparinga’, and ‘Noarlunga’ have their origins in Kaurna language.

Fishes :- Over 30 species of fish have been identified from the Onkaparinga estuary to date (Branden et al. 1974, Sinclair Knight Merz [SKM] 2002). The estuary is an important source of food for yellow-eye mullet (Aldrichetta forsteri), black bream (Acanthopagrus butcheri) and jumping mullet (Liza argentea), which have the greatest distributional range and are the most abundant (Branden et al. 1974). Jumping mullet Smallmouthed hardyhead (Atherinosoma microsotoma) appear to feed mainly on microalgae, yellow-eye mullet on algae that are epiphytic on seagrass, and black bream have a diet ranging from algae to molluscs (Branden et al. 1974). The estuary and particularly the seagrass is widely accepted to provide a nursery area for those fishes and others, including whiting species and mulloway (Argyrosomus japonicus), that are fished recreationally and/or commercially (Bryars 2003). Jumping mullet and black bream migrate to the upper estuary to spawn during spring and summer (Branden et al. 1974).

Birds :-The Friends of Onkaparinga Park community group have recorded over 100 bird species in the estuary and its associated habitats. A number of waterbirds migrate internationally (see Table 2), and the estuary provides a small but useful habitat in the life cycle of these species (DEH 2004). Some migrate from arctic Siberia to Australia e.g. sharp-tailed sandpiper (Calidris acuminata), while others such as the greenshank migrate from Asia. Migratory birds covered by international treaties or agreements are automatically listed (and therefore protected) under the Environment Protection and Biodiversity Conservation Act 1999 as “Matters of National Environmental Significance”. Over 30 other bird species found in or near the Onkaparinga estuary are protected under the same act as listed marine species. Waterbirds recorded in the area that are considered threatened in South Australia include the musk duck (Biziura lobata), Cape Barren goose (Cereopis novaehollandiae), and Australasian bittern (Botaurus poiciloptilus).

The Onkaparinga river estuary and wetlands extend for over 10 kilometres from the river mouth at Port Noarlunga to the historic township of Old Noarlunga. The subtle beat of the wetland is most vibrant in spring, after the winter rains. The Wetland Trail in Onkaparinga National Park gives an informative insight into the environment and offers good opportunities for walkers, bird watchers and photographers alike. A parking area with barbecues lies at the head of the trail, off River Road. The river estuary is a popular spot for local fishermen in search of mullet and black bream.

Saltbush, samphire and sedges:-The estuary contains shrubland of samphire and saltbush, wetlands of bull rushes, club rush and cutting grass. These plants have the ability to survive in saline environments by special adaptations that help them expel salt. Records show that 180 bird species inhabit the park and river, with birds being found from the plains and backwaters to the highest cliffs. The park and river is a birdwatcher’s paradise. Within the gorge, remnant woodlands of Pink Gum, River Red Gum, Grey Box, sheoak and native pine and significant grasslands have survived some 160 years of livestock grazing, timber harvesting and cropping. Since the protection of this landscape combined with revegetation efforts, large areas of native vegetation have prospered. Considerable effort has been applied by government and volunteers to control pest.

Fishing:- Fishing is permitted in the estuary waters  but size and bag limits, and seasonal restrictions apply. Please remember that a healthy river relies on healthy riverbanks and water quality.

Picnicking:- Barbecue, picnic shelters and toilet facilities are located at Market Square Reserve in Old Noarlunga.

Wetlands: reed beds, semi-permanent and permanent bodies of water (natural and constructed) and brackish wetlands. Pacific black ducks (Anas superciliosa) and purple swamp hens (Porphyrio porphyrio) nest and feed in the reeds that fringe the river banks. These areas are important for black swan (Cygnus atratus) populations because they require freshwater for breeding and raising their young (OCWMB 2005).

Open Water: main river channel and areas of deeper water that experience river/tidal flow. Swans, pelicans (Pelecanus conspicillatus) and cormorants (Phalacrocorax spp.) all frequent the deeper regions of the river channel searching for food. Swans mainly feed on aquatic vegetation, while cormorants and pelicans are often seen fishing in the deeper pools (OCWMB 2005).

Saltmarsh, mudflats,beaches and shallow water areas: including beaches and shallow water areas. Many bird species found in the Onkaparinga estuary, including egrets and ibis (listed in Table 2), wade in the shallow waters and mudflats searching for juvenile fishes, crustaceans and molluscs.

Floodplain: open woodThe lands, grasslands, coastal heath, plains, pasture and urban areas. upper floodplain regions in the Acacia, eucalypt woodlands and grass plains provide a habitat for those species that search for flowers, seeds and insects. Common species include the New-Holland honeyeater (Phylidonyris novaehollandiae) and willie wagtail (Rhipidura leucophrys). There are also several birds of prey that hunt the plains below including the peregrine falcon (Falco peregrinus).

Wildflowers and wildlife:- The park’s and hills bushland provides a colourful wildflower display during winter and spring. The changing environments along the river corridor are home to echidnas, kangaroos, and many bird and reptile species.