Onkaparinga Chapter

The Onkaparinga Chapter was founded in 2017 by a group of passionate fishers who are motivated to improve fish habitat along the Onkaparinga and reverse decades of environmental degradation

The Chapter provides opportunities for recreational fishers and community members to participate in waterway restoration and fosters environmental stewardship. They firmly believe that community based environmental restoration is a powerful tool that not only repairs damage to ecosystems, it also provides opportunities to build connections between local people and their environment.

Much of the degradation in the region occurred in the 19th century. Land clearing, erosion, sedimentation, desnagging, river flow diversion and extraction, have all lead to habitat degradation, a reduction of biodiversity, and a decline in fish numbers.

Kaurna Aboriginal people are the traditional owners of the Onkaparinga region

Historically a ‘working river’, the Onkaparinga and surrounding catchment have been transformed and degraded by prior land uses including agriculture, mining and as Adelaide’s water source

The OzFish Onkaparinga Chapter has a number of restoration activities in their sights

 

Restoration at Perry’s Bend

Chapter members have been hard at work undertaking river bank restoration activities at Perry’s Bend.

Over the past 150 years, extensive land clearing has taken place along the Onkaparinga. In some sections of the river, vegetation has been cleared right up to the river’s edge leading to erosion and sedimentation.

The project aims to reduce the impacts of erosion by planting trees and installing both snags and concrete blocks. These structures also provide much needed habitat for native fish and other aquatic species.

Modular Wood Habitat Structures

Trialed in 2019, modular wood structures were built by Onkaparinga Chapter members and installed along the shoreline of the restored reach of the river.

Constructing the modular structures is a great way for fishers to participate in the creation of fish habitat. It also facilitates the easy transportation and installation of the structures.

These structures provide cover for juvenile fish and important substrates for filter-feeding marine organisms.

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Underwater Monitoring

In 2018, the Chapter received a City of Onkaparinga Environment Grant to assist with the monitoring of habitat restoration sites.

With the funds, the Chapter built and installed low-cost underwater cameras and have taken some impressive underwater footage.

The cameras have provided empirical evidence that the restoration efforts have been successful and provided valuable fish habitat for the area.

Limestone Block Substrates

The Chapter’s first major restoration project was to build new substrate in the Onkaparinga by installing 180 limestone blocks, creating an artificial reef system.

This has established a range of colony forming filter-feeders. They are already home to barnacles, coraline tubeworms, mussels and native oysters.

A large number of these organisms have attached themselves to the new habitat and significant volumes of water are now filtered of algae, detritus and sediment.

Crabs, shrimp and prawns now benefit from the new grazing surfaces provided by the shellfish, whilst many fish species benefit from the additional cover and food resources provided by the reefs.

The hydrology of this section of the river now more closely reflects what would be natural flows for the locality.

Sounder image of riverbed before limestone blocks

Sounder image of riverbed after limestone blocks installed

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