Restoring Riparian Vegetation in the River

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The application involves 3 parts that are all working to improve fish habitat in the Swan Canning Rivers and Estuary. These include: Restoring riparian vegetation, Resnagging the flats and Introduction of Fish Friendly Infrastructure (FFMI).

The restoration of riparian vegetation would involve local fishers and community members planting above the high water mark, not only improving the health of the river but increasing the fishers custodianship and understanding of the value that riparian vegetation plays as fish habitat. For this part of the application it would be great to get some potential sites from within the City of Canning where you would like to see, or have plans to do planting of riparian vegetation to help show a desire/need for this work to be undertaken.  

The resnagging the flats part of this project is a very visual and exciting part that involves reintroducing large trees into the shallow areas of the flats along the shoreline to provide complex fish habitat and increase biodiversity in the river and estuary (as well as providing bird roosts and shoreline protection) such as the large tree currently on the Attadale flats shown below. We are currently in discussions with DPaW Rivers and Estuaries Division about how best to go about this part of the project.

The final section of this project, Introduction of Fish friendly Marine Infrastructure is an education and extension program to work with local governments and councils to deliver key concepts to ensure new and existing infrastructure within the Swan River Estuary (e.g. boat moorings, armoured shorelines, jetties etc.) be modified, upgraded and retrofitted so that they are ‘fish friendly’.


Restoring Riparian Vegetation in the River

A healthy riparian zone has many benefits for rivers and estuaries including filtering out nutrients and pollutants, providing food sources in the form of insects and bugs for fish, shading shallow areas in summer and providing a natural source for the input of LWD into the system. This project will engage fishers in riparian replanting, with a focus around areas where LWD are being reintroduced to create a long term cycle of large woody debris entering the system. Not only does healthy riparian zones have positive benefits to the estuary, by engaging fishers they will gain a greater appreciation of the value of healthy habitat to healthy fisheries and gain greater custodianship over estuary. During consultation for this project the topic of aesthetics of large trees in riparian areas (blocking views) and on the flats (community members want them quickly removed) highlighted the importance of engaging the local community in riparian replanting as part of this project. This also builds greater education around the importance of riparian areas and LWDs and builds long term ongoing support for better fish habitat. The works will not be limited to trees but will include Shrubs, grasses, sedges and aquatic macrophytes as appropriate to the site.

Resnagging the flats

Historically floods and storm events would have meant that large woody debris from riparian vegetation made up of fringing woodland areas (e.g. flooded gum, Eucalyptus rudis and melaleuca species) and wetlands areas (e.g. swamp paperbark Melaleuca rhaphiophylla, moonah Melaleuca preissiana and swamp sheoak Casuarina obesa) would have been dragged into the estuary. However, clearing of riparian vegetation and catchments means that trees and woody debris no longer fall into the Swan River Estuary. Native fish species which have close affinities to complex nearshore habitat have seen a decline in their health with Black Bream experiencing decreased growth rates and Swan River Cobbler populations declining to a level that have required the closure of this species being closed to fishing. Improving nearshore habitat complexity could benefit both of these species with recent Murdoch University study Swan Fish Track highlighting the preference of complex habitats by black bream, while it is known that Swan River Cobbler use fallen trees as sites to build their burrows.

This part of the project aims to reintroduce LWH to a site in the Swan Canning Estuary. As this is the first time resnagging activities have been undertaken in an estuary in Western Australia the completion of this project will produce a framework for aquatic managers to follow to conduct resnagging activities in other systems throughout Western Australia. It will also build capacity and knowledge within aquatic managers and recreational fishers to ensure the success of future similar habitat enhancement projects in aquatic environments. The designs of the snags to be created using LWHs will be established and placed using best practice developed through resnagging works undertaken in NSW. This includes having rootballs facing upstream, keying in snags together and if necessary adding a ballast to weight them down. It is likely that snags will be made up of full trees with trimmed canopy and rootball intact. There will be ongoing consultation with those experienced in implementing resnagging works (such as Rod Price; DPI NSW and John Larsson; Ozfish Unlimited Richmond Chapter President).

The number of LWH’s deployed as part of this project has been kept small to ensure success but will also depend up availability of wood and approved sites. We will aim for a minimum of 5 large snags to be implemented. It will also ideally be an area accessible to fishers and in an area that will maximise the benefit to fish that are known to utilise complex habitats in shallow areas of the estuary including black bream and cobbler. LWH’s will also give fishers fishing in the growing flathead flats fishery a focus points to target fish. Potential sites include Attadale Flats, Como Flats, South Perth Foreshore and Rossmoyne foreshore but we will be working with local marine managers including Department of Parks and Wildlife and local governing authorities to ensure selected sites will be out of the boating channel to ensure there is no conflict with boat traffic and to ensure snags do not break up or become dislodged creating navigational hazards and to determine a site that maximises benefits to all users.

The snags will be monitored to ensure they haven’t moved using GPS and photography, fish utilising the snags will be identified using BRUV’s and the use of the snags by waterbirds will be monitored by local bird watching groups. There may also be the opportunity to align this project with current fish tagging and tracking projects and utilise the Swan Canning Acoustic Array to identify how fish utilise these habitats.
The Swan River is the most popular estuary for recreational fishers in Western Australia and over recent years there has been a growth in the popularity of fishing the flats in this system for flathead with the social media page, “Perth Flathead Masters” having over 1,500 members and regularly holding social fishing competitions . Habitat enhancement of the flats through resnagging of these areas will provide focal points for fishers and increased fishing amenity. Snags also provide important roosting habitat for waterbirds. Pelicans for example, do not roost under any cover; and rely on either sandbanks or large dead tree snags to roost on day and night. There is anecdotal suggestions that that as these structures are disappearing and as they do, there may be less pelicans in the Swan River. Off-shore timber also means birds can perch safely without disturbance from dogs.

Introduction of Fish Friendly Infrastructure (FFMI)

An education and extension program to deliver key concepts ensuring new and existing infrastructure within the Swan River Estuary (e.g. boat moorings, armoured shorelines, jetties etc.) be modified, upgraded and retrofitted so that they are ‘fish friendly’. Currently many of these necessary existing structures impact negatively on surrounding key fish habitats such as seagrass, resulting in long-term negative influence on the productivity of local fishery resources. However, new innovative techniques can reduce the impact of this infrastructure. Through collation of applicable material, identification of appropriate construction techniques and delivery of training, capacity and understanding will be built around key infrastructure owners/managers and coastal communities.

Increased capacity will enable delivery of new and updated concepts in coastal infrastructure design, construction and management sensitive to surrounding fish habitat supporting productive fisheries. This will be done through engaging local marine infrastructure owners and managers (e.g. local governments) to identify achievable suitable alternatives and highlight their associated benefits to enhance the adoption of FFMI engaging local governments and to show them potential of fish friendly infrastructure and highlight opportunities for implementation.

This image (left) shows marine infrastructure in the form of an armoured shoreline in the Swan River Estuary. These structures offer little habitat benefits to fish and need ongoing upkeep. Developing capacity within local governments to implement fish friendly infrastructure will mean that when it comes time to replacing infrastructure, more “fish friendly” infrastructure can be utilised. A small pilot project with key infrastructure types (walls, jetties, pontoons) will be utilised to test the proposals and to enhance the engagement with local Councils and infrastructure managers.

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