Abstract
Background & Aims
Barapa Barapa Traditional Custodians have expressed interest in determining the presence and distribution of freshwater mussels in Gunbower Forest, as part of broader cultural objectives of healthy wetlands in this area.
This project was a collaboration among Barapa Barapa Traditional Custodians, The Barapa Barapa Wamba Wemba Water for Country Steering Committee, North Central CMA and Charles Sturt University. The aim of the project was to determine the current status of freshwater mussels in wetlands of the lower part of the Gunbower Forest, to inform mussel population management, especially through water delivery.
Besides being important culturally, intact freshwater mussel populations play important functional food web and water quality roles in rivers and wetlands, through their capacity to filter large amounts of water. In turn, mussels require healthy fish populations to complete their life cycle, because fish are hosts for their parasitic larvae, called glochidia.
Methods
In April-May 2023, freshwater mussel surveys were conducted by Barapa Barapa Traditional Custodians and North Central CMA staff in six wetlands of the lower Gunbower Forest: Reedy Lagoon, Barapa (Black) Swamp, Little Reedy Lagoon, Little Gunbower Creek, Green Swamp, and Corduroy Swamp.
Mussels were surveyed using a combination of perimeter searches, looking for shells along the
dry edge of the wetland, and more intensive timed searches, to look for live mussels in the water.
The presence of shells during perimeter searches gave an indication of the likelihood of live mussels being present in a wetland, as well as an indication of past abundances. The timed searches provided data on the presence, relative abundance, spatial distribution, size structure and recruitment of live mussels.
A total of 10.9 km of wetland perimeter was searched for shells (6 km of shallow-water zone perimeter, and 4.9 km of deep-water zone perimeter). The total search time for live mussels in the 6 wetlands was 18 person-hours. The surveys covered 87 ha (7%) of the total area of Gunbower Forest considered either permanent or semi-permanent wetland habitat.
Results
Of the 6 wetlands surveyed, live mussels and mussel shells were only found in Green and Corduroy swamps. A total of 15 shells (including shell fragments) and 12 live mussels were found. In 2-people hours of search time (2 sites, 1 hour search time each), 7 live mussels were found in Green Swamp, and in 3-people hours of search time (3 sites, 1 hour search time each), 5 live mussels were found in Corduroy Swamp. The distribution of mussels was seemingly haphazard, with no dense shoals found. Live mussels were found in depths ranging from 30-120 cm.
All mussels and intact shells were identified as billabong mussels, Velesunio ambiguus. All of the mussels were above 55 mm, the size for sexual maturity.
For wetlands where no live mussels were found (Barapa [Black] Swamp, Reedy Lagoon, Little Reedy Lagoon and Little Gunbower Creek), we cannot be certain that mussels are absent, but the lack of shells observed, either old or new, is a strong indication that mussels are most likely not present.
Barapa Barapa Traditional Custodians have expressed interest in determining the presence and distribution of freshwater mussels in Gunbower Forest, as part of broader cultural objectives of healthy wetlands in this area.
This project was a collaboration among Barapa Barapa Traditional Custodians, The Barapa Barapa Wamba Wemba Water for Country Steering Committee, North Central CMA and Charles Sturt University. The aim of the project was to determine the current status of freshwater mussels in wetlands of the lower part of the Gunbower Forest, to inform mussel population management, especially through water delivery.
Besides being important culturally, intact freshwater mussel populations play important functional food web and water quality roles in rivers and wetlands, through their capacity to filter large amounts of water. In turn, mussels require healthy fish populations to complete their life cycle, because fish are hosts for their parasitic larvae, called glochidia.
Methods
In April-May 2023, freshwater mussel surveys were conducted by Barapa Barapa Traditional Custodians and North Central CMA staff in six wetlands of the lower Gunbower Forest: Reedy Lagoon, Barapa (Black) Swamp, Little Reedy Lagoon, Little Gunbower Creek, Green Swamp, and Corduroy Swamp.
Mussels were surveyed using a combination of perimeter searches, looking for shells along the
dry edge of the wetland, and more intensive timed searches, to look for live mussels in the water.
The presence of shells during perimeter searches gave an indication of the likelihood of live mussels being present in a wetland, as well as an indication of past abundances. The timed searches provided data on the presence, relative abundance, spatial distribution, size structure and recruitment of live mussels.
A total of 10.9 km of wetland perimeter was searched for shells (6 km of shallow-water zone perimeter, and 4.9 km of deep-water zone perimeter). The total search time for live mussels in the 6 wetlands was 18 person-hours. The surveys covered 87 ha (7%) of the total area of Gunbower Forest considered either permanent or semi-permanent wetland habitat.
Results
Of the 6 wetlands surveyed, live mussels and mussel shells were only found in Green and Corduroy swamps. A total of 15 shells (including shell fragments) and 12 live mussels were found. In 2-people hours of search time (2 sites, 1 hour search time each), 7 live mussels were found in Green Swamp, and in 3-people hours of search time (3 sites, 1 hour search time each), 5 live mussels were found in Corduroy Swamp. The distribution of mussels was seemingly haphazard, with no dense shoals found. Live mussels were found in depths ranging from 30-120 cm.
All mussels and intact shells were identified as billabong mussels, Velesunio ambiguus. All of the mussels were above 55 mm, the size for sexual maturity.
For wetlands where no live mussels were found (Barapa [Black] Swamp, Reedy Lagoon, Little Reedy Lagoon and Little Gunbower Creek), we cannot be certain that mussels are absent, but the lack of shells observed, either old or new, is a strong indication that mussels are most likely not present.
| Original language | English |
|---|---|
| Place of Publication | Albury, NSW |
| Publisher | Charles Sturt University |
| Commissioning body | North Central Catchment Management Authority |
| Number of pages | 54 |
| Publication status | Published - 2023 |