ENVIRONMENTAL
RESULTS
AREA: 70.14 km2
ABOUT THE ZONE
Rodds Bay is located to the south-east of the Outer Harbour Zone. It is connected to Colosseum Inlet by a narrow channel behind Hummock Hill Island. The eastern side of Rodds Bay includes a number of mangrove islands. The creeks that flow into the bay are also mangrove-lined and contain large areas of salt pans. This zone includes three monitored seagrass meadows and the Rodds Bay Dugong Protection area. This is a relatively pristine zone that has significant biodiversity value.
This zone has three water and sediment monitoring sites, three seagrass monitoring meadows, four fish monitoring sites, one mud crab monitoring site and four mangrove monitoring sub-zones.
WATER & SEDIMENT
Rodds Bay received an overall water quality score of 0.86 (B).
Sediment quality of Rodds Bay was very good with an overall score of 1.00 (A).
The following graphs compare the Water and Sediment scores reported for 2023 (top line) to those from the previous year.
WATER
SEDIMENT
Very good (0.85-1.00)
Poor (0.25-0.49)
Good (0.65-0.84)
Satisfactory (0.5-0.64)
Very Poor (0.00-0.24)
No data available
Overall, Water quality in the Rodds Bay (0.86) scored higher than the 2022 report card and resulted in an improvement to the overall grade (very good, A). This score was calculated by aggregating the three sub-indicator and associated measure scores (Physiochemical – pH and turbidity, Nutrients – total nitrogen, total phosphorus and dissolved metals, and dissolved metals – aluminum, copper, lead, manganese, nickel and zinc).
Within the Physiochemical sub-indicator, Graham Creek received a score of 1.00 and a very good grade (A) for pH indicating that the average pH was well below the guideline value. This zone received a score of 0.67 and a good grade (B) for turbidity indicating that average turbidity was below the guideline value.
Within the Nutrient sub-indicator group, total nitrogen (0.71) and chlorophyll-a (0.71) received good grades (B) indicating concentrations for these measures were below guideline values. Total phosphorus (0.85) received a very good grade (A), indicating that average concentrations for this measure was well below the guideline value.
All six Dissolved metals received high scores (1.00) and very good grades (A) indicating that average concentrations were well below the water quality guideline values.
For Sediment quality, Rodds Bay received an overall score of 1.00 and a very good grade (A), also a similar result to the previous year. This score was calculated by aggregating one sub-indicator and associated measure scores (Metal and metalloids – arsenic, cadmium, copper, lead, mercury, nickel and zinc).
In 2023, all seven Metal and metalloid sub-indicator measures received very high scores (0.98–1.00) and very good grades (A), indicating that average concentrations were well below the guideline values for this zone.
HABITATS
SEAGRASS RESULTS
Meadow 94
Meadow 96
Meadow 104
There are three intertidal monitoring meadows in Rodds Bay: Meadows 94, 96 and 104.
The overall zone score in 2023 (0.38) was similar to the previous year (0.42) with both years receiving a poor grade (D). While scores for the biomass and area sub-indicators declined for Meadows 96 and 104, Meadow 94 saw an increase in the area score and significant improvement in species composition. Biomass score for Meadow 94, and species composition for Meadows 96 and 104 remained similar to the previous year.
MANGROVE RESULTS
No mangrove assessment was conducted in 2023, results are from monitoring conducted in 2019. The overall score for Rodds Bay was 0.64 (C) indicating a satisfactory condition for mangroves in this zone. Mangrove extent (0.68) and shoreline condition (0.67) were good while canopy condition was satisfactory. This zone may benefit from being further removed from the direct impacts of clearing and development that occurred in the more central zones.
The overall score in Rodds Bay declined from 0.71 (B) in 2018 to 0.64 in 2019 as a result of a fall in canopy condition. This change may reflect the impacts off decreased rainfall over the reporting year.
FISH & CRABS
FISH HEALTH RESULTS
FISH RECRUITMENT RESULTS
Fish recruitment was assessed for two species: Yellowfin bream Acanthopagrus australis and Pikey bream Acanthopagrus pacificus. The overall score for 2023 was higher than the previous year (2022: 0.45, 2023: 0.64) and increased one grade to satisfactory (C). This increase in score is a result of an increase in number of bream caught during the 2022–23 reporting period (2022 report card: 75 fish, 2023 report card: 166 fish).
Fish health is assessed though two sub-indicators, Fish condition and Fish Health Assessment Index (HAI).
The overall score for Fish health in 2023 was 0.81 and received a good grade (B). The 2023 results were calculated by the average of the Fish HAI score (0.90; results carried over from 2021) and new assessment of Fish condition which scored similar to the previous year (2022: 0.74, 2023: 0.73).
MUD CRAB RESULTS
Rodds Bay received an overall zone score of 0.67, resulting in a good grade (B). The previous calculations for this zone were in 2021 (an insufficient number of crabs were caught in 2022). As with other zones, the 2023 results show an improvement in sex ratio and low prevalence of rust legions as reflected by higher scores. The abundance scores were consistently low across years.