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
WATER
SEDIMENT
Rodds Bay received an overall water quality score of 0.76 (B). This score was based on the scores for physicochemical (0.77), nutrients (0.51) and dissolved metals (1.00).
Sediment quality of Rodds Bay was very good with an overall score of 1.00 (A).
MEASURES RESULTS
WATER
SEDIMENT
pH = acidity TN = Total nitrogen TP = Total phosphorus Chl-a = Chlorophyll-a Al = Aluminum Cu = Copper Pb = Lead Mn = Magnesium Ni = Nickel Zn = Zinc
As = Arsenic Cd = Cadmium Cu = Copper Hg = Mercury Pb = Lead Ni = Nickel Zn = Zinc
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
Rodds Bay received a very good score of 1.00 for pH indicating that the average pH was well within the guideline value range. This zone received a satisfactory score for turbidity (0.54) indicating that average turbidity was below the guideline value.
All six dissolved metals received very good scores (1.00) indicating that average concentrations were well below the water quality guideline values.
Rodds Bay received a satisfactory overall score for nutrients (0.51). Total phosphorus had a good score (0.77), indicating that average concentrations for these measures were below the guideline values for this zone. In contrast, total nitrogen (0.45) and chlorophyll-a (0.32) had poor scores as the average concentration was above the guideline value.
HABITATS
SEAGRASS RESULTS
There are three intertidal monitoring meadows in Rodds Bay—Meadows 94, 96 and 104.
The overall condition of this zone was poor (0.42, D) in 2022. This was a continued decrease from the peak score in 2020 (0.87, A) when Rodds Bay received the best overall condition score of the past decade.
Results were driven by a marked decline in scores at Meadow 94. In 2022 there was a large decline in seagrass area, biomass and species composition resulting in a very poor score at Meadow 94. The remaining two meadows within Rodds Bay received the same grade as the previous year. However, the overall score at Meadow 96 also decreased (0.65 in 2022, 0.75 in 2021) which further contributed to the overall poor score (0.42, D) at Rodds Bay.
MANGROVE RESULTS
Very good (0.85-1.00)
Good (0.65-0.84)
Satisfactory (0.5-0.64)
Poor (0.25-0.49)
Very Poor (0.00-0.24)
No data available
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
HARBOUR SCORE
OVERALL VISUAL FISH CONDITION: HARBOUR SCORE
VISUAL FISH CONDITION: HARBOUR SCORE
FISH HEALTH ASSESSMENT INDEX: HARBOUR SCORE
Very good (0.85-1.00)
Good (0.65-0.84)
Satisfactory (0.5-0.64)
Poor (0.25-0.49)
Very Poor (0.00-0.24)
No data available
Fish Health (Overall)
The overall score calculated for fish health in 2022 was 0.80 (B), which is an average of the scores for Fish Condition 0.72 (B) and the Health Assessment Index 0.90 (A).
Visual Fish Condition:
The overall score for Fish Condition (0.72) is an average of 0.97 (A) for Fish Visual Condition (FVC) and 0.47 (D) for Fish Body Condition (FBC).
The high scores for FVC are a result of a low incidence of poor visual health. All fish species assessed for this metric received very good scores ranging from 0.90 (A) to 0.98 (A). This result was similar to the HAI scores for external measures where a very low number of external health issues were recorded.
The poor score for FBC in 2022 was a result of poor scores for yellow-finned bream (0.43), pikey bream (0.46) dusky flathead (0.43), and barred javelin (0.44). Almost all species assessed had a mean body condition below the long-term average (2003 – 2021). However, the remaining species assessed, mangrove jack, had a satisfactory score of 0.50.
Fish Health Assessment Index (HAI):
The overall HAI score for Gladstone Harbour was 0.90 (A), as data from the 2021 Gladstone Harbour Report Card was reused.
This was comprised of scores from five fish species, barramundi 0.98 (A), barred javelin 0.90 (A) and blue catfish 0.81 (B), bream 0.98 (A) and mullet 0.81 (B).
In general, the surveyed fish species showed very few signs of external health issues, a similar result to the Fish Visual Condition sub-indicator. Scores for internal organs were also low indicating good to very good fish health.
FISH RECRUITMENT RESULTS
Fish recruitment was assessed for two species: yellow-finned bream Acanthopagrus australis and pikey bream Acanthopagrus pacificus. The overall score for 2022 was 0.57 (C) similar to the 2020 score of 0.62. The final scores were measured against a 2012 to 2021 baseline. The 2022 score for fish recruitment indicates a season with higher recruitment rate (increased catch rate) relative to the mean reference level determined over the baseline period. The total number of bream caught in the 2022 reporting year was 764, 316 yellow-finned bream and 448 pikey bream.
MUD CRAB RESULTS
Rodds Bay is located to the south-east of the Outer Harbour zone. The eastern side of Rodds Bay includes a number of mangrove islands. The creeks that flow into the bay are mangrove-lined and contain large areas of salt pans.
Only four mud crabs were caught in Rodds Bay over the two sampling rounds. As such the overall score, sex ratio and prevalence of rust lesions could not be calculated owing to the insufficient sample size. Abundance was scored as very poor (0.00).