ENVIRONMENTAL
RESULTS
ABOUT THE ZONE
Calliope Estuary is fed by Gladstone Harbour’s largest freshwater catchment. The main tributaries of the Calliope River include Oakey, Paddock, Double and Larcom Creeks.
WATER & SEDIMENT
Calliope Estuary received an overall water quality score of 0.88 (A).
Sediment quality of Calliope Estuary was very good with an overall score of 0.97 (A).
​
The following graphs compare the Water and Sediment scores reported for 2025 (top line) to those from 2024.
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 Calliope Estuary scored 0.88 and received a Very Good grade (A), an improvement to the 2024 Report Card. This score was calculated by aggregating the three sub-indicator and associated measure scores (Physicochemical – pH and turbidity, Nutrients – total nitrogen, total phosphorus and chlorophyll-a, and dissolved metals – aluminum, copper, lead, manganese, nickel and zinc).
​
Calliope Estuary received a Very Good (A) grade for pH (1.00), turbidity (0.90), and a Good (B) grade for total phosphorus (0.81) and chlorophyll-a, and a Satisfactory (C) for total nitrogen (0.53). All six of the dissolved metals received a Very Good (A) grade, indicating that average concentrations for these measures were within the guideline values for this zone.
For Sediment quality, Calliope Estuary received an overall score of 0.97 and a Very Good grade (A), 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). The results reflect that all concentrations were below the guideline values for this zone. Nickel received a Good (B) grade, reflecting its natural occurrence within the harbour and may not be associated with anthropogenic inputs.
HABITATS
MANGROVE RESULTS
The 2025 Gladstone Harbour Report Card incorporates the 2024 Mangroves results. Mangrove condition has historically remained stable due to strong buffering capacity, and since 2019, monitoring has been undertaken every five years. In 2024, the overall grade for Mangroves at Calliope Estuary improved from Satisfactory (C) to Good (B).
The mangrove extent sub-indicator, which measures changes in canopy cover relative to saltmarsh and saltpan areas, improved from a Good (B) to a Very Good (A) grade. The canopy condition indicator, based on remote sensing of canopy density and health, also improved from Poor (D) to Good (B). Shoreline condition, assessed through aerial surveys of mangroves bordering Gladstone Harbour’s water quality zones, increased from Poor (D) in 2019 to a Satisfactory (C).
FISH & CRABS
FISH RECRUITMENT RESULTS
Fish recruitment was assessed for two species: Yellowfin bream Acanthopagrus australis and Pikey bream A. pacificus. The overall score for 2025 was higher than the previous year (2024: 0.50, 2025; 0.65) and improved from a Satisfactory (C) to a Good (B) grade. This is a result of increased catch numbers of Yellowfin bream (2024: 8, 2025: 21), though Pikey bream declined (2024: 23, 2025: 21).
MUD CRAB RESULTS
The overall zone score for Mud crabs for Calliope Estuary was 0.27 and graded Poor (D), a decline in score to 2024 (0.38, Poor, D). At the sub-indicator level, abundance remained at a Very Poor (E), reflecting a low catch per unit effort. Mud crab populations may be influenced by both human activities and natural factors, including habitat, reproductive cycles, and environmental conditions like temperature and water movement.
​
In Queensland, it is illegal to take female crabs, hence changes in the ratio of male to female crabs can indicate changes in fishing pressures. Sex ratio for Calliope Estuary remained at a Very Poor (E) grade in 2025, indicating an imbalance of males and females. The prevalence of rust lesions declined from a Very Good (A) grade to a Satisfactory (C), with the percentage influenced by small capture numbers despite low incidence of rust lesions.