ENVIRONMENTAL
.RESULTS
ABOUT THE ZONE
Graham Creek is a mangrove-lined tidal inlet located near the south-west corner of Curtis Island. It is approximately 9 km long and flows into the southern end of The Narrows.
WATER & SEDIMENT
Graham Creek received an overall water quality score of 0.80 (B).
Sediment quality of Graham Creek was very good with an overall score of 0.96 (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)
Good (0.65-0.84)
Satisfactory (0.5-0.64)
Poor (0.25-0.49)
Very Poor (0.00-0.24)
No data available
Overall, Water quality in Graham Creek scored 0.80 and received a Good (B) grade, a decline from the 2024 Report Card (0.90, Very Good, A). 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 – aluminium, copper, lead, manganese, nickel and zinc).
​
Graham Creek received a Very Good (A) grade for pH (1.00), and a Good (B) grade for total phosphorus (0.75). Turbidity (0.61) and total nitrogen (0.51) were both graded a Satisfactory (C). All six dissolved metals received a Very Good (A) grade with a score of 1.00. This indicates that average concentrations for these measures were within the guideline values for this zone. Chlorophyll-a received a Poor (D) grade and a score of 0.48.
​
For Sediment quality, Graham Creek received an overall score of 0.96 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 with a score of 0.83. Nickel is naturally occurring 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 Graham Creek improved from a Satisfactory (C) in 2019, to a Good (B).
​​
The mangrove extent sub-indicator, which measures changes in canopy cover relative to saltmarsh and saltpan areas, retained a Good (B) grade. The canopy condition indicator, based on remote sensing of canopy density and health, declined from a Satisfactory (C) to Poor (D). Shoreline condition was not observed at Graham Creek in 2024.
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: 0.54, 2025; 0.69) and improved from a Satisfactory (C) to a Good (B) grade. This is a result of increased catch numbers of both Yellowfin (2024: 1, 2025: 5) and Pikey (2024: 49, 2025: 63) bream.
MUD CRAB RESULTS
The overall zone score for Mud crabs in Graham Creek was 0.35 and retained a Poor (D) grade between years. At the sub-indicator level, abundance remained stable at a Very Poor (E) grade, though score increased slightly between years (2024: 0.00, 2025: 0.12). 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 Graham Creek was similar between years (2024: 0.20, 2025: 0.24), receiving a Very Poor (E) grade. The prevalence of rust lesions also remained stable, receiving a Good (B) grade and indicating a low number of crabs with rust lesions.