ENVIRONMENTAL
RESULTS
ABOUT THE ZONE
The Boyne River is dammed at Lake Awoonga to provide potable water for the Gladstone area. Large numbers of barramundi are stocked in Lake Awoonga and may be introduced into the Boyne Estuary when the dam overtops. The Boyne Estuary was the site of large-scale mortality of many of these introduced barramundi and other fish in 2011. The lower reach of the Boyne River flows from the dam through predominately agricultural land that has pockets of remnant vegetation. Before entering the south-eastern section of the Mid Harbour Zone the Boyne River flows through the residential communities of Boyne Island and Tannum Sands.
WATER & SEDIMENT
Boyne Estuary received an overall water quality score of 0.68 (B).
Sediment quality of Boyne Estuary was very good with an overall score of 0.98 (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 Boyne Estuary scored 0.68 and received a Good (B) grade, a decline in score to the 2024 Report Card (0.84, Good, B). 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).
​
Boyne Estuary received a Very Good (A) grade for pH (1.00), and a Satisfactory (C) for total phosphorus (0.51). All of the six of the dissolved metals received between a Very Good (A), indicating that average concentrations for these measures were within the guideline values for this zone. Turbidity (0.27), total nitrogen (0.25), and chlorophyll-a all received a Poor (D) grade.
For Sediment quality, Boyne Estuary received an overall score of 0.98 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.
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 Boyne Estuary improved from a Poor (D) to a Good (B) grade.
​
The mangrove extent sub-indicator, which measures changes in canopy cover relative to saltmarsh and saltpan areas, improved from Poor (D) to Satisfactory (C). The canopy condition indicator, based on remote sensing of canopy density and health, improved from Very Poor (E) to Poor (D). Shoreline condition, assessed through aerial surveys of mangroves bordering Gladstone Harbour’s water quality zones, improved several grades from a Very Poor (E) to a Very Good (A) 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: 0.64, 2025; 0.74) and improved from a Satisfactory (C) to a Good (B) grade. This is a result of increased catch numbers of Yellowfin bream (2024: 43, 2025: 71), though Pikey bream declined (2024: 35, 2025: 13).