ENVIRONMENTAL
.RESULTS
unchanged
high
confidence
OVERALL HARBOUR .RESULTS
The following graph shows the scores received in 2025 (top line) versus the score received in 2024 for each indicator (bottom row)
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
RESULTS
The overall score for the Environmental Health component was 0.70, an improvement from the 2024 score (0.67), remaining at a Good grade (B).
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Overall, the Water and Sediment Quality indicator group scored the similar to the previous year (2024: 0.89, 2025: 0.87) and has consistently received a Very Good (A) grade for the past nine years. The 2025 Water quality indicator score declined slightly (2024: 0.83, 2025: 0.79), but maintained the same grade (Good, B). Sediment quality received a Very Good grade (A), the same as 2024 (2024: 0.96, 2025: 0.96).
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In comparison to 2024, the Habitats indicator group received a higher overall score, and improved to a Satisfactory (C) grade. This was due to an improvement in Seagrass scores (2024: 0.68, 2025: 0.81). In 2024 and 2025, Coral scores remained low (2024: 0.14, 2025: 0.09) corresponding to a Very Poor grade (E). Mangroves were assessed in 2024 and the results carried over to the 2025 Report Card (0.63, C (Satisfactory).
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The Fish and Crabs indicator group improved in score from the previous year (2024: 0.62, 2025: 0.71) improving from a Satisfactory (C) grade to a Good (B) grade in 2025. The Fish health indicator improved in score (2024: 0.84, 2025: 0.91), resulting in an improved grade (2024: Good (B), 2025: Very Good (A). Fish recruitment also improved in score (2024: 0.57, 2025: 0.70) and in grade, from Satisfactory (C) in 2024 to Good (B) in 2025. The Mud crabs score increased in both score (2024: 0.46, 2025: 0.54) and grade (2024: Poor (D), 2025: Satisfactory (C).
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​To learn more about these results and the various factors that determined each score, see our Technical Report or FAQ sheet.
Water & Sediment Results
Fish Recruitment
Results
Seagrass
Results
Mudcrab
Results
Coral Results
Results by Harbour Zone
Mangrove Results
Fish Health
Results
WHAT WAS MEASURED?
The Environmental Health of Gladstone Harbour was assessed based on three indicator groups: Water and Sediment Quality, Habitats, and Fish and Crabs.
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WATER AND SEDIMENT QUALITY
Water and Sediment Quality scores are based on 11 Water quality and 6 Sediment quality measures. Under a data-sharing agreement, the Port Curtis Integrated Monitoring Program provide GHHP with water and sediment quality data. Samples were collected from 51 sampling sites across 13 harbour zones. Water quality data collection was conducted quarterly, and sediment sampling was conducted annually in May 2025.
HABITATS
Three indicators make up the Habitats indicator group: Seagrass, Coral and Mangroves.​
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The Seagrass indicator consists of three sub-indicators: Biomass, Area and Species composition. Data is provided by TropWATER at James Cook University with agreement from the Gladstone Ports Corporation and is collected from 14 seagrass meadows in six harbour zones. The monitoring is conducted annually in October/November around the annual peak of seagrass abundance.
​The Coral indicator consists of four sub-indicators: Coral cover, Change in cover, Macroalgal cover and Juvenile density. Coral monitoring is conducted annually in April at two reefs in the Outer Harbour zone and four reefs in the Mid Harbour zone.
The Mangrove indicator consists of three sub-indicators: Mangrove extent, Mangrove canopy condition and Shoreline condition. Data were collected from the 13 harbour zones which are split into twenty-three sub-zones. Mangroves were assessed in 2024 as part of a five-year monitoring repetition.
FISH AND CRABS
The Fish and Crabs indicator group consists of three indicators: Fish health, Fish recruitment and Mud crabs.
Fish health is measured via two sub-indicators: the Fish Health Assessment Index (HAI) and Fish condition. The sub-indicator Fish HAI provides a thorough assessment of internal and external measures of fish health and was reassessed for the 2025 Report Card for the first time since 2021. The sub-indicator Fish condition uses data collected by recreational fishers. Anglers in fishing competitions use a mobile phone app to capture an image of the fish for assessment with an object detection algorithm, as well record of fish length and weight. The data used to calculate this score were collected in the 2024-25 report card year. Data collection for both sub-indicators occur throughout the harbour, and a single harbour-wide score is provided.
The Fish recruitment indicator is based on the total catch of juveniles of two bream species (Yellowfin bream and Pikey bream). It provides a measure of juvenile fish entering the breeding population. Fish recruitment is measured in tributaries to Gladstone Harbour and includes all harbour zones except the Outer Harbour.
​Three sub-indicators of Mud crab health were assessed: sex ratio, abundance and prevalence of rust lesions. Biannual mud crab monitoring is conducted in February and June in seven harbour zones.
WATER QUALITY
Overall Harbour Scores for Water quality sub-indicators
2025 (top line) 2024 (bottom line)
In the 2025 Report Card, the Water quality indicator score declined slightly (2024: 0.83, 2025: 0.79), but maintained the same grade (Good, B). This decrease was due to slightly lower scores in the physicochemical and dissolved metals sub-indicators.
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Within the Physicochemical sub-indicator, all zones scored very high (1.00) corresponding to a Very Good grade (A) for pH. In contrast, the turbidity scores varied (0.27–0.90) and grades ranged from Poor (D) to Very Good (A). This resulted in an overall harbour score of 0.61 and a Satisfactory grade (C) for turbidity.
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The overall harbour score for Nutrients (0.57) was the lowest amongst all Water quality sub-indicators and graded Satisfactory (C), a decline from 2024 (0.69, Good, B). Total nitrogen ranged from 0.25 in the Boyne Estuary to 0.61 in the Inner Harbour, resulting in zones grades ranging receiving either a Poor (D) or a Satisfactory (C). For total phosphorus, most zones received between a Satisfactory (C) grade, and a Very Good (A) grade (scores: 0.51–0.94), with only one zone, Boat Creek, receiving a Poor grade (D; score: 0.33). Similar to total nitrogen, chlorophyll-a results were varied, with zone scores ranging from 0.42–0.76 and grades ranging from Poor (D) to Good (B).
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Overall, the dissolved metals in all 13 zones were graded Very Good (A). Consistent with the 2024 Report Card, the dissolved metals measures all received high scores (0.80–1.00). Auckland Inlet received a Good (B) for copper (0.74) and manganese (0.84).
SEDIMENT QUALITY
Overall Harbour Scores for the Sediment quality sub-indicator
2025 (top line) compared to 2024 (bottom line)
The overall Sediment quality scores were derived from one sub-indicator – metals and metalloids. Six metals (cadmium, copper, lead, mercury, nickel and zinc) and the metalloid arsenic were assessed. The harbour score for Sediment quality was 0.96 and graded Very Good (A), the same as 2024. While scores for most measures were Very Good (A), there were several Good (B) or Satisfactory (C) grades for arsenic and nickel. However, it should be noted that arsenic and nickel are naturally occurring within the harbour, hence these metals are not necessarily associated with anthropogenic inputs.
SEAGRASS
Overall Harbour Scores for Seagrass
2025 (top line) compared to 2024 (bottom line)
Overall, Seagrass received a score of 0.81 and was graded Good (B). These results mark the second subsequent year of a Good (B) grade and remains a marked improvement from the overall condition observed from 2015 to 2018 (0.35–0.43; Poor grade, D).
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Five zones, The Narrows, Western Basin, Mid Harbour, South Trees Inlet, and Rodds Bay were graded in a Good (B) or Very Good (A) condition. Of note, Mid Harbour improved from a Poor (D) in 2024 (0.49) to a Good (B) in 2025 (0.70). Inner Harbour improved from a Poor (D) in 2024, to a Satisfactory (C) in 2025, as a result of an improvement in species composition (2024; 0.00 (E), 2025; 0.49 (D)), although biomass and area both declined slightly from Very Good (A) to Good (B).
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Over twenty years of annual monitoring in seagrass condition around Gladstone Harbour indicates a strong relationship between seagrass condition and influences such as rainfall and river flow. Improvements in Seagrass condition in the 2025 Gladstone Harbour Report Card may be attributed to optimal growing conditions over the past reporting year, along with increased biomass across five of the six monitored zones, allowing megaherbivores such as turtles and dugongs to move to other areas and decreasing grazing pressure.
CORAL
Overall Harbour Scores for Coral sub-indicators
2025 results (top line) compared to 2024 (bottom line)
Coral health was monitored at six locations in Gladstone Harbour, involving four locations within the Mid Harbour reporting zone and two locations in the Outer Harbour reporting zone.
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In 2025, corals were in a very poor condition for the eighth consecutive year and received an overall score of 0.09, corresponding to a Very Poor grade (E). This was a result of a low cover of living coral, high macroalgal cover, low abundance of juvenile corals, and a very poor overall score for change in hard coral cover. At the sub-indicator level, all scores declined, particularly change in high coral cover, which decreased from 0.27 (Poor, D) in 2024 to 0.09 (Very Poor, E) in 2025.
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Initial coral monitoring in 2015 noted very low coral cover, which reflected the severe impacts of the 2013 flooding. Subsequent monitoring has shown a lack of recovery in coral condition. Ongoing pressures such as high macroalgal cover and the prevalence of bio-eroding sponges continue to limit the recovery of these reefs. Based on various sub-indicator scores, the corals of Gladstone Harbour demonstrated limited recovery potential in 2024.
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The condition of reefs in the harbour are comparable with other severely impacted reefs in Keppel Bay and the Whitsundays. Given the depleted state of coral cover, recovery will be largely dependent on connectivity with reefs beyond Gladstone Harbour.
MANGROVES
Overall Harbour Scores for Mangroves sub-indicators
2024 results (top line) compared with 2019 (bottom line)
No new assessment of Mangroves was conducted in 2025, and the Report Card uses results from 2024. The overall score for Mangroves was 0.63, a small increase from the 2019 score (0.57), however the grade remained the same (Satisfactory, C).
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​Seven zones, Graham Creek, Western Basin, Boat Creek, Calliope Estuary, Boyne Estuary, Outer Harbour, and Colosseum Inlet were in good condition. ​Two zones, Auckland Inlet and Mid Harbour were in poor condition. Decreases in shoreline condition and mangrove extent respectively contributed to the poor grades at these two zones. In the 2024 reporting year, several issues were observed across the study area, with human activities significantly impacting developed shoreline areas near mangroves. The most affected zones were the Inner Harbour, Calliope Estuary, Auckland Inlet, Mid Harbour, South Trees Inlet and Boyne Estuary, while the Western Basin showed lesser but still notable human influence. These findings were consistent with previous observations from 2018 and 2019. In addition to human-induced changes, natural climatic events, such as heavy rainfall, storms, and rising sea levels, continued to influence mangrove recovery, which has been slow but steady.
FISH HEALTH
Overall Harbour Scores for Fish health sub-indicators
2025 results (top line) compared with 2024 (bottom line)
The overall score calculated for Fish health in 2025 was 0.91, corresponding to a Very Good grade (A). This score was calculated by averaging the Fish condition score (0.90) and the Fish Health Assessment Index (HAI; 0.91). Note: the Fish HAI results are the product of a new assessment in 2025, the first since 2021.
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Fish Condition
The overall score for Fish condition (0.90) is calculated as the aggregation of visual fish condition and fish body condition for two fish species – Yellowfin bream and Pikey bream – in Gladstone Harbour. Visual fish condition was not calculated for Dusky flathead, Mangrove jack, and Barred javelin as sample sizes were low and insufficient data were available. In 2025, no fish body condition data was collected for Barred javelin and Dusky flathead, as these fish species were not included in the Boyne Tannum HookUp live weigh-in. This limits comparisons with scores from previous years. Visual fish condition received high scores (0.96-0.99) for five species: Yellowfin bream, Pikey bream, Barred javelin, Dusky flathead and Mangrove jack. For fish body condition two species, Yellowfin bream and Pikey bream, were graded as Very Good(A).
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Fish HAI
A new assessment of Fish HAI was undertaken in 2025 reporting year. The Fish HAI is comprised of scores from five fish species. However, in 2025, Barramundi were no longer included in the assessment. All four fish species monitored in 2025 scored very highly, namely Barred javelin (0.94), Bream (0.85), Blue catfish (0.88), and Sea mullet (0.98) received Very Good grades (A). In general, the surveyed fish species showed very few signs of external health issues, a similar result to the Fish condition sub-indicator. Scores for internal organs were also low, indicating good to very good fish health.
FISH RECRUITMENT
Overall Harbour Scores for Fish Recruitment
2025 results (top line) compared to 2024 (bottom line)
The size distribution of fish within the juvenile population gives an indication of the number of juvenile fish maturing and entering the breeding population.
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A score of 0.50 equates to a reporting year (season) at the median reference level, indicating no increase or decrease in the catch rate from the long-term average (2011–2023). In 2025, Fish recruitment scored 0.70, equating to an overall Good grade (B) across the harbour. This is an improvement from 2024 (0.57, Satisfactory (C) and 2023 (0.47, Poor (D). In 2025, all twelve zones assessed increased in score and/or grade for fish recruitment.
MUD CRABS
Overall Harbour Scores for Mud crab sub-indicators
2025 (top line) compared with 2024 (bottom line)
The overall score for Mud crabs in the 2025 Gladstone Harbour Report Card was 0.54 resulting in an improvement from a Poor (D) grade in 2024 to a Satisfactory (C) grade in 2025. These results are due to an increase in sex ratio scores (2024; 0.09, E, 2025: 0.53, C).
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The harbour score for abundance was low (0.29) and graded Poor (D), similar to the 2024 score of 0.32, Poor, D. The Narrows and Boat Creek received high scores (0.67 and 1.00 respectively) and received either a Good (B) or Very Good (A) grade for abundance. However, five zones – Graham Creek, Calliope Estuary, Inner Harbour, Auckland Inlet and Rodds Bay – received very low scores (0.00-0.21) and Very Poor (E) grades. Caution is required when interpreting abundance scores as catch per effort data can be highly variable.
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For sex ratio there was an increase from the previous year’s results. Three of the seven zones received a score of 1.00, resulting in a Very Good (A) grade. However, the remaining four zones received very low scores (0.00-0.24) and Very Poor grades (E). A higher proportion of females compared to males of the same size (>15 cm carapace width) suggests that fishers are observing regulations for the release of female crabs. Natural factors (temperature, reproduction cycle, etc.) may also be influencing sex ratio scores and cannot be ruled out. Research is required to understand how mud crab populations are impacted by a female-dominated sex ratio.
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In the 2025 Report Card, the prevalence of rust spot lesions declined to a Good (B) grade from a Very Good (A) grade in 2024. Four of the seven zones received a Very Good (A) grade, indicating little to no rust spot lesions in crabs captured. Graham Creek received a Good (B) grade, similar to 2024. However, two zones – Calliope Estuary and Rodds Bay – decreased in grade to Satisfactory (C) and Poor (D), respectively. Small capture numbers at Calliope Estuary and Rodds Bay meant the percentage of crabs with lesions was relatively high despite low incidence.
