unchanged from 2022
WHOLE HARBOUR RESULTS
The following graph shows the scores received in 2023 (top line) versus the score received in 2022 for each indicator (bottom row)
Very good (0.85-1.00)
Very Poor (0.00-0.24)
No data available
[UPDATE] Of the three indicator groups, water and sediment quality received the highest score of 0.89 (A). This score was a result of good water quality (0.81) and very good sediment quality (0.96) scores.
The overall score for the habitat indicator group was 0.48 (D). The poor habitat score was due to a good score for seagrass (0.70), a satisfactory score for mangroves (0.57) and a very poor score for corals (0.15). This is the third year in a row that seagrass has received a good grade and the fifth consecutive year coral has received a very poor score.
The overall score for the fish and crab indicator group was satisfactory 0.57 (C). The fish health score was good (0.80), the fish recruitment score was satisfactory (0.57) and the score for mud crabs was poor (0.39).
To learn more about these results and the various factors that determined each score, check out our Technical Report or FAQ sheet.
WHAT WAS MEASURED?
[UPDATE] The environmental health of Gladstone Harbour was assessed based on three indicator groups: water and sediment quality, habitats and fish and crabs.
WATER AND SEDIMENT QUALITY
Water and sediment quality scores are based on eleven water quality and six sediment quality measures. Water and sediment quality data were collected from 51 sampling sites across thirteen harbour zones. Water quality data collection was conducted quarterly, and sediment sampling was conducted in conjunction with the water quality sampling in May 2022.
There are three habitat indicators within the environmental component: seagrass, coral and mangroves.
The seagrass indicator consists of three sub-indicators: seagrass biomass, seagrass area and species composition. Data is collected from fourteen seagrass meadows in six harbour zones. The monitoring is conducted annually in October/November around the annual peak of seagrass abundance.
The coral indicator group consists of four sub-indicators: coral cover, coral cover change, macroalgal cover and juvenile density. Coral monitoring is conducted annually in May 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 is collected from the 13 harbour zones which are split into twenty-three sub-zones. Mangroves were last assessed in 2019 and this data is used for the 2022 report card.
FISH AND CRABS
The fish and crabs indicator group consists of two fish health indicators, a fish recruitment indicator and an indicator for mud crab health.
Fish Health is measured in two separate projects:
Fish Health Assessment Index.
Visual Fish Condition.
The first sub-indicator (HAI) provides a thorough assessment of internal and external measures of fish health. This HAI sub-indicator was last assessed in 2021 and this data is used in the 2022 report card. The second sub-indicator (FC) uses a mobile phone app to capture an image of the fish for assessment with an object detection algorithm, as well as a visual assessment and record of fish length and weight by the angler. The data used to calculate this score was collected in the 2021-22 report card year. Data collection for both sub-indicators occurs 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 (yellow-finned 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. Annual mud crab monitoring is conducted in February and June in seven harbour zones.
WATER AND SEDIMENT
[UPDATE] Water quality was relatively uniform across the harbour with 10 of the 13 environmental monitoring zones receiving an overall rating of good. The remaining three zones received an overall rating of very good. The water quality score was lower compared the 2021 score of 0.91, which was the highest in the GHHP monitoring program. This was due to lower scores for turbidity and the three nutrient measures, which may have resulted from higher-than-average rainfall.
The physicochemical scores (pH and turbidity) were mostly good in the 13 monitoring zones. At the measure level, scores for pH were uniformly very good (1.00). Turbidity scores were variable (0.49 to 0.91), with 12 zones being ranked as satisfactory, good, or very good.
Similar to previous report cards, nutrients received the lowest score (0.61) among the water quality sub-indicators. Eight zones were scored as satisfactory, and five zones were scored as good. At the measure level, total phosphorus received the highest scores, total nitrogen received the lowest scores, and chlorophyll-a scores were more variable, ranging from 0.32 to 0.72. All three sub-indicators showed a reduced score compared to the previous year.
All 13 environmental monitoring zones had consistently very good scores (0.95–1.00) for dissolved metals overall. The same was true at the measure level, with all six metals receiving very good scores across the 13 zones.
Sediment quality scores were very good across all zones of Gladstone Harbour owing to low concentrations of all measures (arsenic, cadmium, copper, lead, mercury, nickel and zinc). While scores for most measures were very good, there were several good or satisfactory scores 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.
[UPDATE] The overall condition of monitored seagrass meadows in Gladstone Harbour was good (0.70) in the 2022 reporting year. This is the third consecutive year of good condition, a marked improvement from 2015–2018 when the overall condition was poor.
Overall, 12 of the 14 monitored meadows were in satisfactory, good, or very good condition. Although the overall seagrass condition was good, changes from the previous year varied meadow to meadow. Nine of the 14 meadows showed an improved score—four of which showed a marked increase in score—when compared to the previous year. However, exceptions to recovery were seen in the Inner Harbour due to very poor species composition and in Rodds Bay where there were large declines in all three measures at a single meadow (Meadow 94).
As in the preceding three report card years, results suggest that the dry, benign weather conditions provided ideal conditions for seagrass recovery in the 2022 reporting year. Seagrass meadows in Gladstone Harbour started 2022 with a high level of resilience to external pressures. As such, Gladstone Harbour seagrasses should be well placed to cope with large rainfall events recorded in March and May of 2022 that may cause low light conditions detrimental to seagrass health.
[UPDATE] The 2022 Gladstone Harbour Report Card scores for the Mid Harbour are based on data collected from four reefs: Facing Island, Farmers Reef, Manning Reef and Rat Island. In 2022, the coral communities in Gladstone Harbour were in very poor condition. The overall grade for corals remained an E (0.15) for the fifth consecutive year. This was a result of low coral cover, low juvenile density, high macroalgal cover and a poor overall score for hard coral cover change at most of the surveyed reefs.
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 2022.
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.
The overall score for coral health in the Gladstone harbour was 0.15 indicating a very poor condition. This score was an increase from the 2021 score (0.14).
The coral cover score was very poor overall at 0.09. Similarly, the Gladstone Harbour received a very poor score for macroalgae cover of 0.04, an improvement from the 2021 score of 0.0. Both low coral cover and high macroalgal cover has been evidenced since 2015.
The harbour received a very poor score for juvenile density (0.12), indicating a low potential for coral recruitment. This is a reduction in score compared to 2021 (0.15), and the fourth consecutive year of a very poor juvenile density score for the Gladstone harbour.
Hard coral cover change remained poor (0.37), showing an increase compared to the 2021 score (0.34). The continued poor score indicates that the rate of increasing coral cover in this zone was lower than that observed at other nearshore reefs in the Great Barrier Reef.
[UPDATE] The overall score for mangroves was 0.57 (C), a small decrease from the 2018 score. This is a possible reflection of impacts on canopy condition from lower rainfall and delayed impacts from flooding. This is reflected in the decline in the overall harbour score for canopy condition and to a lesser extent for shoreline condition.
Four zones, Colosseum Inlet, Outer Harbor, Auckland Creek, and The Narrows were in good condition.
Two zones Boat Creek and Boyne Estuary were in poor condition. Decreases in canopy condition at these two zones was most likely to be because of the low rainfall levels observed in the reporting year. The Boyne Estuary also contained areas of dieback indicative of flood and erosion damage, which was first observed in the 2018 surveys. The slow recovery of mangroves in this area may have been exacerbated by access tracks, clearing and cutting of dead vegetation which is preventing and inhibiting seedling recruitment and re-establishment.
The remaining seven zones all had satisfactory scores similar to those recorded in the previous year with five zones showing a slight reduction in the overall score.
[UPDATE] 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).
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.
The overall Health Assessment Index (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.
[UPDATE] The size distribution of fish within the juvenile population gives an indication of the number of juvenile fish maturing and entering the breeding population.
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 – 2021). For 2022 fish recruitment scored 0.57 equating to an overall grade of C for fish recruitment across the harbour. This is an increase in catch rate compared to the long-term average and is similar to last year’s score of 0.62 (C).
[UPDATE] The overall score for mud crabs in Gladstone Harbour was 0.39 (D) indicating a poor condition. Please note, mud crabs are a novel indicator developed specifically for GHHP. Greater confidence in this indicator will develop over time.
The harbour score for abundance was very poor (0.18) and were the lowest observed since GHHP monitoring began. Four zones—Graham Creek, Calliope Estuary, Auckland Creek and Rodds Bay—received the lowest possible scores (0.00, E) for abundance. Caution is required when interpreting abundance scores as CPUE data can be highly variable.
Sex ratio received very poor scores (0.00) in three zones and poor scores (0.29–0.43, D) in two zones where it could be calculated. It is important to note these scores were based on a relatively small sample of mud crabs. A general pattern of predominantly very poor has been evident since 2017, indicating a higher proportion of females compared to males of the same size (>15 cm spine width). This pattern suggests that fishers are observing regulations for the release of female crabs. Natural factors (temperature, reproduction cycle, etc.) may also be influencing scores and cannot be ruled out. Research is required to understand how mud crab populations are impacted by a female-dominated sex ratio.
Prevalence of rust spot lesions was very low in most zones, with four zones receiving very good scores (0.98–1.00). In contrast, the Inner Harbour received a poor score (0.32) for this sub-indicator. The average incidence of rust spot lesions across the seven monitored zones was 7% in February and 4% in June, considerably lower than the 37% incidence recorded in 2012 or less than half of the 22% recorded in the late 1990s.