3

Western Basin

AREA 39.19 km2
 Overall Result

The Western Basin is located near the north-western end of Gladstone Harbour. Three large-scale Liquid Natural Gas (LNG) plants have been constructed on the south-western shore of Curtis Island. The first of these commenced operation in late 2014. Large industrial plants located on the western shore of this zone include Queensland Energy Resources, Rio Tinto Yarwun, Orica, Transpacific Waste and Cement Australia. Areas of mangroves and mudflats remain between Fisherman’s Landing and the Wiggins Island Coal Export Terminal (WICET) and on the southern tip of Curtis Island.

This zone has six water and sediment monitoring sites, six monitored seagrass meadows, one fish monitoring site, and two mangrove monitoring sub-zones.

Water & Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Water quality
Western Basin received an overall water quality score of 0.95 (A). This score was based on the scores for physicochemical (0.97), nutrients (0.87) and dissolved metals (1.00).

Sediment quality
Sediment quality of Western Basin was very good with an overall score of 0.99 (A).


Measures Results

Water
Sediment

Western Basin received a very good score of 1.00 for pH indicating that the average pH was well within the guideline value range. This zone received a very good score for turbidity (0.94) indicating that average turbidity was well below the guideline value.

All six dissolved metals received very good scores (1.00) indicating that average concentrations were well below the water quality guideline values.

Western Basin received a very good overall score for nutrients (0.87). Total phosphorus (1.00) and chlorophyll-a (0.92) had very good scores and total nitrogen had a good score (0.71), indicating that average concentrations for these measures were below the guideline values for this zone.

Habitats

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
4 1.00 0.97 0.91 0.94 0.75
5 0.86 0.82 0.82 0.82 0.75
6 0.88 0.94 0.62 0.75 0.75
7 0.63 0.74 1.00 0.63 0.75
8 0.86 0.69 0.57 0.63 0.75
52-57 0.71 0.95 1.00 0.71 0.75

The Western Basin includes six monitored seagrass meadows, five of which are intertidal and one subtidal (Meadow 7).

This zone was in good condition (0.75) for the third consecutive year. All seagrass meadows received were in satisfactory or better condition—with two meadows scored as satisfactory, three meadows scored as good, and one meadow scored as very good.

Results were somewhat mixed among the various meadows. Meadow 4 was in very good condition (0.94) for the second year and the only meadow to show a higher meadow score than the previous year. The remaining five meadows had slightly lower meadow scores than the previous year; however, meadow scores were driven by different sub-indicators at each meadow.

Mangrove Results

The overall zone score for the Western Basin was 0.51 (C) indicating a satisfactory condition. While mangrove extent (0.76) received a good score, both canopy condition (0.39) and shoreline condition (0.37) had poor scores.

The overall score for Western Basin fell from 0.57 in 2018 to 0.51 in 2019. This was largely a result of changes in canopy condition where the score declined from 0.60 in 2018 to 0.39 in 2020. This may reflect the impacts off decreased rainfall over the reporting year.

Fish and Crabs

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Fish Health Results

Harbour Score
Visual fish condition (VFC) 0.74
Fish health assessment index (HAI) 0.90

Visual Fish Condition: Harbour Score
FVA - Fish Visual Assessment
FBC - Fish Body Condition
Fish Health Assessment Index: Harbour Score
HAI - Health Assessment Index

Fish Health (Overall):

The overall score calculated for fish health in 2021 was 0.82 (B), which is an average of the scores for Visual Fish Condition 0.74 (B) and the Health Assessment Index 0.90 (A).

Visual Fish Condition:

The overall score for the visual fish condition is an average of 0.97 (A) for Fish Visual Assessment (FVA) and 0.50 (C) for Fish Body Condition (FBC).

The high scores for FVA are a result of a low incidence of poor visual health. All fish species assessed for this metric received very good scores ranging from 0.94 (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 satisfactory score for FBC in 2021 was a result of poor scores for yellow-finned bream (0.47) and pikey bream (0.48). Both species assessed had a mean body condition below the long-term average (2003 – 2020). However, the remaining three species assessed all had satisfactory scores ranging from 0.54 to 0.55.

Fish Health Assessment Index:

The overall HAI score for Gladstone Harbour was 0.90 (A).

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 Visual Fish Condition sub-indicator. Scores for internal organs were also low indicating good to very good fish health.

Fish Recruitment Results

Zone ID Score
3. Western Basin 0.94

Fish recruitment was assessed for two species: yellow-finned bream Acanthopagrus australis and pikey bream Acanthopagrus pacificus. The overall score for 2021 was 0.62 (C) similar to the 2020 score of 0.64. The final scores were measured against a 2012 to 2020 baseline. The 2021 score for fish recruitment indicates a season with higher recruitment rate (increased catch rate) relative to the mean reference level determined over the baseline period. The total number of bream caught in the 2021 reporting year was 626, 329 yellow-finned bream and 297 pikey bream. Pikey bream tended to dominate in the northern sites while yellow-finned bream tended to dominate in the southern sites.