ENVIRONMENTAL
.RESULTS
ABOUT THE ZONE
The Narrows is lined by mangroves and saltmarsh, provides sheltered water for mud crabs and is an important area for recreational and commercial mud crab fishers.
WATER & SEDIMENT
The Narrows received an overall water quality score of 0.79 (B).
Sediment quality of The Narrows was very good with an overall score of 0.95 (A).
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The following graphs compare the Water and Sediment scores reported for 2024 (top line) to those from 2023.
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 The Narrows scored 0.78 and received a good grade (B), similar to the 2023 report card. This score was calculated by aggregating the three sub-indicator and associated measure scores (Physicochemical – pH and turbidity, Nutrients – total nitrogen, total phosphorus and dissolved metals, and dissolved metals – aluminium, copper, lead, manganese, nickel and zinc).
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Within the Physicochemical sub-indicator, The Narrows received a score of 1.00 and a very good grade (A) for pH, indicating that the average pH was within the guideline value range. This zone received a score of 0.57 and a satisfactory grade (C) for turbidity, indicating that average turbidity met the guideline values in both wet and dry seasons.
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Within the Nutrient sub-indicator, both total nitrogen (0.50) and chlorophyll-a (0.53) had satisfactory grades (C), indicating that average concentrations for these measures were below guideline values for this zone. Total phosphorus had a higher score (0.66) and a good grade (B).
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All six Dissolved metals received high scores (1.00) and very good grades (A) indicating that concentrations were well below the water quality guideline values.
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For Sediment quality, The Narrows received an overall score of 0.91 and a very good grade (A), a similar result to the previous year. This score was calculated by aggregating measure scores (Metal and metalloids – arsenic, cadmium, copper, lead, mercury, nickel and zinc).
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In 2024, five of the seven Metal and metalloid sub-indicator measures received very high scores (0.89–1.00) and very good grades (A), while two measures – nickel (0.66) and arsenic (0.69) – received a good grade (B). These results reflect that all concentrations were below the guideline values for this zone.
HABITATS
SEAGRASS (MEADOW 21)
The Narrows has one monitored Seagrass meadow at Black Swan Island. It is an intertidal meadow with variable biomass.
The overall grade for this meadow was very good (A), similar to the previous year. All three sub-indicators received very high scores – demonstrating the high meadow biomass, a very good meadow area and a high presence of the historically dominant species.
MANGROVE RESULTS
In 2024, the overall grade for Mangroves at The Narrows decreased from good (B) in 2019 to satisfactory (C). Mangrove extent retained a good (B) grade at The Narrows in 2024. The grade for canopy condition at The Narrows improved from a satisfactory (C) in 2019 to a good (B) in 2024. Shoreline condition of mangroves at The Narrows declined in grade to a poor (D) in 2024.
FISH & CRABS
FISH RESULTS
Fish recruitment was assessed for two species: Yellowfin bream Acanthopagrus australis and Pikey bream Acanthopagrus pacificus. The overall score for 2024 was higher than the previous year (2023: 0.37, 2024: 0.44) but remained as satisfactory (C).
MUD CRAB RESULTS
The overall zone score for Mud crabs for The Narrows was 0.65, indicating a good grade (B). Improved catch rates resulted in improved scores for the abundance sub-indicator, which rose from a satisfactory (C) grade in 2023 to a very good (A) grade in 2024. The sex ratio remained unbalanced (low score), while the prevalence of rust lesions remained low (reflected by a high score).