Water quality The Mid Harbour received an overall water quality score of 0.91 (A). This score was based on the scores for physicochemical (0.92), nutrients (0.80) and dissolved metals (1.00). Sediment quality Sediment quality of the Mid Harbour was very good with an overall score of 0.96 (A).

The Mid Harbour 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 good score for turbidity (0.84) indicating that average turbidity was below the guideline value.

All six dissolved metals received very good scores (0.98–1.00) indicating that average concentrations were well below the water quality guideline values.

The Mid Harbour received a good overall score for nutrients (0.80). Total phosphorus had a very good score (1.00) and total nitrogen (0.66) and chlorophyll-a (0.74) had good scores, indicating that average concentrations for these measures were below the guideline values for this zone.

Mid Harbour has two monitored meadows adjacent to the south-east corner of Curtis Island. Meadow 43, known locally as Pelican Banks, is the largest and most productive seagrass meadow assessed in the Gladstone Harbour Report Card. Pelican Banks is an intertidal meadow while Meadow 48 is a subtidal meadow neighbouring the eastern side of Quoin Island.

Overall condition of the Mid Harbour seagrass remained poor (0.48) for the second consecutive year.

The overall poor condition was largely driven by Pelican Banks, which received a poor score (0.33) for the sixth consecutive year. While seagrass area remained very good and has improved markedly since 2017, biomass has remained poor or very poor since 2016. Species composition at Pelican Banks was satisfactory but has shown a similar declining trend as biomass.

In contrast, Meadow 48 was in satisfactory condition (0.64), showing satisfactory biomass, good area, and very good species composition scores. This was the first time since 2011 that this meadow was composed of the dominant species H. uninervis.

The overall score for corals in the Mid Harbour was 0.16 indicating a very poor condition. This score was a decrease from the previous year (0.20).

All four reefs in this zone received very poor scores for coral cover ranging from 0.02 at Manning Reef to 0.15 at Rat Island. Macroalgae cover also received very poor scores at all four reefs (0.00), indicating very high levels of macroalgae.

Juvenile density was very poor at Facing Island (0.02), Manning Reef (0.18) and Rat Island (0.10) and poor at Farmers Reef (0.30). At the zone level, the juvenile density score declined substantially since 2018.

Hard coral cover change in the Mid Harbour remained poor (0.43), showing a minor decline compared to the 2020 score (0.44). The continued poor score indicating that the rate of increasing coral cover in this zone was lower than that observed at other nearshore reefs in the Great Barrier Reef.

The overall zone score for the Mid Harbour was 0.55 (C) indicating a satisfactory condition for mangroves in this zone. This was a result of a poor score for mangrove extent (0.39), and satisfactory scores for canopy condition (0.63) and shoreline condition (0.63).

This overall score for 2019 was identical to the score recorded in 2018.

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.