Mud crab indicators for the Gladstone Harbour Report Card: Project ISP015-2021

Giant mud crabs (Scylla serrata) are a recreationally and commercially important species in Gladstone Harbour, an iconic seafood item, and have cultural value to Indigenous Australians. The Gladstone Harbour Report Card mud crab indicator provides scores and grades for three metrics: abundance (catch per unit effort), prevalence of rust lesions, and sex ratio. The mud crab indicator has been monitored in seven Gladstone Harbour zones since 2017, and this report presents the results of the fifth year of sampling, 2021. Two field sampling events were conducted during 2021, one in February and one in June. Scores and grades were calculated using both 2021 data sets for the three metrics within each of the seven recommended long-term monitoring zones in Gladstone Harbour. The scores for each of the three measures were averaged across all zones first to give a harbour average for each measure, and then the average of the three harbour averages was calculated as a harbour-wide score and grade for the mud crab indicator.