Mud crab indicators for the Gladstone Harbour Report Card: Project ISP015-2020

Mud crabs (Scylla serrata) are recreationally and commercially important species in Gladstone Harbour, as well as an iconic seafood item, with cultural value to Indigenous Australians. The Gladstone Harbour mud crab indicator provides scores and grades for three metrics: abundance (catch per unit effort), prevalence of rust lesions and sex ratio. In 2020, mud crab monitoring was conducted in seven Gladstone Harbour zones for the fourth consecutive year since the indicator was developed in 2017. Two field sampling events were conducted in March and June. Scores and grades were calculated using both data sets for the three metrics for each of the seven recommended long-term monitoring zones in Gladstone Harbour. Following a change in averaging order requested by the GHHP Independent Science Panel (ISP), each of the three measure scores were averaged across all zones first, and then the average of the three ‘measure’ harbour scores was calculated to obtain a harbour-wide score and grade for the mud crab indicator.