Fish health indicator scores and grades for the 2020 Gladstone Harbour report card: Final project report - Project ISP023-2020

Fish can be used as indicators of environmental contamination as they are frequently the dominant taxa in aquatic ecosytems, play a variety of important ecological roles, are continuously exposed throughout their life cycle and have high importance to the community. Fish exposed to contamination can be affected from the population level (numbers and diversity of fish species) down to biochemical impacts on single cells within individual fish. In 2018, Gladstone Healthy Harbour Partnership (GHHP) and the Fisheries Research and Development Corporation (FRDC) commissioned CQUniversity (CQUni) to investigate potential fish health indicators for the Gladstone Harbour Report Card that would be suitable for adaptation across ports and estuaries of Northern Australia. The research identified and tested a range of potential indicators that were low-medium cost and complexity. The indicator that was found to be most suitable for long term application in the Report Card is a version of the Health Assessment Index (HAI), a composite metric that integrates observer evaluations of multiple organs and tissues. The premise of the HAI is that scores will cumulatively reflect the acute and chronic stressors present in the fish’s environment, with poorer anatomical condition resulting in higher HAI scores, indicative of a more stressful environment. In 2019, GHHP commissioned CQUni to continue to monitor fish health in Gladstone Harbour using methods developed in 2018 and provide scores and grades for the Gladstone Harbour Report Card. Sampling was conducted across Gladstone Harbour and at two reference sites twice during the 2019 reporting year. For the 2020 Report Card, GHHP reduced the sampling to a single event, which was conducted in October 2019. Sites sampled included a range of estuarine environments in the northern, middle and southern parts of the harbour and a single reference site (Baffle Creek).