Studying the iconic gilled species of Gladstone's Harbour

08 June 2021

If you are out on the Gladstone Harbour' chances are you will catch CQUniversity Research Fellow' Dr Nicole Flint and her team monitoring the health of local fish and mud crabs.

The Gladstone Harbour may be known nationally as the gateway to the Southern Great Barrier Reef' but it is also Queensland's largest' and Australia's fifth largest' multi-commodity port.

As such' the Gladstone Healthy Harbour Partnership (GHHP) commissioned CQUniversity's Coastal Marine Ecosystems Research Centre to develop mud crab' fish health' and social' cultural' and economic indicators.

Dr Flint says these indicators are used to independently monitor' and report on' the health of the harbour against GHHP environmental goals' and inform annual Gladstone Harbour Report Cards.

"Report cards are used to communicate the condition of coastal and riverine environments to key stakeholders and the community' by synthesising complex data drawn from the indicators'"

she says.

"The mud crab indicator focuses on three key metrics: abundance (catch rates)' the prevalence of rust lesions' and sex ratio.

"Given how important mud crabs are to Queensland's economy – supporting commercial and recreational fisheries – a standardised field monitoring program was also developed for the harbour.

"The program' delivered in partnership with the Gidarjil Development Corporation Sea Rangers' involves setting twenty heavy-duty pots at each of seven sites across Gladstone Harbour' twice a year.

"While fully submerged' to minimise mortality of any fish or other bycatch' the pots soak for at least five hours. Upon retrieval' indicator data is gathered from mud crabs' and general health assessments are undertaken.

"All mud crabs and any bycatch species are then released at the capture location.

Dr Flint says the fish health indicator is slightly different' and its development was part-funded by the Fisheries Research and Development Corporation.

"To provide scores and grades on fish health' CQUniversity research staff and Gidarjil Development Corporation Sea Rangers' collect samples of five target fish groups from the harbour'"

she says.

"A laboratory assessment of fish health is then undertaken' scoring the skin' eyes' fins' gills' liver' spleen' kidney' hindgut' and parasite load.

"The results are combined and standardised to develop a score and grade for each species group' and for the harbour overall.

"The most recent GHHP report card' for 2020' grades fish and crabs as "C"' satisfactory."

This research contributed to CQUniversity's success in the recent Times Higher Education Impact Rankings' under the United Nation's Sustainable Development Goal (SDG) 14 Life Below Water.

CQUniversity ranked 29 out of 379 participating institutions (top seven per cent' globally) for its commitment to local marine ecosystem maintenance' education' and action.

Dr Flint' who discovered her passion for the ocean as a child' says it is extremely rewarding to be part of a long-term marine ecology initiative.

"I grew up on a boat' so I knew from a young age that I wanted to be a marine biologist. Given that I was always in or near the water' my interest in sea life developed very quickly'"

she says.

"Now' I'm able to help improve our understanding of the ecology of marine and freshwater species.

"I have a great appreciation for the social and economic importance of crabs and fish to communities in regional Queensland' and the data we provide can contribute to sustainable use of these resources.

"Not only are we still monitoring and gathering data' but we're inspiring the next generation of scientists. In fact' two of my research higher degree students have projects linked to our mud crab and fish health research.

"A PhD project aims to identify how environmental and biological factors affect moulting' mating behaviour' and reproductive outputs of mud crabs in Gladstone Harbour and nearby estuaries.

"We also have a Masters student whose project investigates the occurrence of fluctuating asymmetry in fish in northern Australian estuaries' including Gladstone Harbour."

Dr Flint hopes that these indicators will be used elsewhere in the future' particularly in other ports and estuaries of northern Australia.

"Given the reporting success of the indicators' there is merit in using these to monitor the health of other harbour locations' where there is both economic and community importance'"

she says.

For more information on CQUniversity's commitment to SDG 14' visit