Sand flathead under threat
POST-Christmas and everyone who is on holidays and into fishing have been telling of some wonderful captures from around the state.
Hotspots include the Swan River, Scamander River plus George’s Bay in the east and Marion Bay and waters around Maria Island in the south.
Captures are run of the mill as water warms and these include gemfish, King George whiting, calamari squid and, of course, the humble flathead.
An interesting report released before Christmas by the Institute of Marine and Antarctic Studies has found that most Tasmanian fish stocks are sustainable, however, changes will be coming for the capture of sand flathead and some other species as the fish has been determined to be threatened by overfishing.
IMAS has released the Tasmanian Scale Fish Fishery Assessment for 2020-21 which involved researchers evaluating 22 of the state’s most important species.
Data showed most fish stocks were in a healthy position, with 12 species classed as sustainable.
However, high fishing pressure is a concern for six popular species, the sand flathead, striped trumpeter, bastard trumpeter, southern garfish and blue warehou (snotty trevally) all being classified as depleted, while southern calamari stocks were found to be depleting.
Sand flathead are Tasmania’s most popular recreational species with recreational fishers taking more than 98 per cent of fish caught.
Size and bag limit changes introduced in 2015 were initially believed to be supporting stock recovery; however, new analysis showed that the biomass and reproductive potential of populations in most regions had declined below critical levels.
In a report by Kate Fraser from IMAS, she stated that heavy fishing pressure on sand flathead across Tasmania was likely to be unsustainable and would prevent stock recovery in most regions, specifically where stock rebuilding was most urgently needed, including the D’Entrecasteaux Channel, Frederick Henry Bay, Norfolk Bay and Great Oyster Bay.
Dr Fraser also said sand flathead were not reaching the 32cm minimum size limit in many areas and once they grew to this size, they were generally caught within a short time period, which undermined reproductive ability.
Fish that reach sexual maturity before reaching the minimum size limit produce substantially fewer eggs than larger fish, and their offspring tend to have a reduced chance of survival.
It is also important to note females grow larger than males, so receive less protection from size limits. Their protection relies heavily on catch controls.
To address concerns about sand flathead stocks, IMAS is leading a research project involving the development of a new monitoring regimen and stock assessment for sand flathead in Tasmania.
This has funding from the Australian government through the Fisheries Research and Development Corporation. (frdc.com.au/ project/2020-005.
IMAS is also leading a broader investigation profiling recreational fishers to understand what they value about the Tasmanian recreational sand flathead fishery.
This project is funded by the Tasmanian government. frdc.com.au/project/ 2021-116.
Dr Fraser said IMAS was continually improving the scale fish stock assessment, using internationally recognised, up-to-date assessment approaches.
“The aim is to refine and improve population status estimates of our scale fish species, which will help ensure communities have long-term access to these highly valued fishery resources,” she said.
The full report can be read here, imas.utas.edu.au/ __data/assets/ pdf_file/0005/1632515/ Scalefish-Assessment_202021.pdf
Have a happy and safe New Year.