New insights into Victorian mulloway populations

Recreational fishing licence fees have helped anglers and scientists learn more about mulloway populations in several Victorian estuaries.

Fisheries Victoria acting Executive Director Mark Edwards said the Nature Glenelg Trust had received a $5,000 Small Grant to undertake the project, which relied heavily on anglers and the donation of their mulloway frames for dissection.

"Twenty three volunteer anglers who fished the Glenelg, Hopkins, Barwon and Fitzroy rivers, along with the marine waters near Portland and off South Australia, donated 77 mulloway frames to the study, which began in August last year," Mr Edwards said.

"From behind the brain of the fish, scientists recovered small and hard calcium carbonate structures called otoliths that were then analysed to reveal the age of each mulloway.

"Otoliths help fish with balance, orientation and sound detection, but thin slices of them placed under a microspore also reveal the age of a fish, similar to counting rings on a cross-section of a tree trunk.

"All of the 77 mulloway were between three and eight years of age, but the majority of them fell between three and four years of age, highlighting the likely importance of estuarine habitats to the early life stages of mulloway populations.

Dr Lauren Veale from the Nature Glenelg Trust said the study had filled several knowledge gaps about the biology of the species and their age-at-length.

"We compared these results to a previous Fisheries Victoria study that estimated the age of 133 mulloway collected from the Glenelg River between 2008 and 2011," Dr Lauren said.

"Mulloway caught from our more recent study were generally longer at any given age."

"This fluctuation in age-at-length is not uncommon in estuarine species and has been observed in black bream populations elsewhere in Victoria."

The Nature Glenelg Trust hopes to undertake further research on mulloway on the back of this pilot project, which will yield valuable information that can be used to guide the future monitoring and management of the species.

For more information about the results of this pilot study, contact Dr Lauren Veale via email at lauren.veale@natureglenelg.org.au