Dam spill shakes up barramundi results
THE Crystal Bowl report on barramundi statistics for 2017 has delivered mixed results for the species in Gladstone.
The report, complied by InfoFish Australia's Bill Sawynok with the help of data collected by recreational fishers, indicated a drop in legal to trophy-size barra (58-99.9cm) in 2017, but there is better news predicted for 2018.
Data is collected using 'citizen science' with catch details based on the top 20 per cent of fishers (T20) who catch 80 per cent of the fish.
Their catch rates do not reflect the catch rates of the total fishing population.
The report collected information from 50 fishers from 194 fisher days during the 2017 season.
Highlights of the report indicated catch rates were on track as forecast until fish spilled from Lake Awoonga in April and forecasts were revised upward to account for the influx.
However, fish that spilled from Awoonga were largely confined to the Boyne River with little evidence of barra in Gladstone Harbour or the Calliope River.
The report also states in the last 10 years there have been 2.43 million barramundi fingerlings, ranging from 30-70mm, stocked into Lake Awoonga with 191,000 added in 2017.
While the April spill at Awoonga Dam had an impact on barra size and numbers, the effects of last month's spill won't be known until the 2018 season.
The biggest change between the 2017 forecast and the actual results from this year delivered an anomaly in the percentage of legal to trophy-size barramundi caught.
The 2017 forecast indicated 70 per cent of fish caught would fall within the legal to trophy-size range but the actual result was a surprising 52.9 per cent.
Mr Sawynok said there was a simple explanation for the 17 per cent difference in the forecast.
"The fish that spilled from Awoonga were generally of a smaller size than the spill of 2011 and so that brought the average size down," he said.
"Because a lot of the stats are dominated by fish in the Boyne River that's why it's reflected in those sizes."
On the plus side, the number of legal to trophy-sized barra is tipped to rise to 60 per cent in 2018.
"Because the fish coming over the spillway at Boyne are in that 50-55cm size range, come next year those will be legal size," Mr Sawynok said.
"So what we'll see is a slight increase in the proportion of legal-size fish."
Although more legal-sized barra are tipped to be on the bite next season, which opens at midday on February 1, trophy-size fish (more than 1m) will drop from 11.3 per cent to roughly five per cent.
"Previously there was a lot of trophy-size fish in the Boyne, particularly from 2011, so that kept a lot of the trophy-size fish up in the years after that," Mr Sawynok said.
"Now with the smaller numbers of trophy-size fish coming over, and generally those fish get taken out periodically either by the commercial guys or some by recreational, we'll see a slight decline in trophy fish."
Recreational fisher Ryan Paterson is one of dozens of anglers who tag and record fish for the InfoFish Australia database.
He prefers to fish in the net-free zones near Port Alma but has had plenty of success on the Boyne this year despite the presence of commercial fishers.
"The Boyne doesn't fish as well as it used to because of the nets, but you can still have some awesome sessions," he said.
"This season I've done a lot more fishing up at the net-free zones and that's been incredible."