Novel New Fish Projects Evoke Passion and Calm

According to BYM Marine Environment News, scientists are investigating a mystery: why pond grown male prawns are often not up to the job of breeding.

This research into prawn fertility is being conducted by the Queensland Primary Industries and Fisheries (QPIF) and CSIRO at the QPIF's Bribie Island Aquaculture Research centre.

Minister for Primary Industries, Fisheries and Rural and Regional Queensland Tim Mulherin said the black tiger prawn contributed over $30 million to Queensland's economy last year.

"Black tiger prawns grow to a large size fairly quickly and are a very popular farmed prawn. They represent the bulk of the Queensland prawn farming industry," the Minister said.

"Historically, farmers have captured brood stock from the wild but are now looking to not only grow and maintain domesticated stock, but to breed selected lines. However, one major obstacle in this process is the sometimes questionable fertility of pond-grown males. If farmers are going to maintain hundreds of male brood stock over winter they need to know that they will perform come breeding season. To date scientists and farmers alike have been baffled as to why pond-grown male brood stock can be less reliable than wild or tank-grown stock," he said.

The Minister said scientists suspect that low winter temperatures and/or overcrowding are putting pond-grown males off their game.

"Solving this mystery could lead to a more consistent supply of prawns for consumers and contribute an additional $3 million to the Queensland prawn farming industry.

Lead QPIF scientist Dr Brian Paterson said if the project is successful, prawn farming companies operating their own selective breeding programs will benefit from more efficient production of brood stock.

"The sooner these companies can produce stock in excess of their own requirements, the sooner the benefit will flow on to the wider industry through the sale of post-larvae to other farms," he said.

"And of course Queensland consumers will benefit from a larger supply of fresh, locally produced tiger prawns."

The Minister said scientists are also working to reduce mud crab mortality rates while being transported.

"Mud crabs can become stressed as they are transported for days at a time. QPIF researchers used stress biomarkers to understand which handling steps along the chain imposed the greatest stress on the crabs. It was determined that the major causes of stress are holding crabs out of water, handling disturbances and temperature changes," he said.

"The major recommendation from our study is the inclusion of a recovery step within the distribution chain for live mud crabs, including re-immersion of crabs for more than three hours in oxygenated fresh water.

"By simply treating live mud crabs to oxygenated water, scientists have seen a 50 percent reduction in mortality rates from 10 percent to 5 percent during live shipment.

QPIF scientist Sue Poole said the State's mud crab industry was losing more than $750,000 a year due to mud crab mortality.

"The research has seen many people in the industry change the way they handle their stock," she said.

"It is clear mud crabs need time to recover in fresh, oxygenated water before reaching markets.

"Wide industry adoption of the research has already been achieved at the harvest and wholesale levels with the retail sector the next target.

The mud crab project was funded by the Australian Government's Fisheries Research Development Corporation.