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Tagged Prawns Assist Fishery Management

18 February 2014

AUSTRALIA - The Spencer Gulf prawn fishing industry and State Government researchers are collaborating on a prawn tagging study to improve understanding of growth and movement patterns of prawns in southern Spencer Gulf.

Together they have tagged 6000 western king prawns in this region over the past two years, around 100 of which have been recaptured by prawn fishers and sent to researchers for analysis. Some prawns had travelled more than 50 kilometres within the Gulf.

Fisheries Minister Gail Gago said the idea for the project came from prawn fishers searching for ways to improve their management practices.

“Little is known about the movement of prawns that occupy the southern region of Spencer Gulf, and fishing strategies have therefore erred on the side of caution,” Ms Gago said.

“The Spencer Gulf prawn industry and the State Government are keen to improve understanding of how prawns use the southern region of the gulf, or if they eventually move out of the gulf permanently.

“Knowing more about prawn movement will help gauge their contribution to stock and spawning, and improve our management of the already internationally-accredited Marine Stewardship Council-certified fishery.

“It is exciting to see responsible fisheries initiating projects such as this to provide a better picture of this species and the fishery.”

SARDI scientist Dr Craig Noell said prawns in the southern section of Spencer Gulf tend to be larger than average, although the population was not as dense as those further north.

Dr Noell said when a tagged prawn is recaptured during commercial trawling, it is placed with a label in a bag by the prawn fisher, frozen and sent for analysis by SARDI researchers.

“The information we need is the tag number, date of recapture, and GPS location,” he said.

“When this information is matched up with information recorded about when the prawn was tagged and released, growth and movement of the prawn can be established.”

Dr Noell said prawn fishers and SARDI tagged 2000 prawns in one night in 2012 and 4000 over two nights in 2013 in the deep central water in the southern Spencer Gulf, and near Thistle Island and Corny Point.

A tag gun is used to insert the tag in the third abdominal segment of the prawn. The tags last longer than the life cycle of a prawn, which is up to four years.

More tagged prawns are expected to be recaptured during the 2014 fishing season.

“The more tag-recapture data that is obtained, the better our understanding of the movement and growth of prawns in the southern part of the gulf,” Dr Noell said.

“This in turn helps to improve the scientific advice provided by SARDI to managers and industry for developing appropriate fishing strategies.”

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