Study tracks movements of tagged prawns across NSW
They are one of the Aussie seafood favourites but have you ever wondered where prawns travel before they make it to our plates? A NSW study has revealed the movements of thousands of these crustaceans — with one tagged prawn travelling 713km before being caught.
NSW
Don't miss out on the headlines from NSW. Followed categories will be added to My News.
It was a mighty journey for a diminutive crustacean — 713km along the east coast from NSW into Queensland, surviving an ocean full of fish keen to make it dinner.
The eastern king prawn was one of 7500 fitted with tiny yellow, numbered tags and released off the coasts of Ballina, Yamba and South West Rocks on the state’s north coast, as part of a NSW Department of Primary Industries Fisheries study investigating their movements and whether areas closed to prawn trawling contribute to more bigger and plumper prawns being caught for market by NSW commercial fishers.
Prawn trawlers reported the recapture of 795 of the tagged prawns, and prawn No.2645 had swum the longest distance.
It had been caught, tagged and released in the ocean just offshore from Ballina on February 21, 2016, and ended its days in the net of an ocean prawn trawler 713km away, near Yeppoon, on September 29 that year.
Prawn No.2645 was about 14cm long when it was tagged and it was estimated it had swum about five million times the length of its body. And it was an odyssey made all the more miraculous by the fact almost every ocean predator, from octopus to sharks, loves to eat prawns.
The fastest swimming tagged prawn paddled 4.5km a day, having been tagged off South West Rocks and recaptured by a trawler 18km away, four days later.
GET MORE CONNECTED:
What you get as a subscriber to The Daily Telegraph
Download our app and stay up to date anywhere, anytime
NSW Fisheries Principal Research Scientist Dr Matt Taylor said eastern king prawns spawn off the northern NSW coast, where the eggs hatch, and then hitch a lift along with Nemo on the East Australian Current and end up in our estuaries,
That’s where they grow up — and are caught on summer nights by holiday makers with a hand net and torch — before returning to the sea and generally swimming north to spawn.
Prawn No.2645 was exceptional in the distance it travelled, but the reason this particular prawn swam so far was unknown.
“Unfortunately I’ve never interviewed a prawn after capture to discover its motivation,” he laughed.
Dr Taylor said his research showed inshore commercial prawn fishing closures put in place in the 1990s were working in helping allow younger eastern king prawns to reach a much larger size before capture.
“There are areas closed to commercial prawn trawling dotted along the NSW coast in the ocean just off major estuary systems which means they can’t be caught until they’ve had time to grow bigger,” he said.
“Letting them grow up before they can be caught provides a better economic return through a heavier prawn.”
According to the status of Australian Fish Stocks, 3550 tonnes of eastern king prawns were caught commercially off eastern Australia in 2016-17, worth an estimated $50 million.
And despite their world fame and association with a carefree Australian lifestyle thanks to that Paul Hogan ad campaign, we actually didn’t eat that many prawns until relatively recently, with the introduction of modern refrigeration.
Today’s most common method of commercial prawn fishing, using a net spread between a pair of underwater “otter boards” and towed behind a boat, started in Australia in Sydney Harbour in 1926.
The technique spread north to the Clarence and Hunter Rivers and to nearby Hawkesbury and Botany Bay in the 1940s.
Originally published as Study tracks movements of tagged prawns across NSW