Research for the sustainability of prawn resources
Montgomery, S., 2011. Research for the sustainability of prawn resources. DVD production, duration: 4 min 16 sec.
Prawns are one of the most economically valuable seafood resources in New South Wales and are a vital part of the aquatic food web. Each year around 2,000 tonnes of prawns are landed by commercial fishers with at least another 50 tonnes caught by recreational fishers. Eastern king prawns and School prawn make up almost 97% of all prawn catches in NSW. This video reports on the research done by scientists at Industry and Investment NSW (I&I NSW) in collaboration with the commercial fishing industry to collect the information necessary to assess these stocks.
Regularly measuring prawn sizes allows scientists to study prawn growth using Length Frequency Analysis, where the growth of groups of prawns that were born at around the same time is traced monthly.
Scientists also study growth, mortality and movements by tagging prawns through the tail with a yellow strip of plastic which has a unique number so each recaptured prawn can be identified. Commercial and recreational fishers and the public are relied upon to report tagged prawns in their catches and purchases.
Results from these studies show that eastern king prawns grow to approximately 70 mm carapace length or about 150 grams. School prawns can reach a size of approximately 35 mm carapace length or roughly 30 grams in weight. King prawns can live for up to three years but the faster-growing school prawns live for less than two years. Most deaths in prawn populations are due to natural causes rather than fishing but records show that at times fishing can account for at least 50% of the mortality. School prawns stay in ocean waters close to the estuary from which they migrated as adolescents whereas eastern king prawns travel northwards, covering distances of more than 1000 km, further than any other prawn species in the world.
All this information collected by staff of the Wild Fisheries Unit provides solid scientific evidence to help researchers, fishery managers, and the fishing industry work out how best to maintain a sustainable harvest from NSW’s prawn resources. This work has been funded by Industry & Investment NSW and by the Fisheries Research and Development Corporation (Grant #2001/029).