Ask Dr Dazza | Prawns

Published 11:21am 1 December 2021

Ask Dr Dazza | Prawns
Words by Dr Dazza

AS WE lead up to Christmas, a lot of our culinary focus turns to prawns and Moreton Bay produces some wonderfully tasty product.

Wild-caught tiger prawns are always popular at Christmas time and Moreton Bay is a significant area of production for the trawlers that catch them. There are a couple of different species of tiger prawns, with the brown tiger prawn the most commonly caught species in Moreton Bay.

The brown tiger prawn is endemic to Australia and Moreton Bay is the southernmost location on the Australian east coast where they are highly abundant, although their range does extend to mid-NSW.

Seagrass is critical for the lifecycle of tiger prawns. No seagrass = no tiger prawns. Juvenile tiger prawns are most abundant in sparse seagrass habitat. The striped colouration of the tiger prawns provides camouflage for them as juveniles. While their diet is broad, plants including algae, seagrass and seagrass seeds are essential in the diet for the health of juvenile brown tiger prawns. They do become more carnivorous as they grow, eating larger relative volumes of animals such as small crustaceans and molluscs. Brown tiger prawns are nocturnal foragers. They spend the day hiding in seagrass or buried in the seabed.

Unlike the eastern king prawn which are highly migratory and leave Moreton Bay as adults, most tiger prawns spend their entire lifecycle within the bay. In Moreton Bay, the spawning period of brown tiger prawns peaks between October and November. Peaks of juvenile brown tiger prawns appearing in their seagrass nursery habitat occur between September and November and late January to April. The lifespan of a brown tiger prawn is between approximately 18 months to two years. As tiger prawns mature, they move progressively into deeper waters.

The size of the brown tiger prawn population each year varies. Temperature is the most significant explanatory factor for annual variation in brown tiger prawn recruitment and increased temperatures have increased recruitment of brown tiger prawns.

If you are tucking into wild-caught tiger prawns this Christmas, think about the important role seagrass habitat in maintaining catches of this tasty critter. Remember, no seagrass = no tiger prawns.


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