Most prawns sold in Australian fish shops are caught by trawlers in tropical and subtropical waters, in places such as the Gulf of Carpentaria, Shark Bay, Exmouth and off the east coast of Australia. Other fisheries exist in estuaries farther south including Lakes Entrance, Gulf St Vincent and Spencer Gulf in South Australia. In Australia, prawns are also farmed in seawater ponds on coastal farms.
Prawns are the scavengers of the seas, eating almost anything they come across. The flavour and texture of prawns are a direct reflection of the environment in which they come, from the grassy taste and soft texture of the river or lake school prawn to the umami-rich and crisp bite of the mighty Skull Island tiger prawn from the Gulf of Carpentaria.
As a general rule, if you are going to use a prawn for a hot dish, buy them raw and cook them once. If you are going to use them for a salad, buy them pre-cooked. Pre-cooked prawns are mostly cooked live on the boat or at the farm, then refreshed in brine ice. Handled this way, the prawns will always be firmer, crisper and sweeter than a dead, raw prawn put through the same process.
Prawns are arguably one of the most fragile proteins you will handle in your kitchen, buying frozen is a genuine option. The integrity and quality of a raw prawn packed and frozen from live will often be superior to one which has endured days of variable handling in a ‘fresh’ highly fragile state.
Prawns are graded in pieces per pound, thus if a prawn is graded as U6, it indicates there are approximately #14 pieces per kg; a 10–15 indicates there are approximately 22 to 36 pieces per kg. Consider what you are going to use the prawns for, they don’t always have to be the biggest and the smaller grades are generally cheaper than the larger ones. Prawns vary in price almost as much as they do in quality — price is not exclusively an indicator of quality. But you can expect to pay more for Australian produced prawns than imported and more for wild caught than farmed.