Effects of cyclones on seagrass communities and penaeid prawn stocks of the Gulf of Carpentaria

Abstract

Seagrass beds are important habitats for juvenile commercial prawns. Since the start of the CSIRO seagrass and cyclone program in 1984, there have been four cyclones in the western Gulf of Carpentaria. Of these, only two have affected seagrass beds, and only one of these, cyclone 'Sandy', had a severe effect. The extent of damage to the seagrass beds is probably the result of a combination of factors, including the path of the cyclone, the strength of the winds and the currents associated with the cyclone, the height of the tide at the time of the cyclone and whether the storm surge associated with the cyclone is positive or negative. Cyclone 'Sandy' removed about 183 km2 of seagrass from the Gulf of Carpentaria, which has resulted in the juvenile prawn populations in the area changing from commercially important tiger and endeavour prawns to non-commercial species. The catch of tiger prawns in this area has been consistently lower than in unaffected areas. Seagrasses have begun to grow in the area again. However, it is a very slow process and small species that do not provide a suitable habitat for juvenile prawns are the first to colonise. In addition, the sediment in some areas may now be unsuitable for seagrass. Seagrass revegetation and recolonisation by juveniles of commercially important prawns is likely to take at least 10 to 15 years

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