Influence of natural fluctuations in seagrass cover on commercial prawn nursery grounds in a subtropical estuary

Abstract

Juvenile prawns were captured with a beam trawl from two intertidal seagrass sites (one sparsely and one densely vegetated) in Tin Can Bay, a subtropical estuary in south-eastern Queensland. The abundance and recruitment patterns of two commercial prawn species (Penaeus plebejus and Metapenaeus bennettae) were investigated. P. plebejus was the dominant species at both the sparse and dense seagrass sites. Die-back of the above-ground vegetation in the sparsely vegetated site coincided with a significant increase in the abundance of both P. plebejus and M. bennettae at this site. Natural loss of intertidal vegetation may cause an immediate reduction in the total fisheries value of an area because of fewer herbivorous commercial fish entering the area. In the longer term, this reduction in the fisheries value of the area may be compensated by an increase in value as a nursery ground for juvenile P. plebejus, thereby providing the potential for higher adult P. plebejus recruitment to local commercial fisheries and maintaining the overall value of the area.