HABITAT TYPE INFLUENCES THE MICROHABITAT PREFERENCE OF JUVENILE TIGERPRAWNS (PENAEUS-ESCULENTUS HASWELL AND PENAEUS-SEMISULCATUS DE-HAAN)

The microhabitat preferences of juvenile tiger prawns (3-10 mm carapac e length), Penaeus esculentus and Penaeus semisulcatus, were tested in the field at Groote Eylandt, in the western Gulf of Carpentaria, Aust ralia. A partitioned apparatus containing live seagrass was used. Both species of prawns selected seagrass (Syringodium isoetifolium) over b are substrate. Juvenile P. esculentus, the most abundant species in th is region, were also given paired choices of seagrasses with different leaf morphologies (representing a range of structural complexity) and sediments of different particle size. They selected a seagrass with b road, long leaves (Cymodocea serrulata) over one with narrow, long lea ves (S. isoetifolium), which in turn was selected over the seagrasses with narrow, short leaves (Halodule uninervis and shortened S. isoetif olium). Predation experiments have shown that juvenile P. esculentus a re detected and eaten less often in broad, long-leaved seagrass than i n narrow, short-leaved seagrass or bare substrate, so the:ir preferenc e for the former may shelter them from predators. No habitat preferenc e was evident for P. esculentus when offered a choice between sediment s consisting mainly of sand (71% sand particles) and silt (60% of silt and clay). The selection by both species of tiger prawn of seagrass o ver bare substrate, and P. esculentus's selection of seagrass with lon g, broad leaves, provides an explanation for the distribution of juven ile tiger prawns in the field. Thus, in the seagrass beds around Groot e Eylandt, P. esculentus is more abundant in seagrass with broad, long leaves than in seagrass with short, thin leaves. In addition, its dis tribution in this region is relatively independent of sediment type. L eaf surface area (or habitat structural complexity) appears to be the main determinant of distribution for juvenile P. esculentus. (C) 1997 Academic Press Limited.