Habitat type influences the microhabitat preference of juvenile tiger prawns (Penaeus esculentus Haswell and Penaeus semisulcatus De Haan)

The microhabitat preferences of juvenile tiger prawns (3-10 mm carapace length), Penaeus esculentus and Penaeus semisulcatus, were tested in the field at Groote Eylandt, in the western Gulf of Carpentaria, Australia. A partitioned apparatus containing live seagrass was used. Both species of prawns selected seagrass (Syringodium isoetifolium) over bare substrate. Juvenile P. esculentus, the most abundant species in this regions 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 broad, long leaves (Cymodocea serrulata) over one with narrow, long leaves (S. isoetifolium), which in turn was selected over the seagrasses with narrow short leaves (Halodule uninervis and shortened S. isoetifolium). Predation experiments have shown that juvenile P. esculentus are detected and eaten less often in broad, long-leaved seagrass than in narrow, short-leaved seagrass or bare substrate, so their preference for the former may shelter them from predators. No habitat preference was evident for P. esculentus when offered a choice between sediments consisting mainly of sand (71% sand particles) and silt (60% of silt and clay). The selection by both species of tiger prawn of seagrass over bare substrate, and P. esculentus's selection of seagrass with long, broad leaves, provides an explanation for the distribution of juvenile tiger prawns in the field. Thus, in the seagrass beds around Groote Eylandt, P. esculentus is more abundant in seagrass with broad, long leaves than in seagrass with short, thin leaves. In addition, its distribution in this region is relatively independent of sediment type. Leaf surface area (or habitat structural complexity) appears to be the main determinant of distribution for juvenile P. esculentus