Why are some prawns found in seagrass? An experimental study of brown (Penaeus esculentus) and grooved (P. semisulcatus) tiger prawns

Abstract

A laboratory-based study was made of the responses of juveniles (8 to 24 mm carapace length) and adults (over 24 mm CL) of brown (Penaeus esculentus) and grooved (P. semisulcatus) tiger prawns to two habitats: simulated seagrass and bare sand. At night, the brown tiger prawns spent about 80% of their nonswimming time in seagrass, whereas the grooved tiger prawns spent equal amounts of time in both habitats. In daylight (0830 to 0930 hours), the brown tiger prawns were found mainly in the seagrass, with most of those larger than 15 mm CL buried in the substrate whereas smaller individuals were divided equally between standing on the bottom, burying in the sand, or clinging to the seagrass, mainly to the upper half of the fronds. Grooved tiger prawns between 15 and 25 mm CL were also found mainly in seagrass in the morning, but both smaller and larger animals were found equally in both habitats. Most grooved tiger prawns found in seagrass during the day were buried; few were clinging to the seagrass or standing on the substrate. The results show that both species of tiger prawns show preferences with respect to structures in their environment and that these preferences are influenced by the size of the animals.