Scylla serrata
in a South African estuary occurred more frequently in that part which had the highest number of prey organisms. Food location was by contact chemoreception, using the dactyls of the walking legs. Major prey groups were burrowing bivalves, attached bivalves and small crabs, s. serrata showed a preference for small crabs as prey. Because of their larger mass and higher energy content compared with other prey organisms, these crabs represented the major energy source of s. serrata in this area.
I ntroduction Materials and Methods
Scylla serrata Forskal is a large crab
Survey of Tracking Area
found through much of the Indo-West Pacific region in estuaries, mangrove Seven transect lines 30 to 40 m apart swamps and sheltered bays (Macnae, 1968). were set up in the tracking area de-It is a predator which feeds on slow moving and sessile benthic invertebrates (Hill, 1976). A diet of this nature in which the major component is sessile or near-sessile requires a predator to forage for its food. Tracking observations by Hill (1978) showed that adult male s. serrata in the Kowie estuary in South Africa lived a free-ranging, non-territorial existence. The feeding of s. serrata and the distribution of food organisms in the area where tracking was carried out were investigated. Prey species were identified from gut analyses of s. serrata, and measurements were taken of their energy content and of their size, abundance, and distribution in the study area. The relative proportion of time spent by s. serrata in various parts of the tracking area was calculated from tracking data (Hill, 1978) and compared with the distribution of prey.