Movement patterns and habitat use of the exploited swimming crab Scylla serrata (Forskal, 1775)

Abstract

Mangrove ecosystems are highly productive, providing habitat for a variety of species, of which many are harvested. In times of rapid global change, due to natural as well as anthropogenic drivers, these ecosystems are increasingly placed at risk, and so are the species living within them. The mud crab Scylla serrata (Portunidae) (Forskål, 1775) is a highly valued and exploited species associated with mangrove ecosystems in the Indo-West-Pacific. Its complex life-cycle includes a dispersing larval phase and a benthic phase as juveniles and adults. The planktonic larvae are restricted to oceanic waters, since they are stenohaline and therefore dependent on stable, high salinity conditions in order to survive. Benthic juveniles and adults are physiologically adapted to changing temperatures and varying salinities, conditions that typically occur in mangrove habitats. Movement and habitat use of large juveniles and adults are well studied and these life stages are known to move between various mangrove habitats including intertidal mangrove area flats as well as subtidal channels and flats. Females undertake long distance movements from brackish inshore waters to waters with oceanic conditions for (supposed) spawning. However, little is known about larval stages, and early benthic stages are underrepresented in the literature. The aim of this thesis is to provide deeper insights into movement patterns and habitat use at these particular life stages and to understand how these characteristics might be affected by environmental factors, such as seascape and rainfall.