Notes on the ecology and behaviour of the pebble crab Eriphia smithi McLeay (Decapoda brachyura)

Abstract

Eriphia smithi McLeay (Decapoda Brachyura) is a common Xanthoi-dea inhabiting most of the exposed Indo-Pacific rocky shores. It lives mostly in the cliff holes, between MWL and LWNT. It is a typical isospatial intertidal animal subject to large foraging excursion during which it feed on the cliff (especially the young) and on the intertidal platform on algae and every sort of invertebrates and fishes. In a 14 m wide cliff section, 120 crabs were individually marked and followed during a full synodic month, during nearly all the diurnal and nocturnal LWs. The crabs are active only at LW; nocturnal LWs are preferred by large crabs while young are more diurnal. Feeding excursions are much wider during nocturnal than diurnal LWs. The number of foraging crabs is larger and the excursions wider at a ST tide than at NT, with a very drastic variation. During LW, only 2/3 of the time available for excursion is exploited and crabs get back to their holes much earlier than the rising of the tide. The holes are occupied for long time by the same crab which can relocate its own hole even after 30-40 m excursion. Holes are used by males for copulating with freshly moulted females and for both sexes, if deep and narrow enough, are the only protection against the many strong predators (fishes) which invade the area during HW. The holes are actively defended against conspecific and the possibility of their being the main limiting factor of E. smithi population is discussed. © 1987 Taylor & Francis Group, LLC.