Juvenile Habitat & Distribution

Juvenile western rock lobsters predominantly inhabit the inshore shallow (< 40 m) reefs of Western Australia, from North West Cape, to Cape Leeuwin (Bellchambers et al. 2012). Surveys using pots specialised for catching undersized lobsters have shown that they are most abundant in the shallow nearshore reefs and reduce in density with increasing water depth (de Lestang et al. 2016). Since rock lobsters are nocturnally active, their habitat use and distribution are diurnal in nature. During the day lobsters shelter in holes, cracks or dens in the reef, while at night they leave the reef to forage in nearby seagrass meadows and algae habitats.

During the juvenile stage of the WRL life cycle, there is an ontogenetic shift in habitat use, that is a change in habitat that relates to the animal’s development. Post puerulus juveniles (< 25 mm CL), shelter individually in small holes on the face and ledges of the reef, preferring holes with additional cover, typically seagrass and/or algae. Larger juveniles (> 25 mm) on the other hand, are rarely found on the reef face, rather preferring to co-habitat ledges and in caves (Jernakoff 1990). Larger juveniles (> 25 mm) on the other hand, are rarely found on the reef face, rather preferring to co-habitat ledges and in caves (Jernakoff et al. 1994). This pattern of habitat use is consistent with increasing gregarious behaviour with increasing size. It is thought that the ontogenetic change in sheltering habitat reflects a need for larger shelters as they preferentially seek to shelter in groups. An alternative hypothesis suggests that, as predation risk is size dependent, smaller lobsters shelter in small holes with cover, as it offers higher protection from predation, especially from fish (Howard 1988).