Rock face incline and height above sea bed of holes used as shelters by pueruli and juvenile Japanese spiny lobsters Panulirus japonicus

Abstract

A predominantly vertical reef face adjacent to the Banda Marine Laboratory of Tokyo University of Fisheries, Chiba Prefecture, Japan, was regularly surveyed for pueruli and juvenile Panulirus japonicus (Von Siebold) over a 21 month period. The height above the sea bed and the incline of the reef face at which pueruli and juvenile lobsters occurred in holes during the daytime were recorded. The rock face (53.2m super(2)) ranged in height from 0.9-1.4m above the sea bed (85% was between 1.0-1.1m). Pueruli (postlarvae) and first instar juveniles were distributed non-randomly on the rock face. Near horizontal sections of the reef and areas immediately adjacent to the sand sediment were less favored. Small juveniles (8-20mm carapace length) generally showed similar shelter preferences as pueruli and first instar juveniles. Larger juveniles (20-40mm CL), however, showed a reduced shelter preference in relation to both height above the sea bed and the angle of rock face incline and this appears to be related to limitatioas in the availability of holes for this size group on the reef face. Most pueruli and first instar juveniles were observed in an inverted (ventral side up) position (91.5%) in holes, this percentage decreased markerdly as lobsters grew