Characterising shelter preferences in captive juvenile Jasus edwardsii (Palinuridae)

Abstract

Any attempt to enhance rock lobster production by increasing survival after settlement, or by ongrowing or outplanting young juveniles, requires knowledge of the shelter preferences of young juveniles. For juvenile Jasus edwardsii in the wild these are not well known. Information available suggests that juveniles up to c. 35 mm carapace length (CL) occupy shelters that generally conform closely to their body dimensions but that larger juveniles use shelters of more variable dimension, often much larger than their body size. We investigated mainly physical factors important in shelter choice by 15–59 mm CL (c. 2–24-month-old juveniles) in laboratory tank experiments. In overnight tests, all sizes of juvenile lobster chose to occupy holes (shelters with sides) over open horizontal gaps. Preference for open horizontal gaps versus horizontal crevices (where the height reduces from a maximum at the mouth to zero at the opposite end) was much less clear-cut; choice varied according to lobster size. For the number of entrances into holes, there was evidence for an ontogenetic shift in preference, small lobsters preferring two openings over one, whereas those >30 mm CL (c. 9 months old) preferred one over two. For lobsters <40 mm CL, the hole size and gap size preferences revealed were generally consistent with the field evidence for J. edwardsii in that there was a close and proportional relationship between lobster size and shelter size; what differed was that the open gaps chosen in the tanks by the smallest lobsters (15–19 mm CL) were larger than the holes used in the tank experiments and 30–50% larger than those reportedly used in the field. For lobsters >40 mm CL, the holes and gaps chosen in the tanks were generally larger and more variable in size, as in the field. © 2005, Copyright Taylor & Francis Group, LLC.