Stocking density and shelter type for the optimal growth and survival of western rock lobster Panulirus cygnus (George)

Abstract

The growth and survival of three size classes of wild caught western rock lobster, Panulirus cygnus (post-pueruli: mean 2.140.07g, 13.20.1mm CL; year1: post-settlement juveniles, 57.11.1g, 38.70.28mm CL; and year2 post-settlement juveniles, mean 138.22.26g, 51.90.25mm CL) were examined at combinations of two stocking densities (post-pueruli: 50 and 100myear1: 11 and 23m2; year2: 10 and 19m2) and two shelter types (a novel rigid plastic mesh shelter or bricks) over a period 6months. Survival of lobsters held at the lower densities (90 95%) was significantly greater than for lobsters held at higher densities (post-pueruli=78%, year1=86%, year2=88%). Post-pueruli survival was significantly higher in tanks with mesh shelters (91.7%) than brick shelters (75.8%) with a similar trend exhibited by year1 and year2 lobsters. Densities tested did significantly affect lobster growth for any size class. Growth of post-pueruli was considerably higher in tanks with mesh shelters (641.7% weight gain; specific growth rate 1.07BWday1) (p<0.05) but there was no difference in the growth of year1 and lobsters between mesh and brick shelters. Feed intake (g pellet dry matter lobster1day1) was not significantly different between densities. This study has shown that P. cygnus is well suited for aquaculture based on the collection and ongrowing of wild caught pueruli, as this species exhibits good survival at high densities (up to 100m2) without adverse effects on growth, and shows captivity-related health problems. We recommend mesh shelters, with stocking densities of 50m2 for post-pueruli and between and 25m2 for year1 and year2 juveniles, to maximise survival and production.