Growth and moulting in the mud spiny lobster, Panulirus polyphagus (Herbst, 1793)

Abstract

Growth rates in the mud spiny lobster, Panulirus polyphagus held in captivity were assessed and compared with growth estimates derived from length composition of these lobsters in trawl landings at Veraval, north-west coast of India. The von Bertalanffy‘s growth parameters ‘L∞’ and ‘K’ derived for male P. polyphagus were 135 mm (carapace length, CL) and 0.46 y-1 in the wild and 144.8 mm (CL) and 0.51 y-1 in captivity. The values derived for female P. polyphagus were 124.7 mm (CL) and 0.38 y-1 in the wild and 119 mm (CL) and 0.43 y-1 in captivity. There was a clear difference in the growth curves of males and females in captivity and in the natural habitat. The VBGF curves indicated that males had a better growth output than females, both in the wild and in captivity. Juvenile lobsters exhibited higher moulting frequency, with the intermoult period increasing steadily as CL increased. Increments in CL at each moult showed significant correlation with increasing CL in both males and females. The rate of growth was found to decrease with age in both sexes. In males there was renewed burst of growth after the attainment of sexual maturity (65-75 mm CL) but beyond 80 mm CL, the growth was steady. In females however, there was drastic reduction in growth rates in the 63-68 mm CL range, and it steadied at 70-80 mm CL when the breeding and rematuration processes are more prominent in its life cycle.