Optimising tank colour for enhanced growth, survival, and carapace colouration for megalopa and instar purple mud crab (Scylla tranquebarica)

Abstract

The influence of tank background colour on the growth and survival of the purple mud crab (<i>Scylla tranquebarica</i>) megalopa and instar was elucidated to refine the mud crab seed production techniques. Both megalopa and instar stages were reared in five background colours: black, white, blue, green, and red, in triplicate groups for 14 days and 8 weeks, respectively. The megalopa metamorphosed into instars 1 and 2 (C1 and C2) at the end of the megalopa experiment. Growth and survival of C1 and C2 were highest in the blue tank, as indicated by total yield (641.5 mg), overall survival rate (67.9%), and relative contribution of C2 (64.9%). The instar metamorphosed into a juvenile after 8 weeks. The juvenile total yield was comparable in all treatments, with a higher trend observed in blue and red tanks than in other treatments. The juvenile's survival rate was significantly greater in the blue tank (53.3%) than in the other treatments. The juveniles reared in the black tank exhibited significantly darker carapaces than the others. This study provides baseline data on the rearing of purple mud crab megalopae to juveniles for seed production, indicating that blue tanks are suitable for nursery-phase rearing of both stages.