Growth performance, molting frequency and carapace coloration of marbled crab (Pachygrapsus marmoratus) in different salinity levels

Abstract

This study was conducted to evaluate the parameters on growth performance, molting frequency and carapace coloration of marbled crab (Pachygrapsus marmoratus Fabricius, 1787). Crabs were collected from Urla, İzmir. The experiment was performed in 10 L plastic containers filled with 6 L of seawater at four different salinity levels (5‰, 15‰, 25‰ and 35‰). Ten crabs with an initial mean weight of 0.78±0.03 g were placed in each container with three replicates. Crabs were fed once a day with a commercial diet (46% protein and 18% lipid) for 12 weeks. At the end of the study, the final mean weight (FMW) of the 25‰ group was significantly higher than the 5‰ and 15‰ groups (P<0.05). Specific growth rates (SGR) of the 15‰ and the 35‰ groups and feed conversion ratio (FCR) of the 25‰ group were significantly higher than the 5‰ group (P<0.05). The mean molting frequency (MMF) of the 25‰ group was significantly higher than the 5‰ group (P<0.05). Final lightness (L*) of the 5‰ and 15‰ were significantly lower than their initials (P<0.05). Final redness (a*) of the 25‰ group was the highest among the experimental groups (P<0.05). Final yellowness (b*) of the 25‰ group was significantly higher than the 5‰ and 15‰ groups (P<0.05). According to the results, it is recommended to keep the salinity at 25‰ under marble crab rearing conditions. Further studies are needed to reveal the potential properties of this species in marine aquariums.