Morphological characters of mud crabs (Scylla spp.; Portunidae) in North Kalimantan

Utilization of mud crab resources through crab farming is basically carried out based on collection of crabs from the wild. However, the average growth of mud crab production in several main mud crab-producing areas tends to decline. The purpose of this study was to identify the morphological character of the mud crab species associated with mangrove vegetation. Sampling was performed using simple random sampling method at three stations. The obtained morphological, morphometric, and meristic characters were converted into binary form (matrix 0-1) using Ms. Excel 2013. Character data processing was processed using the MVSP 3.1 program with the UPGMA clustering method and the Nei and Li's Coefficient to reconstruct the dendrogram. The collected mud crabs from three stations were consisted of three species of mud crabs, namely: Scylla serrata, S. tranquebarica, and S. olivacea. The carapace length of the three mud crab species collected from the three stations was ranged from 3.5 to 6.6 cm, carapace width ranged between 5.5 to 10.1 cm, propodus length ranged between 0.7 to 1.9 cm, and an average total weight of 36.3 to 212.1 grams. The overall value of R2 of the relationship between carapace length and carapace width was ranged from 0.853 to 0.987 (close to 1.00). Based on the dendrogram, the population of S. tranquebarica obtained from the three sampling stations has a similarity level 73%. The association results between mud crabs and mangrove ecosystems indicated that the types of mangroves in each station were different, in accordance with the ecological conditions suitable for the growth of the mud crabs. The level of mangrove vegetation was associated with the size and weight of crabs found at the ST 1 sampling station, which originally had a higher density of mangrove vegetation than other stations. In addition, the largest S. serrata with carapace length of 9.0 cm and a weight of 400 grams was also found in that particular station.