MULTIVARIATE-ANALYSIS OF THE MUD CRAB SCYLLA-SERRATA (BRACHYURA, PORTUNIDAE) FROM 4 LOCATIONS IN SOUTHEAST-ASIA

The large, edible mud crab Scylla serrata (Forskal) exhibits different phenotypes which are recognised by the fishermen of Southeast Asia an d are given local names such as ''white'', ''green'', ''red'' or ''bla ck'' crabs on the basis of their colouration. A preliminary study usin g multivariate techniques was undertaken in order to examine the degre e of dissimilarity between the different morphs of commercially fished stocks of S. serrata. Twenty-two morphometric and 20 meristic charact ers were measured on male crabs from four locations in three countries in Southeast Asia, including Surat Thani in Thailand where ''black'' and ''white'' morphs exist sympatrically. Canonical Variate analysis ( CVA) on the morphometric data discriminated three groups with no chain -linking. Surat Thani ''white'' crabs and those from south Vietnam wer e phenotypically similar and formed one distinct group; st second grou p contained crabs from Ranong (Thailand) and Sarawak which were phenot ypically ''black''; the third group contained ''black'' crabs from Sur at Thani. CVA on meristic data confirmed two groupings, but implied th at the Surat Thani ''black'' morph may only be a variant of the Surat Thani/Vietnam ''white'' form, rather than a third species. These findi ngs are discussed in relation to the ecology, fishery management and a quaculture potenial of S. serrata.