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The present study provides novel information on carapace width-weight (CWR) relationship and growth parameters of the mud crabScylla olivacea(Herbst, 1796) inhabiting the Pichavaram mangroves, east coast of India based on length frequency data sets during June 2010 to May 2012. CWR revealed linear regression between carapace width and weight in both sexes, and overall CWR exponent (b) values acquired for males and females are 3.035 (r2= 0.962) and 2.925 (r2= 0.933) respectively. The growth parameters, CW∞,Kandtoderived for males and females were 148.05, 0.762 year−1and −0.637 and 138.80 mm, 0.856 year−1and −0.681 respectively. The growth ofS. olivaceawas assessed through various methods in such a way that the outcome of one method functions as a rider, check and control over the other.

Occurrence of abnormal rays reported in Indian waters was stumbled upon in the late 19th Century, but it was revised in the early 20th Century and in the past two decades. Reported morphological abnormalities for elasmobranchs in the Indian waters are restricted to pectorals that fail to unite with the sides of the head and fins that developed thick muscular segments. The occurrence of the malformed or adapted specimen Gymnura poecilura suggested reasons for adaptations or malformations.