The natural
range of
S. serrata is in the
Indo-Pacific. It is found from South Africa, around the coast of the Indian Ocean, where it is especially abundant in
Sri Lanka, to the Southeast Asian Archipelago, as well as from southern Japan to south-eastern Australia, northern New Zealand, and as far east as Fiji and Samoa. The species has also been
introduced to Hawaii and
Florida. In
Hawaii, mud crabs are colloquially known as Samoan crabs, as they were originally imported from American Samoa. As these crabs are known for their robust size and dense meat content, they have been greatly sought after over the years. As a result of overcrabbing, local government efforts have restricted harvesting of crabs smaller than 6 inches (width across back) and to harvest females of any size is illegal. ==Ecology==