Collapse of sand lobster fishery in Bombay waters

Abstract

The sand lobster Thenus orientalis started appearing in trawl catches at Bombay in 1978 and reached a peak of 374.71 in 1982. During 1983-1987 period the catch remained stable around annual average of 260.9 t and contributed 0.34% of the total fish and 43.8% of the total lobster catch. After the second peak of 334.0 t in 1986, the catch declined rapidly to 2.2 t in 1994 and afterwards no catch was recorded. The entire fishery that lasted for 17 years, has been described in three phases, the developing, stabilized and declining phases. Biological investigations revealed that this slow growing species breeds only once a year during October-January and has low fecundity. The exploitation of spawning stock during the breeding period led to recruitment overfishing and consequent decline in the catches. In the absence of any stock management efforts, the removal of the spawning stock continued in the declining phase, which has led to total collapse of the fishery. In order to salvage this valuable resource, management option of banning further exploitation and returning the ovigerous female back to the sea have been suggested. Stock building process through sea-ranching of the species should be undertaken immediately. Introduction The scyUarid lobsters, commonly called sand lobsters, slipper lobsters or squat lobsters, constitute one of the important crustacean resources in the Indo-Pacific region. These lobsters grow to a moderate size and support fisheries of localised importance. In India, only one species of sand lobster, Thenus orientalis (Lund) occurring along both west and east coasts, forms a resource of commercial importance in Gujarat, M a h a r a s h t r a and Tamil Nadu. In Maharashtra, T. orientalis fishery gained importance after the export of frozen rock lobster tails since early seventies. Initially, because of the taste and the attractive colouration, rock lobster tails were exported and they gained popularity in foreign markets. The sand lobsters, however, on account of their muddy, unattractive colouration and small size were not appreciated. But slowly, owing to their fine delicate meat and the taste, the demand for sand lobsters went on increasing. Consquently the trawlers in Maharashtra exploited more and more sand lobsters to meet this unsatiable demand. The average annual landing of lobsters in the state during 1978-'88 period was 429 tonnes of which nearly 29% (1241) was contributed by the sand lobsters (Kagwade et al., 1991). But Eifter 1986 there was a continuous decline in the catch, and finally after 1994,