ABSTRACT
Commercially exploited, edible lobsters in India belong to the families Palinuridae and Scyllaridae, the latter representing only one species, Thenus orientalis (Lund, 1793). The introduction of mechanized trawlers for fishing and the attractive prices that export of frozen rock lobster tail fetched in the early 1970s resulted in the exploitation of lobster resources on a commercial scale. Thenus orientalis found along both the east and west coasts of India formed and continues to sustain fisheries of importance along the northwest and southeast coasts, where their landings are mainly as by-catch of trawlers. India has a multispecies lobster fishery: T. orientalis dominates the fishery in Gujarat and northern Tamil Nadu, Panulirus polyphagus Herbst, 1793 dominates in Maharashtra, Puerulus sewelli Ramadan, 1938 dominates in Kerala and Panulirus ornatus Fabricius, 1798 and P. homarus Linnaeus, 1758 dominates in southern Tamil Nadu. The total landings of lobsters by trawlers in the country improved from 800 metric tons in 1968 to 4075 metric tons in 1985, fluctuated around 2200 metric tons for more than a decade, and then declined to 1438 metric tons in 2004. The northwest region, accounted for more than 50% of the catch, followed by the southwest and southeast regions. In the waters off Mumbai, the fishery for T. orientalis showed a phase of development during 1978 to 1982 with an average annual catch of 160 metric tons, a more or less stable phase during 1983 to 1987 with an average annual landing of 261 metric tons, and a phase of decline during 1988 to 1994, the catch being just 2 metric tons each in 1994 and 1996. Mortality estimates and stock assessment of the fishery for the period 1980 to 1985 showed that the exploitation ratio of males was 0.85 (Z = 4.59 and M = 0.69), while that for females was 0.82 (Z = 3.84 and M = 0.69). The Emax was only 0.55 for both the sexes. This was a classic example of recruitment overfishing of T. orientalis resulting in rapid decline of the fishery and annihilation of the stock. In the state of Gujarat where the maximum landings of T. orientalis are reported, size groups of 60 to 80 mm carapace length formed the mainstay of the fishery in 2004. Analysis of gut contents showed that bottom sediment was more frequent in the guts of smaller-sized lobsters, whereas mollusks were more common in the guts of larger animals. Analysis of the length frequency of T. orientalis collected at Mumbai during 1980 to 1986 showed that the males and females had an asymptotic total length (L∞) of 257.3 ± 7.7mmand 256.4 ± 9.5 mm, respectively, while the growth coefficients (K) were 0.53 ± 0.04 and 0.46 ± 0.04, respectively. Higher incidence of mature and berried females was noticed during October to March, indicating a specific spawning season for the species. Captive breeding and larval rearing of T. orientalis was achieved under laboratory conditions; in addition, both T. orientalis and Petrarctus (formerly Scyllarus) rugosus (H. Milne Edwards, 1837) attained sexual maturity, mated, and spawned under captive conditions. The spermatophoric mass adhered to the postventral sternite and anterior abdominal region of female in the form of a white, longitudinal, jellylike mass. Oviposition was completed within six to eight hour and the spermatophore was lost in about 12 h after mating. For T. orientalis the incubation period was 35 days. The phyllosoma larvae metamorphosed through four stages and molted into the nisto stage in 26 days, with a survival rate of 22%. The nisto, a nonfeeding stage, molted into juvenile in four days. Fishery regulations for each maritime state have to be formulated and implemented considering the resource status of each state. Currently comanagement of the resource through participatory approach is practiced, and in consideration of the socioeconomic impact of the lobster fishery, enforcement of regulations currently considers the socioeconomic and livelihood issues of various stakeholders.
