No abstract

Commercial exploitation of lobsters from the Indian seas began in the 1950s. Annual landings have been declining from a peak of 4075 t in 1985 to 1364 t in 2002. Major fisheries were located on the north-west, south-west, and south-east coasts. Among the 12 species recorded, only four species of spiny lobsters (three littoral and one deep sea) and one species of slipper lobster are commercially important. At Kayalpattinam and Tharuvaikulam, on the south-east coast, lobster landings sharply declined for the gill-net fishery. Of the two species that contributed to the fishery, Panulirus ornatus and Panulirus homarus, the latter has been more affected owing to high vulnerability to fishing activities. Catch composition analysis of the trammel-net fishery showed that 35% of the landings consisted of P. homarus in the size range of 23-50 mm carapace length. On the north-west coast, the spiny lobster Panulirus polyphagus and the slipper lobster Thenus orientalis are incidentally caught in trawl nets. However, the fishery for T. orientalis in the waters off Mumbai lasted only up to 1994. Largescale exploitation of spawning females, which formed 60% of the total catch, might have been detrimental to the recruitment process resulting in rapid decline and total collapse of the fishery. Abundance of P. polyphagus reached its maximum during September, constituting 23% of the average annual landing during [1988][1989][1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002]. A high exploitation ratio (>0.7) indicated over-fishing of the stock. Repeated spawning and high annual egg production are probably responsible for sustaining the stock, despite over-exploitation. Major problems confronting the resource management of the multi-gear and multispecies lobster fisheries in India are discussed. An operational project, involving fisher community, has been taken up for creating awareness of the need for sustainable exploitation of the resource. Regulatory measures, such as closure of the fishery during the peak of the breeding season, ban on trammel-net, mandatory release of egg-bearing lobsters, and establishment of lobster sanctuaries are suggested to the State Governments for implementation.

Lobsters constitute low-volume high-value crustacean fishery resource along Indian coast. For the conservation and management of this declining resource, accurate identification of species and larvae is essential. The objectives of this work were to generate species-specific molecular signatures of 11 commercially important species of lobsters of families Palinuridae and Scyllaridae and to reconstruct a phylogeny to clarify the evolutionary relationships among genera and species included in this study. Partial sequences were generated for all the candidate species from sampling sites along the Indian coast using markers like Cytochrome oxidase I (COI), 16SrRNA, 12SrRNA, and 18SrRNA genes, and analyzed. The genetic identities of widely distributed Thenus species along the Indian coast to be Thenus unimaculatus and the sub-species of Panulirus homarus to be P. homarus homarus were confirmed. Phylogeny reconstruction using the individual gene and concatenated mtDNA data set were carried out. The overall results suggested independent monophyly of Scyllaridae and Stridentes of Palinuridae. The interspecific divergence was found to be highest for the 12SrRNA compared with other genes. Significant incongruence between mtDNA and nuclear 18SrRNA gene tree topologies was observed. The results hinted an earlier origin for Palinuridae compared with Scyllaridae. The DNA sequence data generated from this study will aid in the correct identification of lobster larvae and will find application in research related to larval transport and distribution.

No abstract

Thenus unimaculatus is one of the most important commercially exploited lobster species in India. The declining trend in catches as well as collapse of fishery in some localities necessitated assessment of the stock structure to manage this resource sustainably. We ascertained the genetic stock structure of T. unimaculatus along the Indian coast, using molecular markers. RAPD and concatenated dataset of mitochondrial DNA genes (partial sequences of Cytochrome Oxidase I and Cytochrome b) were used to detect population differentiation. RAPD markers showed moderate genetic variability with an overall G ST value of 0.0442, which indicated low genetic differentiation among subpopulations. The mtDNA dataset revealed high haplotype diversity coupled with very low nucleotide diversity that suggested recent population expansion after a period of low effective population size. The median-joining haplotype network showed no geographical clustering of haplotypes. The low levels of genetic differentiation with non-significant P values (F ST =0.0593) may be due high connectivity among shovel-nosed lobster populations and resultant panmixia. This may be due to the planktonic phyllosoma larval phase that extends for[1 month in wild and their transport and dispersal by monsoon currents of Northern Indian Ocean. The results of this study will aid in better management of this dwindling resource.