Indian Journal of Geo Marine Sciences Vol. 48 (06), June 2019, pp. 825-828 Stock assessment and exploitation status of Lethrinus nebulosus (Lacepede, 1802) exploited off Thoothukudi coast, Tamil Nadu, India M. Vasantharajan*, P. Jawahar, B. Sundaramoorthy, & P. Ramyalakshmi Tamil Nadu Fisheries University, Nagapattinam, Tamil Nadu, India. *[E-mail: migusava@gmail.com] Received 18 November 2017; revised 23 April 2018 Lethrinus nebulosus (Lacepede, 1802), although a commercially important fish species, has not been studied (population studies) in Thoothukudi coast of Tamil Nadu, India. Research on recruitment pattern, virtual population analysis and exploitation status of L. nebulosus off Thoothukudi coast was conducted from July 2011 to June 2012. During the study period, 4590 specimens of L. nebulosus were collected for studying the above said parameters by using FiSAT software. Recruitment pattern of the species expressed continuously with one peak each in April and August. The fishing pressure occurred more in the length group of 43 cm onwards. The results revealed that the total annual catch of 7566.28 tonnes was obtained from 52210 boat days. The maximum catch per unit was during December and January. The maximum sustainable yield (MSY) was estimated at 12203.68 tonnes. The discrepancy between MSY and annual catch was 4664.399. The present fishing effort may be increased to 61.29% to achieve MSY with 19310 boat days. It was revealed that L. nebulosus is underexploited in this region. [Keywords: Lethrinus nebulosus; Stock assessment; Thoothukudi coast] Introduction India has a coastline of 8129 km with the water expanse of continental shelf as 0.5 million sq km and EEZ of 2.02 million sq km 1 . Good perch grounds are found in the north-east coasts from the depth of 60-70 m, located in the range between 18° to 20° N and 84° to 87° E, as recorded 2 . In south-east Asia, the Gulf of Mannar was declared as the first Marine Biosphere Reserve to protect the invaluable fauna and flora inhabiting this region 3 . Among the maritime districts of Tamil Nadu, Thoothukudi is considered one of the most potential fishing areas covering 163.5 km in the Gulf of Mannar Marine Biosphere 4 . Perches contribute about 5.1% of the total marine fish catch of Tamil Nadu state, out of which Thoothukudi district alone contributes around 11.08% of total marine fish catch of the state 5 . The Lethrinidae family fish also known as emperor is economically important among the demersal fish species. The lethrinid juveniles preferred the sea grass-replenished reefs only and not the sea grass-free reefs 6 . Fisheries management assigns due weightage to fish population dynamics aspects while determining the biological parameters, size at maturity, spawning season, as well as growth and mortality estimates 7 . Sustainable fisheries management of fish stocks is a challenge, since stock assessments are based on accurate information from relevant quantitative and qualitative sources of uncertainty 8 . Lethrinus nebulosus is widespread broadly not beyond the Indo-West Pacific region and expanding from Red Sea and east Africa to southern Japan and Samoa 9 . Studies on population parameters from Tamil Nadu coast, particularly from the Gulf of Mannar region are limited. Therefore, the study was carried out on the recruitment pattern, virtual population analysis and exploitation status of L. nebulosus. Materials and Methods The present research was conducted from July 2011 to June 2012 in Thoothukudi Coast. The major lethrinids species available along Thoothukudi coast are: Lethrinus nebulosus, L. nebulosus, L. ornatus, L. elongatus, L. microdon, L. mahsena, L. harak, L. ramak. L. conchyliatus, L. rubiroperculatus, Gymnocranius robinsonii, and G. griseus. From this 12 lethrinid species, L. nebulosus was preferred for this investigation. A total of 4590 individuals were collected on weekly basis from Thoothukudi coast (Fig. 1). Data on frequency, catch and effort were loaded in FiSAT software to assess the recruitment pattern, virtual population analysis and exploitation