Background: The Gulf of Mannar, situated on the southeast coast of India, is a unique distinctive productive marine ecosystem and is rich in biodiversity. Its significance stems from the presence of a string of 21 islands spanning 140 km between Rameswaram and Tuticorin, each adorned with a wealth of coral reefs and hosting a variety of ornamental and marine fish species despite their small and uninhabited nature. It is also first Marine Biosphere Reserve in South and South-East Asia, covers approximately an area of 19,000 sq. km. 
 
Methods: Fish samples were collected monthly from three major fishing harbours situated in the Gulf of Mannar along the southeast Coast: Thoothukudi Fishing Harbour, Pamban Fishing Harbour and Chinnamuttom Fishing Harbour from December 2022 to November 2023. These species are caught using trawl net, gill net and hook and line and collected specimens were identified using FAO sheets and standard literature. 
 
Result: In this study, a total of 405 specimens were collected. The length weight relationship was estimated for male: W = 0.0522.57, r2 = 0.94, female; W = 0.0572.51, r2 = 0.94; and pooled; W = 0.0632.54, r2 = 0.90, respectively. Fulton condition factor (KF) value for male: 1.22, female: 1.33; and pooled: 1.19, respectively. Gonadosomatic index (GSI) of L. microdon was ranged between 1.21-2.21 for male and 1.85-2.31 for female and Gastrosomatic index (GaSI) varied from 1.45-2.37 for male whereas 1.89-4.43 was found for female. Hepatosomatic index (HSI) of L. microdon was ranged between 0.45-2.54 for male while for female was ranged between 1.11-3.21. The male and female (M:F) sex ratio was estimated 1:0.67. The peak spawning season was observed in June to August. The results provide the baseline biology information required to evaluate the fisheries and sustainable management of these underexploited fishes in the Gulf of Mannar ecosystem.

Feeding Aspects and Reproductive Biology of Smalltooth Emperor, Lethrinus microdon (Valenciennes, 1830) in the Gulf of Mannar along the Indian Southeast Coast