Population structure and biological characteristics of Siriella gracilis (Mysida) from the Exclusive Economic Zone of India

Abstract

The abundance, population structure and other biological aspects of Siriella gracilis were evaluated based on zooplankton collections in the Exclusive Economic Zone of India (Arabian Sea, Bay of Bengal and Andaman Sea) as a part of a multidisciplinary project, Marine Research on Living Resources Assessment Programme. S. gracilis exhibited a wide range of variations in its population dynamics in the study area and the population density over the entire study area ranged from 0 to 29?250 ind. per 1000 m3. The highest abundance was in the Arabian Sea (70.1% of the total sampled population) followed by the Andaman Sea (22.7%) and the Bay of Bengal (5.2%). Temperature and salinity appeared to have little influence on the general distribution of S. gracilis in the study area. The number of eggs/embryos carried by females exhibited a positive correlation with female size and the maximum brood size was 11. The egg diameter ranged from 0.32 to 0.46 mm and was independent of female size. Even though no significant body length difference was found between spent females and breeding females ( p > 0 . 05 ), wet mass of spent females and breeding females was significantly different ( p < 0 . 0001 ), obviously resulting from the added weight of the brood in ovigerous individuals.