Distribution of prawn seed according to water depth in shallow areas of Cochin backwaters

Abstract

In order to study the distribution and abundance of seed of Penaeus indicus, Melapenaeus dobsoni and M. monoceros according to depth gradient in the shallow water areas of Cochin backwaters, two sampling stations were selected and sampling for seed and sediment was carried out using a QSS (quantitative seed sampler) from different depth zones during premonsoon, monsoon and postmonsoon period of 1988. As a whole the average prawn seed density was 14/m2for P. indicus, 16/m2for M.dobsoni and 6/m2for M. monoceros. Seed of P. indicus found to be more concentrated at 10 and 30 cm depth zones where substratum was sandy. But in the case of M. dobsoni and M. monoceros the seed were abundant at deeper zones of 60 and 90 cm where soil was silty or clayey in texture. Percentage of organic matter in the soil did not show any important role in determining the depth variation in the abundance of seed of penaeids. The size-wise distribution of the seed is also discussed.