Prawn seed calendars of Cochin backwater

The paper presents a consolidated monthly picture of the availability of penaeid prawn seeds. In Cochin backwater (between Thoppumpady and Mulavukad) based on the results of routine monitoring studies carried out from 1967 to 1979, using plankton net, try net (miniature trawl) and velon screen drag net. The prawn seed population, comprising postlarval and early juvenile stages, is represented by thirteen species, of which, Metapenaeus dobsoni, M. affinis, M. monoceros, Penaeus indicus and P. semisulcatus are the most common. While M. dobsoni forms the chief constituent in the plankton collections (88 %) and try net catches (46%), P. indicus predominates in the velon screen drag nets (93 %) operated in shallow areas close to the shore. M. affinis occurs in greater abundance in the deeper areas as evidenced by its high percentage (45 %) in the try net catches. The environmental conditions of the backwater and the relative abundance and size distribution of the seeds of different species as represented in the three methods of collections are summarized month-wise. Although prawn seeds are available throughout the year, the peak seasons of important species are August-January for M. dobsoni, May-July for M. affinis, December-April for M. monoceros, March-May for P. indicus and January-March for P. semisulcatu