Lunar, diel and tidal variability in penaeid prawn larval abundance in the Mandovi estuary, Goa

Abstract

Prawn larvae were studied to determine suitable lunar and tidal phases and time for large scale seed collection for prawn acquaculture. Larvae and postlarvae of 8 commercially important species were observed in the surface and bottom zooplankton samples. These were in order of abundance, Metapenaeus dobsoni (Miers), M. affinis (H. Milne-Edwards), M. monoceros (Fabricius), Parapeneopsis stylifera (H. Milne-Edwards), Penaeus merguiensis De Man, P. indicus H. Milne-Edwards, P. monodon Fabricius and P. semisulcatus De Haan. The mysis stages were dominant. Water temperature and salinity variations were meagre and do not seem to influence larval abundance. However, lunar phases, diel cycles and tidal oscillations influenced their occurrence. The preponderance of protozoea and mysis stages was noticed in samples taken during day time while postlarvae were common at night. Total ingression of penaeid prawn larvae was more during full moon and hightide compared to new moon and low tide periods.