Meiobenthic fauna of the traditional prawn culture systems around Cochin

Abstract

The distribution and abundance of meiobenthos, hydrography and sediment characteristics of three different types of traiditonal prawn culture systems around Cochin were studied for a period of two years (1988-1990). Nematodes were the most dominant group (79.6%) of the total meiofaunal count followed by harpacticoids and polychaetes. Others like oligochaetes, bivalves, ostracods, amphipods and tanaids had only stray occurrences and together formed a meagre 0.30% of the total. The upper 0-5 cm layer harboured 79.5% of the meiofaunal population. The perennial ponds had the highest abundance of meiobenthos (69.9%) followed by canals (17.9%) and seasonal fields (12.2%): The meiobenthic biomass ranged from 0.84 mg/ 10 cm2 to 5.7 mg/lO cm2in different stations. Meiofauna did not show a significant positive correlation with the different environmental parameters. However, during the southwest monsoon period, the population showed a sharp decline. Meiobenthos were found to be abundant at stations where the sand content varied from 60-7870 and silt from 15-29%, and were lowest at stations with high clay content. High content organic carbon also did not favour a high abundance of meiofauna. The presence of nematodes(80%) in the gut content of the prawns indicates a trophic chain involving meibenthos.