The impact of suspended culture of the edible oyster Crassostrea madrasensis (Preston) on benthic faunal assemblages

Abstract

The impact of suspended farming of the edible oyster, Crassostrea madrasensis (Preston) on the benthic faunal community structure was studied. The species composition of the faunal samples collected during January to September 2002 from an experimental farm which supported an oyster biomass of 27 to 288 kg in 25 m2 area in Ashtamudi Lake, Kerala, were compared with that of a reference (non-farming) site. The faunal density was almost similar at the farm site, 1278 no. m-2 and at the reference site 1470 no. m-2. At the farm site, 22 species of annelids belonging to 16 genera and at the reference site 23 species under 19 genera were recorded. The Shannon Weiner function (H’) was only slightly higher (2.64) at the reference site, than at the farm site (2.53). Almost similar Simpson (1-λ) dominance indices were also obtained. The Pielou’s (J’) evenness index was 0.79 at the reference site while at the farm site it was marginally lower (0.75). The Margalef (d) species richness index was higher (4.05) at the farm site than at the reference site (3.70). These differences in univariate diversity indices were not significant (P>0.05). The benthic faunal community structure at both sites were similar and there was no negative impact due to short-term farming of oysters.