A comparison of the efficiency of the bottom samplers used in benthic studies off Cochin

Abstract

The efficiency of the van Veen and Foerst `Petersen' grabs used in sampling the bottom fauna near the Cochin Harbour area has been compared in two selected stations having different hydrographic and substratic conditions The results indicate that the heavier grab is generally more efficient than a lighter one, especially when the substratum is sandy An examination of the quantity of the sediment and the total number of species brought by the two grabs showed that the design of the van Veen is superior to the `Petersen' type grab used in the present study However, due to the highly patchy distribution of the organisms the superiority of the van Veen was less evident when a comparison was made of the total number of animals sampled by the two grabs When the distribution is `bunched' it is suggested that samples are drawn, as far as possible, from the same sampling position The grabs should also be of the same weight and biting area