Sampling by a commercial trawler was, conducted during February 1984 in the Chilaw Sea, Sri lanka, in order to assess the‘stock size and to , study the depth.1 anti' substrata related distributions of prawij. The entire extent of the prawn'distrip ution w as divided into different depth strata;, and then into a number of feet/ahglds for trawl sampling. Each trawl tow was approximately one hour long. Surface Salinities and temperatures were recorded for each haul. Mud samples, were taken from each rectangle to assess qualitatively their organic content arid ,particle Size. Two way analysis of variance for catch per unit of effort values of Major Species of prawn indicated a significant variation areawise in the catch Rates of Parapenaeopsis stylifera. The same analysis- on prawn length data showed a progressive increase in lengths towards the south from the Dediifu river estuary and the Chilaw lagoon mouth for Penacus indicus. This area appears to be .as source of recruitment. Based on stocks abundance estimated by the swept "area method, there were substantial reductions in Metapenaeus dobsoni and Parap. stylifera. This study also indicated that the prawn resources in the Chilaw sea were confined to the 0 - 8 fathom depth range, and. were abundant on sand and mud patches’with organic material.