Distribution and size composition of penaeid prawns, Penaeus monodon and Penaeus indicus in Saadan estuarine area, Tanzania

Penaeus monodon and Penaeus indicus are found in sandy beaches and mangrove areas in Saadan estuary (Tanzania). Artisanal prawn fishers harvest penaeids in the estuary all year-round causing growth overfishing and reduction of broodstock which in turn affect inshore recruitment and offshore stock recovery. Scientific information on the distribution of penaeid prawns in the estuaries based on Codex Alimentarius Commission Grading Systems for Capture and Culture Prawns is lacking, which is an obstacle for fisheries management. This study investigated the distribution and size composition of two major commercial species of prawns in Tanzania, P. monodon and P. indicus in Saadan estuary. Environmental parameters such as water temperature, salinity, substrate particle size and substrate's organic matter were investigated. The area was divided into 5 transects, each 3.7 km apart and perpendicular to the estuary. Samplings were conducted three times per month from January to April 2011 and 2012 respectively, the period that represents two seasons: dry season (January to February) and wet season (March to April) the peak season for prawn fishery in Saadan estuary. Data of exported prawns from all estuaries country-wide were collected and the number of individuals of F2 generation was projected. The study found that salinity affects distribution and the estuary contains all prawns categories based on Codex Alimentarius Grading System for Capture and Culture Prawns particularly during the peak season hence, proposes temporal closure from fishing by artisanal prawn fishers during the wet season to prevent overharvesting of spawners to enhance prawn recruitment and stock recovery.