Biomass estimation, opening and closure of Shrimp (Penaeus semisulcatus) fishery in Bushehr waters (Persian Gulf)

Abstract

From June 2004 to March 2006, a survey in Iran waters (Bushehr province) has completed. Sampling was accomplished in two area, north and south. In this period 15 cruises achieved in summer and 3 cruises in autumn and winter. In each cruise of north and south area 18 and 30 stations were sampled respectively. Stations row on three depth stratums that is, below 10 m, 10-20 m, and 20-30 m in total area from Bahrekan to Motaf. Some Biological parameters such as sex stages, sex ratio, mean total length, species composition were measured. Duration of shrimp fishing season in years 2004, 2005 and 2006 were 40, 44 and 40 days in summer respectively. In June and august the Catch per Unit Effort (CPUE) in south was more than northern area. CPUE increases in north area especially at the end of summer during fishing season gradually. Computing on Biomass estimation resulted 674, 1024 and 873 ton in years 2004, 2005 and 2006 respectively for all shrimp species (usually tiger shrimp, white shrimp and other). Total commercial landing of shrimp catch in above years were 1602, 1597 and 1110 ton respectively. Percentage of tiger shrimp in commercial landing in above years was 77, 75 and 84 respectively. We found that the least mean length of tiger shrimp was observed in southern area especially from Motaf to Rodmond stations. The schools of prawn penaeus semisulcatus enter to Bushehr waters from southern area that is Motaf region. Other than Motaf; Nakhilu, Rase khan and Rod-mond show same characteristics. Also in this region, density of shrimp increases with depth in most summer cruises. The result from analyses of gonad maturation studies shows the adult and mature females (stages III and IV) of P. semisulcatus accumulate in northern area at the end of autumn. This stock catches in autumn by illegal fishing.