Fisheries and aspects of the biology of penaeid shrimps of Bahrain
Shrimp are the most valuable fish stock in Bahrain waters, the fishery being based on a single species P. semisulcatus which forms about 95 percent of the total landings. In 1993, shrimp landings formed 23.8 percent of the total Bahrain fish landing, which totalled 2,128 tonnes at a first sale value of 5.4 million Bahraini Dinars (1 DS$.0.380 BD). Beside the increased fishing effort, the marine habitat of Bahrain suffers from several sources of pollution. Most evident is dredging and reclamation which have altered most of the coastal areas. Despite the shrimp fishery importance and the development-related stresses on Bahrain coastal environments, there were limited basic data on this valuable stock. The current study aimed to provide as full an understanding as possible of the shrimp fishery of Bahrain. Several surveys were conducted on the shrimp populations and their environment. A sediment survey was conducted from 9 August to 26 October. From May 1991 to May 1992, a regular sampling programme was initiated to record the physical properties of the sea water at fixed stations in TUbli Bay and off Mina Sulman. Physical properties of sea water were also recorded in the open sea during June 1980, October and December 1991. Plankton collection was conducted mainly through two sampling programmes. The first was conducted in the open sea from September 1991 to January 1992 (excluding November 1991). The second programme was restricted to Tubli Bay; samples were obtained over periods from May 1991 to June 1992 inclusive and from March to May 1993. Two major benthic surveys were completed. The first was conducted from June 1980 to June 1981 using an industrial trawler, covering the whole shrimping ground, except TUbli Bay. A second survey was carried out on the shrimp population in TUbli Bay from May 1991 to June 1993 in three time periods, from May 1991 to June 1992, November 1992 and from April to June 1993. Based on the above surveys, physical properties of sea water and bottom sediment of the shrimping ground were described. Also the bionomics of the seven penaeid species found in Bahrain waters were determined. Benthic and plankton surveys revealed spawning activities of P. semisulcatus restricted to the offshore waters. Also prolonged spawning activity was determined for this species, which most significantly occurred from August to March. P. semisulcatus main recruits appeared in the shrimping grounds from April to July, originating from nurseries found within the areas A and B. Two migration patterns were determined for P. semisulcatus within Bahrain shrimping grounds throughout a season. The updated information on shrimp fishery generated by the current work provides a basis for identification of areas for further improvement of this fishery. Consequently, the work determines of future investigations necessary for Bahrain shrimp fishery.