The role of restocking bream for improvement of the natural stock

Abstract

Abramis brama orientalis is a valuable fish species in the Caspian Sea. Its stock after has been faced with pronounced depletion since 1941. The release of millions of its fry have not been successful to restore its stock. A slim fluctuation were observed in its natural stocks during last seven years in the Iranian coastal areas. In comparison to 1992-1993, catch showed a 4.4 tons increment in 1998-99. No pronounced increase was observed considering release of 70.46 million fry during mentioned period. Young and immature fish provide main part of the catch while mature individuals provided a small part of it during 1978-1979. For most rate of catch comprised by young and immature fish and the number of brood-stock fish were very small amount in the catch as in the year of 1998-1999, 20.3% of catch formed by one year old fish and 37.3% by two years old. The average length, weight and age of bream in the years of 1998-99 calculated 22.5cm, 212.2gr and 2.4 years respectively. The depletion of the stock could be attributed to the following important cases, such as non-rational catch practicing, environmental, pollution, destruction of natural spawning grounds, the existence of predatory fish for example Pike and Sheatfish in fries unloading site, and lack of necessary arrangement relevant to artificial spawning. The rate of recruitment of Bream to fisheries calculated 4.6% in 1991 and 2.7% in 1992.