The effects of stock enhancement of pikeperch (Sander lucioperca) in Iranian coastal waters of the Caspian Sea

Annual landings of pikeperch (Sander lucioperca) in Iranian coastal waters of the Caspian Sea in the early years of its exploitation, the late 1920s and early 1930s, reached some 3000 t. However, after 1935, catches declined drastically through overfishing, declining sea level, and the destruction of spawning grounds in the Anzali Lagoon. In 1990, Iran initiated a programme of artificial culture to enhance the local stock. The aim of the programme was and still is to restore the formerly abundant population of this predatory fish and to increase the profitability of the beach-seine fisheries of fishers who had stopped deploying gillnets, which pose a threat to the valuable species of sturgeon in the Caspian. Analysis of the age composition of pikeperch catches indicates that the use of beach-seines does not prevent overfishing of young pikeperch released as fingerlings in the same calendar year in which the fishing season started. No undersized fish are discarded back into the sea, because there is market demand for even the smallest fish, and a lack of communication exists between the programme beneficiaries and the management and research units. Some 15 years after it was initiated, the effectiveness of stock enhancement at a level of 4-6million fry per year remains uncertain.