Natural, social, economical and political influences on fisheries: a review of the transitional area of the Polish waters of the Vistula Lagoon.

A 60 year (1948-2007) dataset gathered by Polish researchers working on the Vistula Lagoon fish assemblages and fisheries has shown this stressed transitional environment to be always been dominated by a few highly abundant fish species. During this period, the surrounding countries Poland and Russia (Kaliningrad) were transformed from centrally-planned economies with fixed prices to free market systems. The organization of the fishery evolved from one in which the majority of the fishing effort was expended by cooperatives, to one which was characterized by individual economic activity. The fishing gear deployed also evolved from cotton to monofilament, as well as from large sailing vessels with small-sized pair trawls to fyke nets targeting eel (Anguilla anguilla) and pound nets targeting herring (Clupea harengus). Small-sized gillnets targeting perch (Perca fluviatilis) grew in popularity as eel and pikeperch (Sander lucioperca) catches decreased. Cooperation between Polish and Russian fishery managers began in 1952 with the aim of implementing joint agreements to establish protection guidelines. The substantial nutrient loads into the lagoon in 1970 and 1980 put very large pressure on the environment, and contributed to the loss of macrophytes as well as the development of non-commercial fish populations. One of the consequences of these changes was the rapid growth of a black cormorant (Phalacrocorax carbo) breeding colony. These multi-faceted changes are considered to be the factors that have influenced the exploitation of fish assemblages in the Polish part of the Vistula Lagoon. The most evident change in the fish assemblage structure during the study period was the permanent decrease in the basin's top predators--pike (Esox lucius) and pikeperch. Eel stocking was initiated in 1970 following a crucial decline in yield from natural recruitment, and stocking was successful in increasing eel abundance.