Role of fishing in the Black Sea ecosystem

The Black Sea anchovy has experienced the most severe decline of the past 50 years and the responsible factors are not yet clearly understood. This is mainly due to the possible existence of several factors which may be equally probable. Some of these factors are: the increased eutrophication which changed the oligotrophic character of the Black Sea into a dystrophic one; the introduction of ctenophore medusa, Mnemiopsis sp; the outstanding exploitation pressure of the over-capitalised fishing fleet, and alterations in river discharges and hydrologic conditions at the straits. In this study, the contribution of fishery to anchovy collapse has been evaluated. For this purpose, i) the increase of fishing power by the recent introduction of purse seiners and sonars and their effects on over-wintering stocks along the Turkish coasts, ii) the condition index as an indicator of starvation of anchovy for pre and post Mnemiopsis period, iii) the spawning behaviour of anchovy, and iv) the coexistence of anchovy and Mnemiopsis during the anchovy spawning season, have been reviewed. It was concluded that effects of over-capitalisation of the fishing sector, especially of Turkey, on anchovy collapse and to an extent on the catastrophic changes in the Black Sea ecosystem, should not be overlooked as secondary