Incidental catches of Acipenseridae in the estuary of the River Evros, Greece

Abstract

Sturgeons are primitive large-bodied anadromous fish with most of the species living in the sea and reproducing in rivers. Because of their complex life history and their intensive exploitation, sturgeons are considered as globally threatened species and close to extinction (Gessner, 2000). Presently, fishing by-catch, poaching, habitat degradation, and physical obstacles to migration are major threats to the survival of these species (Ludwig, 2008). The River Evros basin, including in its lower drainage the tributaries Arda, Tundja and Ergene, with a total length of 550 km and a total catchment area of 39 000 km is the second largest river system in the Balkans, after the Danube. The river and the sea around its estuary (Thracian Sea) were the last fishing areas for A. sturio in Greece. This fishery sustained a small-scale canning industry, which during the early 1960s gave a production of 90–120 kg of sturgeon caviar annually (Georgacas, 1978). The River Evros population of A. sturio showed signs of decline already in the 1960s with the catches decreasing dramatically in the 1970s. Since 1980 only one catch of a mature female is reported by the Local Fishing Cooperative of Alexandroupolis in 1991. Consequently, A. sturio was considered as extinct from the river, despite the fact that this was never reported officially. During the recent years sporadic capturing of sturgeons has been recorded in the estuary of the River Evros (Koutrakis and Economidis, 2006). Herein, by employing morphological and molecular tools, we describe the taxonomic identification of three specimens captured in the years 2005 and 2006.