Short communication Incidental catches of Acipenseridae in the estuary of the River Evros, Greece By E. Koutrakis 1 , A. Sapounidis 1 , L. Favre-Krey 1 , G. Krey 1 and P. S. Economidis 2 1 NAGREF – Fisheries Research Institute, Nea Peramos, Kavala, Greece; 2 Karakasi, Thessaloniki, Greece Introduction 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 2 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 Cooper- ative 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. Materials and methods The specimens that were caught alive were transported to the facilities of the Fishing Cooperative of Alexandroupolis. Following mild anesthesia, morphometric counts were taken according to Holcik et al. (1989). A small piece from the anal fin was also obtained and conserved in ethanol for DNA analysis. The fish were released in the same area where they were captured. For the DNA analysis, genomic DNA was extracted from a piece of the anal fin. The 3¢-end of the mitochondrial cytochrome b gene was PCR-amplified using primers CytbI- 6F and THR-Fish2-R according to protocol 14 described in Sevilla et al. (2007). Following amplification, the 698 bp DNA fragment was purified and its nucleotide sequence established (612 bp, after primer sequence removal and trimming of ends). For comparison purposes, the same procedure was followed on tissue samples from two A. sturio specimens (specimens IIIA and 4682) and from one specimen of each of A. ruthenus, and A. baerii, all provided by the Genetic Material Bank of the European Sturgeon Center (ESC) in Dordogne, France. All sequences generated were deposited to the GenBank (http:// www.ncbi.nlm.nih.gov/Genbank/) under accession numbers EU733248 to EU733253. Results Seven years after the last recorded catch of a sturgeon in the Thracian Sea (a juvenile Acipenser stellatus was caught in the area of Porto Lagos in 1999 (Economidis et al., 2000). Additionally, three other juvenile sturgeons have been caught in the area of the Evros Delta. Specifically, the 350 mm (TL) specimen caught in late October 2005 in the mouth of the river, was preliminarily identified as Acipenser sturio by virtue of its small mouth and narrow and rounded snout (Table 1). This identification was confirmed by DNA sequence of the 3¢-end of the mitochon- drial cytochrome b gene (GenBank access. no. EU733248). As shown in Table 2, the 612 bp sequence presented 100% identity to the sequence obtained from the ESC A. sturio reference specimens (specimens IIIA and 4682, GenBank access. no EU733249 and EU733250, respectively), as well as to the cytochrome b sequence for A. sturio available in the GenBank (access. no AJ245839). This identification represents the first report of the species in the area since 1991. The 703 mm (TL) specimen was captured in mid-November 2005 and according to its morphometric and meristic charac- teristics (Table 1) was identified as Acipenser gueldenstaedtii (Russian sturgeon). The species identity was also confirmed by the cytochrome b sequence (GenBank access. no. EU733252) and by comparison with previously published sequences (Ludwig et al., 2000; Birstein et al., 2005; Rastorguev et al., 2008; Krieger et al., 2008 – Table 2). This is the first record of the species in the Mediterranean, including its NE area (Thracian Sea). The last specimen, of 364 mm total length (Table 1), was found in the same area during the summer of 2006. Its large mouth, as well its other morphometric and meristic traits (Table 1) are very characteristic for Huso huso (Beluga). Unfortunately, this fish did not survive in captivity. However, the fisherman that caught it mentioned that, in the previous days, five similar juveniles were caught in the area and were released again into the river. Discussion The origin of the sturgeon specimens described above is presently unknown. However, the fact that all specimens were J. Appl. Ichthyol. 27 (2011), 366–368 Ó 2011 Blackwell Verlag, Berlin ISSN 0175–8659 Received: August 10, 2010 Accepted: January 10, 2011 doi: 10.1111/j.1439-0426.2011.01729.x U.S. Copyright Clearance Centre Code Statement: 0175–8659/2011/2702–0366$15.00/0 Applied Ichthyology Journal of