RANGE EXPANSION OF AN INVASIVE ALIEN SPECIES, CHINESE SLEEPER, PERCCOTTUS GLENII DYBOWSKI, 1877 (TELEOSTEI: ODONTOBUTIDAE) IN THE VISTULA RIVER DRAINAGE

In October 2007 an invasive alien species, the Chinese sleeper, Perccottus glenii Dybowski, 1877 (known also as the Amur sleeper), was recorded in carp ponds in Kraków-Mydlniki (southern part of Vistula River drainage). As far as we know, this is the uppermost site in the Polish part of the Vistula River drainage. Thirty-six individuals of P. glenii were collected during fishery works. Basic morphometric measurements were obtained, following the commonly accepted procedures, in order to describe the general body shape of P. glenii.

. Occurrence of the Perccottus glenii in Poland: 1, Antychowicz (1994); 2, Terlecki (1995); 3-5, Woźniewski (1997); 6-7, Kakareko (1999); 8, Kostrzewa et al. (1999); 9-13, Kostrzewa et al. (2004); 12, Wiśniewolski and Woźniewski (pers. comm.); 14, Andrzejewski and Mastyński (2004); 15, Rudawa river in Kraków, presently reported study (2007) However, Witkowski (2003) estimated that the total number of P. glenii sites in Poland reaches 1000. In 2002 Andrzejewski and Mastyński (2004) speculated that P. glenii had broken the borderline of the Vistula River drainage and it will probably continue its dispersal into the western parts of Europe. As far as we know the species has not been recorded in the Odra (Oder) River drainage, although such assumption cannot be rejected (Freyhof 2003). During the last decade a fast spreading of P. glenii in south-eastern Europe has been noticed. In 1998 the species was recorded in Latvia (Plikšs and Aleksejevs 1998). In the same year it was collected in the Gulf of Finland (Panov et al. 1999). During the last few years Chinese sleeper has been consecutively found in the Tisza River drainage area in Ukraine, Slovakia, Hungary, and Romania (Koščo et al. 2003, Hegediš et al. 2007) and in Danube River within the territory of Serbia and Bulgaria (Jurajda et al. 2006, Hegediš et al. 2007. P. glenii was also found in White Sea and Arctic Ocean basins (Bogutskaya and Naseka 2002;Koščo et al. 2003). Furthermore the species spreads through the Asian part of Russia Naseka 2002, Reshetnikov 2004).
In the middle of October 2007 more than 40 individuals of P. glenii were collected during fishery works in the "Podkamycze II" carp pond (the Experimental Fisheries Station "Mydlniki", Department of Ichthyobiology and Fisheries, Agricultural University of Krakow). This was the first time the species was reported in the area (lat 50°03'N, long 19°56'E). The fish were harvested in the pond with well developed water vegetation, with predominant species such as: Phragmites australis, Glyceria aquatica, Typha latifolia, Potamogeton perfoliatus, and P. crispus. Chinese sleeper co-occurred with the following fish species: common carp, Cyprinus carpio (age 2+); Prussian carp, Carassius gibelio; and pikeperch, Sander lucioperca (2+). This site seems to be the uppermost limit of its distribution area in the Vistula River drainage within the territory of Poland.
Thirty-six specimens of P. glenii were anaesthetised with Propiscin and preserved in 4% formaldehyde. Then, in order to describe better the general body shape of the collected fish, 22 morphometric-and 6 meristic characteristics were measured, according to Hubbs and Lagler (1947) (Fig. 2, Tables 1, 2). As far as we know, such characteristic has never been used in Poland for such purposes. Standard length (SL) and head length (HL) were measured from the tip of the snout (upper jaw) to, respectively, posterior end of hypural complex (localised by bending out the caudal fin) and posteriormost point of the opercular membrane. All measurements were taken as straight lines, by the "point-to-point" method. Circumference (cf) and circumpeduncular (cp) rows of scales were counted, respectively, in advance of the dorsal fin and at the lowest point of the caudal peduncle.
The occurrence of P. glenii in ponds in Kraków-Mydlniki denotes the invasive character of this species. It is potentially dangerous not only to the fishes, but also to the other indigenous animals (Reshetnikov 2003). Furthermore, P. glenii has no economic importance, attaining only about 250 mm in total length and up to 250 g in weight, though the most specimens do not exceed 120 mm total length (Berg 1949, Koščo et al. 2003, Reshetnikov 2003. Its appearance and dispersal in Polish water bodies, simultaneously with other non-indigenous species (e.g., brown bullhead, Ameiurus nebulosus; pumpkinseed, Lepomis gibbosus; round goby, Neogobius melanostomus; and stone moroko, Pseudorasbora parva) could cause serious problems to the local fauna. P. glenii threat the native ichthyofauna by competition, displacement, and direct predation (Bogutskaya and Naseka 2002, Koščo et al. 2003, Witkowski 2003, Reshetnikov 2003, 2004, Kostrzewa et al. 2004, Copp et al. 2005. Furthermore, it has been demonstrated that this species may be a vector of certain parasites and fungi (Czeczuga et al. 2002, Koščo et al. 2003, Uzunova and Zlatanova 2007. Sustained monitoring of the spreading of this species is needed to prevent, if possible, new invasions (Witkowski 2003, Kostrzewa et al. 2004). Due to its resistance to adverse ecological conditions, gluttony and dispersal caused by floods (Bogutskaya and Naseka 2002, Koščo et al. 2003, Reshetnikov 2003, 2004, Kostrzewa et al. 2004) a consecutive dispersal of this species in the territory of Poland is expected, as well as in other regions of Eurasia.
The origin of the individuals of P. glenii collected in Kraków-Mydlniki is another question. They probably have been brought with juveniles of Carassius gibelio which were purchased a few times. The possibility of releasing them from aquarium cultures is also taken into account. Despite all efforts to annihilate all the specimens of P. glenii   D1, number of rays in first dorsal fin; D2, number of rays in second dorsal fin; A, total number of rays in anal fin; sq, numbers of scales in lateral row; cf, circumference rows of scales; cp, cicumpeduncular rows of scales.

Fig. 2.
Measurement diagram of the Perccottus glenii according to Hubbs and Lagler (1947) scheme; characters description as in Table 1 in ponds and to prevent its dispersal outside, some individuals were found in the draining ditches emptying to the Rudawa River, the left-bank tributary of the Vistula River. It could cause a new invasion to the Rudawa River system, and subsequently also the Vistula River. As far as we know, all attempts of eradication of P. glenii from various bodies of water have failed (Bogutskaya and Naseka 2002, Reshetnikov 2003, 2004, what does not make an optimistic prediction for the future.