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NEW DATA REGARDING THE DISTRIBUTION AND ICHTHYOCOENOLOGICAL AFFINITIES OF THE UKRAINIAN BROOK LAMPREY, LAMPETRA (EUDONTOMYZON) MARIAE (CEPHALASPIDOMORPHI: PETROMYZONTIFORMES: PETROMYZONTIDAE), IN SOUTHERN POLAND

Fifteen new localities of the Ukrainian brook lamprey, Lampetra (Eudontomyzon) mariae, were found within 2008–2010. The majority of them are located in the Nida River drainage. Additionally, the occurrence of that species in the Strwiąż River, a tributary of the Dniester, was confirmed. The cluster analysis performed suggests, that L. mariae exhibits strong affinity to the stone loach, Barbatula barbatula, and the Eurasian minnow, Phoxinus phoxinus. We believe that the distribution of L. mariae on the territory of Poland seems to be strongly underestimated.

Data on coenological affinities of L. mariae are even less available. As far as the authors are aware, any single study regarding the ichthycoenological preferences of that lamprey species on the territory of Poland has been carried out so far.
In the present study certain new findings of L. mariae in southern Poland are presented together with results of the investigation on coenological affinities of that species.
Ichthyological surveys were carried out in the period of 2008-2010 in the upper Vistula River drainage. Fish were sampled by upstream electrofishing with a back-pack electroshocker (IG-600T, Hans Grassl GmbH). Lampreys are difficult to catch during the electrofishing targeting on fish monitoring and thus their occurrence is often missed or underestimated (Moser et al. 2007, Szczerbik and Nowak, personal observation). After capture and identification, all the specimens were promptly released.
Species identification was based on certain key characters: pigmentation of the caudal fin and shape of caudal fins in both ammocoetes and adults, body colouration pattern in ammocoetes and relative eye size in adults (Rembiszewski 1967, 1968, Marszał et al. 1993, Holčík and Delić 2000, Kottelat and Freyhof 2007, Stefanov and Holčík 2007, Naseka et al. 2009).
The ichthyocoenological affinities were ascertained by cluster analysis. The presence or absence of a species on localities was coded by 1 or 0, respectively, and such a matrix was used for clustering with Ward's method and Euclidean distance. All the analyses were performed using the R ver. 2.9.2 software (The R Foundation for Statistical Computing, 2009).
New data on occurrence and identification. During the period 2008-2010 a total of 15 new localities of L. mariae were discovered. Two of them, on the Krzywica River, a tributary of the Wilga River, were localised in the surroundings of the city of Kraków. Remaining 13 sites were found within the Nida River drainage: in Belnianka, Bobrza, Czarna Nida, Mierzawa, Sufraganiec and Nida rivers ( Fig. 1). Additionally, the presence of L. mariae was also confirmed in the Strwiąż River, from where the species has been known for over 40 years Rembiszewski (1971).
On these 15 localities a total number of 98 specimens of L. mariae (73 ammocoetes, 3 subadults and 22 adults) were collected. In gross majority of these localities L. mariae was very rare species, not exceeding 1% of the total fish abundance. Only in two sites on the Sufraganiec Stream in Kielce City the lampreys were more frequent, reaching ca. 10% of the total fish caught. All the adults and subadults had notable dark pigmentation of the caudal fin (this trait is lacking in L. planeri) and relatively small eye diameter. Dark colouration of the dorsum was contrasting with bright lateral sides. The ammocoetes had mottled colouration of the body and dark pigmented caudal fin, too (Fig. 2). Dark pigmentation of the branchial area reached the branchial vents, as described by Rembiszewski (1971). Any single ammocoete deviated from this colour pattern. The caudal fin was spade-like, in contrast to L. planeri in which this fin is more rounded (Rembiszewski 1971, Stefanov andHolčík 2007). Due to the fact, that all the lampreys occurring in Poland are protected by law (Anonymous 2004), they were released into water immediately after collection and identification in the field. Thus, the teeth formula has not been investigated. However, the external traits, as body colouration and eye diameter have been considered valid and crucial for the identification of both L. mariae and L. planeri by a number of authors (Rembiszewski 1967, 1968, Marszał et al. 1993, Holčík and Delić 2000, Stefanov and Holčík 2007, Naseka et al. 2009). According to Rembiszewski (1971), dark pigmentation of the caudal fin is fully developed in specimens larger than 60 mm in total length. All of the specimens collected were larger than 100 mm in total length. Thirteen out of 15 new localities of L. mariae reported in the current study were within the Nida River drainage, a largest left-bank tributary of the upper Vistula drainage (Sufraganie, Silnica, Bobrza, Lubrzanka, Belnianka, Czarna Nida and Nida). This river system was thoroughly investigated in the past twice: in 1968-1969 (Penczak 1971) and 1998-1999(Buras et al. 2001. Neither Penczak (1971), nor Buras et al. (2001) reported the occurrence of L. mariae in that territory. On the other hand these authors recorded on a number of sites other lamprey species, L. planeri. Our surveys revealed pres-ence of L. mariae on a majority of localities reported previously for L. planeri. It should be noted that sympatric occurrence of the both species is found extremely rare (Marszał et al. 1993). Thus, we concluded that either L. mariae has invaded the Nida River drainage in recent years, or in the earlier papers it was confused with L. planeri. The former hypothesis seems far less probable than the latter, especially considering a short time, namely 10 years, since the last report of L. planeri (see Buras et al. 2001). It seems hardly impossible that L. mariae could successfully colonised and totally replaced L. planeri in a number of localities within a large river system. Of course, one cannot definitely exclude the opinion of Marszał (2001), that L. mariae has substituted L. planeri in certain water courses, however, it does not seem in the case of the Nida River drainage. The hypothesis of incorrect identification has already been stated by Rembiszewski (1967). Also the first records of L. mariae on the Polish territory were as well verifications of earlier misidentifications (Oliva and Hensel 1962). Unexpected numerous findings of L. mariae in the middle Vistula River drainage prompted Rembiszewski (1967) to the conclusion, that this species might be much wider distributed throughout Poland, than it has been previously considered. Despite the subsequent ichthyological surveys performed since then, it should be definitely considered, that L. mariae is still a poorly known species and data on its distribution remains scarce.
As far as the authors are aware, there is a significant lack of comparative data on ichthyocoenological affinities of lampreys, especially L. mariae. Irrespectively, Ševc and Koščo (unpublished data) found that L. planeri in the Poprad River system preferred habitats shared with brown trout, Salmo trutta "fario" L.; European grayling, Thymallus thymallus (L.); and P. phoxinus. In comparison to the results of the presently reported study, as well as regarding the literature on the habitat preferences of lampreys and the present authors' own field observations, it could be concluded that both "brook" lampreys choose shallow parts of streams and rivers, with sandy bottom covered with a thin layer of organic sediments. The same sites are preferred by common eurytopic fishes with some affinities to water current, as B. barbatula, G. gobio, P. phoxinus, or L. leuciscus, what was revealed by our cluster analysis.