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Almost six years after the first finding of the round goby Neogobius melanostomus (Gobiidae) in the Netherlands, several specimens of this invasive Ponto-Caspian benthic fish were also recorded in the Belgian part of the River Scheldt and in the Albert Canal. This is the first record of the round goby in Belgium.
The round goby, Neogobius melanostomus (Pallas, 1811) was introduced into southern Baltic waters (including the Vistula Lagoon) from the Black Sea and Sea of Azov in the early 1990s. This study describes the parasites of the round goby in its new environment. In 2004, 486 round goby specimens from the Vistula Lagoon were examined for parasites. The following taxa were identified: Dermocystidium sp.; Protozoa: Trichodina domerguei domerguei (Wallengren, 1897); Digenea: Cryptocotyle concavum (Creplin, 1825), Diplostomum spp., Tylodelphys clavata (Nordmann, 1831), Bunodera luciopercae (M¨uller, 1776); Cestoda: Bothriocephalus scorpii (M¨uller, 1776), Eubothrium crassum (Bloch, 1779), Paradilepis scolecina (Rudolphi, 1819), Proteocephalus filicollis (Rudolphi, 1802), P. gobiorum Dogel et Bychovsky, 1939, Proteocephalus sp.; Nematoda: Anguillicola crassus Kuwahara, Niimi et Itagaki, 1974, Camallanus truncatus (Rudolphi, 1814), Contracaecum spp., Cystidicoloides ephemeridarum (Linstow, 1872), Dichelyne minutus (Rudolphi, 1819), Hysterothylacium aduncum (Rudolphi, 1802); Acanthocephala: Echinorhynchus gadi M¨uller, 1776, Pomphorhynchus laevis (M¨uller, 1776). The parasites found were all local species, already reported from Poland. Except for Dermocystidium sp., C. concavum, P. gobiorum, and D. minutes, they have already been recorded in other fish species in the Vistula Lagoon. The prevalence and mean intensity of infection was low (18.3%; 4.0 indiv. – this value does not include ciliates). The most frequent parasites included H. aduncum (9.9%, 1.2 indiv.) and A. crassus (9.1%, 1.2 indiv.). In addition, Dermocystidium sp., B. luciopercae, E. crassum, P. scolecina, P. filicollis, C. truncatus and C. ephemeridarum are reported from the round goby for the first time. As the fish has only recently appeared in the Vistula Lagoon, its parasitic fauna has not yet developed to the full.
The genetic diversity of Neogobius melanostomus populations was investigated by means of allozyme electrophoresis. 28 loci coding for 16 enzyme systems were examined. Samples originated from the Gulf of Gdańsk (Baltic Sea, newly founded population) and the north part of the Black Sea, off the Crimean Peninsula (centre of range). Despite their considerable geographical isolation, the genetic distance was not high (DNₑᵢ = 0.0353), also the populations had shown great similarity at the polymorphism level and the mean number of alleles per locus. High level of polymorphism and no signs of the founder effect in the Baltic Sea population could indicate that colonisation was very intensive.
The round goby (Neogobius melanostomus) is a non-indigenous species in the Baltic Sea, introduced to its waters (the Gulf of Gdańsk) from the Black, Azov, and Caspian Seas. For this reason, an attempt was made to determine the species' parasitic fauna in its new environment. Within 1994-2000, a total of 201 round goby specimens caught in the Gulf of Gdańsk were examined. The parasites found represented protozoans (Trichodina domerguei domerguei), digencans (Diplostomum spp. metacercariae), cestodes (Bothriocephalus scorpii, plerocercoids), nematodes (Hysterothylacium aduncum L₃, L₄, and adults), and canthocephalans (Echinorhynchus gadi and Pomphorhynchus laevis). The parasitic species found are common in the Gulf of Gdańsk. It should be emphasized that, since the round goby has only recently appeared in the Gulf, the parasitic fauna of this fish is not yet complete.
The present work constitutes an attempt of assessment of the expansion of the round goby, Neogobius melanostomus Pallas, 1811 in the waters of the southern Baltic Sea. It is based on frequency analysis of this species in the survey catches conducted within 1993-1999 by R/V Baltica of the Sea Fisheries Institute in Gdynia, Poland. Since 1996 the round goby has become noticeable in the catches carried out in the Gulf of Puck. A constant increase of the catches of this species has been recorded in catches conducted outside the Gulf of Puck on the fishing grounds: Bromka, Wisłoujście, and Krynica Morska.
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