Structure of the gut of the racer goby Neogobius gymnotrachelus (Kessler, 1857)

The morphological and histological features of the gut of juvenile racer goby Neogobius gymnotrachelus [range of body mass 0·2–0·9 g and standard length ( L _S) 20·0–38·8 mm] were examined in fish collected from the Włocławek Reservoir on the Vistula River, Poland. Evidence is provided of the stomachless nature of the gut of the racer goby. The intestine of the juveniles lacks the intestinal bulb. A particular feature of the racer goby gut is the secretory oesogaster (the transitional region where the secretory oesophagus merges into the intestine) with multicellular alveolar glands that secrete via a common duct to the surface between the mucosal folds. The cells in the secretory oesogaster alveolar glands are periodic-acid-Schiff (PAS) positive indicating the presence of neutral mucopolysaccharides. It is hypothesized that the secretory oesogaster is evidence of the loss of the functional stomach in this species. There are two sphincters: the oesogaster–intestinal and the intestinal–rectal in the racer goby gut. It can be concluded that the oesogaster–intestinal sphincter is functionally related to the gastro-intestinal sphincter described in many fish species having a stomach. Enterocytes with a distinct brush border and only a few goblet cells are observed in the epithelium along the whole intestine. The existence of vacuoles in the supranuclear region of the rectal enterocytes is also confirmed.     

Diel-feeding activity in early summer of racer goby Neogobius gymnotrachelus (Gobiidae): a new invader in the Baltic basin

The first recording of the Ponto‐Caspian racer goby in Poland was during 1995 in the River Bug (River Vistula system). Within 5 years, the species had spread to the downstream section of the Vistula. One of the potential impacts of invasive species on native fauna is competition for food. Therefore, the diel patterns in diet composition and gut fullness coefficient (FC) of racer goby were examined at one study site in the W?oc?awski Reservoir (lower River Vistula), during May 2003. An average of 20 individuals were examined each 4 h over one 24‐h period (125 fish in total). The proportion of main food items and diet width did not differ among three size‐groups (43–59, 60–79 and 80–97 mm total length), and the relative biomass ratio of main food categories did not differ over the diel cycle. Amphipods constituted 11–70% of total gut content biomass and were found on average in 84% of analysed alimentary tracts. The second prey types were chironomid larvae (16–63% of total food biomass; frequency occurrence: 61–91%), and to a lesser extent chironomid pupa, ceratopogonid larvae, oligochaets, dipteran imagines and copepods, with fish larvae found in the gut of eight gobies. Gut fullness coefficient (FC) differed significantly over the 24‐h period, with the highest value at night and in early morning. In conclusion, racer goby forages mainly on benthos and has a nocturnal‐feeding activity. No significant diet overlap was found between racer goby and native percids, i.e. Eurasian perch Perca fluviatilis and ruffe Gymnocephalus cernuus.     

Genetic and biogeographic relationships of the racer goby Neogobius gymnotrachelus (Gobiidae: Teleostei) from introduced and native Eurasian locations

The racer goby Neogobius gymnotrachelus , along with several other neogobiin fishes, has been spreading north and west from its native Ponto-Caspian range for the past two decades via shipping and canals. It has been predicted as a likely future invader of the North American Great Lakes, where it would join its neogobiin relatives – the round and freshwater tubenose gobies. The present study is the first to analyse the population genetic and biogeographic relationships of the racer goby, establishing a baseline to aid interpretation of its future spread patterns and likely donor-recipient population relationships. The mitochondrial DNA cytochrome b gene was sequenced from representative areas of the racer goby's range, including rivers of the northern Black Sea and areas of spread upstream in the Danube River and outside the Ponto-Caspian region to the Vistula River in Poland. Results discerned nine haplotypes, with few shared among drainages of native rivers and most sites housing unique alleles. Racer goby populations significantly diverged among watersheds, supporting historic low migration and little non-anthropogenic gene flow. The Dnieper River was identified as a likely donor source for the Vistula River colonization, where appreciable variability suggests a relatively large number of founding genotypes.     

Finding round goby Neogobius melanostomus (Pallas, 1814) in the Rybinsk Reservoir

The data from finding a female round goby in June 2010 near the dam in the Central Reach of the Rybinsk Reservoir are presented. The presence of mature reproductive products may indicate the possibility of the successful acclimatization of this species in the Rybinsk Reservoir.     

Seasonal abundance and feeding patterns of the invasive racer goby (Babka gymnotrachelus) in the littoral zone of a lowland European river

Environmental Biology of Fishes - The racer goby (Babka gymnotrachelus), a Ponto-Caspian gobiid, has successfully established in several European rivers since the 1990s, and its range is expanding;...     

Features of biology of the round goby <Emphasis Type="Italic">Neogobius melanostomus</Emphasis> (Perciformes,Gobiidae) in waters of Kuibyshev Reservoir

Based on materials of 2003–2005, the size-age composition, dates of reproduction, distribution, as well the qualitative and quantitative composition of the food of the round goby Neogobius melanostomus in the coastal part of Kuibyshev Reservoir are considered. It is shown that the round goby prefers coastal parts of the reservoir with depths to 10 m and rocky grounds and that its main food are mollusks of the genus Dreissena.     

Some features of biology of big-headed goby <Emphasis Type="Italic">Neogobius gorlap</Emphasis> (Perciformes,Gobiidae) in waters of the Kuibyshev Reservoir

On the basis of materials of 2003–2005, the size-age composition, dates of reproduction, as well as qualitative and quantitative food composition of big-headed goby Neogobius gorlap in the coastal part of the Kuibyshev Reservoir are considered. It is shown that big-headed goby prefers coastal parts of the reservoir with depths up to 2.5 m and rocky, sandy-slimy grounds; the bulk of its feeding consists of crustaceans.     

Correlation between body size and fatty acid and essential amino acid composition of round goby (Neogobius melanostomus) and monkey goby (Neogobius fluviatilis) from the Rhine River (Germany)

In this study correlations between body size and muscle fatty and amino acid content of two species of goby, round goby (Neogobius melanostomus) and monkey goby (Neogobius fluviatilis) caught from river Rhine (Germany) were investigated. Among saturated fatty acids (SFAs), mono- (MUFA) and polyunsaturated fatty acids (PUFAs) only SFAs were significantly higher in round goby than monkey goby (P < 0.05). In general, the correlation between body size of both gobies and the content of most of the individual fatty acids was not significant. In monkey goby, the content of palmitic acid (C16:0) and oleic acid (C18:1 n-9) was positively correlated with weight (r = 0.43) and total length (r = ?0.58), respectively, and the content of docosahexaenoic acid (DHA) increased with condition factor (r = 0.50). The content of threonine, arginine, valine, phenylalanine and isoleucine in monkey goby was higher than those of round goby (P < 0.05). In round goby the three essential amino acids arginine, valine and leucine were positively (P < 0.05) correlated with body length, which indicates that longer round gobies are of higher nutritional value.     

Life-history traits of invasive bighead goby Neogobius kessleri (Günther, 1861) from the middle Danube River, with a reflection on which goby species may win the competition

Life history traits of an invasive population of bighead goby Neogobius kesslerei (Günther, 1861) from the middle Danube, including absolute and relative fecundity, egg size, number of spawning batches and size at first maturation, were examined and evaluated within an epigenetic context. Ripe bighead goby females attained 42.8–142.5 mm L _S, with absolute fecundities ranging from 669 to 5646 eggs (mean 2109 eggs), and relative fecundities of 61.6–174.0 eggs g⁻¹ body weight (mean 119.6 eggs). Egg diameters varied between 0.04 mm and 1.70 mm (mean = 0.57 mm). In the pre-spawning period there was no clear size distinction in eggs (0.12–1.45 mm; mean = 0.52 mm) in 34.1% of females; whereas in 65.9% of females, two egg size groups were distinguished: group I diameters of 0.06–0.85 mm (mean = 0.43 mm), and group II diameters of 0.55–1.70 mm (mean = 1.17 mm). Females with size-group II eggs at the beginning of the reproductive season were assumed to be ready to spawn and the others to be subsequent spawners. Bighead goby appears to be altricial compared to the round goby, although in both species a shift from highly precocial towards a less precocial life history was observed. These differences, affected by epigenetic mechanisms and resulting in alternative ontogenies, may have important implications for a species' potential success in novel environments, favouring the round goby over short time periods (several years) and bighead goby over longer periods of time (decades and longer).     

Contemporary transport of suspended material and its deposition in the Vistula River,Poland

The rate of suspended material transported with the current and its deposition in the Vistula River and its main tributaries was estimated to determine the effects of river regulation in the following periods: (1) between the beginning of engineering works on the Vistula River and the construction of the first dams on its tributaries, (2) in the years 1946-1995 when transport measurements were taken, (3) after the planned completion of the dam system. Those estimates were based on the results of long-term measurements of the rivers, carried out by the State Hydrological Survey at numerous gauging stations, as well as on analysis of maps published after 1780. The combined methods allowed estimating both the differences in deposition of the suspended material along the river and the long-term variability of that process. The initial increase in transport and deposition of the suspended material in the Vistula River during the four decades succeeding the river regulation (1890s–1930s) was followed by a rapid decrease of the material transport caused by the construction of dams and changes in land-use in the river basin.