Bighead Goby Research Articles

Invasive gobies in the Danube: invasion success facilitated by availability and selection of superior food resources

Abstract – We investigated somatic condition, growth rate, diet and food resources of the native (lower Danube) and non‐native (upper Danube) populations of invasive bighead gobyNeogobius kessleriand round gobyN. melanostomuswithin the Danube River to answer the question whether prey availability and type may have facilitated successful goby invasion to the upper Danube. The non‐native populations of both species were in better somatic condition and grew faster. The biomass of nonmollusc macrozoobenthos, dominated by Amphipoda, was markedly higher in the non‐native range while molluscs were recorded frequently in both the native and non‐native ranges. Amphipods were far the most consumed prey by non‐native fish, whereas native fish combined two main prey types – amphipods and fish (bighead goby) and amphipods and bivalves (round goby). A laboratory experiment was conducted to reveal whether the low consumption of bivalves by the round goby in the non‐native range reflects prey encounter rates or alternatively prey selectivity. When bivalves and amphipods were offered simultaneously in excess to the experimental fish, round goby showed strong preference towards amphipods. Molluscs are hypothesised to be an alternative rather than the most preferred prey for the round goby. Rich food resources utilised by the non‐native bighead and round goby contribute to their invasive success in the upper Danube.

Food Resource Partitioning between Two Invasive Gobiid Species (Pisces, Gobiidae) in the Littoral Zone of the River Danube, Hungary

AbstractAt present, the invasive round and bighead gobies are the most abundant benthic fish species in the near shore zone of the Middle Danube. We compared their diet seasonally in natural and artificial habitats and contrasted it with the food supply. The composition of the macroinvertebrate community was determined mainly by seasonal changes, whereas habitat type had smaller effect. Round gobies followed these changes flexibly. They consumed mainly chironomids in the spring, whilst amphipods and molluscs in the summer and autumn. Bighead gobies relied on amphipods in each season and in both habitats, and consumed fish, too, including round goby (intraguild predation). Diet overlap was determined by the morphological differences of the species allowing a varying degree of differentiation according to the seasonally changing food supply. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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

Summary Life history traits of an invasive population of bighead goby Neogobius kesslerei (Gunther, 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 LS, 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 mecha- nisms 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).

Preliminary study of dietary interactions between invading Ponto-Caspian gobies and some native fish species in the River Danube near Bratislava (Slovakia)

Dietary breadth and diet overlap were examined in two native fish species (Eurasian perch Perca fluviatilis, Balon’s ruffe Gymnocephalus baloni) and two invading species (round goby Neogobius melanostomus, bighead goby Neogobius kessleri) in the Middle Danube (Slovakia) at dawn and dusk over two consecutive 24-h periods in late summer 2004. Dietary breadth was narrow in all species/age classes except perch of ages 4 and 5. Dietary overlap between native fishes and the invading gobies was very high, except for age 3 perch. This high overlap was due to a preference, high in some cases, for gammarids. Our preliminary results suggest the potential for competition between the invading and native fishes, which requires further study.

Ontogenetic variability in the external morphology of monkey goby, Neogobius fluviatilis (Pallas, 1814) and its relevance to invasion potential

In the previous decade, four species of non-native gobies have invaded the middle section of the river Danube and its tributaries. An effective tool for understanding biological invasions is the evaluation of various biological traits (morphological, life history, ontogenetic) within an epigenetic context. The present study examines the external morphology of monkey goby Neogobius fluviatilis (Pallas, 1814) from the mouth of the River Hron, the morphological differences among three goby species (monkey, bighead and round) and the relevance of these differences for invasive potential. Monkey goby reach their definite phenotype very early in their ontogeny and thus represent a strongly precocial (specialized) species with direct development. The morphological differences between monkey and two other goby species also reflect its strong specialization for sandy substrata and smaller prey types. Thus, monkey goby are not expected to spread to new areas as fast as the round and bighead gobies, and their distribution is likely to be limited to sandy and/or sandy-gravel substrata. If this assumption is correct, then the potential adverse impact of monkey goby on native fauna or even ecosystem is likely to be less than that of the bighead and round gobies.

Karyological study on bighead goby (Neogobius kessleri) from southern part of the Caspian Sea

Karyological study on bighead goby (Neogobius kessleri) from southern part of the Caspian Sea

Ontogenetic variability in external morphology of bighead goby Neogobius kessleri from the Middle Danube, Slovakia

Summary Over the last decade, four species of goby have invaded the Middle Danube area, and all of them have spread rapidly. In the early 1990s, bighead goby Neogobius kessleri appeared in the Middle Danube, where it now seems to thrive. Relatively little is known of the environmental biology and ontogeny of this species in its native and non-native ranges. In this paper, preliminary results on the external morphology of bighead goby from the Slovak stretch of the Danube are presented within an ontogenetic context. Patterns of relative growth with no apparent changes at small size suggest direct development in bighead goby, although not as profoundly direct as observed in round goby N. melanostomus. Differences in life history between these two closely related species may have important implications for their success in novel environments, favouring the latter in short term (several years) and the former in long term (decades and longer) perspective.

The recent distribution and abundance of non-native Neogobius fishes in the Slovak section of the River Danube

Summary The distributions of invasive Neogobius species were investi- gated in the Slovak section of the River Danube from Bratislava downstream to the village of Chl'aba. During October 2004, the main channel of the Danube was sampled, including by-pass, head-race and tail-race canals of the Gabcˇ ikovo dam, backwaters and the lower-most sections of the tributaries MalyDunaj, Hron, Vah and Ipel. Three Neogobius species already documented in Slovakia were captured (monkey goby Neogobius fluviatilis, bighead goby N. kessleri, round goby N. melanostomus), with the latter two species being found in almost all stretches of the Slovak Danube. Monkey goby had a most limited distribution, and no racer goby N. gymnotrachelus were observed. The abundance of particular Neogobius species appeared to depend on the character of the shoreline habitat, and a possible association between larger towns and the abundance of bighead and round gobies requires further investigation.

New records of non-indigenous gobies (Neogobius spp.) in the Austrian Danube

Summary Beginning in the early 1990s, species of the genus Neogobius rapidly expanded their native range from the Black Sea and the lower reaches of the River Danube upstream to include the middle and upper Danube. In 2002, 83 rip-rap sites at 25 locations along the Austrian section of the River Danube were sampled by catch per unit effort (CPUE) with electrofishing to assess goby distribution. Bighead goby N. kessleri was found in all locations and at 76% of these sites, it was the third-most abundant species (17% of CPUE). Densities of Neogobius spp. were highest in industrial harbours (IH), whereas the native species European bullhead Cottus gobio was found primarily in the main channel and tubenose goby Proterorhinus marmoratus in non-industrial harbours. The history of records and the present distribution of Neogobius spp. suggest that IHs are the main dispersal points.

Abundance and night-time habitat use patterns of Ponto-Caspian gobiid species (Pisces, Gobiidae) in the littoral zone of the River Danube, Hungary

We examined the abundance and meso-habitat use of gobiid species during both day and night along 43 stretches (500-m long) of the littoral zone at five locations of the Middle Danube, Hungary, in spring and in summer 2004. Electro-fishing catch per unit effort sampling revealed significantly higher relative densities at night than during the day. Gobiids occupied all the available habitats encountered during sampling. Habitat-abundance relationships from night-time samples revealed that the two most abundant species, round goby Neogobius melanostomus and bighead goby Neogobius kessleri, were found in highest relative density along gravel beach and artificial rip-rap habitats; these species were in relatively low density in sandy areas. Monkey goby Neogobius fluviatilis was more abundant in natural shorelines than in rip-rap habitats and dispersed more consistently between sandy and gravel beaches. Tubenose goby Proterorhinus marmoratus demonstrated great plasticity in meso-habitat use. In conclusion, Ponto-Caspian gobies occurred rather consistently along the Hungarian section of the Danube, occupying all available habitats examined. Abundance-habitat relations suggest plasticity in meso-habitat use but partial segregation between species. Further studies are required at multiple spatial scales to assess how micro- and meso-habitat use varies with fluctuating population densities.

Metazoan parasites of Neogobius fishes in the Slovak section of the River Danube

Summary Metazoan parasites were investigated in three non-native fishes (monkey goby Neogobius fluviatilis, bighead goby Neogobius kessleri and round goby Neogobius melanostomus) collected from the former and current main channel of the River Danube and from the River Hron, Slovakia, in November 2003. Thirteen parasite species were identified: Triaenophorus crassus, Diplostomum sp., Tylodelphys clavata, Metorchis xanthosomus, Nicolla skrjabini, Gyrodactylus proterorhini, Pomphorhynchus laevis, Contracoecum sp., Raphidascaris acus, Anguillicola crassus, Unio tumidus, Anodonta anatina and Pseudoanodonta complanata. The maximum parasite diversity was found in N. fluviatilis. Total parasite abundance was significantly higher in N. kessleri, but no significant differences among sampling sites were observed. Pomphorhynchus laevis and glochidia of Anodonta anatina reached 100% prevalence in N. kessleri in the new channel of the Danube and, in general, these species were also the most prevalent parasites in all three goby species. For endoparasites, gobies served mostly as intermediate (digenean, cestodes and nematodes) or paratenic (acantocephalan and nematodes) hosts. All parasite species found are common parasites in the Middle Danube basin. No parasites specific to Neogobius, known from their native populations, were observed.

Morphology, Feeding, and Reproduction of the Round Goby, Neogobius melanostomus (Pallas), in the Danube River Basin, Yugoslavia

The round goby Neogobius melanostomus was the last Ponto-Caspian goby species to enter in the Danube River bordered by Serbia and Yugoslavia. There are five Ponto-Caspian goby species in the waters of Serbia including the sand goby Neogobius fluviatilis, the round goby Neogobius melanostomus, the racer goby Neogobius gymnotrachelus, the bighead goby Neogobius kessleri, and the tubenose goby Proterorhinus marmoratus. The sand, bighead, and tubenose gobies occur along the Yugoslav Danube and in the lower reach of the Danube's tributaries; the racer goby is found both upstream and downstream of the Djerdap II dam; and, the round goby has been collected only downstream of the Djerdap II dam. Investigations on the continuous morphological characters of the round goby revealed neither sexual dimorphism, nor significant differences in adult size-classes, although some suggestions of sexual dimorphism were found in cranial skeletal analyses. Analysis of external continuous characters revealed a west-east cline along the distribution range of the round goby in the Black Sea basin. Molluscivory for the round goby was corroborated along the Danube. Standard length of each age class for the round goby in the Danube was less than populations in the Caspian and Azov seas.

Cranial osteology of the bighead gobyNeogobius kesslerifrom the rivers Danube and Sava (Serbia, Yugoslavia)

Abstract Osteological investigations of the Rivers Sava and Danube sampling of the bighead goby Neogobius kessleri skull, pectoral girdle, and gill cover (50 characters) revealed values for some descriptive statistics parameters different from those obtained for the Dnjepar estuary population. Sexual dimorphism was not detected for any character. Certain characters of skull, suboperculum, praemaxilla, and hyomandibular were significantly different in particular length classes. Allometry was not detected. Multivariate analysis revealed that morphology of the biggest specimens is rather different from that of smaller ones. Overall, the results were consistent with a direct morphological formation through the bighead goby ontogeny. It was suggested that great variability in size classes, especially in the largest one, weakens their clear separation, and that the size component has a strong influence on the head skeleton shape.