Checklist of parasites for Ponto-Caspian gobies (Actinopterygii: Gobiidae) in their native and non-native ranges

This study provides a comprehensive checklist of parasites reported for native and non-native populations of seven Ponto-Caspian goby species, i.e. Babka gymnotrachelus, Neogobius fluviatilis, N. melanostomus, Ponticola gorlap, P. kessleri, Proterorhinus semilunaris and P. semipellucidus, all of which have recently expanded their natural range, either by transoceanic translocation or along the three main European intracontinental invasion corridors. In some cases, invasion success is facilitated by loss of natural enemies, such as predators and parasites; thus, knowledge of a species natural parasite fauna is essential for assessments of enemy release in the host's non-native range. The study is based on published literature and personal unpublished data related to parasites of Ponto-Caspian gobiids. A total of 249 parasite taxa have been reported during 1931—2019, with higher numbers reported from native (214) than non-native (151) ranges. This checklist indicates apparent reduction in native parasites in non-native ranges in all goby species, although parasite colonisation in non-native ranges differs between fish species and invasion corridors. Interestingly, the cumulative number of species reported is still gradually increasing in both ranges. Acquisition of high number of local parasite species also indicates competence of Ponto-Caspian gobies to a wide range of generalist parasites.     

Condition status and parasite infection of Neogobius kessleri and N. melanostomus (Gobiidae) in their native and non-native area of distribution of the Danube River

The success of introduced species is often facilitated by escape from the effects of natural predators and parasites. Introduced species can profit from this favourable situation, attaining higher population densities and greater individual sizes in novel areas. In this study, somatic condition and parasite infection were compared between native and non-native populations of Neogobius kessleri Günther; introduced only within the interconnected Danube and Rhine River system, and N. melanostomus (Pallas); widely introduced throughout several river systems in Europe and North America. Higher values of Fulton’s condition factor were observed in non-native populations of both goby species. Neogobius melanostomus attained higher gonadosomatic index values in non-native populations, indicating potential increased investment in reproduction in its new area. A lower splenosomatic index was observed in non-native populations, especially in N. melanostomus. Parasite infracommunity richness and mean abundance were higher in N. kessleri in both native and non-native populations, suggesting higher susceptibility of N. kessleri to these parasites. Non-native populations of both hosts showed higher infra-community richness as a result of acquiring parasites native to the new area, but lower parasite abundance. Differences in success of the introduction and establishment in new areas between the two fish species may be associated with a relatively low parasite infection rate and a higher gonadosomatic index in non-native populations of N. melanostomus in comparison to N. kessleri.     

Some remarks on parasitic infections of the invasive Neogobius spp. (Pisces) in the Hungarian reaches of the Danube River, with a description of Goussia szekelyi sp. n. (Apicomplexa: Eimeriidae)

During a survey of the parasite fauna Neogobius spp., which only recently invaded Hungarian reaches of the Danube River upstream from Budapest, it was found that Neogobius melanostomus and N. fluviatilis had become common species. Neogobius kessleri was less frequent and the previously widespread Proterorhinus marmoratus was drastically reduced. The parasite fauna of the newcomer fish species was characterized by ubiquitous parasites of a wide host range, such as the trematode Nicolla skrjabini, the metacercariae of Metagonimus yokogawai and Apatemon cobitidis, the larval stages of the acanthocephalan Pomphorhynchus laevis and the nematode Rhaphidascaris acus, the glochidia of an Anodonta sp. (Mollusca) and the ciliophoran Ichthyophthirius multifiliis. The specific parasites of Neogobius spp. were represented by three intestinal coccidia: Eimeria daviesae, Goussia kessleri, and a new species described here as Goussia szekelyi sp. n. This survey showed that the rapid invasion of Ponto‐Caspian gobies in the northern Danube caused important changes in the fish fauna composition of the Danube River and enriched the parasite fauna of Hungarian fishes.     

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

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.     

Length‐weight and length‐length relationships of four Alosa species along the southern Caspian Sea coast

This study investigates length‐weight and length‐length relationships of four shad species (Alosa braschnikowi, Alosa caspia, Alosa kessleri, and Alosa saposchnikowii) captured on the southern Caspian Sea coast of Iran. The relationship of total length (TL), fork length (FL) and standard length (SL) and the relationship between total length and body weight are presented.     

New records of endoparasitic helminths in alien invasive fishes from the Carpathian region

Six non-native invasive fish species from the Slovak part of the Tisa River basin, namely Carassius gibelio, Pseudorasbora parva, Ameiurus melas, A. nebulosus, Lepomis gibbosus, Perccottus glenii, and three gobiid species from the Danube River, namely Neogobius melanostomus, N. fluviatilis and N. kessleri, were investigated for endohelminth parasites. The expanding Asian cestode Nippotaenia mogurndae (syn. Amurotaenia perccotti) (Nippotaeniidea) has been introduced to Europe with its invasive host P. glenii. Pumpkinseed, Lepomis gibbosus, is a new definitive host of Proteocephalus percae and it is reported as the second intermediate host of the bothriocephalidean cestode Triaenophorus nodulosus in Slovakia.     

Discrimination between invasive Ponto‐Caspian gobies using a PCR‐RFLP method

Accurate identification of invaders, and especially their juveniles and eggs, is a difficult task if several morphologically similar species co‐occur. The aim of the study was to develop and test a rapid and cost‐effective procedure for identification of five species of invasive gobies occurring in the middle Danube basin, namely round goby Neogobius melanostomus, bighead goby Ponticola kessleri, monkey goby Neogobius fluviatilis, racer goby Babka gymnotrachelus and tubenose goby Proterorhinus semilunaris. First, a 708 bp fragment of the cytochrome oxidase I gene was amplified and sequenced for representative samples of these five species. Appropriate sequences of the five species available in public databases were used for in silico analysis. A digestion of the amplified fragment with the BfaI enzyme was found to be suitable for the species identification, as it showed unique restriction patterns for each species. The technique was also successfully applied for fish remains from burbot Lota lota stomachs. Thus the technique could be a useful tool in monitoring biological invasions, especially by identifying specimens that could not be determined on the basis of morphological features. The results demonstrate that the PCR‐RFLP method may in some cases be more reliable for species identification than a standard DNA sequencing.     

FERRIC CHELATE REDUCTASE ACTIVITY AS AFFECTED BY THE IRON‐LIMITED GROWTH RATE IN FOUR SPECIES OF UNICELLULAR GREEN ALGAE (CHLOROPHYTA)1

Four species of green algae (Chlorella kessleri Fott et Nováková, Chlorococcum macrostigmatum Starr, Haematococcus lacustris[Girod‐Chantrans] Rostaf., Stichococcus bacillaris Näg.) were grown in iron‐limited chemostats and under phosphate limitation and iron (nutrient) sufficiency. For all four species, steady‐state culture density declined with decreasing degree of iron limitation (increasing iron‐limited growth rate), whereas chl per cell or biovolume increased. Plasma membrane ferric chelate reductase activity was enhanced by iron limitation in all species and suppressed by phosphate limitation and iron sufficiency. These results confirm previous work that C. kessleri uses a reductive mechanism of iron acquisition and also suggest that the other three species use the same mechanism. Although imposition of iron limitation led to enhanced activities of ferric chelate reductase in all species, the relationship between ferric chelate reductase activity and degree of iron limitation varied. Ferric chelate reductase activity in C. macrostigmatum and S. bacillaris was an inverse function of the degree of iron limitation, with the most rapidly growing iron‐limited cells exhibiting the highest ferric chelate reductase activity. In contrast, ferric chelate reductase activity was only weakly affected by the degree of iron limitation in C. kessleri and H. lacustris. Calculation of ferric reductase activity per unit chl allowed a clear differentiation between iron‐limited and iron‐sufficient cells. The possible extension of the ferric chelate reductase assay to investigate the absence or presence of iron limitation in natural waters may be feasible, but it is unlikely that the assay could be used to estimate the degree of iron limitation.     

What can morphology tell us about ecology of four invasive goby species?

This study presents a detailed comparative analysis of external morphology of four of the most invasive goby species in Europe (round goby Neogobius melanostomus, bighead goby Ponticola kessleri, monkey goby Neogobius fluviatilis and racer goby Ponticola gymnotrachelus) and interprets some ecological requirements of these species based on their morphological attributes. The results are evaluated within an ontogenetic context, and the morphological differences between the species are discussed in terms of the question: can special external shape adaptations help to assess the invasive potential of each species? The morphometric analyses demonstrate important differences between the four invasive gobies. Neogobius melanostomus appears to have the least specialized external morphology that may favour its invasive success: little specialization to habitat or diet means reduced restraints on overall ecological requirements. The other three species were found to possess some morphological specializations (P. kessleri to large prey, N. fluviatilis to sandy habitats and P. gymnotrachelus to macrophytes), but none of these gobies have managed to colonize such large areas or to reach such overall abundances as N. melanostomus.     

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

The distributions of invasive Neogobius species were investigated 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 Gab?íkovo dam, backwaters and the lower‐most sections of the tributaries Malý Dunaj, Hron, Váh 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.     

Isolation and characterization of microsatellites in Leuciscus cephalus (Cypriniformes,Cyprinidae) and cross‐species amplification within the family Cyprinidae

Thirteen polymorphic microsatellites were isolated from Leuciscus cephalus, a widespread cyprinid species with great ecological tolerance. Together with the cross‐species amplification of six additional loci originally published for three cyprinid fish species, we optimized a multiplex panel for L. cephalus allowing the genotyping of 19 polymorphic loci. Number of alleles and heterozygosity per locus in a sample of 20 fish individuals ranged from two to 16 and from 0.05 to 0.90, respectively. These primers will be useful in determining the population structure of L. cephalus. In addition, successful cross‐amplification was obtained for several species of Cyprinidae.     

Daphnia Pre‐Exposed to Toxic Microcystis Exhibit Feeding Selectivity

In this study, short term feeding experiments were used to determine if Daphnia, pre‐exposed to cyanobacteria, could avoid cyanobacteria through feeding selectively. The results show that Daphnia ambigua were capable of altering the proportion of a single – celled cyanobacterium (Microcystis aeruginosa) to a chlorophyte (Chlorella kessleri) of similar size and shape. Also, D. ambigua pre‐exposed for eight weeks to a toxic strain of M. aeruginosa were more successful at avoiding this strain than D. ambigua pre‐exposed to C. kessleri or to a non‐toxic strain of M. aeruginosa. These experimental results suggest that further investigations of Daphnia 's ability to influence the dominance of cyanobacterial strains in lakes are warranted. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of Nile perch, Lates niloticus, on functional and specific fish diversity in Uganda's Lake Kyoga system

The introduction of Nile perch, Lates niloticus, to Lake Victoria, East Africa, interacted with eutrophication to cause a reorganization of the lake's food web and the extirpation of many endemic fishes. The Lake Kyoga satellite system lies downstream from Lake Victoria. It encompasses species‐rich lakes where Nile perch are absent or very rare, and low diversity lakes where L. niloticus is abundant. In 1999 we surveyed seven lakes in the Kyoga system using experimental monofilament gill nets (1/4–1 inches variable mesh). At Boston University we assessed δ¹⁵N signatures of epaxial muscle from subsamples of the catch (n = 361). These signatures are often highly correlated with the near‐term mean realized trophic position of an individual organism. A neural network analysis of fish length, species name, trophic level, and lake of origin fish explained 94% of the sample variance in δ¹⁵N. We analysed statistical patterns in these signatures at a number of spatial scales. The relationship between trophic level and δ¹⁵N varied greatly among lakes. Higher diversity perch‐free lakes had greater variance in δ¹⁵N values and fish lengths than lower diversity Nile perch lakes, suggesting an important relationship between species diversity and functional diversity. Against expectations, lake size was negatively correlated with δ¹⁵N. Patterns in stable isotope signatures indicated that Nile perch lakes have shorter food chains than perch‐free lakes. The results throw up two management problems for the Kyoga system. Impacted lakes need to be studied to understand and ameliorate the community‐level effects of Nile perch introduction, whereas the species‐rich nonperch lakes, which harbour a large proportion of the remaining diversity of regionally endemic taxa, are in need of conservation planning.     

Distribution,abundance and condition of invasive Ponto‐Caspian gobies Ponticola kessleri (Günther, 1861), Neogobius fluviatilis (Pallas, 1814), and Neogobius melanostomus (Pallas, 1814) in the Sava River basin,Croatia

Distributions, population densities, invasive potentials and adverse impacts of invasive Ponto‐Caspian gobies on native fauna in the Sava River basin remain unknown, whereby 23 locations in the Sava basin were sampled during a three‐year period (2011–2013). Among the five Ponto‐Caspian goby species previously reported in Croatia, only Neogobius fluviatilis (291), Neogobius melanostomus (177) and Ponticola kessleri (21) specimens were collected. Proterorhinus semilunaris and Babka gymnotrachelus were not found. N. fluviatilis was dominant among the invasive gobies at the majority of locations and almost omnipresent (apart from the upper Sava reaches) in the Sava basin. N. melanostomus was found only in the navigable Sava reaches, but its distribution range still seems to be expanding. The status of P. kessleri invasion remains unclear, as it was only found in 2011 at three locations in the lower Sava reaches. No significant (P > 0.05) increase in average catch‐per‐unit‐effort (CPUE) values was observed during the three‐year period. There is some evidence that a decline in Gobio gobio populations might be expected in response to increasing N. fluviatilis population densities. The findings suggest that further range expansions by the Ponto‐Caspian gobies can be expected in Croatia and the implementation of measures to limit their spreading should be considered.     

Fatty acid analysis as a chemotaxonomic tool for taxonomic and epidemiological characterization of four fish pathogenic Tenacibaculum species

Aims: In this work, fatty acid content and profiles were analysed in order to differentiate the species Tenacibaculum maritimum, Tenacibaculum gallaicum, Tenacibaculum discolor and Tenacibaculum ovolyticum that are pathogenic for cultured marine fish and to assess the potential of fatty acid profiles as a tool for epizootiological typing. Methods and Results: The fatty acid methylesters (FAMEs) were extracted from cells grown on marine agar for 48 h at 25°C and were prepared and analysed according to the standard protocol of the MIDI/Hewlett Packard Microbial Identification System. The cellular fatty acid profiles of Tenacibaculum strains tested were characterized by the presence of large amounts of branched (36·1–40·2%) and hydroxylated (29·6–31·7%) fatty acids. The FAME products from the four species significantly (P < 0·05) differed in the content of iso‐C_15:03‐OH, iso‐C_16:03‐OH, iso‐C_15:1G, summed feature 3 (a component that contains C_16:1ω7c and/or iso‐C_15:0 2‐OH), iso‐C_16:0, C_17:1ω6c, C_15:03‐OH, iso‐C_17:03‐OH. Conclusions: Results of present study demonstrated the existence of differences in the fatty acids content between the T. maritimum isolates from different marine fish/geographical origin and between strains of T. maritimum, T. discolor, T. gallaicum and T. ovolyticum. Significance and Impact of the Study: Profiling of fatty acids may be a useful tool to distinguish T. maritimum from other Tenacibaculum species pathogenic for fish as well as for epizootiological differentiation of T. maritimum isolates.     

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.     

Annual trend of fish assemblages associated with FADs in the southern Tyrrhenian Sea

A study on fish assemblage associated with fish aggregating devices (FADs) in Sicily was carried out between January 2000 and January 2001. With a fortnightly periodicity, 156 experimental hauls were carried out by means of a purse seine in a FAD‐containing marine section banned to commercial fishing. A total of 14 229 fish specimens belonging to six families and 10 species was found. These species were Balistes carolinensis, Caranx crysos, Naucrates ductor, Seriola dumerili, Seriola fasciata, Tachurus picturatus, Coryphaena hippurus, Schedophilus ovalis, Thunnus thynnus, Polyprion americanus and showed all young‐of‐the‐year undergoing a rapid growth. The applied ordination technique highlighted the existence of four assemblage periods describing the annual trend. The results confirm that fish assemblages associated with FADs are related to season, following a fish colonization tied to natural recruitment. Comparison of the ecological indices across the four periods showed that the assemblages in the periods from summer to winter were more structured than those in spring. The quantity of individuals also showed a strong variation peaking in the summer period. The results of this study reveal that FADs represent a particular nursery area for the associated species that could influence their survival.     

Gross and fine anatomy of the respiratory vasculature of the mudskipper,Periophthalmodon schlosseri (Gobiidae: Oxudercinae)

To illustrate vascular modification accompanying transition from aquatic to amphibious life in gobies, we investigated the respiratory vasculatures of the gills and the bucco‐opercular cavities in one of the most terrestrially‐adapted mudskippers, Periophthalmodon schlosseri, using the corrosion casting technique. The vascular system of Pn. schlosseri retains the typical fish configuration with a serial connection of the gills and the systemic circuits, suggesting a lack of separation of O₂‐poor systemic venous blood and O₂‐rich effluent blood from the air‐breathing surfaces. The gills appear to play a limited role in gas exchange, as evidenced from the sparsely‐spaced short filaments and the modification of secondary lamellar vasculature into five to eight parallel channels that are larger than red blood cell size, unlike the extensive sinusoidal system seen in purely water‐breathing fishes. In contrast, the epithelia of the bucco‐opercular chamber, branchial arches, and leading edge of the filaments are extensively laden with capillaries having a short (<10 μm) diffusion distance, which strongly demonstrate the principal respiratory function of these surfaces. These capillaries form spiral coils of three to five turns as they approach the epithelial surface. The respiratory capillaries of the bucco‐opercular chamber are supplied by efferent blood from the gills and drained by the systemic venous pathway. We also compared the degree of capillarization in the bucco‐opercular epithelia of Pn. schlosseri with that of the three related intertidal‐burrowing gobies (aquatic, non‐air‐breathing Acanthogobius hasta; aquatic, facultative air‐breathing Odontamblyopus lacepedii; amphibious air‐breathing Periophthalmus modestus) through histological analysis. The comparison revealed a clear trend of wider distribution of denser capillary networks in these epithelia with increasing reliance on air breathing, consistent with the highest aerial respiratory capacity of Pn. schlosseri among the four species. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

The effect of stocking with 0+ year age‐class Atlantic salmon Salmo salar fry: a case study from the River Bush,Northern Ireland

An enhancement programme based on stocking 0+ year age‐class Atlantic salmon Salmo salar, conducted in the River Bush, Northern Ireland, U.K. over the period 1996–2005, was reviewed with reference to the performance and biological characteristics of wild fish. Wild ova to 0+ year fry (summer) survival was c. 8% with subsequent wild 0+ year fry‐to‐smolt survival c. 9%. Stocked unfed 0+ year juveniles gave c. 1% survival to smolt whilst fed 0+ year S. salar stocked in late summer exhibited survival at c. 5%. Stocking with unfed and fed fry contributed to increased smolt production and helped attain local management objectives between 2001 and 2005. Significant differences in biological characteristics were observed between wild and stocked‐origin fish. Wild‐smolt cohorts were dominated by 2+ year age‐class fish on the River Bush whilst smolts originating from fed fry mostly comprised younger 1+ year individuals. The mean mass of 1+ year smolts derived from stocked fed fry was significantly lower than that of wild 1+ year smolts, although these differences were not evident between older age classes. Differences in run timing between wild smolts and smolts derived from stocked fry were also apparent with the stocked‐origin fish tending to run earlier than wild fish. Although the stocking exercise was useful in terms of maximizing freshwater production, concerns over the quality of stocked‐origin recruits and the long term consequences for productivity are highlighted.     

Long‐distance dispersal and local retention of larvae as mechanisms of recruitment in an island population of a coral reef fish

Abstract Although recruitment of pelagic larvae is a fundamental and well‐documented process in the dynamics of benthic marine populations, identifying the sources of recruitment, or the degree to which populations are connected via dispersal of larvae, has remained elusive for most marine taxa. In this study we used natural environmental markers (trace elements) recorded in fish otoliths (ear stones) as tags of natal origin. Specifically, we used the otolith core and edge chemistries of a locally endemic wrasse (Coris bulbifrons) from Lord Howe Island (LHI), Australia, and a widely distributed species (Coris picta) from three potential mainland source regions, to determine the likely sources of recruitment to C. picta populations on LHI. The use of a local endemic species, which is by definition self‐recruiting, is a novel approach for ground‐truthing the dispersal history of non‐endemic coral reef fish. Discriminant function analyses were able to separate LHI from mainland fish, using both edge and core signatures, with a high degree of accuracy, suggesting at least some of the C. picta collected on LHI were of local origin. This result was corroborated when half of the C. bulbifrons and LHI C. picta were introduced as unknowns into a discriminant function analysis using the remaining C. bulbifrons, LHI C. picta, and the mainland C. picta as a training data set. Overall, our findings suggest that both long distance dispersal and local retention are important sources of recruitment to populations of C. picta on LHI and that otolith chemistry of endemic species could be a useful benchmark for determining the prevalence of self‐recruitment in insular populations of other widespread species.