Round Goby Research Articles

Reproductive biology of pioneer round gobies (Neogobius melanostomus Pallas, 1814) at the edge of their invasion front in three small rivers (Lower Danube Basin, Bulgaria)

Reproductive traits are among the most important biological characteristics that facilitate or impede the establishment of non-native fish into new environments. In several tributaries of the Lower River Danube (Bulgaria), the round goby (Neogobius melanostomus Pallas, 1814) is a recent invader. Specimens from the edge of the invasion front were collected monthly (March 2017 to May 2018) from each river. The pioneer individuals displayed relatively small body sizes. First maturation of females occurs at 49 mm total length. Based on the dynamics of oocyte size and GSI, it was established that spawning begins in early spring, at a relatively low water temperature (6-7 °C). The breeding season extended from March to June. Average absolute fecundity was 162 ± 62 oocytes, while average relative fecundity was 94 oocytes/g ± 24. Female fecundity is linearly dependent on the length and weight. Both of the known male alternative reproductive tactics were observed. Body condition factor was lowest during April for both sexes. The relationship between reproductive traits and invasive potential in N. melanostomus is discussed.

Ecological analysis of the fish cestode fauna of the mouth of Kura River

The research was conducted in 2014–2019 in the mouth of Kura River. A total of 334 fish specimens of 24 species were examined by the method of full parasitological dissection. As a result, 17 tapeworm species in two orders and eight families were found: Caryophyllaeus fimbriceps, C. laticeps, Caryophyllaeides fennica, Eubothrium acipenserinum, Bothriocephalus acheilognathi, Ligula colymbi, L. intestinalis, Bothriocephalus acheilognathi, Ligula colymbi, L. intestinalis, Proteocephalus filicollis, P. gobiorum, P. ocellata, P. osculatus, Siluritaenia siluri, Gryporhynchus pusillus, and Paradilepis scolecina. Of these, seven species are specific cyprinid parasites, two species are specific sturgeon parasites, two species are specific to sticklebacks, two species to catfish, and one species to gobies; the other three species parasitize in fishes of various families. The main organ of cestode localisation in the studied fishes is the intestinal lumen, where 11 worm species were found. In other fish organs (body cavity, mucous membrane of the anterior intestine, liver, mesentery, and intestinal walls), the number of tapeworm species ranged from one to four. One cestode species invaded from one to seven fish species. In the bream, we found six tapeworm species, while in the other fish species, from one to five. Among the cestodes found, 14 species infect zooplankton-eating fish and only three species (Caryophyllaeus fimbriceps, C. laticeps, Caryophyllaeides fennica) infect fish that feeds on benthic invertebrates. The largest trophic group was the benthophages; they hosted 12 cestode species. In the planktophages and predators, we found eight and seven tapeworm species, respectively. Predatory fishes like pike, asp, round and bighead gobies accumulate parasites from the bodies of their preys, consequently, their cestode fauna is the richest. Most recorded fishes are euryhaline. Nevertheless, due to the absence of typical marine forms among the found cestodes, we registered more tapeworm species in the fish occurring the highly desalinated area of the Kura mouth than in more mineralized water. Six recorded species (Caryophyllaeus fimbriceps, Bothriocephalus acheilognathi, Ligula colymbi, L. intestinalis, Digramma interrupta, and Paradilepis scolecina) are causative agents of fish diseases. Ligula colymbi and L. intestinalis, which have large plerocercoids, caused pathogenic changes in fish organisms. The other pathogenic species did not induce noticeable disorders. They are much smaller, and, thereto, had comparatively low invasion rate in the examined fish.

Comparison of Behavior and Space Use of the European Bullhead Cottus gobio and the Round Goby Neogobius melanostomus in a Simulated Natural Habitat.

Simple SummaryInvasive round goby and native European bullhead are bottom-dwelling species that occupy a similar niche and are expected to compete for similar resources. Knowledge of how species behave in novel conditions without competition has implications for how they will interact. Our objective was to investigate the space use, flow velocity preferences and tolerance, shelter use, feeding behavior, and activity patterns of specimens of both species to better understand their basic behavior characteristics. Space in a habitat simulator system was divided for purposes of analysis into seven zones among which fish could move freely. We observed individual fish during acclimatization periods and normal behavior periods of darkness and light. The results showed few differences between species. Round goby showed a preference for areas with slow running water, whereas the bullhead gravitated to higher velocity waters. The species exhibited similar patterns in time spent in zones in a given period, spending most of the time in the shelter and the mid-stream zone. Despite the low differences observed, we can conclude that the fish needed a long acclimatization period for behavior stabilization, which should be considered in future studies.The round goby is an invasive fish in Europe and North America that threatens native species by predation and competition. Its habitat preferences are similar to those of the European bullhead, which it displaces from shelters and out-competes for available resources. We assessed the microhabitat preferences, shelter use, and activity of the round goby and European bullhead in single-species experiments in habitat simulator systems to investigate their behavior in a novel environment. Fish were video-recorded for 28 h in the presence of shelter and feed with water velocity ranging from 0.00 to 0.96 m s−1. The two species showed similar behavior under given conditions. A primary difference was in stress-induced behavior in the initial phases of observation. The round goby spent more time in movement when outside the shelter and a longer time in the escape zone in the exploration period during light. Our results confirmed a significant preference of round goby for low velocity areas and a preference for higher velocities in the European bullhead. Both species were able to cope with velocities > 0.7 m s−1. Therefore, the reported invasion success of round goby is probably not driven by space use or activity patterns, but rather by higher adaptability.

Impacts of the invasive round goby (Neogobius melanostomus) on benthic invertebrate fauna: a case study from the Baltic Sea

The round goby (Neogobius melanostomus) was first observed in the Baltic Sea in 1990 and has since displayed substantial secondary dispersal, establishing numerous dense populations where they may outcompete native fish and negatively impact prey species. There have been multiple round goby diet studies from both the Baltic Sea and the North American Great Lakes where they are similarly invasive. However, studies that quantify their effects on recipient ecosystems and, specifically, their impacts on the benthic invertebrate macrofauna are rare, particularly from European waters. In this study, we conducted the first before-after study of the potential effects of round goby on benthic invertebrate macrofauna taxa in marine-brackish habitats in Europe, focusing of two sites in the Western Baltic Sea, Denmark. Results were in line with those from the Great Lakes, indicating negative impacts on specific molluscan taxa (e.g. Cardiidae bivalves and Neritidae gastropods, which both showed a fall in detected densities of approximately 98% within the Guldborgsund Strait). In contrast, many other groups appeared to be largely unaffected or even show positive trends following invasion. Round goby gut content data were available at one of our study sites from the period immediately after the invasion. These data confirmed that round goby had in fact been preying on the subset of taxa displaying negative trends.

The Invasive Round Goby Neogobius melanostomus as a Potential Threat to Native Crayfish Populations.

Simple SummaryNeogobius melanostomus is a highly invasive fish that has colonized most major European rivers and is dispersing into their tributaries. Its foraging behaviour does not show particular prey preferences, which makes predicting its interactions with endangered members of the macrozoobenthic community in tributaries a challenge. We observed the interaction of N. melanostomus and crayfish juvenile or A. aquaticus in single- and multiple-prey systems to better predict its ecological impact. The results suggest an impact of N. melanostomus on crayfish similar to that on A. aquaticus, potentially making it a threat to crayfish population stability. Destabilization of a keystone species such as crayfish in river tributaries may lead to a trophic cascade in the ecosystem with irreversible consequences.Despite the spread of round goby Neogobius melanostomus into freshwater streams, there is a lack of information with respect to its effect on macroinvertebrate communities, especially crustaceans. We studied foraging efficiency of N. melanostomus on Procambarus virginalis and Asellus aquaticus, using a functional response (FR) approach. Stocking density of the prey species was manipulated to determine its effect on consumer utilization, with prey offered separately or combined at 1:1, 3:1, and 1:3 at each tested density. For both prey species, N. melanostomus exhibited type II FR, occasionally with a high proportion of non-consumptive mortality. Procambarus virginalis suffered a significantly higher attack rate compared to A. aquaticus. Neogobius melanostomus killed significantly more of the most prevalent prey, regardless of species. In trials with prey species of equal proportions, a difference in the number of each species killed was observed only at the highest density, at which P. virginalis was preferred. Neogobius melanostomus may be an important driver of population dynamics of prey species in the wild. The non-selective prey consumption makes N. melanostomus a potential threat to macrozoobenthic communities of river tributaries.

Characteristics of sagittae morphology in seven goby species from the Caspian Sea

In this study the sagitta morphology of seven species of Gobiidae including three species of the genera Neogobius and four Ponticola , inhabiting the southern part of the Caspian Sea was described and analysed. The goal was to investigate the usefulness and efficiency of sagitta for species identification. The morphological analysis was based on four shape indices, roundness (4S/πOL 2 ), rectangularity (S/OL×OW), ellipticity (OL-OW/OL+OW), and aspect ratio (OL/OW). The results indicated that otolith morphology and morphometry can be used as diagnostic characters distinguishing the Caspian Sea gobies. While the overall shape of otoliths differentiated the genera, the differences in the shape of the dorsal rim and development of posterior dorsal and anterior ventral lobes were particularly important for inter-specific distinction. The discriminant analysis could separate the specimens of genus Ponticola and Neogobius with 61% and 82% classification successes, respectively, proves that otolith shape indices were a more efficient tool for discrimination of otoliths in Neogobius than Ponticola species. Cluster analysis based on otoliths shape indices showed two main clusters, one cluster contains Neogobius species with higher roundness values, possessed more rounded shaped otoliths and the other includes Ponticola species with spindle and elongated shaped otoliths, except P. bathybius , recognized P. bathybius and Neogobius melanostomus as more similar taxa. These results were consistent with the phylogeny of these species proposed by recent molecular studies and indicated that otolith characteristics are partly genetically encoded and therefore have phylogenetic signals. The current research revealed a high degree of morphological variability of otolith shape in different species and confirmed its usefulness in Gobiidae taxonomy and phylogeny.

2D vs. 3D Numerical Approaches for Fish Habitat Evaluation of a Large River — Is 2D Modeling Sufficient?

Computational Fluid Dynamics is an effective tool for assessing non-present conditions, thus also in habitat evaluation within ecohydraulics. Deciding whether to apply a one-, two- or three-dimensional numerical approach, is an optimization that needs to be performed by every task, given the capability and the demands of specific approaches. In this paper we compare the utility of two-dimensional (2D) versus three-dimensional (3D) hydrodynamical simulations for ecohydraulic purposes. The basis of the comparation were 1) three simulated abiotic variables: water depth, depth averaged flow velocity and bed material composition, and 2) an overall performance in a meso-scale fish habitat evaluation, based on the simulated three variables. The biotic parameters for the models were the habitat suitability curves of three fish species, the Danube streber (Zingel streber), the round goby (Neogobius melanostomus) and the white bream (Blicca bjoerkna). We found that in terms of ecohydraulic utilization, the 2D approach performed sufficiently to simulate the hydrodynamics of a large river. The errors originating from the 3D-2D simplification yielded negligible differences in habitat evaluation, and the agreement in the habitat suitability indices calculated from the simulated metrics was satisfactory. Henceforth, the theory was turned into an application as we performed habitat mapping on a 100 km long, Hungarian reach of the Danube River, with the abiotic parameters resulting from a 2D hydrodynamical simulation. The possibility of simplifying the approach from 3D to 2D provides a cost-efficient numerical tool at larger scales for ecohydraulic studies, and especially for evaluating habitat suitability of riverine fish.

Ecological responses to elevated water temperatures across invasive populations of the round goby (Neogobius melanostomus) in the Great Lakes basin

Climate warming is expected to alter the distribution, abundance, and impact of non-native species in aquatic ecosystems. In laboratory experiments, we measured the maximum feeding rate and critical thermal maximum (CTmax) of an invasive Eurasian fish, the round goby (Neogobius melanostomus), acclimated to a range of temperatures (18–28 °C) reflecting current and projected future thermal conditions for the nearshore Great Lakes. Fish were collected from four distinct populations along a latitudinal gradient from the western basin of Lake Erie to Hamilton Harbour (Lake Ontario) and the upper St. Lawrence River. Thermal tolerance increased with acclimation temperature for populations in Lakes Erie and Ontario. However, the St. Lawrence River populations had lower acclimation capacity and exhibited an unexpected decline in CTmax at the highest acclimation temperature. Maximum feeding rates peaked at 18–24 °C and declined with temperatures above 24 °C. Northern populations in the basin appear poorly adapted to elevated temperatures such that their performance and impact could be reduced by climate warming. Thermal response data from latitudinally distributed populations are needed to inform invasive species risk assessment.

Investigation of Some Morphometric Characteristics of Neogobius melanostomus (Pallas, 1814) from Coast of Ordu (Eastern Black Sea)

Vücut şekli, morfometrik ölçümler ve meristik sayımlar gibi morfolojik karakterler, balık stoklarının tanımlamasında uzun süredir kullanılmaktadır. Kum kaya balığı (Neogobius melanostomus) Gobiidae familyasına ait olup Avrasya'ya özgü bentik, örihalin ve istilacı bir türdür. İstila ettiği bölgelerde yerli balık türleri üzerinde zararlı etkileri olup Avrupa'nın en zararlı 100 istilacı türü listesine dahil edilmiştir. Bu çalışmada Ordu ili kıyılarında (Doğu Karadeniz) yayılım gösteren N. melanostomus türünün bazı morfometrik karakterlerinin ve bunların birbirleriyle olan ilişkilerinin belirlenmesi amaçlanmış olup çalışma sahası içerisinde türün morfometrik karakterizasyonu üzerine araştırmaya rastlanmamıştır. Bireylerde 16 adet farklı konumdan 0,001 cm hassasiyette kumpas ile morfometrik karakter ölçümü yapılmıştır. İstatistiksel analizler için tüm morfometrik karakterlerin tam boya yüzdesel oranı (%TB) kullanılmıştır. İncelenen örnekler üç uzunluk grubuna ayrılmıştır; grup I (10-14,9 cm; 18 örnek), grup II (15-19,9 cm; 26 örnek) ve grup III (20-24,9 cm; 17 örnek). Varyans katsayıları incelendiğinde; DY1 taban uzunluğu (D1T) en değişken karakter, göz çapı (GÇ) ise en az değişken karakter olarak belirlenmiştir. Farklı boy gruplarına ait POU, PA, BD2, D1T, D2T, PU, MxVY ve KSY morfometrik karakteristiklerin tam boya oranları (%TB) üzerinde istatistiksel açıdan anlamlı etki görülmüştür (P<0,05). Doğrusal regresyon değerleri arasında tam boyla en yakın ilişkili olan morfometrik karakter standart boy (r=0,998), en zayıf ilişki olan morfometrik karakter ise preorbital mesafe (r=0,830) olarak belirlenmiştir.

Ancestral Sperm Ecotypes Reveal Multiple Invasions of a Non-Native Fish in Northern Europe.

For externally fertilising organisms in the aquatic environment, the abiotic fertilisation medium can be a strong selecting force. Among bony fishes, sperm are adapted to function in a narrow salinity range. A notable exception is the family Gobiidae, where several species reproduce across a wide salinity range. The family also contains several wide-spread invasive species. To better understand how these fishes tolerate such varying conditions, we measured sperm performance in relation to salinity from a freshwater and a brackish population within their ancestral Ponto-Caspian region of the round goby, Neogobius melanostomus. These two ancestral populations were then compared to nine additional invaded sites across northern Europe, both in terms of their sperm traits and by using genomic SNP markers. Our results show clear patterns of ancestral adaptations to freshwater and brackish salinities in their sperm performance. Population genomic analyses show that the ancestral ecotypes have generally established themselves in environments that fit their sperm adaptations. Sites close to ports with intense shipping show that both outbreeding and admixture can affect the sperm performance of a population in a given salinity. Rapid adaptation to local conditions is also supported at some sites. Historical and contemporary evolution in the traits of the round goby sperm cells is tightly linked to the population and seascape genomics as well as biogeographic processes in these invasive fishes. Since the risk of a population establishing in an area is related to the genotype by environment match, port connectivity and the ancestry of the round goby population can likely be useful for predicting the species spread.

Chironomid diversity in the diets of Ponto-Caspian gobiids in a freshwater habitat: Implications for resource partitioning

Chironomid taxa in the diets of six co-occurring gobiids (Caucasian dwarf goby Knipowitschia caucasica; monkey goby, Neogobius fluviatilis; racer goby, Babka gymnotrachelus; round goby, Neogobius melanostomus; bighead goby, Ponticola kessleri; and western tubenose goby, Proterorhinus semilunaris) were investigated in a freshwater habitat in Ukraine. Overall, 32 chironomid morphotypes were identified, among which the most abundant were Polypedilum convictum, Cricotopus sylvestris, Glyptotendipes spp., and Endochironomus albipennis. The racer and monkey gobies were characterized by the highest diversity of chironomid morphotypes in their diets, while the bighead goby by the lowest diversity. Highest similarities of chironomid assemblages in gut contents were observed among the monkey, racer, and round gobies as well as between the bighead and tubenose gobies, while the lowest similarity was observed between the monkey goby and Caucasian dwarf, tubenose, and bighead gobies. Mean sizes of chironomids in the gut contents of different gobiids varied; Caucasian dwarf and tubenose gobies consumed significantly smaller chironomids. Diversity of chironomid taxa in the diets of gobies depended on the type of each fishes’ habitat. Tubenose and bighead gobies preyed mainly on phytophilous chironomids; the monkey and round gobies preferred bottom-dwelling, burrowing chironomids; while Caucasian dwarf and racer gobies consumed both phytophilous and bottom-dwelling, burrowing taxa.

Incorporation of non-native species in the diets of cisco (Coregonus artedi) from eastern Lake Ontario

Cisco Coregonus artedi was once an important native fish in Lake Ontario; however, after multiple population crashes, the cisco stock has yet to recover to historic abundances. Rehabilitation of cisco in Lake Ontario is a fish community management objective, but the extent to which recent non-native species and pelagic food web changes have influenced cisco is not well understood. We described cisco diets in contemporary Lake Ontario following the addition and spread of non-native zooplankton species. We collected 618 cisco and processed 178 for full diet analysis in eastern Lake Ontario using mid-water trawls and bottom-set gill nets from 2016 to 2020. We found that Lake Ontario cisco were mostly zooplanktivorous, and non-native zooplankton dominated their diet during July and September. Cisco smaller than 300 mm had a more diverse diet including both native and non-native zooplankton, while cisco larger than 300 mm fed almost exclusively on non-native predatory cladocerans Bythotrephes longimanus and Cercopagis pengoi (98.9% consumed prey dry mass). We also found fish eggs, presumed to be of coregonine origin in 75% of non-empty December-collected cisco diets, suggesting eggs subsidize cisco diets when available. Juvenile round goby Neogobius melanostomus, alewife Alosa pseudoharengus and rainbow smelt Osmerus mordax were found in 2% of all analyzed non-empty stomachs. Lake Ontario cisco diet appears to be more similar to zooplanktivorous Lake Superior cisco than Lake Michigan where piscivory is prevalent. Lake Ontario cisco diets reflected zooplankton community changes indicating that non-native predatory cladocerans are now an important energy source supporting this native species.

Ихтиофауна прибрежной зоны Чёрного моря в районе бухты Ласпинская (Крым)

В настоящее время в Чёрном море протекают процессы осолонения и изменения среднегодовой температуры, которые уже обусловили естественное расселение различных представителей фауны Средиземноморского бассейна и Индийского океана и привели к изменению видового состава и структуры сообществ рыб, населяющих прибрежную зону Крымского полуострова. Вследствие этого возникла необходимость в изучении современного состава ихтиофауны и в оценке показателей её видового богатства и разнообразия. Бухта Ласпинская выбрана в качестве модельного полигона на основании следующих причин: относительно невысокий уровень антропогенной нагрузки; принадлежность части её акватории к особо охраняемым природным территориям и отсутствие рыбопромысловой деятельности прибрежными ставными орудиями лова; постоянный свободный заход пелагических видов рыб; наличие разнообразных биотопов; плавный переход глубин. Вышеперечисленные особенности бухты позволяют оценить наличие рыб разных экологических групп и обеспечивают условия для проведения мониторинга. Исследование выполняли в весенне-осенние периоды 1990–1994 и 2017–2018 гг. Материал собирали сетными орудиями лова, крючковыми снастями и ловушками. Постановку сетей проводили на разных глубинах перпендикулярно и параллельно берегу в дневное (10:00–18:00) и ночное (18:00–06:00) время. Также осуществляли визуальные наблюдения. Всего зарегистрировано 70 видов рыб. Из них 14 ранее не были отмечены в данном районе; пять из них [сальпа Sarpa salpa (Linnaeus, 1758), красноротый бычок Gobius cruentatus Gmelin, 1789, лысун Бата Pomatoschistus bathi Miller, 1982, зелёная морская собачка Parablennius incognitus (Bath, 1968) и четырёхполосый хромогобиус Chromogobius quadrivittatus (Steindachner, 1863)] являются недавними вселенцами, активно распространяющимися в Чёрном море только на протяжении последних 15–20 лет. Бόльшая часть проанализированных видов (64) — морские эвригалинные рыбы. Солоноватоводная группа представлена тремя аборигенными для Чёрного моря видами — бычком-рыжиком Ponticola eurycephalus (Kessler, 1874), бычком-кругляком Neogobius melanostomus (Pallas, 1814) и бычком-мартовиком Mesogobius batrachocephalus (Pallas, 1814). Среди проходных рыб зарегистрированы севрюга Acipenser stellatus Pallas, 1771 и два вида семейства сельдевых — черноморский пузанок Alosa tanaica (Grimm, 1901) и сельдь черноморско-азовская проходная Alosa immaculata Bennett, 1835. Установлено, что сезонная динамика видового разнообразия рыб изучаемой акватории связана с изменением численности локальных скоплений ставриды Trachurus mediterraneus (Steindachner, 1868). В апреле — мае, во время подхода данного вида на мелководье для нагула и размножения, индексы имеют наименьшие значения; в августе, когда численность ставрид уменьшается, отмечены максимальные значения.

Age, Growth and Reproduction of Neogobius melanostomus (Pallas 1814) (Perciformes: Gobiidae) in the Southern Black Sea

Round goby (Neogobius melanostomus, Pallas 1814) which belongs to Gobiidae, inhabits in the Black Sea, the Marmara Sea, the Caspian Sea and the rivers that flows into fore stated seas. The main population parameters, such as age, length, sexual composition, length-weight relationship, growth, condition factor, gonadosomatic index and reproduction of N. melanostomus were investigated from coasts of the southern Black Sea in this study. A total of 2408 individuals were sampled between July 2017 and June 2018. Results showed that average length and weight were found 14.97 cm (10.50-26.20) and 43.90 g (15.28-212.2), respectively. Sex ratio between female and male was found 1:1.77 (P>0.05). Age of samples varied between one and eight years old. The von Bertalanffy growth parameters were calculated as L∞ = 26.5 cm, k = 0.1980 year-1 and t0 = -1.3487 year for all individuals. The length-weight relationship was found as W = 0.0069 TL3.1972 for all individuals. Total mortality, natural mortality, fishing mortality, growth performance index and condition factor were calculated as 0.625, 0.479, 0.145, 2.143, and 1.66, respectively. Spawning occurs between March and May and the maximum value of gonadosomatic index reached in April. Average relative fecundity was 318.88 number/g (124.8-958.9), while average diameter of eggs was found 2025.58 µm ± 262.86 (1112.0-2703.4). This study will contribute for information gap on the species as well as provide information source for future studies.

Fish as a winter reservoir for Vibrio spp. in the southern Baltic Sea coast

Vibrio spp. are ubiquitous in aquatic environments. In temperate regions, including the Baltic Sea, these bacteria, which include facultative pathogenic species, proliferate during warm water periods and may thus pose a risk to human health. However, while present at relatively high abundances in the summer months, Vibrio spp. are rarely detected during cold water periods. Several potential winter reservoirs, such as fish and sediment, have been discussed, but the seeding sources that give rise to Vibrio during the summer months are unknown. In this study, we employed a combination of cultivation-independent genus-specific digital droplet PCR, Illumina 16S rRNA gene sequencing, culture-dependent determinations of colony-forming units (CFU) and genus-specific strain isolation to identify possible winter reservoirs of Vibrio spp. Using these techniques, we demonstrate that in the southern Baltic Sea especially fish can serve as a winter reservoir for distinct Vibrio assemblages, including facultative pathogenic V. vulnificus . Particularly the invasive species round goby ( Neogobius melanostomus ), with its potential to appear in high individual densities, has the capacity to carry a comparable Vibrio spp. cell number like water and sediment, while only accounting for 1/1000 of the spatial share in the overall coastal environment. Thus, by providing a winter reservoir for distinct Vibrio communities, coastal fish and, especially areas in which round goby densities are high, may be hot spots of pathogenic Vibrio species. • Fish acts as Vibrio winter reservoir in the Baltic Sea. • Vibrio spp. often highest abundant in connection to invasive species round goby. • Quantitative Vibrio 16S rRNA gene ddPCR without Photobacterium falsification.

Impact of round goby on native invertebrate communities - An experimental field study

This experimental field study provides first insights into the impact of a widely spread non-native fish species, round goby Neogobius melanostomus (Pallas 1814), on the diversity of native epifaunal macroinvertebrate communities in the Baltic Sea. A cage experiment was conducted in a macrophyte habitat in the Åland islands located in the northern Baltic Sea. Round gobies (13.5 ± 0.8 cm) affected macroinvertebrate biodiversity from a taxonomic and a trait-based point of view. Specifically, round goby decreased overall abundance, biomass and taxon richness of epifaunal invertebrates. Additionally, taxonomic and trait-based composition were affected, as the gobies reduced abundances of common bivalve (Cerastoderma spp. and Mytilus sp.) and gastropod species (Hydrobia spp.), and thereby modified the relative trait composition of the invertebrate assemblages. Round gobies consumed mainly larger epifaunal individuals leading to an overall decrease in invertebrate body size. Such alterations in taxonomic and trait-based diversity and composition of invertebrate communities through round goby predation may have implications for native fish species and other trophic levels in the respective food webs through food competition and trophic cascades. Round gobies might therefore affect ecosystem processes in invaded areas, and thus influence ecosystem functioning and services.

Genetic Differentiation of the Round Goby (Neogobius melanostomus) from Certain Localities of the Black and Azov Sea Basin Using Microsatellite Loci

Genetic Differentiation of the Round Goby (Neogobius melanostomus) from Certain Localities of the Black and Azov Sea Basin Using Microsatellite Loci

Breathing space: deoxygenation of aquatic environments can drive differential ecological impacts across biological invasion stages

The influence of climate change on the ecological impacts of invasive alien species (IAS) remains understudied, with deoxygenation of aquatic environments often-overlooked as a consequence of climate change. Here, we therefore assessed how oxygen saturation affects the ecological impact of a predatory invasive fish, the Ponto-Caspian round goby (Neogobius melanostomus), relative to a co-occurring endangered European native analogue, the bullhead (Cottus gobio) experiencing decline in the presence of the IAS. In individual trials and mesocosms, we assessed the effect of high, medium and low (90%, 60% and 30%) oxygen saturation on: (1) functional responses (FRs) of the IAS and native, i.e. per capita feeding rates; (2) the impact on prey populations exerted; and (3) how combined impacts of both fishes change over invasion stages (Pre-invasion, Arrival, Replacement, Proliferation). Both species showed Type II potentially destabilising FRs, but at low oxygen saturation, the invader had a significantly higher feeding rate than the native. Relative Impact Potential, combining fish per capita effects and population abundances, revealed that low oxygen saturation exacerbates the high relative impact of the invader. The Relative Total Impact Potential (RTIP), modelling both consumer species’ impacts on prey populations in a system, was consistently higher at low oxygen saturation and especially high during invader Proliferation. In the mesocosm experiment, low oxygen lowered RTIP where both species were present, but again the IAS retained high relative impact during Replacement and Proliferation stages at low oxygen. We also found evidence of multiple predator effects, principally antagonism. We highlight the threat posed to native communities by IAS alongside climate-related stressors, but note that solutions may be available to remedy hypoxia and potentially mitigate impacts across invasion stages.

Diet, trophic position of upper St. Lawrence River round goby giants reveals greater dependence on dreissenids with increasing body size

Round gobies (Neogobius melanostomus) from the upper St. Lawrence River (USLR) have an abundance of some of the largest individuals recorded from the Great Lakes (>230-mm total-length). We found a distinct separation in diet and isotopic signatures (δ15N and δ13C) between round goby classified as small (≤130-mm; n = 63) and large (>130-mm total-length; n = 75) from USLR coastal bays. At small sizes, round gobies had variable diets indicative of generalist and opportunistic feeding on native and non-indigenous benthic prey. Between 100 and 130-mm total-length, signatures of assimilated carbon (δ13C) indicated a directed shift towards a dreissenid-centric diet and once larger than 130-mm total-length, round gobies appeared to feed proportionally more on dreissenid mussels. We also found that large round gobies fed proportionally more on Hydrobiidae than small round gobies. A weak negative relationship between δ15N (indicative of trophic position) and round gobies total length resulted where smaller round gobies had slightly higher δ15N values than larger conspecifics. Round gobies larger than 180-mm total-length were common in nearshore habitats (≤2-m) during the spring, and dreissenid mussels and Hydrobiidae were the most frequently encountered prey. Our results demonstrate elevated reliance on dreissenids as round goby increased body size, but the diversity of prey suggest more complex trophodynamic pathways associated with coastal bay habitats.

A fish tale: a century of museum specimens reveal increasing microplastic concentrations in freshwater fish.

Plastic is pervasive in modern economies and ecosystems. Freshwater fish ingest microplastics (i.e., particles <5mm), but no studies have examined historical patterns of their microplastic consumption. Measuring the patterns of microplastic pollution in the past is critical for predicting future trends and for understanding the relationship between plastics in fish and the environment. We measured microplastics in digestive tissues of specimens collected from the years 1900-2017 and preserved in museum collections. We collected new fish specimens in 2018, along with water and sediment samples. We selected four species: Micropterus salmoides (largemouth bass), Notropis stramineus (sand shiner), Ictalurus punctatus (channel catfish), and Neogobius melanostomus (round goby) because each was well represented in museum collections, are locally abundant, and collected from urban habitats. For each individual, we dissected the digestive tissue from esophagus to anus, subjected tissue to peroxide oxidation, examined particles under a dissecting microscope, and used Raman spectroscopy to characterize the particles' chemical composition. No microplastics were detected in any fish prior to 1950. From mid-century to 2018, microplastic concentrations showed a significant increase when data from all fish were considered together. All detected particles were fibers, and represented plastic polymers (e.g., polyester) along with mixtures of natural and synthetic textiles. For the specimens collected in 2018, microplastics in fish and sediment showed similar patterns across study sites, while water column microplastics showed no differences among locations. Overall, plastic pollution in common freshwater fish species is increasing and pervasive across individuals and species, and is likely related to changes in environmental concentrations. Museum specimens are an overlooked source for assessing historical patterns of microplastic pollution, and for predicting future trends in freshwater fish, thereby helping to sustain the health of commercial and recreational fisheries worldwide.