Has the invasive round goby caused new links in Baltic food webs?

The Ponto-Caspian round goby (Neogobius melanostomus, Pallas 1814) most probably was established in the Gulf of Gdańsk, Baltic Sea, in the late 1980’s and has since become one of the dominant species in the region. In this study we assess the role of round gobies as prey for two important fish species in the Gulf of Gdańsk, cod (Gadus morhua) and perch (Perca fluviatilis). We compared their present diet with stomach analyses from the area prior the round goby establishment, as well as with diet analysis from Baltic regions where round gobies are absent. There were large differences in the diet between cods from the Gulf of Gdańsk 2003–2006 compared to cods in earlier studies (1977–1981) from the Southern Baltic Sea. There were also large differences in cod and perch diets from areas with and without round goby. Presently, round goby constitutes the most important prey for medium sized cods in Gulf of Gdańsk, and perch from the same area almost exclusively feed on gobiids. Stomach analysis, trophic level estimates, and stable isotope analyses all indicated that cod and perch in Gulf of Gdańsk after the round goby establishment belonged to a similar trophic level. Beside round goby, no mussel feeding fish contributed much to the diet of cod or at all to the diet of perch. Thus, it is likely that round gobies constitute a new energetic pathway from mussels to top predators. However, due to the short time elapsed after round goby establishment, we can only speculate on the species future impacts on Baltic food webs.     

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 round goby (Neogobius melanostomus) in the Gulf of Gdańsk – a species introduction into the Baltic Sea

In recent years, information concerning the awareness of organisms accidentally introduced into the Baltic Sea has substantially improved. Non-indigenous Estuarine and Marine Organisms (NEMO's) are hazardous for the Baltic ecosystem. Currently, about one hundred species are identified as accidentally or intentionally introduced into the Baltic Sea. Ballast waters and escape from aquaculture are the most important invasion vectors. During the last decade, an invasion of the round goby (Neogobius melanostomus) – a Ponto-Caspian fish species has been observed in the Gulf of Gdańsk. The first record of this fish in the Baltic Sea is from 1990. Early detection of the invader enabled the study of population growth and changes in the area. The first years of invasion were characterized by low numbers of individuals and a limited distribution. Later, the round goby gradually colonized all shallow waters in the western part of the Gulf of Gdańsk. Initially the fish inhabited stony and rocky habitats, but later it also occupied sandy bottoms. The round goby is now the dominating fish species in most of the shallow waters of the Gulf of Gdańsk. Two main factors account for the successful invasion of this fish in the region: the state of ecosystem at the time of the invasion and the biological features of N. melanostomus. In the late 1980s, the shallow waters of the Gulf of Gdańsk were almost devoid of piscivorous fishes. Concurrently, bivalves (a preferred prey of the round goby) have increased. Important is also parental care of laid eggs and reproductive strategy. Population growth potential enables the colonization of nearby regions. The first round gobies in the Vistula Lagoon were collected in 1999 and colonization of other Baltic Sea areas is anticipated.     

Evidence for predatory control of the invasive round goby

We coupled bioenergetics modeling with bottom trawl survey results to evaluate the capacity of piscivorous fish in eastern Lake Erie to exert predatory control of the invading population of round goby Neogobius melanostomus. In the offshore (>20 m deep) waters of eastern Lake Erie, burbot Lota lota is a native top predator, feeding on a suite of prey fishes. The round goby invaded eastern Lake Erie during the late 1990s, and round goby population size increased dramatically during 1999–2004. According to annual bottom trawl survey results, round goby abundance in offshore waters peaked in 2004, but then declined during 2004–2008. Coincidentally, round goby became an important component of burbot diet beginning in 2003. Using bottom trawling and gill netting, we estimated adult burbot abundance and age structure in eastern Lake Erie during 2007. Diet composition and energy density of eastern Lake Erie burbot were also determined during 2007. This information, along with estimates of burbot growth, burbot mortality, burbot water temperature regime, and energy densities of prey fish from the literature, were incorporated into a bioenergetics model application to estimate annual consumption of round goby by the adult burbot population. Results indicated that the adult burbot population in eastern Lake Erie annually consumed 1,361 metric tons of round goby. Based on the results of bottom trawling, we estimated the biomass of yearling and older round goby in offshore waters eastern Lake Erie during 2007–2008 to be 2,232 metric tons. Thus, the adult burbot population was feeding on round goby at an annual rate equal to 61% of the estimated round goby standing stock. We concluded that the burbot population had high potential to exert predatory control on round goby in offshore waters of eastern Lake Erie.     

How old are you—Evaluation of age reading methods for the invasive round goby (Neogobius melanostomus,Pallas 1814)

In the Baltic, the first observation of the round goby (Neogobius melanostomus, Pallas 1814) was made in 1990. Within the past decade the species became invasive and spread rapidly throughout the Baltic Sea. Studies about the fishes potential impacts on resident species promote the need for an increasing knowledge of their basic stock structures such as growth rates, longevity and mortality, which all rely on accurate estimates of age. Former studies on the round goby have used several different age reading techniques. In this study, we compared three standard otolith preparation methods for ageing and present the best procedure for the invasive round goby. The results showed significant differences in age estimates of the same fish between the different preparation methods and between readers. The estimation of the first annulus, the first year, was the most problematic. The overall agreement was lowest when reading the whole otoliths while the best performance was achieved with sectioned and stained preparation method. Depending on method used the growth estimates also differed. The results question comparability between previous studies and highlight the importance of harmonised aging procedures for the round goby for obtaining correct estimates of population parameters such as growth rate, age at maturity, and longevity.     

The forgotten feeding ground: patterns in seasonal and depth-specific food intake of adult cod Gadus morhua in the western Baltic Sea

This study presents the diet composition of western Baltic cod Gadus morhua based on 3150 stomachs sampled year-round between 2016 and 2017 using angling, gillnetting and bottom trawling, which enhanced the spatio-temporal coverage of cod habitats. Cod diet composition in shallow areas (<20 m depth) was dominated by benthic invertebrate species, mainly the common shore crab Carcinus maneas. Compared to historic diet data from the 1960s and 1980s (limited to depth >20 m), the contribution of herring Clupea harengus decreased and round goby Neogobius melanostomus occurred as a new prey species. Statistical modelling revealed significant relationships between diet composition, catch depth, fish length and season. Generalized additive modelling identified a negative relationship between catch depth and stomach content weight, suggesting reduced food intake in winter when cod use deeper areas for spawning and during peak summer when cod tend to avoid high water temperatures. The results of this study highlight the importance of shallow coastal areas as major feeding habitats of adult cod in the western Baltic Sea, which were previously unknown because samples were restricted to deeper trawlable areas. The results strongly suggest that historic stomach analyses overestimated the role of forage fish and underestimated the role of invertebrate prey. Eventually, this study shows the importance of a comprehensive habitat coverage for unbiased stomach sampling programmes to provide a more reliable estimation of top predator diet, a key information for food web analyses and multispecies models.     

Long‐term impacts of invasive species on a native top predator in a large lake system

1. Declining abundances of forage fish and the introduction and establishment of non‐indigenous species have the potential to substantially alter resource and habitat exploitation by top predators in large lakes. 2. We measured stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) in field‐collected and archived samples of Lake Ontario lake trout (Salvelinus namaycush) and five species of prey fish and compared current trophic relationships of this top predator with historical samples. 3. Relationships between δ¹⁵N and lake trout age were temporally consistent throughout Lake Ontario and confirmed the role of lake trout as a top predator in this food web. However, δ¹³C values for age classes of lake trout collected in 2008 ranged from 1.0 to 3.9‰ higher than those reported for the population sampled in 1992. 4. Isotope mixing models predicted that these changes in resource assimilation were owing to the replacement of rainbow smelt (Osmerus mordax) by round goby (Neogobius melanostomus) in lake trout diet and increased reliance on carbon resources derived from nearshore production. This contrasts with the historical situation in Lake Ontario where δ¹³C values of the lake trout population were dominated by a reliance on offshore carbon production. 5. These results indicate a reduced capacity of the Lake Ontario offshore food web to support the energetic requirements of lake trout and that this top predator has become increasingly reliant on prey resources that are derived from nearshore carbon pathways.     

Fatty acids differentiate consumers despite variation within prey fatty acid profiles

相似文献   

Seasonal plasticity in telencephalon mass of a benthic fish

To gain a deeper understanding of how environmental conditions affect brain plasticity, brain size was explored across different seasons using the invasive round goby Neogobius melanostomus. The results show that N. melanostomus had heavier telencephalon in the spring compared to the autumn across the two years of study. Furthermore, fish in reproductive condition had heavier telencephala, indicating that tissue investment and brain plasticity may be related to reproductive needs in N. melanostomus.     

On the finding of round goby <Emphasis Type="Italic">Neogobius melanostomus</Emphasis> (Pallas) (Gobiidae) in the food of burbot <Emphasis Type="Italic">Lota lota</Emphasis> (L.) of the Rybinskoe water reservoir

The fish swallowed by the burbot caught with gill nets in the Volzhskii reach of the Rybinskoe water reservoir in 2007 are investigated. Based on the teretial body shape, the absence of a swim bladder, the presence of a pelvic disc, the dimensions of the skull, the body length, the body weight, and the age, the specimens found in the gut of the burbot are identified as round goby Neogobius melanostomus (Pallas). The round goby should be regarded as an adventive (invasive) species because it is not distributed in different biotopes of the Rybinskoe water reservoir.     

Personality-dependent inter- and intraspecific foraging competition in the invasive round goby,Neogobius melanostomus

This study examines the impact of boldness on foraging competition of the highly invasive round goby Neogobius melanostomus Pallas 1815. Individual risk tolerance, or boldness, was measured as the time to resume movement after a simulated predation strike. Fish that resumed movement faster were categorized as “bold,” fish that took more time to resume movement were categorized as “shy” and those that fell in between these two categories were determined to have “intermediate” boldness. Competitive impacts of boldness in N. melanostomus were determined in a laboratory foraging experiment in which interspecific (juvenile Atlantic cod Gadus morhua Linnaeus 1758) and intraspecific (intermediate N. melanostomus) individuals were exposed to either bold or shy N. melanostomus competitors. G. morhua consumed fewer prey when competing with bold N. melanostomus than when competing with shy N. melanostomus, whereas intermediately bold N. melanostomus foraging was not affected by competitor boldness. Bold and shy N. melanostomus consumed similar amounts of prey, and the number of interactions between paired fish did not vary depending on the personality of N. melanostomus individuals. Therefore, intraspecific foraging competition was not found to be personality dependent. This study provides evidence that individual differences in boldness can mediate competitive interactions in N. melanostomus; nonetheless, results also show that competition is also governed by other mechanisms that require further study.     

Ecological tracers reveal resource convergence among prey fish species in a large lake ecosystem

相似文献   

Diel interactions between prey behaviour and feeding in an invasive fish, the round goby, in a North American river

1. We studied the diet of the invasive round goby (Neogobius melanostomus) on a diel basis in the Flint River, a warmwater stream in Michigan, U.S.A. Diet and available prey samples were collected seven times over a 24 h period in four consecutive months. The section of river studied lacked zebra mussels (Dreissena polymorpha), the primary prey of adult round gobies elsewhere in the Great Lakes region. 2. Diet changed on a diel basis with hydropsychid caddisfly and chironomid larvae predominating during the day, chironomid pupae dominating in the evening and heptageniid mayflies dominating at night. Simultaneous study of macroinvertebrate drift suggested that caddisfly and chironomid larvae were most likely picked from submerged rocks, chironomid pupae were most likely taken during their emergent ascent and mayflies were either captured from the drift or picked from rocks. 3. The Flint River lacks a diverse darter (Family: Percidae) and sculpin (Family: Cottidae) fauna and it appears that the round goby has occupied a generalised darter/sculpin niche. Our results indicate that round gobies have the potential to invade successfully riverine systems, particularly those lacking a diverse benthic fish assemblage.     

Seasonal habitat use indicates that depth may mediate the potential for invasive round goby impacts in inland lakes

1. The round goby (Neogobius melanostomus) is among the fastest-spreading introduced aquatic species in North America and is radiating inland from the Great Lakes into freshwater ecosystems across the landscape. Predicting and managing the impacts of round gobies requires information on the factors influencing their distribution in habitats along the invasion front, yet this information is not available for many recently invaded ecosystems. We evaluated the seasonal habitat use and biomass of round gobies in an inland temperate lake to define the spatiotemporal scope of biological interactions at the leading edge of the round goby invasion.
2. Using novel statistical approaches, we combined hierarchical models that control for imperfect species detection with flexible smooth terms to describe non-linear relationships between round goby abundance and environmental gradients. Subsequently, we generated accurate detection-corrected estimates of the standing stock biomass of round gobies.
3. Our results show seasonally differentiated habitat niches, where suitable round goby habitat in summer months is restricted to shallow depths (<18.4 m) with a mixture of vegetative and mussel cover. We found high round goby biomass of 122 kg/ha in occupied habitats during the summer, with a total lake-wide biomass of 766,000 kg. In winter, round gobies migrate to deep offshore habitats and disperse, dramatically altering their scope for biological interactions with resident aquatic species across summer and winter seasons.
4. The results of this study indicate that the scope of biological interactions in inland lakes may be seasonally variable, with potential for high round goby biomass in shallow lakes or at the periphery of deep lakes in the summer months. Such shallow-water habitats may therefore present higher risk of ecological impacts from round gobies in invaded lentic ecosystems. As round gobies expand inland, consideration of seasonal habitat use will be an important factor in predicting the impacts of this pervasive invader.

     

No effect of round goby <Emphasis Type="Italic">Neogobius melanostomus</Emphasis> colonisation on young-of-the-year fish density or microhabitat use

The round goby Neogobius melanostomus has recently invaded several major freshwater systems in Europe and North America. Despite numerous studies predicting an impact on native fish assemblages, few have attempted to demonstrate it. In this case study, we monitored the effect of N. melanostomus colonisation on abundance and habitat utilisation of both young-of-the-year (YOY) native fish and YOY western tubenose goby Proterorhinus semilunaris in a typical, medium-sized European river. Colonisation by N. melanostomus had no apparent effect on either native fish abundance and species richness or P. semilunaris abundance. Moreover, after colonisation, both native fish and P. semilunaris occupied similar niches (i.e. microhabitats) to those occupied before colonisation. While niche use of YOY N. melanostomus and P. semilunaris overlapped significantly, YOY native fish utilised different habitats from the gobiids. We suggest that N. melanostomus did not compete for resources with YOY fish in our study area due to lack of niche overlap and/or surplus resources. As N. melanostomus rapidly dominated the fish assemblage at our site, we further suggest that utilisation of an empty niche, rather than competitive superiority, was the main factor facilitating its success.     

Spread of alien (non-indigenous) fish species <Emphasis Type="Italic">Neogobius melanostomus</Emphasis> in the Gulf of Gdansk (south Baltic)

The round goby (Neogobius melanostomus) was first noticed in the Gulf of Gdansk in 1990. This Ponto-Caspian fish was most likely introduced to the Baltic environment from ships ballast water. During the first years of invasion, slow population growth was observed in the initially colonized regions. From 1994, round goby gradually spread in all shallow water zones of the Gulf of Gdansk. The area occupied by the population and the number of fish grew rapidly. By the end of the nineties, round goby became a dominant fish in shallow waters of the western part of the Gulf of Gdansk, where the fish used all solid substrates on the bottom, including concrete piers, big stones or even dumped waste for spawning and refuge. The presence of round goby in the Vistula Lagoon and shallow waters near Rugia (Western Baltic) was noticed for the first time in 1999. The present state, size and condition of the round goby population in the Gulf of Gdansk led us to predict a continual spread of this species into new regions of the Baltic. In addition, the population of round goby is so large that the species has started playing a part in commercial fishing in the Gulf of Gdansk.     

Feeding behaviour of Black Sea bottom fishes: Did it change over time?

This study was designed to improve knowledge in feeding behaviour of the round goby (Apollonia melanostomus (Pallas, 1814)), the red mullet (Mullus barbatus ponticus Essipov, 1927), the whiting (Merlangius merlangus (Linnaeus, 1758)), the flounder (Platichthys flesus (Linnaeus, 1758)), the sole (Solea solea (Linnaeus, 1758)), the turbot (Psetta maeotica (Pallas, 1814)) and the starry sturgeon (Acipenser stellatus Pallas, 1771) from the north-western Black Sea. Gut content coupled with stable isotope analysis allowed describing food web variations according to species, in two seasons and at two areas located seawards the Danube River. Present results showed that most fishes have likely changed their feeding behaviour compared to past studies from the same area. Trophic niches were reduced and dietary overlap was common, as different fish species consumed the same dominant prey types. Fishes probably adapted their feeding behaviour to the increasingly low biodiversity of the Black Sea communities.     

Secondary invasion of the round goby into high diversity Great Lakes tributaries and species at risk hotspots: potential new concerns for endangered freshwater species

The round goby (Neogobius melanostomus) first invaded North America in 1990 when it was discovered in the St. Clair River. Despite more than 15 years of potential invasion, many Great Lakes’ lotic systems remained uninvaded. Recently, we captured the round goby from several Great Lakes tributaries known as species-at-risk hotspots. With a combination of field sampling of round gobies and literature review of the impact of round gobies on native taxa, we assess the potential impacts of the secondary invasion to native species using three mechanisms: competition; predation; and indirect impacts from the loss of obligate mussel hosts. We estimate that 89% (17/19) of benthic fishes and 17% (6/36) of mussels that occur in these systems are either known or suspected to be impacted by the secondary invasion of round goby. In particular, we note that the distribution of potential impacts of round goby invasion was largely associated with species with a conservation designation, including seven endangered species (1 fish, 6 mussels). As these recent captures of round goby represent novel occurrences in high diversity watersheds, understanding the potential impacts of secondary invasion to native biota is fundamental to prevent species declines and to allow early mitigation.     

Trends in body condition of native piscivores following invasion of Lakes Erie and Ontario by the round goby

相似文献   

Getting What Is Served? Feeding Ecology Influencing Parasite-Host Interactions in Invasive Round Goby Neogobius melanostomus

Freshwater ecosystems are increasingly impacted by alien invasive species which have the potential to alter various ecological interactions like predator-prey and host-parasite relationships. Here, we simultaneously examined predator-prey interactions and parasitization patterns of the highly invasive round goby (Neogobius melanostomus) in the rivers Rhine and Main in Germany. A total of 350 N. melanostomus were sampled between June and October 2011. Gut content analysis revealed a broad prey spectrum, partly reflecting temporal and local differences in prey availability. For the major food type (amphipods), species compositions were determined. Amphipod fauna consisted entirely of non-native species and was dominated by Dikerogammarus villosus in the Main and Echinogammarus trichiatus in the Rhine. However, the availability of amphipod species in the field did not reflect their relative abundance in gut contents of N. melanostomus. Only two metazoan parasites, the nematode Raphidascaris acus and the acanthocephalan Pomphorhynchus sp., were isolated from N. melanostomus in all months, whereas unionid glochidia were only detected in June and October in fish from the Main. To analyse infection pathways, we examined 17,356 amphipods and found Pomphorhynchus sp. larvae only in D. villosus in the river Rhine at a prevalence of 0.15%. Dikerogammarus villosus represented the most important amphipod prey for N. melanostomus in both rivers but parasite intensities differed between rivers, suggesting that final hosts (large predatory fishes) may influence host-parasite dynamics of N. melanostomus in its introduced range.