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Documentation of Freshwater Mussels (Unionidae) in the Diet of Round Gobies (Neogobius melanostomus) within the French Creek Watershed, Pennsylvania
Abstract
The round goby (Neogobius melanostomus) was discovered in 2013 in the French Creek (Allegheny River Drainage) watershed and is the first documented invasion outside of the Lake Erie basin in Pennsylvania. The round goby throughout the Laurentian Great Lakes is known to eat dressenid mussels (Dreissenidae), but consumption of either dressenids or native mussels (Unionidae) in tributaries to Lake Erie is minimal based on low populations of any bivalves. The French Creek watershed, on the other hand, harbors 29 species of native freshwater mussels as well as introduced fingernail clams (Sphaeriidae; Corbicula fluminea). The objectives of this study were to document the diet of round gobies in the French Creek watershed to determine whether consumption of native freshwater mussels was occurring. Round gobies were collected in the summer months (May-Sept.) of 2016 via kick seine in four locations, dissected, and their stomach contents identified to lowest possible taxa. We separated the gobies into categories based on length classes, in order to determine if diet changed with increased size and age. Unionid mussels were consumed by all length classes, particularly in length class one (30-44 mm), but diet shifted to a dominance of sphaeriids in length class four (≥75 mm). Round gobies also consumed benthic aquatic insects, a large percentage of which were chironomids (greater than 24% in all size classes). This is the first documentation of unionid consumption by the round goby in Pennsylvania that poses possible threats to native mussels in the French Creek watershed.
... While the Round Goby was previously restricted to the watershed of Lake Erie (Great Lakes Basin) in Pennsylvania, it has recently spread into the French Creek Watershed (Allegheny River/Upper Mississippi Basin). The introduction of the Round Goby to the French Creek Watershed first colonized a tributary to French Creek (LeBoeuf Creek) in August 2016 [16]. The invasion of an invasive fish has typically been documented and observed after their colonization of particular freshwater systems. ...
... The ability of the non-native, invasive Round Goby to adapt to a variety of habitats and environmental conditions poses a threat to native aquatic life in tributary systems and inland lakes. The recent introduction of Round Goby to portions of the French Creek watershed is a large concern given their potential to consume native freshwater mussels [7,[15][16][17]. Due to its unique and rich biodiversity and outstanding water quality, French Creek is nationally renowned as one of the most important streams in eastern North America and is identified as a globally significant watershed by the Nature Conservancy. ...
... French Creek is considered a stronghold for native freshwater mussels and fishes in the Northeast, as it is home to 80 species of fishes and 29 species of freshwater mussels. The first confirmed case of Round Gobies foraging on freshwater mussels within the upper French Creek watershed was reported in LeBoeuf Creek in 2019 [16], and thus the Round Goby is considered a potential threat to the native freshwater mussel populations in this watershed. ...
Freshwater mussels are an imperiled group of organisms that are vital to aquatic ecosystems. Services performed by freshwater mussels, coupled with their use for biomonitoring, make them an invaluable asset. Neogobius melanostomus (Round Goby), a recently introduced invasive species to the French Creek watershed, was once restricted to the watershed of Lake Erie in Pennsylvania. The Round Goby’s propensity to consume Dreissena polymorpha (Zebra Mussel) and Dreissena bugensis (Quagga Mussel) in their native habitat raises concerns about this recent introduction into Pennsylvania’s Allegheny River watershed. Since the discovery of their introduction within the watershed, we have followed the range expansion and dispersal rate of Round Gobies, which makes this study unique. The objectives of this study were to quantify baseline data on the contemporary diversity and abundance of unionid mussels in the upper French Creek watershed, and to explore potential habitat factors that influence or limit the size of the mussel populations. We gathered baseline data on freshwater mussel diversity and abundances across eight sites in the French Creek watershed and examined substrate particle size and host availability as potential limiting factors of the freshwater mussel distribution. Freshwater mussel surveys were conducted during the summer months (July–September) of 2017 using area-constrained surveys. Results showed a significant relationship between mussel diversity and substrate particle size (p < 0.05). From the data collected, we were able to calculate population estimates for the species found across the sample sites. Our results regarding the locations of native mussel populations and characteristics of their habitat provide the needed insight for establishing priority areas for the conservation of freshwater mussels, facilitating planning for protection, mitigation, and adaptation as the invasive Round Goby continues its spread.
Predation is a dominant structuring force in ecological communities. In aquatic environments, predation on bivalves has long been an important focal interaction for ecological study because bivalves have central roles as ecosystem engineers, basal components of food webs, and commercial commodities. Studies of bivalves are common, not only because of bivalves' central roles, but also due to the relative ease of studying predatory effects on this taxonomic group. To understand patterns in the interactions of bivalves and their predators we synthesised data from 52 years of peer-reviewed studies on bivalve predation. Using a systematic search, we compiled 1334 studies from 75 countries, comprising 61 bivalve families (N = 2259), dominated by Mytilidae (29% of bivalves), Veneridae (14%), Ostreidae (8%), Unionidae (7%), and Dreissenidae and Tellinidae (6% each). A total of 2036 predators were studied, with crustaceans the most studied predator group (34% of predators), followed by fishes (24%), molluscs (17%), echinoderms (10%) and birds (6%). The majority of studies (86%) were conducted in marine systems, in part driven by the high commercial value of marine bivalves. Studies in freshwater ecosystems were dominated by non-native bivalves and non-native predator species, which probably reflects the important role of biological invasions affecting freshwater biodiversity. In fact, while 81% of the studied marine bivalve species were native, only 50% of the freshwater species were native to the system.
In terms of approach, most studies used predation trials, visual analysis of digested contents and exclusion experiments to assess the effects of predation. These studies reflect that many factors influence bivalve predation depending on the species studied, including (i) species traits (e.g. behaviour, morphology, defence mechanisms), (ii) other biotic interactions (e.g. presence of competitors, parasites or diseases), and (iii) environmental context (e.g. temperature, current velocity, beach exposure, habitat complexity). There is a lack of research on the effects of bivalve predation at the population and community and ecosystem levels (only 7% and 0.5% of studies respectively examined impacts at these levels). At the population level, the available studies demonstrate that predation can decrease bivalve density through consumption or the reduction of recruitment. At the community and ecosystem level, predation can trigger effects that cascade through trophic levels or effects that alter the ecological functions bivalves perform. Given the conservation and commercial importance of many bivalve species, studies of predation should be pursued in the context of global change, particularly climate change, acidification and biological invasions.
Indigenous freshwater mussels (Unionidae) are integral to riverine ecosystems, playing a pivotal role in aquatic food webs and providing ecological services. With populations on the decline worldwide, freshwater mussels are of conservation concern. In this study, we explore the propensity of the invasive Round Goby (Neogobius melanostomus) fish to prey upon indigenous freshwater mussels. First, we conducted lab experiments where Round Gobies were given the opportunity to feed on juvenile unionid mussels and macroinvertebrates, revealing rates and preferences of consumption. Several Round Gobies consumed whole freshwater mussels during these experiments, as confirmed by mussel counts and x-ray images of the fishes. Next, we investigated Round Gobies collected from stream habitats of the French Creek watershed, which is renowned for its unique and rich aquatic biodiversity. We developed a novel DNA metabarcoding method to identify the specific species of mussels consumed by Round Goby and provide a new database of DNA gene sequences for 25 indigenous unionid mussel species. Several of the fishes sampled had consumed indigenous mussels, including the Elktoe (non-endangered), Creeper (non-endangered), Long Solid (state endangered), and Rayed Bean (federally endangered) species. The invasive Round Goby poses a growing threat to unionid mussels, including species of conservation concern. The introduction of the invasive Round Goby to freshwaters of North America is shaping ecosystem transitions within the aquatic critical zone having widespread implications for conservation and management.
Bivalves play an important part in freshwater ecosystems and improve water quality; the thick-shelled river mussel Unio crassus is classified as a bioindicator. Unfortunately, the species is regarded as endangered and is under species protection in the whole of Europe. The reasons for the drastic decline of its populations are: considerable eutrophication of waters, anthropogenic influence in its broad sense and the presence of invasive species. The life cycle of U. crassus includes the stage of larva which is an obligatory parasite of fish. This makes it possible for the species to disperse and populate new territories but it limits the development to places where appropriate host species are available. Intensive measures have been taken in Poland to protect U. crassus , while in France numerous new localities of the species have been bar-coded. In 2010–2014 active protection measures were taken in southern Poland, including inventorying, studies of genetic diversity and reintroductions. The project contributed to the increase in population abundance and in the number of localities of the thick-shelled river mussel, which resulted in a twofold increase in the range of occurrence of the species in the river. The procedures presented here can and should be used in further restitution of U. crassus not only in Poland but also elsewhere in Europe.
The Round Goby (Neogobius melanostomus) is an invasive fish species currently found in all five of the Laurentian Great Lakes of the United States. Round gobies have previously been restricted to the Lake Erie watershed of Pennsylvania, however, in fall of 2014, they were discovered in portions of the upper Allegheny River watershed, specifically Lake LeBoeuf and LeBoeuf Creek. This introduction was likely via bait bucket transfer. This paper confirms additional records of Round Gobies, including age zero fish and males in breeding colors, in LeBoeuf Creek as well as in the main stem of French Creek, tributaries to the Allegheny River.
• Freshwater systems are increasingly threatened by human impacts. To effectively monitor and manage these systems, reference or baseline conditions need to be documented to establish restoration or management goals.
• Freshwater mussel (Unionoida) communities are in decline in many river systems worldwide. Yet there are few long‐term quantitative studies in relatively “pristine” habitats that could serve as “reference” locations. Here, we present the results of a 20‐year quantitative monitoring study of mussel assemblages in a federally protected river in the United States.
• We found significant declines in mussel abundance (41%) and species richness (16%) over the 20‐year period, while mussel species evenness and Shannon's diversity index values increased over time (19.3% and 12.1%, respectively). This, combined with an analysis of community composition change trajectories, suggests the declines were disproportionately higher for common species than for rare species.
• Variation in life‐history traits of macroinvertebrates is often used to assess the degree of degradation of aquatic systems. Using Haag's (2012) classification of mussel life‐history traits, we found the proportion of opportunistic species (fast growth, high reproductive output, short lifespan) decreased by 65.3%, while the proportion of equilibrium species (slow growth, long lifespan, lower investment in reproduction) increased by 54.6% and the proportion of periodic species (moderate‐to‐high growth rates, low‐to‐intermediate fecundity, lifespan and age at maturity) increased by 82.4%.
• There were modest changes in human population and land use in the catchment during our study period, and a change in the operation of a hydroelectric dam reduced discharge variability. Sediment size changed at several study sites, increasing at some sites while decreasing at others.
• This study occurred in one of the best‐protected and most pristine rivers in the upper Midwest of the United States, harbouring one of the region's most intact mussel fauna that could be used as a “reference” to set goals for the restoration of mussel fauna in other river systems. Despite the high quality and protection of this river system, we found slow declines in the mussel community but found no evidence that changes in land use, flow regime, water quality, the spread of invasive species or increased sedimentation were responsible for these declines. The slow decline of mussels and lack of specific causes in such a river underscore the imperilment of this fauna, and the need for more aggressive conservation, management and research approaches.
Several studies have shown that round gobies (Neogobius melanostomus) undergo a dietary shift from arthropods to dreissenid mussels as they grow, and this shift is accompanied by changes in pharyngeal morphology associated with durophagy. In contrast, some populations of round gobies prey heavily on various arthropods, but it is unknown whether those populations develop pharyngeal morphology associated with durophagy or if they develop less robust and molarized structures. To test if there is a relationship between food habits and pharyngeal morphology, we compared those characters in round gobies from two sites in Erie Co., Pennsylvania: a dreissenid-present site (Presque Isle Bay, PIB, of Lake Erie) and a dreissenid-absent site (Fairview Gravel Pit, GP). Multivariate analysis of covariance (MANCOVA) revealed consistent ontogenetic changes at both sites in which lower pharyngeals of larger fish were more robust, possessed wider teeth, and had a greater area taken up by large diameter teeth. Pharyngeal morphology also differed between sites, with gobies from PIB having wider and more robust lower pharyngeals. Food habits differed markedly between round gobies from the two sites, with dreissenid mussels being the most important prey item for all length classes in PIB, and crustaceans being the most important prey item for all length classes at the GP. Canonical correlation analysis on all round gobies revealed a correlation between consumption of dreissenid prey and pharyngeal characters associated with durophagy. Although food habits and pharyngeal morphology of round gobies appear to be associated, the mechanism responsible for the association (i.e. phenotypic plasticity versus local adaptation) is not clear.
The relative abundance of Neogobius melanostomus (Round Goby) in the Pennsylvanian waters of Lake Erie, has increased dramatically since 1996. Associated with this increase, all benthic species in the main portion of the lake, except Percopsis omiscomaycus (Trout-perch), decreased in occurrence or were extirpated. Proterorhinus semilunaris (Tubenose Goby), which has established a reproducing population in Presque Isle Bay, Lake Erie, coexists with the Round Goby and Etheostoma exile (Iowa Darter), a candidate species for rarity listing by the Pennsylvania Fish and Boat Commission. Conversely, the decline in potadromous populations of Percina caprodes (Logperch) may be exacerbated by direct competition in the lake, and the presence of Round Gobies in the breeding grounds of tributaries (e.g., Twentymile Creek). In Elk Creek, the presence of Round Goby is associated with dietary shifts of Etheostoma caeruleum (Rainbow Darter), although Rainbow Darters co-exist with the Round Goby. The Round Goby has established a reproducing population in LeBoef Creek, a tributary of French Creek (Allegheny River), and we documented its presence in the main channel of French Creek. We suggest that natural barriers (e.g., waterfalls) may prevent the upstream migration of gobies. Furthermore, providing substrate to facilitate spawning and recruitment of native benthic species may impede the spread of invasive species throughout the tributaries of Lake Erie.
One of the main assumed impacts of invasive gobies is predation on benthic macroinvertebrates. Despite numerous dietary studies, however, quantitative evaluations of impact in European river systems are scarce. Here, we investigate the impact of tubenose (Proterorhinus semilunaris, Heckel 1837) and round (Neogobius melanostomus, Pallas 1814) gobies on macroinvertebrates in a lowland river (River Dyje, Czech Republic) by allowing and preventing gobiid access to rip-rap substrate naturally colonised by invertebrates at two sites (Site 1—tubenose goby only, Site 2—tubenose and round gobies). Gobies had a negative impact on invertebrates at both sites, with overall invertebrate density reduced by 15% (ca. 17.9 g m−2 per year) at Site 1 and 36% (ca. 23.6 g m−2 per year) at Site 2. Both species showed increased impact in summer and ingested larger invertebrates preferentially, resulting in an overall reduction in invertebrate body size. Tubenose gobies had a significant impact on Annelida, Gastropoda, Crustacea and Ephemeroptera nymphs, while tubenose and round goby together impacted Annelida, Bivalvia (Dreissena), Gastropoda, Crustacea, Ephemeroptera nymphs, Odonata nymphs and Chironomidae larvae. Our results confirm that round and tubenose gobies can have a significant negative impact on aquatic invertebrate density and community composition.
The diets and possible competitive interactions related to food were examined for greenside (Etheostoma blennioides), rainbow (E. caeruleum), and fantail (E. flabellare) darters from the Chagrin and Grand Rivers of northeastern Ohio. All 3 species fed heavily upon chironomid larvae in all seasons. In the Chagrin, the chironomids consumed were primarily of the subfamily Orthocladiinae; in the Grand, the subfamily Chironominae was also important to the darters. E. blennioides fed most heavily upon chironomids in both streams in all seasons. E. caeruleum consumed fewer chironomids than did E. blennioides but more than E. flabellare (except in spring). Seasonally important prey taxa for E. blennioides included Simuliidae, Trichoptera, and Ephemeroptera; for E. caeruleum, Trichoptera and Ephemeroptera; for E. flabellare, Plecoptera (especially in winter), Trichoptera, and Ephemeroptera. E. blennioides exhibited greatest selection for Simulium, Orthocladiinae, and Hydroptila; E. caeruleum for Hydroptila, Orthocladiinae, and Baetis. E. flabellare selected for Paracapnia, Baetis, Hydropsyche, and Stenonema. Greatest seasonal dietary overlap was between E. blennioides and E. caeruleum. Lowest overlap was between E. caeruleum and E. flabellare. In both streams, overlap between E. blennioides and E. caeruleum was greatest in winter, lowest in summer. Overlap between either of these darters and E. flabellare was greatest in spring, lowest in winter. Heavy reliance upon the abundant chironomid larvae by the darters may aid in reducing competition and increasing foraging efficiency. Competitive interactions resulting in habitat shifts may result in reduced and different foraging areas for these fishes, which may further decrease competition between these darters.
Status review for a wide-ranging unionid mussel in the United States and Canada
The North America freshwater mussel fauna has suffered an inordinately high recent extinction rate, and the small size and isolation of many remaining populations portends a continued diminishment of this fauna. Causes of extinction and imperilment are varied but revolve around massive habitat loss, deterioration, and fragmentation. The National Strategy for the Conservation of Native Mussels, published in 1997, has guided efforts to address this crisis. Considerable progress has been made toward several of the Strategies’ goals, particularly increasing our knowledge of mussel biology, promoting mussel conservation, and development of techniques for captive mussel propagation. However, mussel conservation should focus more directly on reducing fragmentation through bold and aggressive habitat restoration. In addition to dam removal, improvement in dam tailwater flows, and restoration of channelized streams, identification of factors that eliminated mussels from many otherwise intact streams is critical. Translocation and captive propagation will be key elements in reestablishing mussel assemblages in restored habitats, but these techniques should be used with caution and primarily to increase the occurrence of a species throughout its historical range. Conserving mussel diversity in an ever-changing world is dependent on promoting the natural, long-term sustainability and evolutionary potential of mussel populations.
Round gobies, invasive fish that entered Lake Erie in 1994, are altering energy, contaminant, and nutrient pathways. Our objective was to quantify how they alter energy pathways in the central basin of Lake Erie by describing their diet and identifying the degree to which predatory fish feed upon round gobies. We used bioenergetic models parameterized with data collected in the central basin between 1995 and 2002 to estimate the type and amount of prey eaten, the biomass accumulation rate for the round goby population, and a partitioning of the food energy into “new” energy derived from dreissenids as opposed to existing energy derived from zooplankton and non-dreissenid benthic prey. Mean (± SE) prey consumption peaked at 5.98±2.17×104 tonnes wet mass in 1999 coincident with the maximum population size of 4.2±1.5 billion round gobies. Zooplankton (40.2% by biomass) and dreissenid mussels (38.3%) dominated the prey consumed. Almost 90% of the zooplankton biomass was consumed by age-0 round gobies, while over 80% of the dreissenids were eaten by older ages. Standing stock biomass of round gobies ranged between 203 and 4,803 tonnes y−1 (interannual range), with an additional 475 to 8,943 tonnes of biomass accumulating through growth each year. Piscivorous fish showed an increasing reliance on round gobies as prey, with round gobies being the dominant prey fish in the diets of benthic-oriented predators. Hence, by being one of the few benthivores that exploit dreissenid mussels as prey, our analyses reveal that round gobies transfer new energy up the central Lake Erie food web.
The freshwater mussel (Unionidae: Bivalvia) communities of the French Creek watershed are nationally recognized for their importance to biodiversity. The goal of this research was to gather more information on the distribution and densities of these species throughout the river. This study utilized two-phase sampling with timed searches to characterize mussel species richness in a large number of sites and to calculate catch-per-unit-effort values. The results of the timed search were used to select a subset of sites for quantitative mussel surveys to estimate density and abundance. Starting in New York, the main stem of French Creek was divided into 5.6-km lengths, and one site was randomly chosen within each of those lengths, favoring habitat (large riffle/runs) for rare species and high species diversity. Snorkelers collected as many unionid individuals as possible, with a target search rate of 0.5 m2 min-1. Thirty-two main-stem sites were surveyed with timed searches. Mean species richness was 11.8 (SE = 0.94), and mean CPUE was 59.5 mussels per person-hour (SE = 9.32). Quantitative sampling was performed at ten sites using a double sampling design. Mean density estimates ranged from 0 to 27.98 m-2. Abundance estimates range from 0 to 69,848 live mussels per site. For the main stem, we calculated regression models to estimate densities and abundances at qualitatively sampled sites based on the CPUE at quantitatively sampled sites. Extrapolation yields approximately 22 million mussels in the 2.04 million m2 of large riffle-run habitat in the main stem of French Creek.
Pennuto CM, Krakowiak PJ, Janik CE. Seasonal abundance, diet, and energy consumption of round gobies (Neogobius melanostomus) in Lake Erie tributary streams. Ecology of Freshwater Fish 2010: 19: 206–215. © 2010 John Wiley & Sons A/S
Abstract – The invasive round goby (Neogobius melanostomus) is a benthic invertivore that has become established in many lake and river systems of Europe and the United States, especially within the Great Lakes basin. Multiple reports document its negative impact on benthic macroinvertebrates and fishes in lakes and recent studies show fish and invertebrate communities in streams are equally at risk. We assessed the seasonal abundance of round gobies and their summer diet composition in tributary streams to Lake Erie. Populations of round gobies in the lower reaches of two tributary streams peaked in abundance in early fall, were absent in late winter, and reappeared in early spring, suggesting a possible out-migration to the lake in winter. Population size distributions show a peak recruitment of young round gobies in July and low-level recruitment through October. In this study, round gobies obtained most of their energy from amphipods, chironomids, and caddisflies compared to other invertebrates, and midges were consumed in greater proportion than their availability suggesting a preference for these prey. As the stream lacked molluscs, large round gobies remained generalist invertivores without a diet shift to molluscivory as has been reported in lake studies. The observations on recruitment and abundance, and possible out-migration suggest the lower reaches of tributary streams may act as source populations for lake-bound round gobies. It may be possible to take advantage of this out-migration behaviour as a control strategy to capture large numbers of round gobies each winter.
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.
We determined seasonal foraging modes of four sympatric darter species, Etheostoma lynceum, E. stigmaeum, E. swaini and Percina nigrofasciata, from Beaverdam Creek, Mississippi (USA) at two scales of taxonomic resolution: (1) chironomid prey identified to family
and (2) chironomid prey identified to genus/species. When chironomids were identified to family, high proportional similarity
(PS) and low niche breadth (NB) values suggested the darters fed opportunistically on a relatively small number of available
prey taxa. In contrast, when chironomids were identified to genus/species, concordant low PS and NB values suggested the darters
fed like classic specialists, selecting a small number of prey taxa relative to prey availability in the resource base. The
darters selected just one to four chironomid taxa from 52 available taxa across seasons. Our study shows that the scale of
taxonomic resolution used to identify darter prey may influence the characterization of darter foraging modes.
The round goby (Neogobius melanostomus) first invaded North America in 1990 when it was discovered in the St. Clair River. Despite more than 15years 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.
KeywordsEndangered species-
Neogobius melanostomus
-Round goby-Secondary invasion-Great Lakes-Ecological impact-Species at risk-Invasive species
The round goby Neogobius melanostomus is one of the most wide-ranging invasive fish on earth, with substantial introduced populations within the Laurentian Great Lakes watershed, the Baltic Sea and several major European rivers. Rapid expansion and deleterious ecosystem effects have motivated extensive research on this species; here this research is synthesized. Maps of the global distribution are provided and the invasion history of N. melanostomus, which spread more rapidly at first in North America, but has undergone substantial expansion over the past decade in the Baltic Sea, is summarized. Meta-analyses comparing their size at age, diet, competitors and predators in North American and European ecosystems are provided. Size at age is region specific, with saline habitats typically supporting larger and faster growing individuals than fresh water. Neogobius melanostomus prey differs substantially between regions, demonstrating a capacity to adapt to locally abundant food sources. Neogobius melanostomus comprise at least 50% of the diet of eight taxa in at least one site or life stage; in total, 16 predator taxa are documented from the Laurentian Great Lakes v. five from Eurasia. Invasive N. melanostomus are the only common forage fish to heavily exploit mussels in the Laurentian Great Lakes and the Baltic Sea, facilitating the transfer of energy from mussels to higher trophic levels in both systems. Neogobius melanostomus morphology, life history, reproduction, habitat preferences, environmental tolerances, parasites, environmental effects, sampling strategies and management are also discussed. Neogobius melanostomus inhabit a wide range of temperate freshwater and brackish-water ecosystems and will probably continue to spread via ballast water, accidental bait release and natural dispersal worldwide. Climate change will probably enhance N. melanostomus expansion by elevating water temperatures closer to its energetic optimum of 26° C. Future research needs are presented; most pressing are evaluating the economic effects of N. melanostomus invasion, determining long-term population level effects of egg predation on game-fish recruitment and comparing several variables (density, ecological effects morphology and life history) among invaded ecosystems. This review provides a central reference as researchers continue studying N. melanostomus, often as examples for advancing basic ecology and invasion biology.
A molecular genetic key to the unionids of French Creek, Pennsylvania, an Allegheny River tributary, is presented here. The key is an integral part of a new approach to identifying unionid glochidia larvae attached to host fishes in the drainage. Working with tissue from adult unionids, we used the polymerase chain reaction (PCR) followed by restriction enzyme digests to find species-specific genetic "fingerprints" for the 25 species in the drainage. We have demonstrated the utility of the key by using it to identify 70 glochidia attached to fishes collected in the French Creek drainage.
Etheostoma microperca and E. zonale are diurnal carnivores. Feeding activity in both species increased markedly (on 9-10 September 1977) after sunrise, peaked at midday, and decreased after sunset. Etheostoma microperca fed mainly on copepods (38-76% of all food items); in late afternoon the diet contained fewer copepods than usual and more chironomids. Etheostoma zonale fed most heavily on chironomids (59-96%) at all hours.
Although numerous studies have shown that round gobies (Neogobius melanostomus) prey on dreissenid mussels (Dreissena polymorpha and Dreissena bugensis), there is an apparent shortage of detailed field studies on the subject. The 5-month field study described here quantifies predation by round gobies on dreissenids in Presque Isle Bay, Lake Erie. Dreissenids dominated the diet of round gobies, composing 92% of the prey items recovered. Over half of the 3870 valves (1935 mussels) recovered from 155 round gobies were crushed, while the remainder were swallowed whole. Crushed dreissenids were larger than those swallowed whole, and the tendency to crush dreissenids did not vary among three length classes of round goby. Round goby length was positively related to average size of dreissenids consumed, average size of whole and crushed dreissenids, largest whole dreissenid consumed, and largest crushed dreissenid consumed. Indices of selectivity revealed similarly shaped curves for three length classes of round gobies, a shift toward larger dreissenid size classes with an increase in round goby length, and peak preferences for 8–11mm dreissenids. Factors such as gape limitation, availability and accessibility of differently sized dreissenids, forces generated while removing mussels from the substrate and crushing them, and caloric content of dreissenids all likely play roles in the observed size-selectivity and differential processing of dreissenids. Although factors influencing size-selectivity are not completely understood, the observed preference of round gobies for dreissenids near the size when they are first reproductive could impact the demography of dreissenid populations.
Largemouth Bass were infected with glochidia of the freshwater mussel Lampsilis cardium. Three fishes each were held at 4.5, 10, and 15.5°C; five fish were held at 21°C. By 64 days, metamorphosed juveniles were found in the 15.5 and 21°C trials but not in the 5.5 and 10°C trials, indicating that the lower threshold temperature for metamorphosis was between 10 and 15.5°C for the duration. In a second experiment, Largemouth Bass were infected with glochidia of L. cardium and held at 10°C. A sample of fishes was removed monthly and brought to 21°C. Numbers of glochidia that metamorphosed after being warmed were compared to the number that metamorphosed without warming. The percentage that metamorphosed after warming decreased linearly with time. At one month, 100% of the glochidia metamorphosed after warming. This decreased to 80% by two months, to 30% by four months and 3% by six months. Although this post-warming percentage decreased with time, the total percentage of metamorphosed juveniles (at all temperatures) was not correlated with time. Controls kept at 21°C required three weeks to reach peak metamorphosis, but test subjects subjected to 10°C required less than nine days to metamorphose once warmed. Many overwintering glochidia therefore complete a portion of their development on the host at winter temperatures, but stop short of excystment. Some glochidia metamorphosed without being warmed, but this phenomenon is not understood. This study confirms that glochidia may overwinter on hosts, with some glochidia persisting for more than six months before metamorphosing when warmer conditions return.
The size distribution of zebra mussels atop (exposed to predation) and beneath (protected from predation) rocks were compared at a round goby infested site (Calumet Harbor, IL/IN) and round goby-free site (Evanston, IL) in southern Lake Michigan. The largest zebra mussels were atop rocks at both sites and those from Calumet Harbor were significantly larger than those from Evanston. The smallest zebra mussels were beneath the rocks at both sites and those from Calumet Harbor were smaller than those from Evanston. Nearly all zebra mussels from Calumet Harbor rock tops were larger than the size range preferred by round gobies in published laboratory experiments. Conversely, most of the zebra mussels from rock tops from Evanston were within the size range preferred by round gobies. In a field experiment, glass sheets colonized with zebra mussels from Evanston rock tops were exposed to round goby predation. Predation was videotaped to determine what size zebra mussels were eaten by round gobies. Smaller zebra mussels were consumed more frequently and surviving zebra mussels were either very large or had refuge in the space between larger zebra mussels. The study showed that more effort is required to remove larger zebra mussels than smaller zebra mussels. The results indicate that, while round gobies prefer smaller zebra mussels, the underside of rocks, as well as proximity to larger zebra mussels, can provide refuge for the smaller zebra mussels. Hence round gobies are unlikely to totally remove zebra mussels from a habitat and their impact will likely vary between habitats.
The accidental introduction of round gobies (Neogobius melanostomus) into the North American Great Lakes has raised concerns about their potential impacts on local fauna. Gobies have similar habitat and spawning requirements to mottled sculpins (Cottus bairdi) and slimy sculpins (C. cognatus), and may already be displacing sculpins where the ranges of the species overlap. Like sculpins, gobies are capable of penetrating interstitial spaces to acquire food, and therefore may become predators of interstitially incubating lake trout eggs. Laboratory experiments were conducted to compare egg consumption rates and critical size (the minimum size at which a fish was capable of ingesting an egg) between round gobies and mottled sculpins. Predation by both species on lake trout eggs and fry was also examined in two grades of substrate (cobble and gravel). Mottled sculpins consumed larger numbers of eggs than round gobies of similar size, and were capable of ingesting eggs at smaller sizes than gobies. Both gobies and sculpins had lower foraging success on smaller substrates (gravel) than on cobble. Gobies are currently present at higher densities than sculpins in areas where they are established in the Great Lakes. The similar predation of lake trout eggs by round gobies and mottled sculpin and high densities the goby has achieved at some Great Lakes sites leads to the prediction that the round goby may negatively affect lake trout reproduction and therefore rehabilitation.
A tubenose goby Proterorhinus marmoratus, a European endangered species native to the Black and Caspian seas, was recovered on 11 April 1990 from the travelling screens of the Belle River Power Plant located on the St Clair River, Michigan. Subsequently, anglers caught three round gobies Neogobius melanostomus in the St Clair River near Sarnia, Ontario. Thirty-one tubenose gobies and 11 round gobies were impinged or trawled at or near the Power Plant in the fall and winter of 1990-91. Nine round gobies (29-61 mm total length) are believed to be young-of-the-year. These species were probably transported to the Great Lakes in ballast water, may have successfully colonized the St Clair River, and will probably spread throughout the Great Lakes. They are expected to impact directly other benthic fishes. -from Authors
We investigated the response of the mottled sculpin Cottus bairdi and the johnny darter Etheostoma nigrum to the invasion and proliferation of the round goby Neogobius melanostomus at three near-shore locations in southern Lake Michigan. Fish were collected by trawling from June through August, 1984–2002. Mean annual catches of mottled sculpin in trawl samples ranged from 0 to 4.4 fish/h from 1984 to 1998, whereas mean annual johnny darter catches ranged from 0 to 29 fish/h in the same period. Round gobies were first sampled in 1998, and the relative population abundance increased in the following years, ranging up to 371 fish/h at one site by 2001. From 1999 to 2002, only a single mottled sculpin and only 12 johnny darters were collected in 72 h of trawling. This study documents the rapid decline of the mottled sculpin and johnny darter following the round goby invasion to this portion of the lake.
Round gobies have had significant impacts on benthic fish and invertebrate communities in nearshore habitats of the Great Lakes. As round gobies have become more abundant in lake habitats, there has been an expansion of their populations into tributary streams and rivers. We compared stream invertebrate and fish communities in New York tributaries to Lake Erie with round gobies present and absent. Four of six benthic invertebrate metrics differed between streams with and without round gobies. Streams with round gobies present had reduced Shannon diversity, EPT richness, and EPT/chironomid ratios, and increased macroinvertebrate density relative to streams without round gobies, but there was no difference in non-Diptera density, or total taxa richness. None of the four fish metrics examined differed between streams with and without round gobies. However, darters occurred in all streams lacking round gobies, but did not occur in any streams with round gobies. Comparisons with historical fish and macroinvertebrate distributional data support our suspicion of goby-induced community changes. In these New York streams, round gobies seem to have had significant impacts on invertebrate communities via their consumptive behavior, whereas the impacts on fish communities are less evident. If round gobies continue to expand their distribution inland, the resultant alterations in macroinvertebrate communities may impact the suitability of tributary streams as spawning and nursery habitat for several sport fish species and for energy dynamics in tributary streams.
New or confirmed host identifications were performed for ten freshwater mussels. Fish species were infested with glochidia and monitored during laboratory experiments. Two methods were used: 1) feeding conglutinates to fish and 2) placing fish in aerated buckets of water containing glochidia in suspension. Aquaria contents were sampled every other day and examined for unmetamorphosed glochidia and metamorphosed juveniles under polarized light. Unmetamorphosed glochidia suggested unsuitable hosts, whereas metamorphosed juveniles indicated potentially suitable hosts. Johnny darter, largemouth bass, bluegill, and white shiner were hosts for Elliptio fischeriana. Bluegill and shield darter were hosts for Fusconaia masoni. Silver shiner and creek chub were hosts for Fusconaia flava. Striped shiner, streamline chub, smallmouth bass, largemouth bass, green sunfish, bluebreast darter, greenside darter, rainbow darter, and yellow perch were hosts for Villosa iris iris. Bluntnose minnow, sand shiner, striped shiner, smallmouth bass, largemouth bass, bluegill , and longear sunfish were hosts for Lampsilis radiata luteola. Green sunfish and banded killifish were hosts for Lampsilis cardium. Banded darter, bluebreast darter, and brown trout were hosts for the federally endangered Epioblasma torulosa rangiana. Longnose gar, largemouth bass, yellow perch, longear sunfish, bluegill, slenderhead darter, and logperch were hosts for Megalonaias nervosa. Largemouth bass and Tippecanoe darter were hosts for Anodontoides ferussacianus. Blackside darter, striped shiner, central stoneroller, and logperch were hosts for the federally endangered Pleurobema clava. Freshwater mussels (Bivalvia: Unionidae) are the most endangered group of animals in North America. No other group has as high a percentage of federally and state listed species as the unionids. In the United States, 69 taxa, including subspecies, are currently listed under the Endangered Species Act as endangered and threatened (USFW 1998). Yet, we know very little about the complex life history of these animals. Identification of hosts for freshwater mussels is paramount in their conservation and management. Unionids are parasitic for a portion of their complex life history and require a vertebrate host; generally fish fulfill this role. Glochidia, the parasitic larval stage, attach to gills or fins during a transformation process to juveniles. Freshwater mussel species may have evolved to parasitize a specific fish species, a family of fish (Zale and Neves 1982a,b, Yeager and Saylor 1995), or taxonomically wide varieties of fish (Trdan and Hoeh 1982). At least one species of unionid completes its glochidial metamorphosis to juveniles without a host (Barfield and Watters 1998, Lellis and King 1998), however most evidence suggests that freshwater mussels are obligate parasites.
Preliminary gut analysis of a recent Great Lakes invader, the round goby, Neogobius melanostomus (7.0–8.4 cm), collected from
the Detroit River, showed that they ate zebra mussels (58%), snails (6%), and other invertebrates (36%), including aquatic
insects (Hexagenia), softshelled crayfish, and zooplankton. Because zebra mussels, Dreissena polymorpha, predominated as prey,
we investigated the ability of round gobies to consume different size classes of zebra mussels. In laboratory experiments,
we examined feeding preferences of three size classes of round gobies (5.5–6.9 cm; 7.0–8.4 cm; 8.5–10.3 cm standard length)
on four different size classes of zebra mussels (6.0–9.9 mm, 10.0–12.9 mm, 13.0–15.9 mm, 16.0–18.9 mm). All sizes of round
gobies ate zebra mussels < 10.0 mm. Only the largest size class of round gobies ate larger zebra mussels (10.0–12.9 mm) when
all prey sizes were presented. The association between the total mass of zebra mussels available and the amount consumed by
round gobies increased positively up to about 6.5 g of available mussels and then levelled off. Round gobies consumed an average
of 1.0 g of mussels in 24 h. There was a significant positive relationship between gape size and standard length of round
gobies. Although larger round gobies (over the size range of fish in our study) are able to consume larger zebra mussels,
small mussels were preferred. Our findings suggest that the preference of small zebra mussels by round gobies has the potential
to alter the size structure of zebra mussel populations.
The diets of four species of Etheostoma (E. spectabile, E. caeruleum, E. flabellare and E. nigrum) were investigated from ten Order 3 streams in the White River drainage of southern Indiana. All species fed mainly on insect larvae, primarily chironomids, ephemeropterans and plecopterans. Dietary proportions, as frequency of occurrence, were compared using cluster analysis based on matrices of values of Spearman rank correlation, Schoener index, Jaccard association, and Pearson's r. Certain species and, in some cases, stream pairs within species clustered closely in all analyses or in three of the four. Most clusters do not show closer intraspecific than interspecific similarity and specific streams had more influence than species in forming the logic of some clusters. It can be concluded that these fishes are opportunistic predators.
Round gobies (Neogobius melanostomus), after successfully reproducing in the early 1990s, decimated populations of mottled sculpins (Cottus bairdi) and possibly logperch (Percina caprodes) in the St. Clair River. Studies were conducted during 1994 to determine whether diets of round and tubenose (Proterorhinus marmoratus) gobies overlapped with those of native forage fishes. In the nearshore zone (depth ≤ 1 m), round and tubenose gobies, logperch, and rainbow darters (Etheostoma caeruleum) of similar sizes (total lengths < 75 mm) consumed mainly small-sized macroinvertebrates (dipterans, Caenis, and amphipods) during June 1994. Logperch and rainbow darters were present in the nearshore zone only during this month. At the crest of the channel slope (depth = 3 m), round gobies and northern madtoms (Noturus stigmosus) ate mostly ephemeropteran nymphs (Hexagenia and Baetisca), while predation on zebra mussels (Dreissena polymorpha) and other mollusks by round gobies was minimal. Northern madtoms did not feed on mollusks. Diet overlap between round gobies and native fishes was not observed at the channel slope (depth = 5 m and 7 m) due to heavy predation on mollusks by round gobies. Young-of-the-year (YOY) round gobies migrated to deeper water in autumn and became prey of mottled sculpins and northern madtoms. Eggs and YOY of mottled sculpins may have become vulnerable to predation by both round gobies and native fishes in deeper water, since adult mottled sculpins were apparently confined to the channel with limited home range because aggressive round gobies occupied preferred shallow habitat, including spawning sites.
The round goby (Neogobius melanostomus) has successfully colonized the Great Lakes, where it appears to be out-competing and possibly displacing native fish species. Movement of the round goby into tributary streams of Lake Erie could further jeopardize native species. Sampling was done by electrofishing in six Pennsylvania tributary streams of Lake Erie from June 2000 through October 2001. Round gobies were collected from four of the six streams sampled: Elk Creek, Walnut Creek, Twentymile Creek, and Sixteenmile Creek. The most extensive colonization has occurred in Elk Creek where round gobies comprised 17.1% of the total number of fish where they were present, and occurred as far as 2.25 stream km upstream from the mouth of the creek. Round gobies fed almost exclusively on aquatic insects, and the most important insects in the diet were chironomid larvae. Female round gobies matured at 1+ years old. Individual fecundity ranged from 86 to 591 eggs, and increased with fish length. The plasticity of the diet, high fecundity, and aggressiveness of the round goby may make it a threat to native species in Pennsylvania tributary streams.
Analysis of Historical and Contemporary Consumption of Aquatic Macroinvertebrates in Darter Species of a Highly Diverse Stream
- C Bradshaw
Suitable fish hosts for glochidia of three freshwater mussels: strange floater, ellipse, and snuffbox
- K Hillegass
- M Hove
Fish host determination of endangered freshwater mussels in the Sydenham River
- K Mcnichols
- G Mackie
Glochidial release and reproduction of the snuffbox mussel, Epioblasma triquetra; timing in southern Michigan
- R Sherman
An Illustrated Key to the Freshwater Mussels (Bivalvia: Unionacea) of Wisconsin. Reports of the Museum of Natural History
- E Stern
Cumberlandian mollusk conservation program, activity 3: identification of fish hosts
- D M Hill
Ecological relationships between six rare Minnesota mussels and their host fishes
- M Hove
- A Kapuscinski
Research summary: impacts of gobies on native fishes of the Lake Erie Drainage, Pennsylvania
- C Wilson
- J Stauffer
- J Schnars
Hosts of salamander mussel (Simpsonaias ambigua) and snuffbox (Epioblasma triquetra) from the Meramec River system, Missouri
- C Barnhart
- F Riusech
- M Baird
Freshwater Mollusk Symposia Proceedings. Part I. Proceedings of the Conservation, Captive Care and Propagation of Freshwater Mussels Symposium
- M Hove
- K Hillgas
- J Kurth
A guide to sampling freshwater mussel populations
- D Stayer
- D Smith
Life history of endangered freshwater mussels of the Sydenham River, southwestern Ontario, Canada
- D Woolnough