We describe, explain, and "predict" dispersal and ecosystem impacts of six Ponto-Caspian endemic species that recently invaded the Great Lakes via ballast water. The zebra mussel, Dreissena polymorpha, and quagga mussel, Dreissena bugensis, continue to colonize hard and soft substrates of the Great Lakes and are changing ecosystem function through mechanisms of ecosystem engineering (increased water clarity and reef building), fouling native mussels, high particle filtration rate with selective rejection of colonial cyanobacteria in pseudofeces, alteration of nutrient ratios, and facilitation of the rapid spread of their Ponto-Caspian associates, the benthic amphipod Echinogammarus ischnusand the round goby, Neogobius melanostomus , which feeds on zebra mussels. The tubenose goby, Proterorhinus marmoratus , which does not feed on zebra mussels, has not spread rapidly. Impacts of these benthic invaders vary with site: in some shallow areas, habitat changes and the Dreissena → round goby → piscivore food chain have improved conditions for certain native game fishes and waterfowl; in offshore waters, Dreissena is competing for settling algae with the native amphipod Diporeia spp., which are disappearing to the detriment of the native deep-water fish community. The predatory cladoceran Cercopagis pengoi may compete with small fishes for zooplankton and increase food-chain length.

/pdf/dispersal-and-emerging-ecological-impacts-of-ponto-caspian-joc0llwjvd.pdf

Dispersal and emerging ecological impacts of Ponto-Caspian species in the Laurentian Great Lakes.

A predictive understanding of the ecological impacts of nonnative species has been slow to develop, owing largely to an apparent dearth of clearly defined hypotheses and the lack of a broad theoretical framework. The context dependency of impact has fueled the perception that meaningful generalizations are nonexistent. Here, we identified and reviewed 19 testable hypotheses that explain temporal and spatial variation in impact. Despite poor validation of most hypotheses to date, evidence suggests that each can explain at least some impacts in some situations. Several hypotheses are broad in scope (applying to plants and animals in virtually all contexts) and some of them, intriguingly, link processes of colonization and impact. Collectively, these hypotheses highlight the importance of the functional ecology of the nonnative species and the structure, diversity, and evolutionary experience of the recipient community as general determinants of impact; thus, they could provide the foundation for a theoretical framework for understanding and predicting impact. Further substantive progress toward this goal requires explicit consideration of within-taxon and across-taxa variation in the per capita effect of invaders, and analyses of complex interactions between invaders and their biotic and abiotic environments.

Progress toward understanding the ecological impacts of nonnative 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.

/pdf/twenty-years-of-invasion-a-review-of-round-goby-neogobius-j2vgt8bx22.pdf

Twenty years of invasion: a review of round goby Neogobius melanostomus biology, spread and ecological implications.

Alien species (those carried outside their original ranges by human activities) have strongly affected the distribution and abundance of mollusks in many North American fresh waters The best known of these aliens in North America is the zebra mussel (Dreissena polymorpha), which has nearly extirpated native unionid clams from infested lakes and rivers by fouling their shells and outcompeting them for food Zebra mussels also have reduced populations of native sphaeriid clams, and both increased and reduced populations of snails The effects of the other well-known alien bivalve in North America, Corbicula fluminea, are surprisingly poorly known Corbicula probably caused some populations of native bivalves to decline, but other native populations seem to coexist with Corbicula Several plausible mechanisms of interaction between Corbicula and the native biota have been proposed, but not demonstrated Other aliens, including the recently arrived snail Potamopyrgus antipodarum, probably compete strongly wi

Effects of Alien Species on Freshwater Mollusks in North America

https://www.reabic.net/Publ/Janssen_et%20al_2001_Cottus_Neogobius.pdf

Recruitment Failure of Mottled Sculpin Cottus bairdi in Calumet Harbor, Southern Lake Michigan, Induced by the Newly Introduced Round Goby Neogobius melanostomus

https://www.reabic.net/Publ/Dubs_Corkum_1996.pdf

Derek O.L. Dubs

Papers

Behavioral Interactions Between Round Gobies (Neogobius melanostomus) and Mottled Sculpins (Cottus bairdi)