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Several species of fish in large lakes and marine environments have a pelagic larval stage, and are subject to variable transport that can ultimately regulate survival and recruitment success. Alewife, Alosa pseudoharengus, are subject to... more
Several species of fish in large lakes and marine environments have a pelagic larval stage, and are subject to variable transport that can ultimately regulate survival and recruitment success. Alewife, Alosa pseudoharengus, are subject to transport by complex coastal currents during their pelagic larval stage (~ 30 d). We assessed backward‐trajectory simulations, consisting of a Lagrangian particle dispersion model linked to the Finite Volume Community Ocean Model, to estimate likely hatch locations of aged larval alewife collected from locations on both the eastern and western sides of Lake Michigan during July 2015. We used four deployments of three satellite‐tracked drifter buoys in coastal waters to assess model skill in estimating the origin of a drifter from its final location. We found that the trajectories of drifters varied greatly, depending on wind events and associated coastal transport processes, including upwelling/downwelling and coastal jet currents. In 2 of 12 cases, the backward trajectory simulations failed to predict the drifter origin, associated with transport of 170 km in a narrow coastal jet current. In the remaining 10 cases, the known drifter origin was within 3.5 km of the spatial patch of predicted possible origins for a scenario of horizontal diffusivity (188 m2 s−1) consistent with the offshore model grid resolution. Modeled backward trajectories estimated that alewife originated from the same side of the lake where they were collected, within ~ 100 km of the collection site. Our paper demonstrates the utility of hydrodynamic models to estimate a region of origin for aged larval fish.
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Research Interests: Biology, Predation, Fisheries Sciences, Zooplankton, Ecosystem, and 3 moreLarva, Aquatic science, and Alewife
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Aquatic invasive species (AIS) can cause catastrophic damages to lake ecosystems. Bigheaded carp are one such species that pose a current threat to Lake Michigan. Bigheaded carp are expected to have spatially differentiated impacts on... more
Aquatic invasive species (AIS) can cause catastrophic damages to lake ecosystems. Bigheaded carp are one such species that pose a current threat to Lake Michigan. Bigheaded carp are expected to have spatially differentiated impacts on other aquatic species in the metapopulation. Policymakers must decide how much to invest in mitigation or conservation policies, if at all, by understanding how invasions impact social welfare or social wellbeing. Estimates of social welfare implications, however, may be biased if important interactions between species and space are overly simplified or aggregated out of the model. In this analysis, a bioeconomic model that links an ecological model with an economic model of recreational fishing behavior is used to complete a comparative analysis of the social welfare implications across several different ecological specifications to demonstrate what biases exist if species interactions are neglected or if ecological characteristics are assumed to be h...
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Human-driven environmental change underlies recent changes in water clarity in many of the world’s great lakes, yet our understanding of the consequences of these changes on the fish and fisheries they support remains incomplete. Herein,... more
Human-driven environmental change underlies recent changes in water clarity in many of the world’s great lakes, yet our understanding of the consequences of these changes on the fish and fisheries they support remains incomplete. Herein, we offer a framework to organize current knowledge, guide future research, and help fisheries managers understand how water clarity can affect their valued populations. Emphasizing Laurentian Great Lakes findings where possible, we describe how changing water clarity can directly affect fish populations and communities by altering exposure to ultraviolet radiation, foraging success, predation risk, reproductive behavior, or territoriality. We also discuss how changing water clarity can affect fisheries harvest and assessment through effects on fisher behavior and sampling efficiency (i.e., catchability). Finally, we discuss whether changing water clarity can affect understudied aspects of fishery performance, including economic and community benefit...
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Effective engagement among scientists, government agency staff, and policymakers is necessary for solving fisheries challenges, but remains challenging for a variety of reasons. We present seven practices learned from a collaborative... more
Effective engagement among scientists, government agency staff, and policymakers is necessary for solving fisheries challenges, but remains challenging for a variety of reasons. We present seven practices learned from a collaborative project focused on invasive species in the Great Lakes region (USA‐CAN). These practices were based on a researcher–manager model composed of a research team, a management advisory board, and a bridging organization. We suggest this type of system functions well when (1) the management advisory board is provided compelling rationale for engagement; (2) the process uses key individuals as communicators; (3) the research team thoughtfully selects organizations and individuals involved; (4) the funding entity provides logistical support and allows for (5) a flexible structure that prioritizes management needs; (6) a bridging organization sustains communication between in‐person meetings; and (7) the project team determines and enacts a project endpoint. We...
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Bighead carp H. nobilis and silver carp Hypothalmichthys molitrix (collectively bigheaded carps, BHC) are invasive planktivorous fishes that threaten to enter the Laurentian Great Lakes and disrupt food webs. To assess the likelihood of... more
Bighead carp H. nobilis and silver carp Hypothalmichthys molitrix (collectively bigheaded carps, BHC) are invasive planktivorous fishes that threaten to enter the Laurentian Great Lakes and disrupt food webs. To assess the likelihood of BHC establishment and their likely effects on the food web of Saginaw Bay, Lake Huron, we developed a multi-species individual-based bioenergetics model that tracks individual bighead and silver carp, four key fish species, and seven prey biomass groups over 50 years. The model tracks the daily consumption, mortality and growth of all individuals and the biomass dynamics of interacting prey pools. We ran simulation scenarios to determine the likelihood of BHC establishment under initial introductions from 5 to 1 million yearling and older individuals, and assuming variable age-0 carp survival rates (high, intermediate, and low). We bounded the survival of age-0 BHC as recruitment continues to be one of the biggest unknowns. We also simulated the pote...
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As bighead (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix)—collectively bigheaded carp (BHC)—arrive at Lake Michigan's doorstep, questions remain as to whether there is sufficient food to support these... more
As bighead (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix)—collectively bigheaded carp (BHC)—arrive at Lake Michigan's doorstep, questions remain as to whether there is sufficient food to support these invasive filter‐feeding fishes in the upper Laurentian Great Lakes. Previous studies suggest that suitable BHC habitat is limited to a few productive, nearshore areas. However, those studies did not consider the influence of BHC's diet plasticity or the presence of spatially‐discrete subsurface prey resources. This study aimed to characterise Lake Michigan's suitability for BHC and evaluate the importance of these considerations in habitat suitability assessments. We used simulated outputs of prey biomass (phytoplankton, zooplankton, and detritus) and water temperature from a three‐dimensional biophysical model of Lake Michigan to evaluate growth rate potential (GRP, quantitative index of habitat suitability) of adult BHC throughout the entire vo...
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Owing to the enormity and complexity of the Laurentian Great Lakes, an ecosystem classification is needed to better understand, protect, and manage this largest freshwater ecosystem in the world. Using a combination of statistical... more
Owing to the enormity and complexity of the Laurentian Great Lakes, an ecosystem classification is needed to better understand, protect, and manage this largest freshwater ecosystem in the world. Using a combination of statistical analyses, published knowledge, and expert opinion, we identified key driving variables and their ecologically relevant thresholds and delineated and mapped aquatic systems for the entire Great Lakes. We identified and mapped 77 aquatic ecological units (AEUs) that depict unique combinations of depth, thermal regime, hydraulic, and landscape classifiers. Those 77 AEU types were distributed across 1997 polygons (patches) ranging from 1 to >48 000 km2in area and were most diverse in the nearshore (35 types), followed by the coastal margin (26), and then the offshore (16). Our classification and mapping of ecological units captures gradients that characterize types of aquatic systems in the Great Lakes and provides a geospatial accounting framework for reso...
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High‐turbidity events (HTEs) are common phenomena in shallow‐water environments that can alter ecological interactions. The relative contributions of river input (external loading) vs. resuspension (internal loading) to the occurrence,... more
High‐turbidity events (HTEs) are common phenomena in shallow‐water environments that can alter ecological interactions. The relative contributions of river input (external loading) vs. resuspension (internal loading) to the occurrence, duration, and influenced areas of HTEs are not fully understood in most systems, owing to the lack of long‐term, source‐specified sediment maps. Using a Finite Volume Community Ocean Model‐based wave‐current forced sediment model, we investigated sediment dynamics in the shallow, river‐dominated Western Lake Erie during ice‐free cycles (April–November) of 2002–2012. Results indicated that wind waves predominated sediment dynamics in the offshore areas, with river discharges causing substantial inshore to offshore gradients. Owing to varying wind waves and river discharges, both the mean and extreme sediment dynamics had distinctive seasonal variations. The basin was turbid during spring and fall, with frequent (> 15%), broad (O [102–103 km2]), and ...
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Efficient management and prevention of species invasions requires accurate prediction of where species of concern can arrive and persist. Species distribution models provide one way to identify potentially suitable habitat by developing... more
Efficient management and prevention of species invasions requires accurate prediction of where species of concern can arrive and persist. Species distribution models provide one way to identify potentially suitable habitat by developing the relationship between climate variables and species occurrence data. However, these models when applied to freshwater invasions are complicated by two factors. The first is that the range expansions that typically occur as part of the invasion process violate standard species distribution model assumptions of data stationarity. Second, predicting potential range of freshwater aquatic species is complicated by the reliance on terrestrial climate measurements to develop occurrence relationships for species that occur in aquatic environments. To overcome these obstacles, we combined a recently developed algorithm for species distribution modeling—range bagging—with newly available aquatic habitat‐specific information from the North American Great Lak...
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Offspring size determines offspring survival rates; thus, understanding factors influencing offspring size variability could elucidate variation in population dynamics. Offspring size variation is influenced through multigenerational... more
Offspring size determines offspring survival rates; thus, understanding factors influencing offspring size variability could elucidate variation in population dynamics. Offspring size variation is influenced through multigenerational adaptation to local environments and within‐lifetime plastic responses to environmental variability and maternal effects among individuals. Moreover, offspring size variation may represent trade‐offs in energy allocation within individuals that influence lifetime reproductive success. However, the mechanisms whereby environmental conditions influence offspring size, e.g., via inducing adaptive and plastic variation in population‐scale maternal effects, remain poorly understood. We evaluated intra‐specific variation in maternal effects, egg size, and intra‐individual egg size variation in six populations of walleye (Sander vitreus) and related among‐ and within‐population patterns to thermal conditions. Egg size was conserved within populations and negat...
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Abstract The role of alternative prey on predator diet selection and survival of juvenile (parr) Chinook salmon ( Oncorhynchus tshawytscha ) is not well understood in the Laurentian Great Lakes. Therefore, measures of predator foraging... more
Abstract The role of alternative prey on predator diet selection and survival of juvenile (parr) Chinook salmon ( Oncorhynchus tshawytscha ) is not well understood in the Laurentian Great Lakes. Therefore, measures of predator foraging ecology (prey species and size selection), prey densities, and functional response relationships were determined for adult walleye ( Sander vitreus ) and brown trout ( Salmo trutta ) (hatchery-reared) feeding on parr and alternate prey in the Muskegon River, a tributary of Lake Michigan, USA, from 2004 to 2007. Walleye selected for smaller than average brown trout and rainbow trout (hatchery-reared) but walleye prey size (within-prey) was independent of predator size. In general, walleye showed neutral selection for all prey species but, in some years, showed positive selection for rainbow trout and negative selection for parr. Hatchery-reared brown trout selected the smallest parr in the environment although prey size was independent of predator size. Parr were positively selected by brown trout only in April. Functional response curves were fit to describe the consumption of parr and other prey types by walleye (type II) and brown trout (type I). Interactions among rainbow trout, walleye, and brown trout favored parr survival, i.e. the presence of alternate prey (rainbow trout) significantly influenced walleye predation on parr, while brown trout appeared to become quickly limited by size or escape ability of parr. Our results should enhance understanding of food web dynamics in Great Lakes tributary habitats.
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Bighead and silver carp ('AC') threaten to invade the Great Lakes and disrupt aquatic food webs and fisheries. We used a risk-based bioeconomics model to evaluate the potential impact of AC on food web structure, fish production... more
Bighead and silver carp ('AC') threaten to invade the Great Lakes and disrupt aquatic food webs and fisheries. We used a risk-based bioeconomics model to evaluate the potential impact of AC on food web structure, fish production and fisheries in Lake Erie's central basin, which supports important recreational and commercial fisheries and provides nursery habitats for many ecologically or economically important fishes. We used the Ecopath with Ecosim (EwE) food web model to evaluate AC impacts on Lake Erie's food web. We used data collected from 1994-2005 to configure and balance the food web in Ecopath, then used Ecosim to simulate potential AC impacts on food web structure and fish production under current conditions of nutrient loading, fish stocking and harvest. We quantified uncertainty in Ecopath model inputs using expert judgement solicitation, which was incorporated into Ecosim to evaluate uncertainty in model forecasts. To forecast regional economic impacts o...
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Physical processes may affect ecosystem structure and function through the accumulation, transport, and dispersal of organic and inorganic materials, nutrients, and organisms; they structure physical habitat and can influence... more
Physical processes may affect ecosystem structure and function through the accumulation, transport, and dispersal of organic and inorganic materials, nutrients, and organisms; they structure physical habitat and can influence predator–prey interactions and trophic production. In the Laurentian Great Lakes, horizontal currents generally dominate, but little is known about the effects of vertical mixing on lake food webs. We developed a linked earth system model and used it to explore how vertical mixing affects the productivity of Lake Michigan (LM), the world’s fifth-largest lake, whose food web and fisheries have been adversely affected by invasive Dreissena mussels. We hypothesized that higher vertical mixing would result in higher food web biomass by making phosphorus more available to the lower food web, and that filtration by invasive mussels would counter the effects of mixing and decrease food web biomass. Using linked climate, hydrodynamics, and ecosystem models, we projecte...
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Hydroelectric dams may affect anadromous fish survival and recruitment by limiting access to upstream habitats and adversely affecting quality of downstream habitats. In the Manistee River, a tributary to Lake Michigan, two hydroelectric... more
Hydroelectric dams may affect anadromous fish survival and recruitment by limiting access to upstream habitats and adversely affecting quality of downstream habitats. In the Manistee River, a tributary to Lake Michigan, two hydroelectric dams poten-tially limit recruitment of anadromous rainbow trout (steelhead) by increasing tailrace water temperatures to levels that signifi-cantly reduce survival of young-of-year (YOY) fish. The objectives of this study were to determine whether proposed restoration scenarios (dam removals or a bottom withdrawal retrofit) would alter the Manistee River thermal regime and, con-sequently, improve wild steelhead survival and recruitment. Physical process models were used to predict Manistee River ther-mal regimes following each dam alteration scenario. Empirical relationships were derived from historical field surveys to quantify the effect of temperature on YOY production and potential recruitment of Manistee River steelhead. Both dam altera-tion sc...
3 Research Fishery Biologist, National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, Ann Arbor, Michigan, 48108
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Risk analysis of species invasions links biology and economics, is increasingly mandated by international and national policies, and enables improved management of invasive species. Biological invasions proceed through a series of... more
Risk analysis of species invasions links biology and economics, is increasingly mandated by international and national policies, and enables improved management of invasive species. Biological invasions proceed through a series of transition probabilities (i.e., introduction, establishment, spread, and impact), and each of these presents opportunities for management. Recent research advances have improved estimates of probability and associated uncertainty. Improvements have come from species-specific trait-based risk assessments (of estimates of introduction, establishment, spread, and impact probabilities, especially from pathways of commerce in living organisms), spatially explicit dispersal models (introduction and spread, especially from transportation pathways), and species distribution models (establishment, spread, and impact). Results of these forecasting models combined with improved and cheaper surveillance technologies and practices [e.g., environmental DNA (eDNA), drone...
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Identifying which nonindigenous species will become invasive and forecasting the damage they will cause is difficult and presents a significant problem for natural resource management. Often, the data or resources necessary for ecological... more
Identifying which nonindigenous species will become invasive and forecasting the damage they will cause is difficult and presents a significant problem for natural resource management. Often, the data or resources necessary for ecological risk assessment are incomplete or absent, leaving environmental decision makers ill equipped to effectively manage valuable natural resources. Structured expert judgment (SEJ) is a mathematical and performance-based method of eliciting, weighting, and aggregating expert judgments. In contrast to other methods of eliciting and aggregating expert judgments (where, for example, equal weights may be assigned to experts), SEJ weights each expert on the basis of his or her statistical accuracy and informativeness through performance measurement on a set of calibration variables. We used SEJ to forecast impacts of nonindigenous Asian carp (Hypophthalmichthys spp.) in Lake Erie, where it is believed not to be established. Experts quantified Asian carp biom...
Research Interests: Conservation Biology, Fisheries, Forecasting, Population Dynamics, Invasive Species, and 15 moreRisk assessment, Biological Sciences, Lakes, Environmental Sciences, Humans, RECREATION, United States, Animals, Fishes, Ecological forecasting, Ontario, Introduced species, Risk Assessment, Carps, and Conservation of Natural Resources
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Research Interests: Environmental Science, Ecology, Population Dynamics, Eutrophication, Growth, and 15 moreFISH, Density dependence, Ecological, Population Density, Life Cycle, Mathematical Model, Feeding Functional Response, Age and growth, Lac, Ecological Applications, Population dynamic, Individual Based Model, Mortality rate, Functional Response, and Model simulation
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Classical predator-prey dynamics highlight the numerical response of a predator population to changes in the prey population (Lotka 1925, Volterra 1926). In the Laurentian Great Lakes, however, predator populations are artificially... more
Classical predator-prey dynamics highlight the numerical response of a predator population to changes in the prey population (Lotka 1925, Volterra 1926). In the Laurentian Great Lakes, however, predator populations are artificially controlled by hatchery production ...
ABSTRACT Following the precipitous decline of alewives in Lake Huron, early life survival and subsequent recruitment of walleye in Saginaw Bay has dramatically increased. However, the mechanisms facilitating increased early life survival... more
ABSTRACT Following the precipitous decline of alewives in Lake Huron, early life survival and subsequent recruitment of walleye in Saginaw Bay has dramatically increased. However, the mechanisms facilitating increased early life survival of walleye have not been fully explored. Previous studies suggest that the majority of young walleye are produced via natural reproduction in the Tittabawasee River, but it is not clear if other habitats have become important for reproduction during this period of walleye resurgence. During 2009 and 2010, we collected larval walleye in various Saginaw Bay habitats using a push net, paired bongo nets, and a neuston net. We estimated the ages of walleye larvae using otolith incremental analysis. To further evaluate the suitability and potential utilization of alternative spawning habitats, we placed egg mats in areas of historical walleye spawning reefs. In 2011, we also characterized habitat quality using a towed side-scan sonar of surrounding potential reef structure. We observed interannual variability in spatial and temporal distributions of walleye (e.g., walleye emerged earlier during a warm year, 2010, as compared to a cold year, 2009). Based on age determinations and capture locations, we speculate that walleye are successfully reproducing in multiple habitats. Young walleye in Saginaw Bay appear to benefit from a diverse set of habitats. Such diversity could temper interannual recruitment variability, and hence, should be a goal for managers.
Predation mortality among Chinook salmon Oncorhynchus tshawytscha parr can act at small spatiotemporal scales and cause variability in parr survival and potential recruitment. We analyzed predator diets and multiplied per capita... more
Predation mortality among Chinook salmon Oncorhynchus tshawytscha parr can act at small spatiotemporal scales and cause variability in parr survival and potential recruitment. We analyzed predator diets and multiplied per capita consumption rates by predator population estimates to evaluate the relative effect of predation by stocked sport fishes on the variability in survival of Chinook salmon parr in the Muskegon River, Michigan, from 2004 to 2007. Brown trout Salmo trutta were a major predator of Chinook salmon parr, consuming from 15% to 34% of the total number available, while walleyes Sander vitreus consumed from 0.2% to 15%. Walleyes also consumed large quantities of brown trout and rainbow trout O. mykiss. Brown trout predation on Chinook salmon parr was largely dependent on parr size, while walleye predation was buffered by the availability of rainbow trout and brown trout. Predation mortality appeared to be responsible for a more than three-fold difference in the survival of Chinook salmon parr in the Muskegon River. The vulnerability of Chinook salmon parr to predation appeared to be controlled by parr growth rates, brown trout stocking dates, and the number of brown trout stocked. Fishery regulations to manipulate piscivore abundance may lead to higher survival and lower variability in the survival of Chinook salmon parr.Received May 6, 2010; accepted November 30, 2010
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ABSTRACT Reductions in nutrient loads and impacts from invasive species may lower recruitment potential of Great Lakes fishes. Filtration by invasive quagga mussels has reduced phytoplankton biomass, shifted energy flow from pelagic to... more
ABSTRACT Reductions in nutrient loads and impacts from invasive species may lower recruitment potential of Great Lakes fishes. Filtration by invasive quagga mussels has reduced phytoplankton biomass, shifted energy flow from pelagic to benthic pathways, and restricted phosphorus transport from nearshore to offshore. Biomass of large cladocerans and adult planktivorous fishes has declined from impacts of quagga mussels and the predaceous cladoceran, Bythotrephes. These multiple stressors have altered zooplankton distributions and densities, and may lower larval fish growth and survival. Yet, in Lakes Michigan and Huron, some fish species still grow and recruit well in nearshore and offshore areas. To understand what drives fish recruitment, we sampled nutrients, fish larvae, and lower and upper food webs on nearshore-offshore transects from 2010-2013 in Lakes Huron and Michigan. A compensatory shift from large phytoplankton to the microbial food web—utilizable by both copepods and small cladocerans— may have mitigated its loss to zooplankton. In high recruitment years, larvae consumed small cladocerans and copepods, and grew well. Larval foraging efficiency may have increased due to increased light penetration and co-occurrence with zooplankton in the metalimnion. Our results suggest compensatory responses to multiple stressors by some zooplankton species may explain recent trends in fish recruitment.
ABSTRACT Knowledge of invasive species dispersal is key for early detection and rapid response. We studied potential dispersal of invasive ruffe and golden mussel (Limnoperna) larvae in Lake Michigan using a 3D particle transport model.... more
ABSTRACT Knowledge of invasive species dispersal is key for early detection and rapid response. We studied potential dispersal of invasive ruffe and golden mussel (Limnoperna) larvae in Lake Michigan using a 3D particle transport model. Advection fields were derived from 10-year hydrodynamic model runs. We predicted larval transport from ballast release points located along major shipping lanes, ports (and vicinity), and major tributaries. Ruffe larvae were released daily at surface from mid-April to mid-May and tracked for 7 days while Limnoperna larvae were released from mid-May to September and tracked for 70 days. We targeted larvae settlement in nearshore waters: ruffe settles in waters < 10 m deep while Limnoperna settles in waters < 50 m deep. In mid-lake ballast releases, Limnoperna larvae drifted eastward (reflecting prevailing surface currents) and colonized nearshore areas on the east coast. In contrast, due to differences in seasonal and drift duration, dispersal of ruffe larvae was minimal, reducing chances of survival. Larvae released from ports and river mouths showed very small dispersal for both species, drifting only a few kilometers before settling (although Limnoperna spread was stronger). Dispersal was much stronger from ballast release locations near ports (5 and 10 km offshore), especially for Limnoperna.