William Lindsay Chadderton

The Nature Conservancy · Great Lakes Project

Detection of invasive species before or soon after they establish in novel environments is critical to prevent widespread ecological and economic impacts. Environmental DNA (eDNA) surveillance and monitoring is an approach to improve early detection efforts. Here we describe a large-scale conservation application of a quantitative polymerase chain...

Risk assessment tools for non-native species can avert ecological and economic harm when they inform regulatory or voluntary management actions that seek to reduce the probability of introducing high-risk species. The Laurentian Great Lakes region contains many aquatic invasive plants, non-native species whose introduction causes economic or enviro...

Environmental DNA (eDNA) is a sensitive technique for early detection of rare species, including bighead (Hypophthalmichthys nobilis) and silver (Hypophthalmichthys molitrix) carp, which are incipient invaders of the Great Lakes. Since 2009, 2822 samples have been collected from the Great Lakes basin to delimit the extent of Asian carp incursions....

Unlabelled: The goal of most invasive species suppression programs is to achieve long-term sustained reductions in population abundance, yet removal programs can be stymied by density-dependent population responses. We tested a harvest removal strategy for invasive Rusty Crayfish (Faxonius rusticus) at two nearshore native fish spawning habitats i...

The goal of a harvest removal program to control invasive species is usually to achieve sustained reductions in population abundance. Yet removal efforts may be counteracted by density-dependent processes by increasing available resources and reducing stage-specific mortality. We tested a harvest removal strategy for invasive Rusty Crayfish ( Faxon...

Carolina fanwort (Cabomba caroliniana A. Gray, fanwort) is a submerged macrophyte invasive in Asia, Australia, Europe, and parts of North America that degrades the structure, function, and use of aquatic ecosystems. Several herbicides have been evaluated for fanwort control in laboratory and mesocosm studies, but few have been assessed in a field s...

At least 65 aquatic plant species have been identified as part of a surveillance list of non-native species that pose a threat to biodiversity and ecosystem services in the Laurentian Great Lakes. Early detection of these potentially invasive aquatic plants (IAP) could minimize impacts of novel incursions and facilitate successful eradication. We d...

High densities of invasive rusty crayfish on critical spawning reefs present a potential impediment to the recovery of native fish in the Laurentian Great Lakes. Suppression of rusty crayfish on spawning reefs to protect fall spawning native fishes in the Great Lakes is hampered by regular storm events and ambient weather conditions, limiting the n...

In an effort to harmonize multi-jurisdictional surveillance and detection of aquatic invasive species, regional stakeholders have called for the development of a Great Lakes Aquatic Invasive Species Surveillance Framework to identify species that pose a risk to the basin, quantify the relative risk of various pathways of introduction, provide guida...

Ecosystem managers confronted with newly invasive species may respond with a program of suppression or eradication. Suppression of an invasive species refers to management of a species such that its effect on other biota in the local ecosystem is acceptable. Eradication is the removal of all individuals of a species from a defined region. We examin...

Bigheaded carps (BHCs; Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis) are economically and culturally important in Asia and Europe but are considered highly invasive throughout the Mississippi River watershed and pose a threat to the food web and fisheries of the Laurentian Great Lakes. We used the Ecopath with Ecosim model fr...

Non-native rusty crayfish are abundant egg predators on spawning reef habitats for lake trout and coregonines in northern Lake Michigan. To better understand rusty crayfish life-history on these unique habitats, we conducted monitoring in 2012 and 2013 at four locations previously identified as spawning areas for native fish. With the aid of a grap...

The inconsistency in regulated species lists across the shared waters of the Great Lakes undermines the collective prevention efforts of the region, resulting in a "weakest link" problem; some jurisdictions regulate more than 100 species, others fewer than 20. We examine progress over the last twelve years toward more consistent regulated species l...

Knowledge about the size of environmental DNA (eDNA) and eDNA-bearing particles in aquatic environments is integral to efficient and sensitive analyses. To explore the influence of environmental factors on eDNA particle size distribution (PSD), we manipulated fish communities across nine experimental ponds, which led to differences in a suite of en...

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–...

Risk-based prioritization for early detection monitoring is of utmost importance to prevent and mitigate invasive species impacts and is especially needed for large ecosystems where management resources are not sufficient to survey all locations susceptible to invasion. In this paper we describe a spatially-explicit and quantitative approach for id...

Ballast water is a leading vector for the introduction of aquatic invasive species worldwide and, once a novel species is established, regional ballast water exchange between ports can accelerate secondary spread. The importance of shipping induced invasions in the Laurentian Great Lakes has resulted in policies that require more stringent ballast...

Photoquadrats and underwater video surveys are standard non-destructive monitoring methods in marine ecosystems and are becoming more common in freshwater systems. The high water clarity found in most of the Laurentian Great Lakes make them ideally suited for photoquadrat sampling. We compared the effectiveness of baited photoquadrats to monitor be...

The ongoing threat of introduction of invasive species, including crayfish, to the Laurentian Great Lakes has motivated the development of predictive models to inform where these invaders are likely to establish. Our study is among the first to apply regional freshwater-specific GIS layers to species occurrence data to predict ecosystem suitability...

Bighead and Silver Carp (collectively, bigheaded carps ‘BHC’) are highly invasive planktivorous fish that threaten to invade and impact Great Lakes food webs. We used the Ecopath with Ecosim food web model to simulate potential BHC biomass and food web impacts across Great Lakes habitats that vary in productivity, prey and predator biomass, and spe...

Following decades of ecologic and economic impacts from a growing list of nonindigenous and invasive species, government and management entities are committing to systematic early- detection monitoring (EDM). This has reinvigorated investment in the science underpinning such monitoring, as well as the need to convey that science in practical terms...

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 fre...

Environmental DNA (eDNA) analysis of extracellular material shed by aquatic organisms is a noninvasive genetic tool that can improve efficiency and reduce costs associated with species detection in aquatic systems. eDNA methods are widely used to assess presence/absence of a target species, and have also recently demonstrated potential for estimati...

Knowledge of aquatic invasive species (AIS) dispersal is important to inform surveillance and management efforts to slow the spread of established invaders. We studied potential dispersal of invasive Eurasian ruffe Gymnocephalus cernua and golden mussel Limnoperna fortunei larvae in Lakes Michigan and Erie using a three-dimensional particle transpo...

Forecasts of the locations of species invasions can improve by integrating species-specific climate and habitat variables and the effects of other invaders into predictive models of species distribution. We developed two species distribution models (SDMs) using a new algorithm to predict the global distributions of two nonindigenous species, grass...

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 opportunit...

With new introductions of invasive species occurring at an alarming rate, resource managers must be able to rapidly determine the source of introduction if there is to be a chance of preventing further spread or future invasions. The first North American populations of reproducing northern snakehead (Channa argus) were detected in Maryland in 2002...

Environmental DNA (eDNA) is useful for delimiting species ranges in aquatic systems, whereby water samples are screened for the presence of DNA from a single species. However, DNA from many species is collected in every sample, and high-throughput sequencing approaches allow for more passive surveillance where a community of species is identified....

The use of environmental DNA is a rapidly evolving approach for surveillance and detection of species. Often water samples are collected in the field and then immediately cooled, filtered, and the resulting filters are stored in freezers to preserve the DNA for subsequent analyses. Recently it was shown that filtered samples could be stored at room...

Ballast water in ships is an important contributor to the secondary spread of invasive species in the Laurentian Great Lakes. Here, we use a model previously created to determine the role ballast water management has played in the secondary spread of viral hemorrhagic septicemia virus (VHSV) to identify the future spread of one current and two pote...

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 poi...

Naturally reproducing populations of lake trout and cisco remain highly suppressed in Lake Michigan, and many conservation plans call for an improved understanding of mitigating factors impeding successful recruitment and implementation of conservation actions. Recovery of lake trout and cisco has suffered due, in part, to poor recruitment resultin...

Due to socioeconomic differences, the accuracy and extent of reporting on the occurrence of native species differs among countries, which can impact the performance of species distribution models. We assessed the importance of geographical biases in occurrence data on model performance using Hydrilla verticillata as a case study. We used Maxent to...

Intentional introductions of nonindigenous fishes are increasing globally. While benefits of these introductions are easily quantified, assessments to understand the negative impacts to ecosystems are often difficult, incomplete, or absent. Grass carp (Ctenopharyngodon idella) was originally introduced to the United States as a biocontrol agent, an...

Environmental DNA (eDNA) surveillance holds great promise for improving species conservation and management. However, few studies have investigated eDNA dynamics under natural conditions, and interpretations of eDNA surveillance results are clouded by uncertainties about eDNA degradation. We conducted a literature review to assess current understan...

eDNA surveillance is an effective tool for the detection of aquatic species in areas of low population abundance (e.g. rare or threatened species and aquatic invasive species at the leading edge of an invasion front). However, the utility of this method depends upon our ability to maximize DNA collection in the field and DNA recovery in the laborat...

The application of environmental DNA in aquatic systems for detecting rare species is rapidly advancing both in technology and use. However, few studies have focused on the sampling design for eDNA collection. Using conventional study designs (i.e., random) for species with low detection probabilities is often cost and logistically prohibitive. Tar...

Despite the wide use of grass carp as an effective control strategy for nuisance aquatic macrophytes, there has been a great deal of uncertainty in terms of its perceived risk to North American aquatic ecosystems. Recent observations of feral (and sometimes diploid) individuals in the Great Lakes (GL) Basin have spurred interest in re-evaluating th...

Desiccation following prolonged air exposure challenges survival of aquatic plants during droughts, water drawdowns, and overland dispersal. To improve predictions of plant response to air exposure, we observed the viability of vegetative fragments of ten aquatic plant species (fanwort, coontail, common elodea, Brazilian elodea, parrotfeather, vari...

In many North American rivers, populations of multiple species of non-native cyprinid fishes are present, including black carp (Mylpharyngodon piceus), grass carp (Ctenopharyngodon idella), bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), common carp (Cyprinus carpio), and goldfish (Carassius auratus). All six o...

With increasing pressure placed on natural systems by growing human populations, both scientists and resource managers need a better understanding of the relationships between cumulative stress from human activities and valued ecosystem services. Societies often seek to mitigate threats to these services through large-scale, costly restoration proj...

Impacts of nonindigenous crayfishes on ecosystem services exemplify the mixture of positive and negative effects of intentionally introduced species. Global introductions for aquaculture and ornamental purposes have begun to homogenize naturally disjunct global distributions of crayfish families. Negative impacts include the loss of provisioning (e...

Background/Question/Methods Invasive bighead carp (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix) established in the lower Mississippi River and continue to spread into the Upper Mississippi Basin and threaten to invade the Laurentian Great Lakes. We sought to estimate the potential distribution of these species in Nort...

Background/Question/Methods The perceived ecological impact of a species motivates policy and management. In the 1960’s, herbivorous grass carp (Ctenopharyngodon idella) was imported to the U.S. as a biocontrol tool for aquatic weeds prior to a thorough assessment of its potential risk to ecosystems. Shortly after its introduction, observations o...

Background/Question/Methods The Great Lakes are subject to multiple stressors, and assessing their impacts is challenging when these stressors have different spatial distributions and their impacts vary among habitats. The ability to map the presence or intensity of individual stressors across the Great Lakes, weight individual stressors for thei...

Background/Question/Methods Many plant species are transported globally outside of their native ranges. Only a small proportion of the species that are introduced outside of their native ranges become established, and of those, an even smaller number become invasive. Risk assessment tools have the potential to prevent importation of invasive spec...

We tested the accuracy of an invasive aquatic plant risk assessment system in the United States that we modified from a system originally developed by New Zealand's Biosecurity Program. The US system is comprised of 38 questions that address biological, historical, and environmental tolerance traits. Values associated with each response are summed...

Comparison of questions and scoring between the New Zealand Aquatic Weed Risk Assessment [3], [28], [29] and the USAqWRA used for the analyses described. (DOC)

Non-native species present in the US for over 30 years that were assessed in the development of the USAqWRA system. (DOC)

Ten invasive and ten non-invasive species assessed for USAqWRA system validation. (DOC)

A priori classification for test species based upon their status in the US and predicted invasiveness risk level using the USAqWRA system. (DOC)

USAqWRA system results for the 20 validation species. (DOC)

Three mantras often guide species and ecosystem management: (i) for preventing invasions by harmful species, 'early detection and rapid response'; (ii) for conserving imperilled native species, 'protection of biodiversity hotspots'; and (iii) for assessing biosecurity risk, 'an ounce of prevention equals a pound of cure.' However, these and other m...

Casey et al. correctly identified a need for clarification re-garding the detection limits we reported for two PCR as-says (Jerde et al. 2011). Serial dilutions of purified PCR amplicon DNA (not total genomic DNA) were used to evaluate sensitivity. One microliter of purified ampli-con DNA from each assay was added to 25 μL reac-tions and the lowest...

Vegetative reproduction promotes human-mediated dispersal of aquatic invasive plants as fragments “hitchhike” between water bodies on boats and trailers. However, desiccation of plant fragments may also reduce fitness, decreasing the likelihood of fragment survival as transport distances increase. Current inter-lake invasive species spread models d...

Although New Zealand has strong legislative and policy directives to protect a representative range of riverine ecosystems, implementation of comprehensive and adequate protection has been slow. In addition, there are increasing concerns about biodiversity loss in many lowland rivers and streams, given land-use intensification. A number of initiati...

The giant kokopu, Galaxias argenteus, is a native New Zealand freshwater fish which optionally undergoes a marine larval phase after hatching near a river mouth. The marine phase is indicated by a high Sr:Ca ratio in the core of the otolith of the adult fish. Elemental scanning for Sr and Ca with a proton microprobe is one of the most useful techni...

Background/Question/Methods Along with environmental tolerances and biotic interactions, dispersal represents a key determinant of whether an organism will persist in a given ecosystem. In the case of aquatic plants, major mechanisms of dispersal of seeds and vegetative structures among waterbodies are thought to include waterfowl, moose, and, mo...

Effective management of rare species, including endangered native species and recently introduced nonindigenous species, requires the detection of populations at low density. For endangered species, detecting the localized distribution makes it possible to identify and protect critical habitat to enhance survival or reproductive success. Similarly,...

1. Previous attempts to identify nationally important wetlands for biodiversity in New Zealand were based on expert panel opinions because quantitative approaches were hampered by a lack of data. We apply principles of systematic conservation planning to remote sensing data within a geographical information system (GIS) to identify nationally impor...

Summary 1. Classifications that group rivers and streams with similar ecological characteristics are used increasingly to underpin conservation and resource management planning. Uses include identifying systems that may respond similarly to human activities or management actions, setting guidelines and standards to manage human impacts, interpreti...

Trailered boats have been implicated in the spread of aquatic invasive species. There has been, however, little empirical research on the type and quantity of aquatic invasive species being transported, nor on the efficacy of management interventions (e.g., inspection crews, boat washing). In a study of small-craft boats and trailers, we collected...

We compared macroinvertebrate communities colonising multiplate samplers constructed from perspex or tempered hardboard (wood) with an alternative artificial substrate constructed from folded coconut fibre matting (coir) enclosed in nylon netting. Substrates were incubated for 62 days over January to March 2007 at six sites over 240 km along the Wa...

Aim To examine the relationship between diadromy and dispersal ability in New Zealand’s freshwater fish fauna, and how this affects the current environmental and geographic distributions of both diadromous and non-diadromous species. Location New Zealand. Methods Capture data for 15 diadromous and 15 non-diadromous fish species from 13,369 sites th...