FISH 423 Final

Ecological impacts

(1) Geneic effects • hybridization (2) Individual effects demographic rates such as mortality and growth (3) Population effect abundance, population growth, etc. (4) Community effects species richness, diversity, trophic structure (5) Ecosystem effects nutrient availability, primary productivity, etc

management

1. Prevention (i.e., reduce the likelihood of invasion), or 2. Mitigation (i.e., reduce the impact of invasion).

Factors influencing impact

1. Traits of non-native species 2. Recipient community structure 3. Species niche differences 4. Environmental conditions 5. Organism Influx 6. Synergistic effects

Types of dispersal pathways

Dispersal pathway refers to the combination of processes and opportunities resulting in the movement of propagules from one area to another Major pathways differ with respect to: - Frequency of dispersal events (propagule number) - Propagule size - Number of donor and recipient regions

adaptation to local envrionment

Organisms can be viewed as sets of morphological traits, life-history characteristics and behaviors that were shaped by natural selection to match a set of local environmental and biological conditions. • Organisms are expected to be adaptive, because they rely on cues that, over evolutionary time, reliably correlated with survival and reproductive success. • However, organisms are only as complex as necessary to promote survival and fitness in the environment in which they evolved, and not so complex as to cover suddenly new conditions.

Food web and stocking

Several fish species have been widely stocked throughout the world. • These species have generally been viewed as "desirable" non-natives because they provide valuable recreational fisheries. • However, the broader food-web and ecosystem consequences of these introductions are becoming increasingly apparent. Stocking of fishes into fishless aquatic systems has occurred in at least 60% of western mountain lakes. • Trout introductions typically... community composition and oRen result in the loss of native aquatic species. Epanchin et al. (2010) • Trout can reduce the availability of prey subsidies from aquatic to terrestrial habitats, and thereby impact terrestrial consumers.

Reaction-diffusion example

Short-distance dispersal of rusty crayfish • Rusty crayfish (Orconectes rusticus) has expanded its distribution over the last 50 years to waters throughout the U.S. and Canada. Rusty crayfish may have been introduced by bait bucket releases, by lake users desiring to rid their lake of nuisance weeds, and by commercial harvesters. • Once established, crayfish may move within and between lakes via natural dispersal. • Rusty crayfish took 20 years to completely disperse around the littoral zone, advancing at an average rate of 0.7 km/year

successful eradication

Sufficient economic resources must exist for the project to be completed. 2. Clear lines of authority; someone must be in charge and must be able to compel cooperation. 3. The biology of the target organism must make it susceptible to control measures. . Re-invasion must be prevented. 5. Invasive species must be detectable at low levels. 6. Eradication might require restoration of the community or ecosystem following the removal of a "keystone" target species. Is the effort of eradication worth it if rapid re-invasion is likely? • In many circumstances, even a successful eradication campaign can be a wasted effort because of re-invasion. • In Washington state, there was an intensive campaign to rid Long Lake (130 ha) of Eurasian water milfoil (Myriophyllum spicatum). • However, a public boat ramp permitted quick re-invasion, and Thurston county switched to a program of maintenance management by hand-pulling.

Caribbean Black-striped Mussel

The Caribbean black-striped mussel (Mytilopsis sallei), was discovered in 1999 in Cullen Bay, Darwin Harbor, Australia. • Within nine days the bay had been quarantined and treated with 160,000 liters of bleach and 6,000 metric tons of CuSO4. • The long-term environmental consequences of this eradication program are unknown.

ecological risk modeling

The ecological niche of a species is modeled based on occurrence patterns within the species' native distribution. • This model is then projected to other regions to identify areas potentially habitable by non-native populations of the species.

evolution of native species in response to an invader

- Native species may lack defenses to a newly introduced predator, competitor or pathogen due to the absence of a coevolutionary history between the two. Native species within an invaded habitat frequently exhibit adaptive responses to introductions of novel species. • In special cases where the introduced species is a novel predator, native prey species can experience abrupt changes in the intensity or direction of natural selection. • In order to persist during changes in the selective environment, native prey populations require rapid evolution of morphology, behavioral or life history traits.

policy

• Lacey Act (1900) • Nonindigenous Aquatic Nuisance Prevention and Control Act (NANPCA) (1990). • National Invasive Species Act (NISA) (1996)

evolutionary consequences

• When non-native species are introduced to a new environment they may experience an array of new selective pressures. • At the same time, nonnative species act as novel selective agents on native taxa in the invaded ecosystem. • Thus, conditions are favorable for rapid evolution of both the invaders and the species they interact with in the new range.

benefits to invasive species

-habitat modification (- Willow flycatcher and salt cedar) -trophic subsidies (New Zealand mud snail) -competitive release -predator release Red swamp crayfish provide a prey resource to native birds • Native predatory birds in Spanish rice fields consume nonnative red swamp crayfish • This prey resource has facilitated recolonization of many birds to degraded wetlands. • King et al. (2006) investigated the effects of the invasive round goby (Neogobius melanostomus) on diet composition, growth rate, and body size of the Lake Erie Water Snake (Nerodia sipedon insularum). Competitive release: The reduction in the abundance of a competitive dominant can indirectly facilitate competitively inferior na've species. - European green crab Predatory release: The reduction of na've consumers by invasive species can indirectly result in increased abundance or biomass of na've prey. - Freshwater crayfish and trout

quantitative risk assessement

. Identify potential donor regions and dispersal pathways - The presence of strong dispersal pathways and vector activity between the potential donor and target regions may indicate a high probability of future invasion. • Integrated Vector Management aim to reduce the introduction of non-native species via particular transport vectors. • Vector Management is comprised of four core components: - Analysis, Strength, Interruption, and Effectiveness 2. Select potential invaders using biological criteria - After having identified a potential donor region, a pool of probable invaders are selected based on a general biological profile of invasive species. Ricciardi and Rasmussen (1998) • Once identified, species traits can be used to develop screening profiles that allow for the prevention of new invasive species. 3. Forecast the potential geographic range of the invader - Predict areas of habitat suitability according to the invader's ecological requirements. • Several studies have attempted to use information about a species' ecological requirements to predict areas with significant establishment risk. • This approach is based on the concept of ecological niches as a constraint on the distributional potential of species.

gravity model example

Bythotrephes longimanus (spiny water flea) is a parthenogenetic waterflea native to European lakes. • It was first reported in Lake Ontario in 1982, and established populations likely as a consequence of ballast water discharge by a ship. • The species subsequently colonized each of the other Great Lakes, as well as inland lakes and reservoirs. • MacIssac et al. (2004) assessed the spread of Bythotrephes to inland Ontario lakes from the Great Lakes based upon human-mediated vector flows. • Their results revealed a "stepping stone" pattern of invasion. • Species spread occurred via a combination of dominant, local diffusion (median=12.5 km) and rare, long-distance (>100 km) dispersal.

tamarix and market/non market costs

Consumes water more rapidly than most native vegetation (transpiration) Draws down water table, dry's desert springs, lowers flow rates and lake levels Promotes wild fires Lacks palatable fruits and seeds and structure does not support many native faunal groups Municipal Water Losses • The Metropolitan Water District (MWD) has turned to buying water from farmers with priority water rights and long term interstate buying schemes to supplement water supply Agricultural Water Losses The value of water to crop production ranges from 17 to 650 USD per 1000 m³ Hydropower Generation The cost of getting the same power provided by hydroelectric means via coal fired steam or gas turbine generation Eradication costs range from 500 USD ha⁻¹ to 7,500 USD ha⁻¹ (excluding post planting of native vegetation) One estimate is that costs would be offset by economic benefits within 25 years of the invaders initial removal

regulation of live animal import

Current federal approaches to risk assessment of non-native species rely exclusively on qualitative, expert opinion. • Too few USDA and USFWS employees have jobs dedicated to evaluating the risk associated with the importation of live organisms. • National screening processes have been "successful" in reducing rates of invasions in Australia and New Zealand, but have been relatively ineffective in the U.S.

milfoil and direct/non direct impacts

Decrease quantity and quality of recreational activities such as angling, boating, swimming, water skiing and nearshore recreation Decrease profitability of agricultural production Increase the costs of electricity generation and affect provision of municipal water supplies Depress passive use values of freshwater ecosystems Collected data for 1,300 lakeshore property sale transactions of single family homes in 41 lakes located in King County Milfoil lakes = 17 (611 total transactions) Milfoil-free lakes = 24 (647 total transactions) Property values were adjusted to 2006 USD using the annual average consumer price index • After accounting for structural (e.g., house size), locational (e.g., boat launch), and environmental characteristics (e.g., water clarity) of lakes, Eurasian milfoil has a significant negative effect on property sales price ($94,385 USD lower price), corresponding to a 20% decline in mean property values. • The aggregate cost of milfoil invading one additional lake in the study area is, on average, $380,000 USD per year. • Strong incentives for the public to prevent or control aquatic invasive weeds

adjustments to a new environment

Evolutionary adjustments of an invader to a new environment. - When species are introduced to an environment that is environmental unsuitable, they may be required to rapidly adapt to the new circumstances. Individuals in non-native populations are constrained in their growth, reproduction, and survival by a different set of factors than individuals in the source population. • If any environmental factor acts in a consistent manner to eliminate particular phenotypes, we should expect the population evolve towards the favored phenotype. • Potential for rapid evolution depends, in large part, on the level of genetic variability in the founding population and the conditions of the invaded environment. • Cane toads have astonishing locomotor abilities (they move up to 2 km per night • Question: Does this remarkable ability result from selection for enhanced dispersal during the toads' colonization history? • The morphological trait most often linked to locomotor ability in frogs/toads is leg length. • If the invasion process has been assisted by the evolution of improved dispersal ability among toads at the invasion front, three consequences would be expected. • First, longer-legged toads should be disproportionately common among the first wave of arrivals at any site. • Second, toads at the invasion front should be longer-legged than toads from older populations. • Third, the rate of progress of the toad invasion front should increase through time.

Extinction by hybridization

Example: ducks Mallard duck introductions have been purposeful introduced throughout the world. • Mank et al. (2004) used museum specimens and present-day samples to examine the degree of hybridization between mallards and native black ducks in eastern North America. • Hybridization has resulted in a significant reduction in genetic differentiation. • Pre-1940: GD = 0.146 Post-1998: GD = 0.008

Genetic effects

Genetic effects of invasive species are defined as alterations to the gene pools of native species usually through the processes of hybridization and introgression. • When hybrids are fertile and readily backcross with the parental taxa, genetic mixing can be extensive. • This introgressive hybridization alters the genetic composition of the native population and can result in extinction of the native genotypes. Hybridization and introgression is prevalent in highly isolated ecosystems, such as river basins and lakes. • Hydridization can lead to the decline of species through outbreeding depression - referring to decreased fitness in offspring that arises whether hybrids survive or not. • There are numerous examples of hybridization between invasive and native populations. - Invasive rainbow trout and endemic Apache and Gila trout in southwestern U.S. - Eurasian watermilfoil with native milfoil in northeastern U.S.

gravity models

Gravity models provide an approach to modeling stratified diffusion involving both local and jump dispersal. • These models relate the force of attraction between an invaded site and a non-invaded site as a function of the distance between them, in a manner similar to how Newton's Theory of Gravity measures the attractive force between two masses. • Geographers have used gravity models to predict human dispersal patterns by estimating the flow of people based on the distance to and attractiveness of destination points. A gravity model may be superior to a reaction-diffusion model in forecasting spread of invading species because it allows dispersal to occur in heterogeneous environments over both short and long distances. • Bossenbroek et al. (2001) developed a production constrained gravity model to forecast spread of zebra mussels in four Great Lakes states. • This study demonstrated that a gravity model better predicts the overland spread of zebra mussels as compared to the diffusion model.

Hybridization between native introduced trout

Hybridization threatens the persistence of several species of native salmonids in the western U.S. • Weigel et al. (2003) examined the occurrence of hybridization in native westslope cutthroat and introduced rainbow trout populations.

Impact

Impact is the final and often dramatic stage of the invasion process. • However, the definition of an impact is problematic because there are scientific and societal factors that influence our perception. • Where do we draw the line for non-native species having no impact? • Is it possible for a species to invade a new environment and truly have no impact? • Ecological impact is defined as a measurable change to the properties of an ecosystem by a nonnative species. • Parker et al. (1999) proposed a simple equation based on the total area occupied by the nonnative species in its novel range (R), its abundance (A, in numbers or biomass per square meter), and its per capita effect (E). I = R x A x E

biocontrol negatives

In many settings non-native species have come to replace the functions formerly served by native species. • Therefore, the control or eradication of non-native species could have undesirable effects when it provides food or habitat for an imperiled or declining native species. ex: tamarix and the bird

Ecosystem level effects

Invasions can occur across all trophic levels with effects propagating throughout entire ecosystems via direct and indirect pathways. • Species causing ecosystem-level impacts are considered the most important to prevent introduction, control and eradicate. • Documenting ecosystem effects is challenging, in large part because large replication is usually not feasible. 3 primary ways: 1. non natives can differ in use of resources, thus effecting resource availability 2. can alter flow of energy by changing food web, such as introducing top predator 3. effect disturbance regimes, such as ecosystem engineers

ecosystem engineers

Invasive species can be ecosystem engineers when they create, destruct or modify the physical habitat. • Some of the most familiar exotic engineers are introduced, landscape-altering plants. • In riparian ecosystem, salt cedar (Tamarix) can lower the local water table and cease water flows and seeps, thus impacting native plants and animals depending on this resource. TAMARIX • In coastal ecosystems, Atlantic cordgrass (Spar;na alterniflora) and the Japanese eelgrass (Zostera japonica), are encroaching upon unvegetated tidal flats. • The introduced cordgrass can grow lower in the intertidal than native cordgrass, whereas Japanese eelgrass is able to live higher in the intertidal than native eelgrass. CORDGRASS • In freshwater ecosystems, the common carp and red swamp crayfish increase turbidity and nutrient loads via destructive feeding on macrophytes. CARP AND RED CRAYFISH • In marine systems, the periwinkle snail (Li@orina li@orea) bulldozes sediments during grazing and inhibits plants and algae communities of intertidal habitats. • In freshwater ecosystems, hydrilla, Eurasian water milfoil, and water hyacinth are capable of creating thick beds that limit water movement and light penetration. HYDRILLA, MILFOIL

lacey act

Lacey Act (1900) • Under the Lacey Act, the Secretary of the Interior is authorized to regulate the importation and transport of species determined to be injurious to the health of humans, the interests of agriculture, horticulture or forestry, and the welfare and survival of wildlife resources of the U.S. • For decades, the Lacey Act was primarily a white list law— prohibiting importing "any foreign wild animal or bird" except under special permit, as well as banning all imports of mongoose, fruit bats, English sparrows, and starlings • The 1949 amendments of the Lacey Act transformed the injurious species provision into a purely black list law, by excising the language that barred import of "any foreign wild animal or bird" failures: • The listing process is not timely • The Lacey act includes no emergency measures • Listing under the Lacey Act is often too late • The Lacey Act does not effectively regulate the interstate transport of invasive species. • The Lacey Act has no authority, nor does it entail any funding, to manage the spread of established wild populations.

prevention or cure?

Leung et al. (2002) presented a bioeconomic model to identify the optimal allocation of resources to prevent versus control of zebra mussel in a lake containing a power plant. • They modeled changes in zebra mussel population over time, and focused on the impact on industry of reduced water intake efficiency caused by fouling of pipes Assuming a constant probability of invasion, the model indicated that to reduce the probability by 10% it would be beneficial for society to pay up to $27,000 per month ($324,000 per year) on prevention for a single lake containing a power plant. • The US Fish and Wildlife Service spent $825,000 in 2001 to manage all aquatic invaders in all US lakes.

market vs non market impacts

Market impacts • Refer to changes in prices due to reduced productivity of commodities sold within the marketplace. • Example include: - Decreases in fisheries and aquaculture production - Decreases in the availability of water for industries - Decreases in the navigability of lakes and rivers - Declines in property values Non-market impacts • Refer to economic losses associated with changes in human capital, social capital and ecosystem services. • For example, these costs may be related to changes in native biodiversity or changes to natural habitats caused by invasive species. • Non-market costs are usually not considered in assessments of economic damage because they are much more difficult to quantify. • Non-market value of natural ecosystems are based on contingent valuations in which an assessment is made of an individual's "willingness to pay". • This approach enables a financial assessment of environmental non-market goods and services (e.g. aesthetic value, space for recreational activities). • However, it is subjective because it varies among interest groups and geographic areas, and therefore is considered controversial.

Modeling geographic spread

Models that forecast geographic spread help ecologists: - Anticipate which non-native species will quickly spread. - Identify the life history traits or ecological conditions that are the most important in allowing rapid expansion. - Target management efforts towards stopping or slowing the rate of spread in an effective manner. • Reaction-diffusion models are most commonly used to model short-distance spread and are based simply on dispersal and reproduction Gravity models provide an approach to modeling stratified diffusion involving both local and jump dispersal.

limitations of economics

Most assessments of economic costs have been limited to specific invasive species within particular localities, and have considered only direct costs associated with control or loss of marketable goods or services. • More inclusive models of economic costs of invasive species are difficult to develop owing to the lack of data pertaining to indirect market costs, as well as both direct and indirect, non-market costs • Most evaluations focus on the negative effects and ignore the positive economics • Policymakers need information on the benefits and costs of invasive species in order to make informed management decisions. • This information is essential for developing bioeconomic models that aim to predict the optimal allocation of resources to prevention versus control. • Comprehensive programs for the management and prevention of new invasions will undoubtedly require significant national funding.

Measure impact

Much of the discussion involving the ecological effects of invasive species has been purely descriptive. • As a result, the case against introducing non-native species is often poorly supported. • Those studies attempting to quantify impacts have often done so in a largely correlative manner. • In order to generalize about the impacts of non-native species we require ways to define, assess, and compare impacts across taxonomic groups and ecological levels. • Calculating the economic cost in terms of damages or eradication/control is one useful approach to measuring the impact of an invader. • Unlike monetary cost, however, many different types of ecological metrics can be used to assess impacts on native populations and ecosystems. • Most studies of the effects of invaders are of short duration and are conducted more or less indiscriminately along the time course of invasions

Bass and food webs (lake trout!)

Native to eastern North America, smallmouth bass (Micropterus dolomieu) and rock bass (Ambloplites rupestris) are continuing to spread rapidly. • While stocking of nonnative game fishes by resource management agencies is no longer a common practice, bass continue to expand their range. • Vander Zanden et al. (1999) used stable isotope techniques to quantify the food-web consequences of recent invasions of smallmouth bass and rock bass in 18 central Ontario lakes. • Carbon and nitrogen stable isotope ratios (δ13C and δ15N) provide valuable information about aqua'c food webs. • There is an increase in δ15N from prey to predator, such that δ15N can be used to estimate trophic position. • Benthic algae are enriched in 13C relative to phytoplankton, such that δ13C can be used to estimate the energetic contributions of litioral versus pelagic prey. Basically, lake trout prefer pelagic prey and when both pelagic and littoral prey are present they are happy campers with or without bass. When bass are present and they have to compete for littoral prey, shit gets rough • Trophic position of lake trout averaged 3.3 in invaded lakes (indicating a plankton-based diet) compared with 3.9 in reference lakes (indicating a fishbased diet). • Lake trout from invaded lakes averaged 20% litioral prey, compared with 80% in reference lakes lacking pelagic prey.

More dispersion information

Rate of range expansion was consistently slower for marine vs. terrestrial invaders • Directional vs. nondirectional dispersal? • Explained by marine dispersal during larval stages via adventive sea-surface currents? One common feature of invasions is a lag time between initial colonization and the onset of rapid population growth and range expansion. • Unfortunately, we often lack data! • Many examples exist where non-native species can exist in relatively low numbers for decades before exploding • There are 4 main causes of time lags -degree of biotic resistance changes -necessary mutualistic partners -allee effects/propagules -environmental changes through time

control

Rather than attempting to eradicate an invasive species, reducing population numbers over a large area provides an opportunity to control their density. • Invasion control can be accomplished by: - Physical removal of non-native organisms. - Restoration of natural habitats to suppress nonnative population. - Enhance predation pressure on non-native population.

Spread

Spread of non-native species is a microcosm of the entire invasion process involving: - the dispersal or transport of individuals into a new habitat, and - the establishment of a self-sustaining population Factors regulating the speed of spread include: - Type of dispersal pathway - Propagule pressure - Reproductive rates and other life-history characteristics - Environmental and landscape characteristics - Ecological attributes of the recipient communities

evolutionary release

The interaction between two species that do not share an evolutionary history could also result in a positive outcome for one or both species. • For example, introduced American bullfrog (Rana catesbeiana) prey upon native anuran tadpoles. • Naïve prey cannot recognize bullfrog as potential predators, and as a result bullfrogs have been released from some of the difficulties of finding prey.

chinese mitten crab

The most likely introduction pathway of mitten crabs into the U.S. are ballast water or intentional introduction via the live seafood trade. • Chinese mitten crabs are catadromous (adults return to brackish waters to reproduce). Herborg et al. (2007) used data on ballast water discharge and environment factors from the species' native range in Asia to predict the potential range of the Chinese mitten crab in North America. • The authors then refined these predicted distributions based upon the distance to the sea in which the crab must reproduce. • They identified major ports that are most at risk of mitten crab establishment based on a combination of environmental match and volume of unexchanged ballast water received.

biocontrol of milfoil

The native milfoil weevil (Euhrychiopsis lecontei) feeds and reproduces on northern milfoil (milfoil native to North America) as well as the Eurasian water milfoil.

Caulerpa taxifolia

The tropical alga Caulerpa taxifolia could have been eliminated in the Mediterranean soon after its discovery, when it was restricted to a few square meters in front of the Oceanographic Museum of Monaco. • But the effort was delayed for years and the alga now infests several thousand hectares of European coastline. • Banned under the US Federal Noxious Weed Act (1999).

evolutionary trap

cane toad! • In environments that have been rapidly altered, organisms can become "trapped" by their evolutionary responses to formerly reliable cues (Schlaepfer et al. 2005). The cane toad has been introduced to many regions of the Pacific and the Caribbean islands as a method of agricultural pest control • All life stages of the cane toad (Bufo marinus) contain a toxin that is unique to toads and that serves as a chemical defense. • Because there are no toad species native to Australia, cane toads are both evolutionarily novel and toxic to native Australian predators. • Naïve Australian predators will attack the toads, presumably because of their morphological resemblance to Australian frogs, and the predators will sicken or die as a result of ingesting the toxic chemicals. • Declines in native snakes, lizards and marsupials following the invasion of cane toad probably result, at least in part, from this evolutionary trap.

Nonindigenous Aquatic Nuisance Prevention and Control Act (1990) NANPCA

mostly focused on ballast water prevent invasions minimize impact

biological controls

• Biological control of invasive species using co-evolved natural enemies has long been considered a safe, cost effective, and environmentally benign tool for pest management. • About one in three attempts at biological control results in the establishment of a new natural enemy; half of these have led to complete control of the target species. • Biocontrol species can have negative impacts on populations of non-target species. • Classic biological control uses non-native agents that are host specific (i.e. attack only the species targeted for control). • Native species are also used as biological control agent. • General biological control uses control agents that are not host specific and will not target specific species (e.g., grass carp control of aquatic nuisance species).

challenges of risk assessment

• Development of scientifically justified risk analyses is difficult. • Risk assessment is an imperfect activity, and risk management is often flawed. • Risk analysis (both assessment and management) is a society activity, the cost of prevention cannot be excessive and should probably not exceed its perceived benefits.

eradication

• Eradication is the removal of every potentially reproducing individual of a species or the reduction of their population density below sustainable levels. • Although politicians occasionally call for eradication of a new invader, the total removal of every single individual is unlikely to succeed, it may be costly, and it may impose substantial collateral damage.

management implications

• Evolutionary processes are too rarely integrated into conservation and management strategies explicitly. • However, many examples of rapid behavioral responses and contemporary evolution (i.e. on the order of years and decades) in response to human activities have recently been described. • These examples open the exciting possibility of managing the selective regimes of native species to meet the conservation goal of long-term persistence. • A management plan that subsidizes the survival of native species long enough to allow a transition to their novel selective regime is likely to be more successful.

zoo plankton and invaders

• Fisk et al. (2007) examined the evolutionary response of native zooplankton populations to the introduction of non-native salmonids in alpine lakes. • Many fish species, including salmonids, are highly efficient visual predators that selectively feed upon larger, more conspicuous zooplankton. • The study compared morphological and life-history traits in populations of Daphnia with a known history of introduced salmonids and populations that have no history of introductions. • Daphnia from fishless lakes were significantly larger at birth, matured at a larger body size, and produced larger offspring than Daphnia from lakes containing fish. • Results showed that Daphnia populations coexisting with fish have undergone rapid adaptive reductions in body size and in the timing of reproduction. Fisk et al. (2007) also found significant correlation between trait divergence and the duration of exposure to salmon

Brook trout vs new competitors

• Freshwater lakes offer two functional habitats: the littoral (nearshore) and pelagic (open water) zones. • Generally, fish with a bottom-oriented mouth are more efficient when feeding on benthic prey, while fish with terminal mouths are more efficient at capturing surface and mid-water prey. • As a result, trophic polymorphisms in fish have evolved in response to food availability. Bourke et al. (1999) found that the introduction of benthic-feeding white suckers to lakes has resulted in a marked decrease in the benthic forms of native brook charr compared to pelagic forms.

cane toad and snakes

• In Australia, invasive cane toads (Bufo marinus) are highly toxic to most snakes that attempt to eat them. • Snakes are gape-limited predators with strong negative allometry for head size • Therefore, the probability of eating a toad large enough to be fatal) decreases with an increase in snake body size. • Thus, the arrival of toads should exert selection on snake morphology, favoring an increase in mean body size and a decrease in relative head size. • As predicted, two toadvulnerable species showed a steady reduction in gape size and a steady increase in body length with time since exposure to toads. • In contrast, two species at low risk from toads showed no consistent change in these morphological traits as a function of the duration of toad exposure.

Individual effects

• Individual-level impacts of invasive species can alter the morphology, behavior or vital rates of individuals, and are frequently the easiest to measure. • Obvious examples of individual-level impacts are changes in response to predation or competition. • Ecologists are typically interested in the population-level consequences of invasive species resulting from individual-level responses. • The round goby (Neogobious melanostomus) is native to the Ponto Caspian region and has been introduced into Western Europe and Laurentian Great Lakes mainly via ballast water discharge from ships. • Steinhart et al. (2004) studied the effects of round goby on the nest guarding native smallmouth bass

Population effects

• Invasive species can carry non-native parasites that can infect native populations. • One of the most well known and most dangerous fish parasites is the Asian tapeworm (Bothriocephalus opsarichthydis); first described from the intestines of grass carp The Japanese mudsnail has lead to the local extirpation of native mud snail populations in salt marshes of northern California (Byers 2000). Native Sacramento perch showed reduced growth in the presence of non-native bluegill sunfish due to interspecific competition (Marchetti 1999). • Brown trout in New Zealand trout have replaced native galaxiid fishes in some streams, and have affected the distributions of crayfish and other large invertebrates (Townsend 2003).

risk assessment of the great lakes

• Kolar and Lodge (2002) developed quantitative models using fish species traits to predict the identity of potential invaders into the Laurentian Great Lakes. • First, they identified the 24 established and 21 introduced but not established non-native fishes. • Second, they identified those established fishes that spread quickly through the lakes and those that are perceived as a nuisance. For each fish species, the authors collected data on 24 species-specific traits from literature, and developed models to predict establishment, spread and impact. • Their goal was to develop a risk screening protocol for identifying potential invasive species. • A classification tree successfully discriminated between successful and failed species with 87% accuracy. • Spread model (94%) and impact model (89%) were also highly predictive. The models were used to predict the risk of future introductions. • 22 out of 110 total potential species were classified as posing a significant invasive risk. • 16 species were predicted to spread rapidly and 5 become a nuisance.

Lionfish and reefs

• Lionfish(Pterois volitans and Pterois miles) are generalist piscivores that consume herbivorous reef fish. • Native predators avoid consuming lionfish. • As a result, lionfish have altered both the structure and func'oning of Caribbean and Bahaman coral-reef ecosystems.

Community effects

• Population-level effects can lead to substantial changes in community composition if the invader adversely impacts more than one native species. • When community-level impacts are measured (which is not often), they are usually framed in terms of community measures including species richness, evenness, and various indices of diversity. • Species invasions can lead to mass extinctions when an evolutionarily isolated system receives a novel predator or herbivore. • A now-classic example involves the introduction of the piscivorous Nile perch (Lates niloticus) into Lake Victoria in 1954 by British colonials. • Lake Victoria is the birthplace of nearly 400 native cichlid fish species. • In the 1970s, native cichlids declined due to competition with the introduced ominvorous fish and predation from the Nile Perch. • Nile Perch populations boomed around 1980, going from 1% of the annual harvest in 1978 to 97% in 1987. Kaufman (1992) 1968 1990 • During the 1980s, ca. 200 previously recorded native cichlid species disappeared completely.

containment

• Rather than attempting to eradicate an invasive species, slowing or stopping its rate of spread is considered be more cost effective. • In the United States, small electric barriers have been used to contain non-native grass carp in aquaculture ponds and to prevent sea lampreys from invading streams that flow into the Great Lakes. • A similar approach is being used to prevent the upstream colonization of bighead carp and silver carp into Lake Michigan. • In 1996, as part of the National Invasive Species Act, Congress authorized the Army Corps of Engineers to build an experimental electrical barrier in the Chicago Ship Canal. • An electrical barrier was operational in 2002 • Cost = $9.1 million • At stake: $7 billion • Testing with Asian carp have shown good results. Army Corps of Engineers acknowledge that Asian carp have breached the electrical barrier No evidence that carp have reached Lake Michigan

reaction-diffusion model

• Reaction-diffusion models are most commonly used to model short-distance spread and are based simply on dispersal and reproduction. • Dispersal involves the active movement of adults or the passive movement of individuals, seeds, eggs or larvae by wind, water or animal vectors. Limitations: Although diffusion models have provided important insight into the dynamics of spatial spread, they have three important assumptions. • Dispersal in freshwater and marine ecosystems is typically structured by unidirectional forces associated with water currents. A wide range of organisms typically show leptokurtic or "fattailed" distributions in movement.

risk analysis

• Risk assessments are typically used to create black lists of non-native species that are most likely to colonize, establish and cause ecological/ economic damage in a region. • Prevention or mitigation efforts are then targeted towards highrisk species. • USFWS Injurious-species List • USDA Noxious Weed List

National Invasive Species Act (1996)

• The National Invasive Species Act (NISA) is a federal law intended to prevent invasive species from entering inland waters through ballast water carried by ships. • NISA reauthorized and amended a previous measure, the NANPCA. • One major criticism of NISA is that it does not reach far enough. • Facilitate development of a coordinated network among federal agencies to document, evaluate, and monitor invasive species impacts • Prepare and issue a National Invasive Species Management Plan

Boom and bust

• There are instances where non-native populations will increase dramatically in their numbers and geographic range after initial establishment, and then suddenly crash down to extinction. Lockwood et al. (2013) • Competition with new non-native species • Exhaustion of resources • Parasitism by newly introduced species • Adaptation by native predator • Changes in the local environment • Effects of dispersal on detection Boom and "bust" of zebra mussel • Dreissena polymorpha population densities and biomass were followed in three Belarusian lakes with different trophic status over a 12-year period subsequent to initial colonization.

economic costs and the golden apple snail

• Understanding the scope of economic costs associated with invasive species is important for environmental policy and management, yet few studies have evaluated the cost to national economies. • The first estimate of the costs of invasive species found that 79 invasive species in the United States resulted in economic losses of about $97 billion in United States dollars between 1906 and 1991 (OTA 1993). • Pimentel et al. (2000, 2005) estimated total damage and control costs of $137 billion USD per year for all invasive species in the United States. The golden apple snail was introduced into Asia in 1980 to be cultured as a high-protein food source for local consumption and export. ¡ It has invaded rice fields (via extensive irrigation channels) where it feeds heavily on rice seedlings. ¡ In the Philippines, actual production losses equal approx. 100,000 tons of paddy, valued at $13-18 million USD. ¡ Total costs ($28-45 million) are associated with loss of yields, control measures, and seedling replanting;