Presence Of Exotic Species Research Articles

Human Impacts on Drainages of the Mesa Central, Mexico, and Its Genetic Effects on an Endangered Fish, Zoogoneticus quitzeoensis

The Mesa Central of Mexico is of special conservation interest due to its high richness of freshwater fish species, of which the goodeines are one of the most representative groups. Through an integrated approach, we determined conservation priorities for goodeine populations. We based our recommendations on the genetic diversity (variation in five microsatellite DNA loci) in 10 populations of Zoogoneticus quitzeoensis and on an analysis of ecological (e.g., presence of exotic species), social (e.g., political situation), and environmental (e.g., pollution) information for 52 historical occurrence points for species in the genus Zoogoneticus. Patterns of genetic erosion and genetic diversity indices were closely associated with human impact. Recent bottleneck events were most evident in the populations from remnants of the lakes drained at the beginning of the twentieth century. We identified seven operational conservation units (OCUs), all of which should be conserved because they contain unique portions of the total variation of the species. Special attention needs to be given to increase genetic variability, recover population sizes, and reestablish contact among populations within OCUs. It is imperative to create an integrative and effective approach for the recovery and conservation of the freshwater fish diversity of Central Mexico that is based on social and natural sciences.

Exotic invertebrate species on offshore oil platforms

We report the presence of 3 exotic invertebrate species inhabiting offshore oil and gas platforms on the Pacific offshore continental shelf (POCS) of central and southern California, USA. These exotic species occur in high cover or density and may negatively affect populations of native species on the platforms. Conspicuous exotic species (the bryozoan Watersipora?subtorquata and the anemone Diadumene sp.) were detected on 2 of 7 platforms surveyed. An inconspicuous exotic species (the amphipod Caprella mutica) was detected on 2 of 2 platforms surveyed for such smaller species. In addition to serving as a potential source of exotic species to natural reef habitats, the presence of exotic species on oil platforms may influence the degree to which these structures provide the ecological services of natural reefs. The presence of exotic species on platforms also has consequences for various platform decommissioning options in California and elsewhere (there are an estimated 7000 offshore platforms/installations worldwide), including the removal and transport of platforms for use as artificial reefs, if removals are conducted without regard for the potential transport/dispersal of these species. Further knowledge of the identity of exotic species on oil platforms, their potential for dispersal and interaction with native species, and whether these species can also occur on artificial reefs, will improve our understanding of the effects that artificial structures in general have on the ecological functioning of coastal ecosystems.

Costs and benefits of stock enhancement and biological invasion control: the case of the Bay of Brest scallop fishery

This paper deals with the economic impact of the invasion of a scallop fishery by an exotic shellfish that was accidentally imported some decades ago. The invasive alien species, a slipper-limpet, Crepidula fornicata, is a space competitor for local scallops, and its spread threatens the sustainability of the ongoing scallop restocking program. Facing this invasion, the local fisheries committee has initiated a containment project intending to make the restocking program consistent with the exotic species presence in the fishery. The issue is complicated by the occurrence of occasional toxic micro-algae blooms affecting the scallop fishery. The paper presents a model dealing with the economic impact of the invasive process, and a methodology for cost-benefit analysis of invasion management. According to numerical simulation, the invasion is a serious threat to the economic viability of the restocking program, and invasion management would help maintaining the long term sustainability of the fishery. Sensitivity tests highlight the importance of long term equilibrium scallop catches on the program result, depending on scallop farming technical performance and ecosystem disturbance.

Comparison of vegetation conditions along two backcountry trails in Mount Robson Provincial Park, British Columbia (Canada)

Vegetation conditions, i.e., plant cover, species richness, and the presence of exotic species, are compared along a high-use trail (Berg Lake Trail—BLT) and a low use trail (Mt. Fitzwilliam Trail—FWT) in Canada's Mt. Robson Provincial Park. We established 71 paired quadrats (1 m×1 m), and assessed the amount of vegetation cover and species richness by four main lifeforms, i.e., woody species, herbaceous species, ferns, and moss, lichen and fungi. The following hypotheses were tested: (1) differences exist between control and trailside quadrats in vegetation cover, species richness and floristic diversity, and (2) differences exist between the high and low-use trails in the above-mentioned three parameters. Results show that for the majority of variables the differences between the control and trailside quadrats are statistically not significant. Variables showing significant differences are relative vegetation cover (for BLT only), exposed soil (BLT and FWT), herbaceous cover (FWT), moss, lichen and fungi cover (BLT), overall species richness (BLT), and herbaceous species richness (BLT). Ruderal and exotic species are present but only on trailside quadrats of the high-use trail. Results indicate that the Park administration's strategy to disperse use in the Mt. Robson Provincial Park should be examined critically, and some guidelines for acceptability of changes should be developed.

Hybridization of Snake River Cutthroat in the Lower Gros Ventre River

The cutthroat trout Oncorhynchus clarki is Wyoming's only native trout. The Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) is designated as a "species of special concern" by a number of agencies and conservation groups. Although the Yellowstone cutthroat trout has recently avoided federal listing because of robust headwater populations (USFWS 2006), they face continued threats across their range. The fine-spotted Snake River native trout is a morphologically divergent ecotype of the Yellowstone subspecies, although it is not genetically distinguishable (Allendorf and Leary 1988, Novak et al. 2005). The Gros Ventre, an important tributary of the Snake River located partially in Grand Teton National Park, historically supported robust populations of fine­ spotted Snake River cutthroat trout. Principal threats to Gros Ventre native trout, especially in the lower end of the drainage within the park boundaries, include both water diversions (loss of water and fish into irrigation ditches) and presence of exotic species.

Synergistic impact of water level fluctuation and invasion of Glyceria on Typha in a freshwater marsh of Lake Ontario

The effects of multiple stressors on the native Typha marsh community (mainly Typha latifolia) were examined using historical records of water levels, human census population, and field vegetation maps. Percent cover of the major plant species was estimated in a GIS, and the percent cover of Typha was related to changes in water level, human population growth, and percent cover of exotic Glyceria maxima and invasive Phragmites australis. Water level fluctuation was the major natural disturbance and it alone accounted for 88% of the variation in Typha. After partitioning out the effect of water level, both human population growth and the presence of exotic species were still significantly related to the decline of native Typha. We suggest that multiple stressors interact with each other to influence changes in native Typha community and cause greater detrimental impact. An important implication of our results is that projected water level decline due to climate change may not necessarily favor the restoration of a desirable native marsh because of the presence of other disturbances such as exotic and invasive species and altered nutrient regime.

STATUS OF DIONDA DIABOLI AND REPORT OF ESTABLISHED POPULATIONS OF EXOTIC FISH SPECIES IN LOWER SAN FELIPE CREEK, VAL VERDE COUNTY, TEXAS

Abstract Sampling from April 2001 to March 2003 revealed San Felipe Creek, Val Verde County, Texas, still supported a breeding population of the threatened Devils River minnow (Dionda diaboli). The species was restricted to creek habitats and was not found in the outflow channels of San Felipe Springs. We determined that breeding populations of introduced tropical fish species Hypostomus (a South American armored catfish) and Oreochromis aureus (an African cichlid) also were present in San Felipe Creek. We obtained evidence to suggest that presence of exotic species, particularly Hypostomus, might have a negative effect on the Devils River minnow. We recommend periodic monitoring of fish populations in San Felipe Creek to document future changes in the population of Devils River minnow and other endemic species, and to facilitate design and implementation of conservation plans in San Felipe Creek.

Do Non-Native Species Threaten The Natural Environment?

Conservation biologists and other environmentalists confront five obstacles in building support for regulatory policies that seek to exclude or remove introduced plants and other non-native species that threaten to harm natural areas or the natural environment. First, the concept of “harm to the natural environment” is nebulous and undefined. Second, ecologists cannot predict how introduced species will behave in natural ecosystems. If biologists cannot define “harm” or predict the behavior of introduced species, they must target all non-native species as potentially “harmful”. an impossibly large regulatory task. Third, loss of species richness may constitute harm to an environment, but introduced organisms typically, generally, and significantly add to species richness in ecosystems. If species richness correlates with desirable ecosystem properties, moreover, such as stability and productivity, as some ecologists believe, then introduced organisms, by increasing species richness, would support those desirable properties. Fourth, one may plausibly argue that extinction constitutes environmental harm, but there is no evidence that non-native species, especially plants, are significant causes of extinction, except for predators in certain lakes and other small island-like environments. Fifth, while aesthetic, ethical, and spiritual values may provide a legitimate basis for invasive species policy, biologists often cite concepts such as “biodiversity” and ecosystem “health” or “integrity” to provide a scientific justification. To assert that non-native species threaten biodiversity or undermine ecosystem health, however, may be to draw conceptual entailments or consequences from definitions of “biodiversity” and “integrity” that arbitrarily exclude non-native species or make the presence of exotic species a per se indicator of decline.

Ability of taxonomic diversity indices to discriminate coastal lagoon environments based on macrophyte communities

Lagoons are highly productive areas representing more than 50% of the coastline area in Languedoc-Roussillon (South of France, Mediterranean sea). These lagoons are very different in their environmental conditions, human influences, eutrophication levels and aquaculture intensity. Based on macrophyte communities associated with soft substrates, two indices of taxonomic diversity (the average taxonomic distinctness (Delta(+)) and the variation in taxonomic distinctness (Lambda(+))) were used to discriminate four of these lagoons (Thau, Salse-Leucate, Bages-Sigean and Mauguio). Bages-Sigean presented a significant higher average taxonomic distinctness (p 0.05) and Salse-Leucate had a significant higher variation in taxonomic distinctness (p 0.05) without considering exotic species. The index values were neither influenced by sample size nor by presence of exotic species. Thus, the average taxonomic distinctness was related to human activities and eutrophication level whereas the variation in taxonomic distinctness was more related the environmental variability, associated with the prime stressor of salinity in brackish coastal lagoons.

Survival of native plants of Hawkesbury Sandstone communities with additional nutrients: effect of plant age and habitat

Australian soils are naturally low in nutrient concentrations, particularly nitrogen (N) and phosphorus (P). Native plants are well adapted to low-nutrient soils, and can be adversely affected when exposed to higher concentrations of nutrients. The Hawkesbury Sandstone soils in northern Sydney are naturally low in nutrients, but often receive additional nutrient input from urban stormwater run-off. Increases in soil nutrients in urban bushland are associated with the presence of exotic species, and the decline in the diversity of native species. This study tested the hypothesis that high concentrations of nutrients, in particular P, in the disturbed soils of urban bushland, reduce survival of native plants. We examined the survival of native species under five different nutrient concentrations that are typical of nutrient-enriched urban bushland soil, in two glasshouse experiments. The experiments examined both survival of seedlings and survival of 6-month-old plants. We used native species that are adapted to both nutrient-poor and nutrient-rich soils. In general, the survival of native plants decreased with increasing nutrient concentrations. At soil total-P concentrations >200 mg kg–1, most plants died. Seedlings were more sensitive to added nutrients than the 6-month-old plants. Species that were from higher-nutrient soil had consistently higher survival than species from low-nutrient soils, under the nutrient addition treatments. These results suggest that at high soil nutrient concentrations typical of stormwater-affected urban bushland, native plant species of low-nutrient soils will be unable to survive. If ecological restoration works are to be done in such areas, replanting with more mature plants from naturally high-nutrient habitats is likely to be the most successful. However, restoration of these areas may have limited success and they are likely to remain dominated by exotic plant species.

VARIABILITY AND DYNAMICS OF A DESERT STREAM COMMUNITY

Communities can be highly variable over a few years, but remain fairly constant over the long term. Evaluating measures and examining the variability associated with long‐term change is useful because it increases our understanding of and our ability to predict responses to disturbances. We used long‐term fish community data from Aravaipa Creek, Arizona, USA, a Sonoran Desert stream, to determine whether there had been long‐term changes in the community composition, what measures best describe these shifts, and what environmental factors are correlated with the changes. Aravaipa Creek is an intrinsically variable system and one of the few remaining desert streams to support its complete historical assemblage of native fishes. Multivariate analyses illustrated important changes in composition of the native fish community that were not described by traditional measures of persistence and stability. In the early 1980s, changes in community composition were correlated with alterations in base flow, while more recent changes are likely associated with the presence of exotic species. Changes in stream morphology, hydrology, and climate have decreased flow variability, thereby increasing the likelihood of exotic establishment, and may have increased the downstream connection between Aravaipa Creek and the San Pedro River thus increasing the likelihood of repeated invasions by nonnative species. These results support previous research in intrinsically variable desert systems, which conclude that retention of high flow variability is important to conservation of the native fish community. In addition, although connectivity in aquatic lotic systems is important, isolation from large river systems teaming with exotics may be important in preserving these remnant native fish assemblages.

Pesque-pague: negócio ou fonte de dispersão de espécies exóticas?

Commercial business (named here as 'fish-and-pay' - pesque-pague , which uses people’s interest in fishing) became widespread quickly in Brazil. But among the species used in 'fish-and-pay' ponds, many are exotic. Thus, the 'fish-and-pay' ponds are, through escape, potential sources for introduction of alien organisms into the natural water bodies. Considering this, the purposes of this paper are: i) to analyze the problems related to the activity; ii) to verify the occurrence of spawning of the species used in ponds of the fish-and-pay and in the natural environment; iii) to register the presence of exotic species in the natural environments close to the 'fish-and-pay' ponds. To meet these objectives, a questionnaire with broad questions was applied to 'fish-and-pay' owners. In addition, the 'fish-and-pay' ponds (seining nets) and the natural environments (streams; casting nets, seining nets and seine) were sampled. The interviewed owners demonstrated poor ability to administrate the business. As a result of that, escapes from the ponds are inevitable but measures to remedy this situation are necessary. Related authorities should help in the project of those ponds construction and monitor nearby stream areas

Urbanization and exotic plants in northern Sydney streams

AbstractThe vegetation and sediment of urban and non‐urban streams in the northern Sydney region were compared to examine the possible effects of urbanization on within‐stream vegetation. Many sediment characteristics were significantly different in urban streams. At least one exotic plant species was found in each urban stream sampled, but none were found in the non‐urban streams. The presence of exotic species led to the overall number and abundance of plant species being significantly higher in urban streams. Interestingly, the number and abundance of native species at the urban sites were the same as non‐urban sites, but a different suite of species was usually present. This suggests that urban streams favour exotic plants and certain native plants that are adapted to the modified conditions. The differences between the plant communities in the urban and non‐urban streams appeared to be associated with the increased level of nutrients in the urban stream sediment. Several multivariate techniques were used to assess the relative importance of individual nutrients, but no nutrients were directly associated with the observed differences. In particular, total phosphorus levels were less important in explaining the vegetation patterns than a combination of nutrients. It is therefore likely that the general increase of nutrients in stream sediment has enhanced exotic invasion and altered stream plant communities in Sydney streams.

Understory vegetation in old and young Douglas-fir forests of western Oregon

We studied understory composition in thinned and unthinned Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco)/western hemlock ( Tsuga heterophylla (Raf.) Sarg.) stands on 28 sites in western Oregon. These stands had regenerated naturally after timber harvest, 40–70 years before thinning. Commercial thinning had occurred 10–24 years previously, with 8–60% of the volume removed from below with the intent to homogenize spacing among trees. Undisturbed old-growth Douglas-fir stands were present for comparison on 18 of these sites. Total herbaceous cover was greater in thinned (25% cover) stands than in unthinned (13% cover) or old-growth (15% cover) stands. Species richness was also greater in thinned (137) than in unthinned (114) and old-growth (91) stands ( P=0.05). Part of the increased richness was caused by the presence of exotic species in thinned stands, but there were also more native grass and nitrogen-fixing species in thinned stands than in unthinned or old-growth stands. Groups of species differed among stand-types. For example, the frequency of tall cordate-leaved species was greater in old-growth stands ( P=0.009), but their relative cover was different only between old-growth and unthinned stands ( P=0.08). Both the cover and frequency of grasses and sedges in thinned stands were greater than in unthinned or old-growth stands ( P≤0.002). Ordination of shrub cover showed differences among old-growth and unthinned stands compared to thinned stands, mainly because of the amount of Gaultheria shallon Pursh and Polystichum munitum (Kaulf.) Presl in heavily thinned stands. Ordination of herbaceous community data showed that there were much stronger differences among sites than among stand-types. The lack of difference among stand-types demonstrates the resiliency of herbaceous communities to disturbance associated with past and current forest management.

Trail corridors as habitat and conduits for movement of plant species in Rocky Mountain National Park, Colorado, USA

Ground-layer vegetation was sampled along selected trail corridors to determine whether corridors provide habitat for certain species and act as conduits for species movement. Patterns of plant species composition were analyzed in relation to distance from trail edge, level of trail use, and distance from trailheads, junctions, and campgrounds. Species composition was significantly affected by distance from trail edge and level of trail use, as species were favored or inhibited by the corridor, depending upon their growth habits. Species composition was also affected by distance from trailheads. These findings, along with the presence of exotic species, indicate that trail corridors in Rocky Mountain National Park function as habitat and conduits for movement of plant species.

The Freshwater Fishes of Madagascar: A Study of an Endangered Fauna with Recommendations for a Conservation Strategy

Abstract: The native Madagascan fish fauna, and most particularly the endemic freshwater community, has undergone severe attrition throughout the surveyed area The decline of the native fauna is strongly correlated with two primary factors: the presence of exotic species, which are now widespread and habitat degradation resulting from extensive forest clearance. In an attempt to document ichthyofaunal changes through time, we compare our collections with historical distribution records (based on museum collections and literature records) from the same areas. The results of this study reveal a pressing need to consider the islands ichthyofauna, watersheds, and river drainages if design of natural areas and parks is to be effective.

Effects of dredging and dumping on benthos of Saint John Harbour, Canada

Of four impoverished communities of benthic macro-infauna in Saint John harbour, three were attributable to anthropogenic causes: disposal of solid wood wastes, dredging, and dumping activity. Circumstantial evidence indicates that the fourth community resulted from strong tidal currents present in the inner harbour interacting with the sediment causing periodic erosion and deposition, resulting in an impoverished macro-infauna. The dredged area was rapidly recolonized; first by invasive species such as Capitella capitata and Nereis sp. and then by species present in adjacent sediments. The area adversely affected by dumping was of limited extent: of the order of 1 km 2, as indicated by the presence of exotic species in dump soil and the distribution of organic carbon.