Introduction Of Non-indigenous Species Research Articles

Double blow: Alien crayfish infected with invasive temnocephalan in South African waters

Trade in live, freshwater crayfish for ornamental markets, as well as for aquaculture, has grown rapidly and has become the major pathway for the introduction of non-indigenous crayfish species to several countries worldwide. Here we report on the first record of the Australian ‘redclaw’ Cherax quadracarinatus in the natural waters of a game reserve in South Africa. To compound the situation, these redclaw crayfish were infected with a non-indigenous temnocephalan flatworm parasite. Both crayfish and temnocephalan were in full breeding condition, with young. Further spreading of this crayfish to the subtropical, water-rich, northern KwaZulu-Natal Province of South Africa and southern Mozambique is predicted. Not only might the crayfish compete with indigenous aquatic invertebrates but the non-host-specific temnocephalan might transfer to local decapods, such as freshwater crabs.

Domestic ships as a potential pathway of nonindigenous species from the Saint Lawrence River to the Great Lakes

Ballast water moved by transoceanic vessels has been recognized globally as a predominant vector for the introduction of aquatic nonindigenous species (NIS). In contrast, domestic ships operating within confined geographic areas have been viewed as low risk for invasions, and are exempt from regulation in consequence. We examined if the St. Lawrence River could serve as a source of NIS for the Laurentian Great Lakes by surveying ballast water carried by domestic vessels and comparing biological composition in predominant St. Lawrence River-Great Lakes port-pairs in order to determine the likelihood that NIS could be transported to, and survive in, the Great Lakes. Thirteen potential invaders were sampled from ballast water, while 26 taxa sampled from St. Lawrence River ports are not reported from the Great Lakes. The majority of NIS recorded in samples are marine species with low potential for survival in the Great Lakes, however two euryhaline species (copepod Oithona similis, and amphipod Gammarus palustris) and two taxa reported from brackish waters (copepod Microsetella norvegica and decapod Cancer irroratus) may pose a risk for invasion. In addition, four marine NIS were collected in freshwater samples indicating that at least a subset of marine species have potential as new invaders to the Great Lakes. Based on results from this study, the ports of Montreal, Sorel, Tracy and Trois Rivières appear to pose the highest risk for new ballast-mediated NIS from the St. Lawrence River to the Great Lakes.

Management strategies to prevent the introduction of non-indigenous aquatic species in response to the Ballast Water Convention in Taiwan

The Convention for ballast water management is approaching the threshold of enforcement. Many countries around the world formulate national laws and regulations to mitigate the hazards of non-indigenous aquatic species (NIAS) brought about by the discharge of ballast water from ships. Taiwan’s critical location as an important transportation hub in the Western Pacific Ocean makes it a hot spot for the invasion of NIAS. Therefore, devising strategies for the management of ballast water is urgently needed. This study explores the global trend in ballast water management, and discusses the possible strategies which Taiwan may adopt in response to the Ballast Water Convention, from the perspective of Taiwan’s stakeholders in relation to the ballast water issue. Some of the proper actions that Taiwan should take in the future regarding the management of ballast water include: delineating the area for ballast water exchange, establishing the ballast water declaration system for incoming vessels, assisting shipping companies in installing ballast water treatment systems, determining risk priority for incoming vessels, and inspecting ballast water-related parameters by means of port state control (PSC). In this way, the invasion of NIAS may then be prevented in compliance with the global standards.

History of Fish Investigations in the Yadkin–Pee Dee River Drainage of North Carolina and Virginia with an Analysis of Nonindigenous Species and Invasion Dynamics of Three Species of Suckers (Catostomidae)

AbstractNorth Carolina's river drainages continue to lose their faunal distinctiveness as nonnative fish species establish themselves and expand their distributions, resulting in biotic homogenization. One such example is the Pee Dee drainage on the Atlantic Slope. It is the most speciose drainage in North Carolina, inhabited by 113 species of which 34 are nonindigenous, many introduced from adjacent drainages. The history of fish investigations in the Pee Dee in North Carolina and Virginia is detailed herein. The fauna was first sampled by Cope in 1869 at two conjoined sites—Yadkin River and Gobble Creek, a small tributary at the Yadkin River site (Cope 1870). Cope described numerous new taxa from the drainage, and many subsequent researchers provided data that show additions of nonnative faunal elements. As a case study, indications are that Hypentelium roanokense, Roanoke Hog Sucker, Hypentelium nigricans, Northern Hog Sucker, and Moxostoma rupiscartes, Striped Jumprock, were cryptically introduced after the late 1950s. The Roanoke Hog Sucker, introduced as recently as the 2000s, is found only in three tributaries of the Ararat subsystem in North Carolina and Virginia. The Northern Hog Sucker has expanded its range very little, confined primarily to the North Fork Reddies and Ararat subsystems and a short segment of the mainstem Yadkin River in North Carolina. The Striped Jumprock is now in much of the upper Yadkin system, but not in Virginia, and at several sites in the South Yadkin subsystem. Natural dispersal of all three species is limited by dams and impoundments, but the dispersal by Striped Jumprock has probably been aided by multiple bait bucket introductions. Consequences of nonindigenous species introductions in the drainage are well known for some species but unknown for the Roanoke Hog Sucker, Northern Hog Sucker, and Striped Jumprock.

Early biotic interactions among introduced and native benthic species reveal cryptic predation and shifts in larval behaviour

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 488:65-79 (2013) - DOI: https://doi.org/10.3354/meps10416 Early biotic interactions among introduced and native benthic species reveal cryptic predation and shifts in larval behaviour Víctor Ordóñez1, Marc Rius2, Christopher D. McQuaid3, M. Carmen Pineda4, Marta Pascual1, Xavier Turon5,* 1Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Diagonal 643, edifici Prevosti, 08028 Barcelona, Spain 2Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK 3Department of Zoology and Entomology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa 4Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona, Diagonal 643, edifici Margalef, 08028 Barcelona, Spain 5Centre d’Estudis Avançats de Blanes (CEAB-CSIC), Accés a la Cala St. Francesc 14, 17300 Blanes (Girona), Spain *Corresponding author. Email: xturon@ceab.csic.es ABSTRACT: Recurrent introductions of non-indigenous species generate novel interactions that vary with local conditions and the composition of the receiving community. Most studies examine relationships of newcomers with native species, but interactions among introduced species could also affect community shifts. As early ontogenetic stages are particularly vulnerable to biotic interactions, we explored direct and indirect interactions across early life-history stages in space-dominating marine invertebrates. We used introduced ascidians and both native and introduced mussels. To increase generality, we ran our experiments in 2 distant locations, one in the northern and one in the southern hemisphere (Mediterranean and South Africa). We found no sperm interference between the ascidians, nor were there interspecific effects on settlement or metamorphosis success. However, larvae of the ascidian species reacted to each other by shifting from aggregated to random settlement. Juvenile mussels consumed large numbers of ascidian larvae, though larvae that avoided mussel predation showed higher settlement success. Mussel species in the southern hemisphere locality (native Perna perna and introduced Mytilus galloprovincialis) consumed more ascidian larvae than mussels in the northern locality (native M. galloprovincialis), with a tendency for ascidian larvae to avoid settling close to mussels in the northern locality. We conclude that larval consumption by mussels affects the establishment of ascidians, but that the magnitude of this effect is context dependant. These results emphasize the importance of the composition of the receiving community in determining its susceptibility to invasion. Whether the species comprising this community are native or introduced is, however, less important than what manner of species they are. KEY WORDS: Competition · Settlement · Larviphagy · Invasive species · Microcosmus squamiger · Styela plicata · Mytilus galloprovincialis · Perna perna · Ascidians · Mussels Full text in pdf format PreviousNextCite this article as: Ordóñez V, Rius M, McQuaid CD, Pineda MC, Pascual M, Turon X (2013) Early biotic interactions among introduced and native benthic species reveal cryptic predation and shifts in larval behaviour. Mar Ecol Prog Ser 488:65-79. https://doi.org/10.3354/meps10416 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 488. Online publication date: August 15, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Climate change, non‐indigenous species and shipping: assessing the risk of species introduction to a high‐Arctic archipelago

AbstractAimAnticipated changes in the global ocean climate will affect the vulnerability of marine ecosystems to the negative effects of non‐indigenous species (NIS). In the Arctic, there is a need to better characterize present and future marine biological introduction patterns and processes. We use a vector‐based assessment to estimate changes in the vulnerability of a high‐Arctic archipelago to marine NIS introduction and establishment.LocationGlobal, with a case study of Svalbard, Norway.MethodsWe base our assessment on the level of connectedness to global NIS pools through the regional shipping network and predicted changes in ocean climates. Environmental match of ports connected to Svalbard was evaluated under present and future environmental conditions (2050 and 2100 predicted under the RCP8.5 emissions scenario). Risk of NIS introduction was then estimated based on the potential for known NIS to be transported (in ballast water or as biofouling), environmental match, and a qualitative estimate of propagule pressure.ResultsWe show that Svalbard will become increasingly vulnerable to marine NIS introduction and establishment. Over the coming century, sea surface warming at high latitudes is estimated to increase the level of environmental match to nearly one‐third of ports previously visited by vessels travelling to Svalbard in 2011 (n = 136). The shipping network will then likely connect Svalbard to a much greater pool of known NIS, under conditions more favourable for their establishment. Research and fishing vessels were estimated to pose the highest risk of NIS introduction through biofouling, while ballast water discharge is estimated to pose an increased risk by the end of the century.Main conclusionsIn the absence of focused preventative management, the risk of NIS introduction and establishment in Svalbard, and the wider Arctic, will increase over coming decades, prompting a need to respond in policy and action.

Ecophysiological forecasting for environmental change adaptation

Ecophysiological forecasting for environmental change adaptation

What Lies Beneath? An Evaluation of Rapid Assessment Tools for Management of Hull Fouling

Despite an increased understanding of marine invasions, non-indigenous species (NIS) continue to be redistributed at both global and regional scales. Since prevention is an important element of NIS programs, monitoring vectors responsible for NIS introductions and spread, such as hull fouling, has become a priority and methods should be selected carefully to balance accuracy, time, and cost. Two common fouling assessment tools for the marine recreational boating vector were evaluated for accuracy using a traditional underwater SCUBA survey in coastal British Columbia: a dockside level of fouling assessment and a behavioral questionnaire model. Results showed that although rapid, dockside assessments did not provide an accurate assessment of fouling present below the surface, at least not in this region. In contrast, a questionnaire-based model using four easily obtained variables (boat type, age of antifouling paint, storage type, and occurrence of long distance trips) reliably identified boats carrying macrofouling species, a proxy for risk of NIS transport. Once validated, this fouling model tool could be applied in border inspection or quarantine situations where decisions must be made quickly. Further development and refinement of rapid assessment tools would improve our ability to prevent new introductions and manage spread of existing invasive species.

Quantifying non-indigenous species in accumulated ballast slurry residuals (swish) arriving at Vancouver, British Columbia

Ballast tank “swish” samples were collected from ships following their arrival at Vancouver (British Columbia, Canada) after undergoing either a trans-oceanic or a Pacific-coastal voyage. The ballast swish consisted of a residual slurry mixture of sediment and water that remained trapped in ballast tanks following water discharge at port. The ballast tanks of 27 ships were sampled and ballast swish was found on 19 of the 27 ships. These ships were categorized according to ballast water management type: (1) Trans-oceanic=7 trans-oceanic ships undergoing ballast water exchange (BWE)>200nm from shore; (2) Coastal-exchange=7 Pacific-coastal ships traveling from ports south of Cape Blanco, Oregon undergoing coastal exchange>50nm from shore south of Cape Blanco; and (3) Coastal-no-exchange=5 Pacific-coastal ships traveling from ports north of Cape Blanco, Oregon, without undergoing BWE. Invertebrate abundance and taxa richness were directly correlated with ballast-swish turbidity suggesting that highly-productive coastal source waters and ballast tank retention processes contributed to this trend. In turn, invertebrate taxa diversity increased with increasing invertebrate abundance. A Principal Component Analysis of the trans-oceanic data revealed that length of voyage showed a strong inverse relationship with invertebrate abundance for this category. Within the coastal-exchange voyage category, voyage length and ballast water age tended to be of the same magnitude and were directly correlated with both crustacean and nematode taxa. Finally, the coastal-no-exchange PCA results revealed that voyage length and salinity were inversely related due to the high number of river ports located at the southern border of the regulatory BWE exemption zone. Coastal voyages not undergoing BWE and undertaking a direct river-to-river route should be considered risky for the introduction of non-indigenous species, if the source waters contain potentially invasive species. Non-indigenous species were found in all 3 vector pathways, with the highest number of propagules and survivability potential arising from the coastal-no-exchange zone. Ballast “swish” may act as a repository for ballast water organisms within ballast water tanks and may be retained in the tanks over several discharge cycles.

Integration of non-indigenous species within the interspecific abundance–occupancy relationship

There is a broad consensus that habitat disturbance and introduction of non-indigenous species may dramatically modify community structure, particularly in insular ecosystems. However, it is less clear whether emergent macroecological patterns are similarly affected. The positive interspecific abundance–occupancy relationship (IAOR) is one of the most pervasive macroecological patterns, yet has rarely been analyzed for oceanic island assemblages. We use an extensive dataset for arthropods from six islands within the Azorean archipelago to test: (1) whether indigenous and non-indigenous species are distributed differently within the IAOR; and (2) to the extent that they are, can differences can be attributed to two indices of disturbance. We implemented modeling averaged methods using five of the most common IAOR models to derive an averaged IAOR fit for each island. After testing if species colonization status (indigenous versus non-indigenous) may explain the residuals of the IAOR, we identified true negative and positive outliers and tested the effect of colonization status on the likelihood of a species being a positive or negative outlier. We found that the indigenous and non-indigenous species are randomly distributed on both sides of the overall IAOR. Only for Flores Island, were non-indigenous species more aggregated than indigenous species. We were unable to detect a meaningful relationship between deviation from the IAOR and disturbance, despite the undoubted impact of both severe habitat loss and non-indigenous species on these oceanic islands. Our results show that the non-indigenous species have been integrated alongside indigenous species in the contemporary Azorean arthropod communities such that they are mostly undetectable by the study of the IAOR.

Ballast water regulations and the move toward concentration‐based numeric discharge limits

Ballast water from shipping is a principal source for the introduction of nonindigenous species. As a result, numerous government bodies have adopted various ballast water management practices and discharge standards to slow or eliminate the future introduction and dispersal of these nonindigenous species. For researchers studying ballast water issues, understanding the regulatory framework is helpful to define the scope of research needed by policy makers to develop effective regulations. However, for most scientists, this information is difficult to obtain because it is outside the standard scientific literature and often difficult to interpret. This paper provides a brief review of the regulatory framework directed toward scientists studying ballast water and aquatic invasive species issues. We describe different approaches to ballast water management in international, U.S. federal and state, and domestic ballast water regulation. Specifically, we discuss standards established by the International Maritime Organization (IMO), the U.S. Coast Guard and U.S. Environmental Protection Agency, and individual states in the United States including California, New York, and Minnesota. Additionally, outside the United States, countries such as Australia, Canada, and New Zealand have well-established domestic ballast water regulatory regimes. Different approaches to regulation have recently resulted in variations between numeric concentration-based ballast water discharge limits, particularly in the United States, as well as reliance on use of ballast water exchange pending development and adoption of rigorous science-based discharge standards. To date, numeric concentration-based discharge limits have not generally been based upon a thorough application of risk-assessment methodologies. Regulators, making decisions based on the available information and methodologies before them, have consequently established varying standards, or not established standards at all. The review and refinement of ballast water discharge standards by regulatory agencies will benefit from activity by the scientific community to improve and develop more precise risk-assessment methodologies.

High sensitivity of 454 pyrosequencing for detection of rare species in aquatic communities

Summary Concerns regarding the rapid loss of endemic biodiversity, and introduction and spread of non‐indigenous species, have focused attention on the need and ability to detect species present in communities at low abundance. However, detection of rare species poses immense technical challenges, especially for morphologically cryptic species, microscopic taxa and those beneath the water surface in aquatic ecosystems. Next‐generation sequencing technology provides a robust tool to assess biodiversity, especially for detection of rare species. Here, we assess the sensitivity of 454 pyrosequencing for detection of rare species using known indicator species spiked into existing complex plankton samples. In addition, we develop universal small subunit ribosomal DNA primers for amplification of a wide range of taxa for detailed description of biodiversity in complex communities. A universality test of newly designed primers for the hypervariable V4 region of the nuclear small subunit ribosomal DNA (V4‐nSSU) using a plankton sample collected from Hamilton Harbor showed that 454 pyrosequencing based on this universal primer pair can recover a wide range of taxa, including animals, plants (algae), fungi, blue‐green algae and protists. A sensitivity test showed that 454 pyrosequencing based on newly designed universal V4‐nSSU primers was extremely sensitive for detection of very rare species. Pyrosequencing was able to recover spiked indicator species with biomass percentage as low as approximately 2·3 × 10−5% when 24 artificially assembled samples were tagged and sequenced in one PicoTiter plate (i.e. sequencing depth of an equivalent of 1/24 PicoTiter plate). In addition, spiked rare species were sometimes recovered as singletons (i.e. Operational Taxonomic Units represented by a single sequence), suggesting that at least some singletons are informative for recovering unique lineages in ‘rare biospheres’. The method established here allows biologists to better investigate the composition of aquatic communities, especially for detection of rare taxa. Despite a small‐scale pyrosequencing effort, we demonstrate the extreme sensitivity of pyrosequencing using rare species spiked into plankton samples. We propose that the method is a powerful tool for detection of rare native and/or alien species.

Factors affecting the establishment of the invasive crayfish Procambarus clarkii (Crustacea, Decapoda) in the Mediterranean rivers of the northeastern Iberian Peninsula

It is essential to find the combination of factors associated with ecosystem invasibility, as this forms part of basic knowledge on biological invasions and provides important information to guide management and conservation decisions. We surveyed 325 sampling sites in Catalonia to investigate relationships between crayfish presence and a series of biotic and abiotic factors, including fish abundance and species richness, geographical features, and water mineralization and eutrophication. Abiotic data provided by 29 environmental variables were studied by principal-components analysis. We then used a combination of three statistical approaches (comparison of average scores, general linear mixed models, and hierarchical partitioning analysis) to determine the potential relationship between crayfish occurrence and predictors. Our findings seem to indicate that the presence of crayfish was associated with geographical features, water mineralization and eutrophication, and the introduction of non-indigenous fish species to Catalonia. Our results also suggest that re-establishment of the natural hydrology of Mediterranean streams could hinder the spread of Procambarus clarkii. This, combined with preservation of headwater streams and attempts at local extirpation of P. clarkii, would favour native species and, potentially, enable the successful reintroduction of the native white-clawed crayfish (Austropotamobius pallipes species complex).

Ecosystem Transformations of the Laurentian Great Lake Michigan by Nonindigenous Biological Invaders

Lake Michigan, a 58,000-km(2) freshwater inland sea, is large enough to have persistent basin-scale circulation yet small enough to enable development of approximately balanced budgets for water, energy, and elements including carbon and silicon. Introduction of nonindigenous species-whether through invasion, intentional stocking, or accidental transplantation-has transformed the lake's ecosystem function and habitat structure. Of the 79 nonindigenous species known to have established reproductive populations in the lake, only a few have brought considerable ecological pressure to bear. Four of these were chosen for this review to exemplify top-down (sea lamprey, Petromyzon marinus), middle-out (alewife, Alosa pseudoharengus), and bottom-up (the dreissenid zebra and quagga mussels, Dreissena polymorpha and Dreissena rostriformis bugensis, respectively) transformations of Lake Michigan ecology, habitability, and ultimately physical environment. Lampreys attacked and extirpated indigenous lake trout, the top predator. Alewives outcompeted native planktivorous fish and curtailed invertebrate populations. Dreissenid mussels-especially quagga mussels, which have had a much greater impact than the preceding zebra mussels-moved ecosystem metabolism basin-wide from water column to bottom dominance and engineered structures throughout the lake. Each of these non indigenous species exerted devastating effects on commercial and sport fisheries through ecosystem structure modification.

Role of domestic shipping in the introduction or secondary spread of nonindigenous species: biological invasions within the Laurentian Great Lakes

Summary The most effective way to manage invasive species is to prevent their introduction via vector regulation. While progress has been made in the management of transoceanic ballast water, domestic vessels operating within smaller geographic regions such as the Laurentian Great Lakes, Mediterranean Sea, North Sea or Baltic Sea are often exempt from regulations. We randomly surveyed unmanaged ballast water moved by domestic vessels within the Laurentian Great Lakes and compared the results with that of exchanged ballast water from transoceanic vessels to assess invasion risk of zooplankton transported by these two types of vessels. Total abundance and species richness were significantly different between the two vessel types with mean abundance being two magnitudes greater, and species richness being threefold higher in domestic vessels compared with transoceanic vessels. Abundance of restricted taxa – cumulatively the Great Lakes' indigenous and nonindigenous species (NIS) which do not occur in all five lakes – was also significantly higher in domestic vessels (mean densities were 24 170 and 3421 individuals per m3 for domestic and transoceanic vessels, respectively), whereas the abundance of NIS did not differ between vessels (median densities of 2015 and 850 individuals per m3, respectively). We documented 89 species transported by domestic vessels of which 31 had restricted distribution and eight were NIS. While most NIS were already established in all five lakes, Cercopagis pengoi, a NIS of global concern, and Nitokra hibernica have not been identified from Lake Superior, and both were sampled from ballast water destined for discharge in Lake Superior. Beside the risk of spread of NIS between lakes, domestic shipping can act as a vector for homogenization of indigenous taxa, with at least 21 native species (99 events) being moved outside their historical distribution. Synthesis and applications. Our study indicates that management of invasive species should consider ecological, not geographical or political boundaries. Domestic vessels operating within a limited geographic region have high potential to introduce or spread species with restricted distribution, demonstrating importance of intraregional ballast water management. Results presented here should interest policy makers and environmental managers who seek to reduce invasion risk.

Bactericidal efficacy of elevated pH on fish pathogenic and environmental bacteria

Ship ballast water is a recognized medium for transfer and introductions of nonindigenous species. There is a need for new ballast water treatment methods that effectively and safely eliminate or greatly minimize movements of these species. The present study employed laboratory methods to evaluate the bactericidal efficacy of increased pH (pH 10.0–12.0) for exposure durations of up to 72h to kill a variety of Gram-negative and Gram-positive bacteria including fish pathogens (Aeromonas spp., Yersinia ruckeri, Edwardsiella ictaluri, Serratia liquefaciens, Carnobacterium sp.), other common aquatic-inhabitant bacteria (Serratia marcescens, Pseudomonas fluorescens, Staphylococcus sp., Bacillus sp.) and indicators listed in International Maritime Organization D2 Standards; namely, Vibrio cholera (an environmental isolate from fish), Escherichia coli and Enterococcus faecalis. Volumes of 5N NaOH were added to tryptic soy broth to obtain desired pH adjustments. Viable cells were determined after 0, 4, 12, 24, 48, and 72h. Initial (0h) cell numbers ranged from 3.40×104cfu/mL for Bacillus sp. to 2.44×107cfu/mL for E. faecalis. The effective endpoints of pH and treatment duration necessary to realize 100% bactericidal effect varied; however, all bacteria tested were killed within 72h at pH 12.0 or lower. The lowest parameters examined, 4h at pH 10.0, were bactericidal to V. cholera, E. ictaluri, three of four isolates of E. coli, and (three of four) Aeromonas salmonicida subsp. salmonicida. Bactericidal effect was attained at pH 10.0 within 12h for the other A. salmonicida subsp. salmonicida, and within 24h for P. fluorescens, and the remaining E. coli.

Invaders for sale: trade and determinants of introduction of ornamental freshwater crayfish

The trade of live ornamental freshwater crayfish has grown rapidly in the last decade and has become the major pathway for new non-indigenous crayfish species (NICS) introductions into Europe. Here, I report on the German ornamental crayfish trade, the main importer of non-indigenous crayfish into Europe. In total, 120 NICS have been available as ornamental aquarium species. One hundred and five species originate from North or Central America and are, therefore, suspected to be crayfish plague vectors. The import rate since 2005 was estimated to be seven new species per year. Despite many species being imported, only eleven species were found to be very common in the trade. In 2009, 16 online shops offered at least 37 NICS. The availability, price, and size of the offered species were used to predict their introduction status. Multiple binary logistic regression analysis showed that species’ availability and size were the principal predictors of the likelihood of being recorded as introduced from aquaria. NICS introduced from aquaria were found to be more available and larger than those present only in aquaria, and their potential invasiveness was also higher. The findings are consistent with the propagule pressure hypothesis in that a greater availability is likely related to more release events, and large species may be released more frequently as a result of overpopulating or outgrowing their aquaria. Efforts to mitigate the risk of further harmful crayfish introductions from aquaria should aim to drastically reduce the availability of high-risk species.

Secondary production as a tool for better understanding of aquatic ecosystems

A major challenge for ecologists is understanding ecosystem dynamics and function under environmental and anthropogenic stresses. An approach for addressing this challenge is the analysis of the different components contributing to secondary production (i.e., consumer incorporation of organic matter or energy per time unit) and how this production is influenced by external factors. Production studies have been recognized as a powerful tool in aquatic ecology, with applications in energy–biomass flow studies, trophic ecology, management of biological resources, as well as assessment of environmental stress. In this paper, we summarize ideas and techniques related to the estimation of secondary production and discuss how this approach may be used to evaluate ecological change in aquatic ecosystems. We include a critical review of classical methods and empirical models to estimate secondary production and provide several applications of production studies to current stresses affecting aquatic ecosystems, such as climate change, pollution, and the introduction of non-indigenous invasive species. Our goal is to illustrate the advantages of using secondary production as a more integrative tool for the assessment of the ecosystem function, in particular when subjected to strong anthropogenic and climatic stress.

Associations between stream habitat characteristics and native and alien crayfish occurrence

Human mediated introductions of non-indigenous crayfish species (NICS) are responsible for their rapid colonisation of European freshwaters. The introduction of North American crayfish is furthermore linked to the spread of crayfish plague and the decline of indigenous crayfish species (ICS). As the management of ICS and NICS have become necessary, a detailed knowledge on their distribution and ecological requirements is needed. We studied the current range of native noble crayfish Astacus astacus and stone crayfish Austropotamobius torrentium, as well as alien signal crayfish Pacifastacus leniusculus in Carinthia (Austria) and evaluated environmental and physical habitat features in streams with and without crayfish. Meanwhile, the loss of many ICS populations was recorded and alien P. leniusculus was found to be widespread in this region. Most of the habitat features of streams having crayfish differed significantly from sites lacking crayfish for at least one investigated native or alien species. Furthermore, multivariate and regression analyses showed specific differences in the habitat use of the investigated crayfish. Our results showed that the presence of alien P. leniusculus was associated with larger and smoother sloped lowland rivers, while the occurrence of the two native species was confined to smaller streams either at higher altitudes and with distinct physical habitat conditions (A. torrentium) or with moderate water temperatures (A. astacus). This study helps to identify potential refuge areas for the endangered native species and to predict the further spread of the most common non-native crayfish species in European streams.

Seaweed assemblage changes in the eastern Cantabrian Sea and their potential relationship to climate change

Rising sea-surface temperatures (SSTs) over the last three decades in the south-eastern part of the Bay of Biscay could be affecting phytobenthic assemblage distributions. This study assesses recent changes in species abundance and diversity along the western Basque coast by studying 18 locations in summer 1991 and in 2008. There were substantial changes in the structure of subtidal vegetation between the two surveys: 1) an increase in coralline algae; 2) changes in the distribution patterns of the canopy species; 3) disappearance of kelps; 4) increases in warm-water species, mainly morphologically simple forms; 5) introduction and expansion of non-indigenous species, and 6) increases in species richness and diversity. These results are consistent with the rise detected in SST, particularly in summer when SST was found to have risen by as much as 1°C from 1980 to 2008. Furthermore, two extreme warming events occurred in the summers of 2003 and 2006. However, some biological shifts cannot be explained by warmer waters alone. Only limited data are available on changes in nutrient concentrations and water transparency, but these factors are also thought to be involved in the biological changes detected.