Establishment of Corbicula fluminea (O.F. M?ller, 1774) in Lake Maggiore: a spatial approach to trace the invasion dynamics

We analysed the dynamics of the invasive Asian basket clam Corbicula fluminea in Lake Maggiore (Italy), recorded for the first time in August 2010. In order to reveal the extent of its dispersal, we monitored 30 locations along the lake for presence/absence of clams. This assessment of population structure, density and biomass is based on quantitative samples collected along the southern shoreline at four sites with diverse types of habitats. In the present study, the on-going process of Corbicula invasion was analysed from a spatial and temporal perspective. We compared density and size structure of the population among the sites (spatial distribution). We attempted to trace the colonization dynamics of the clams, so the invasion dynamics were tentatively reconstructed from spatial distribution of size /age groups and the contribution of the last recruited cohort to total population density along the lake littoral zone. Results from our surveys conducted in 2010-2011 have demonstrated that the Asian clam was well-established in the lake, thus about one-third of the lake (i.e. the southern basin) was already colonized by C. fluminea in 2011. Size frequency distribution in autumn 2011 further illustrated reproduction events and new recruitments. Population densities in Lake Maggiore were among the highest ever recorded in an Italian lake. Both the rapid spread of Corbicula in the littoral area and the relatively high densities, even at the most recently invaded sites, infer the potential ecosystem impacts associated with a dominant invasive species. Data reported here are not intended to be exhaustive since they concern only two years of investigations, so more detailed studies on both the ecology and invasive habits of this new alien species in Lake Maggiore are planned. The spatial approach used in the present study may clarify the dynamics of this invasion. Future monitoring might help us to disentangle the effects of spatial variability versus temporal succession during the establishment of the invasive species

Alien amphipods in a sea of troubles: cryptogenic species, unresolved taxonomy and overlooked introductions

The large amount of information available on marine alien species distribution can be synthesized into inventories. These are essential tools for management: they allow for the identification of most invasive species and most invaded areas which facilitate management decisions and horizon-scanning initiatives. Here we present an inventory of marine alien amphipods worldwide, with a focus on the quality of available data and on the uncertainty that affects species identity or alien status of amphipod species records. Amphipod records from different world ocean zones were cross-checked and the species with wide disjunct distributions that could be related to human transport were extracted. These were carefully examined for validity of species identification and assessment of alien status. One hundred and five amphipod species were studied. Of these, 55 species are verified aliens at least in one geographical region; the remaining are affected by uncertainty and further investigation is required before they are included in inventories of marine alien species. Many knowledge gaps affect our understanding of the global distribution of marine alien amphipods, as well as many other marine invertebrate groups, and it is possible that our current picture is largely underestimated

Measuring uncertainty of marine alien species: the case of marine alien amphipods worldwide

The present work aims to address the uncertainty regarding marine alien species, by investigating the available knowledge on the taxon of amphipods (Crustacea Peracarida). The main objectives of this study are: i) to develop an inventory of marine alien amphipods worldwide; ii) to discriminate amphipod species with convincing valid alien status from species affected by uncertainty; and iii) to identify and assess the different types of uncertainty that are affecting marine alien amphipod

Specie non-indigene marine e delle acque di transizione e loro distribuzione a livello regionale

A literature survey was performed in order to check the occurrence of non-indigenous marine and brackish species in each Italian region. A total of 613 regional records, referred to 205 non-indigenous species (NIS) were collected. The regions with the highest number of NIS are Sicily, Apulia and Veneto. The number of NIS is positively correlated with the number of ports occurring in each region

Fouling community in the harbour of Piran (Slovenia)

A rapid assessment of the fouling community in the harbour of Piran, Slovenia, was carried out in September 2017. A total of 59 species were collected, out of which 6 were non-indigenous species, all representing new records for Slovenia and 2 of which are also new records for the Adriatic Sea. The usefulness of rapid assessment monitoring programmes is highlighted

Assessing biological invasions in European Seas: Biological traits of the most widespread non-indigenous species

The biological traits of the sixty-eight most widespread multicellular non-indigenous species (MWNIS) in European Seas: Baltic Sea, Western European Margin of the Atlantic Ocean and the Mediterranean Sea were examined. Data for nine biological traits was analyzed, and a total of 41 separate categories were used to describe the biological and ecological functions of these NIS. Our findings show that high dispersal ability, high reproductive rate and ecological generalization are the biological traits commonly associated with MWNIS. The functional groups that describe most of the 68 MWNIS are: photoautotrophic, zoobenthic (both sessile and motile) and nektonic predatory species. However, these ‘most widespread’ species comprise a wide range of taxa and biological trait profiles; thereby a clear ”identikit of a perfect invader” for marine and brackish environments is difficult to define. Some traits, for example: “life form”, “feeding method” and “mobility”, feature multiple behaviours and strategies. Even species introduced by a single pathway, e.g. vessels, feature diverse biological trait profiles. MWNIS likely to impact community organization, structure and diversity are often associated with brackish environments. For many traits (“life form”, “sociability”, “reproductive type”, “reproductive frequency”, “haploid and diploid dispersal” and “mobility”), the categories mostly expressed by the impact-causing MWNIS do not differ substantially from the whole set of MWNIS

Corbicula fluminea ivasion in Lake Maggiore (Italy): population dynamics and comparison of dietary overlap with native mussels

The Asian clam, Corbicula fluminea (M?ller, 1774), was most likely introduced in 2007 in Lake Maggiore, the second largest and deepest lake in Italy. Spatial and temporal variations in abundance, biomass and population structure of C. fluminea at 5 sites, investigated since its first discovery in 2010, confirmed the well known ability of this species rapidly to spread in new recipient environments and to achieve densities of thousands per square meter. In few years Corbicula has colonized about one third of the lake littoral area and has become the dominant littoral benthic species in terms of abundance and biomass, creating the conditions for a competitive interaction for space and food with native mussels. Indeed, a comparison with previous data has evidenced a strong decline of the most abundant native mussel species (Unio mancus), whose actual density is reduced of about 75% after Corbicula invasion. Although native mussel depletion cannot be unequivocally attributed to Corbicula impact, the change in bivalve species dominance could lead to changes in the structure and function of the ecosystem. In spite of similar functional roles, unionids and C. fluminea are likely to differ in filtering efficiency and trophic niche. Therefore, understanding the role that both native and invasive species play in food-web structure and nutrient cycling is essential for predicting how the ecosystem might be altered. Our study aimed to: (i) explore the invasion dynamics of Corbicula in Lake Maggiore; (ii) compare the trophic roles of the native mussel U. mancus and C. fluminea through measurements of respective filtration rates and spectrum of food resources. Filtration rates were measured by the clearance method under different experimental conditions and over the whole diurnal cycle. Dietary composition and overlap were determined through the measurement of the elemental and stable isotopic compositions (δ13C and δ15N) of the respective tissues

Roadmap to the management of marine invasive alien species in Europe: a prioritization exercise in a Mediterranean country

In 2014 the Regulation 1143/14 on invasive alien species (IAS) was issued by the European Community. It provides for important restrictions (as importing and selling) and a set of measures (early detection, rapid eradication or control) that EU member states are required to take for the species included on a list of IAS of Union Concern. The inclusion of a species in this list is based on the results of a risk-assessment procedure. The list, adopted in 2016 and updated in August 2017 contains at present 49 IAS, none of which marine (except from the brackish water crab Eriocheir sinensis). Member states can also adopt a list of “species of national concern” and apply the same measures provided for the species of Union concern. In Italy the scientific community is working on a prioritization exercise to develop a list of IAS of national concern, that may eventually include marine IAS. This list will be composed by both IAS already present and potential new IAS, from a horizon scanning exercise. Their principal pathways have been discussed in relation to the effectiveness of prevention measures. Italy is a major “first hub” for marine introductions in the Mediterranean Sea, with over 200 multicellular marine alien species reported so far. With its central position in the Mediterranean Sea, it shares several species with the Western European countries, carried by ships or with shellfish stocks, as well as a number of Indo-Pacific species with the Eastern Mediterranean countries, entered through the Suez Canal. Therefore, the roadmap that Italy is currently tracing towards the possible inclusion of marine species in the list of IAS to be managed and controlled, is also relevant for other European and Mediterranean countries. This presentation will show how the process has been organized and conducted, and the preliminary outcomes