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As introduced species constitute a major threat to biodiversity, it is crucial to properly monitor their spread to new regions. The present study reports new records of four species: 1) the amphipod Ampithoe valida S.I. Smith, 1873 and 2) the polychaete Polydora colonia Moore, 1907, both new records for Brittany (North-West part of France); 3) the polychaete Bispira polyomma Giangrande & Faasse, 2012, a first finding in the North-East Atlantic; and 4) the flatworm Prostheceraeus moseleyi Lang, 1884 with a confirmed northernmost record in North-East Atlantic. These species were recorded within two semi-enclosed bays: the Morbihan Gulf on the southern coast of Brittany and the Bay of Brest in the North-West part of Brittany. Both localities are already known to host numerous non-indigenous species as well as benthic macrofaunal distributional range limits. Morphological variations and inconsistencies are discussed and reported for A. valida, revealing missing characters and errors in the literature. This work adds three non-indigenous species to Brittany and two nonindigenous species to French waters, for which we discuss potential introduction vectors.

Biological invasions are one of the main global threats to biodiversity in terrestrial, freshwater and marine ecosystems worldwide, requiring effective inventorying and monitoring programs. Here, we present an updated list of non-indigenous species in French marine and transitional waters. Focused on eukaryote pluricellular species found throughout the three metropolitan French marine regions (Western Mediterranean Sea, Bay of Biscay and the Northern Seas), a total of 342 non-indigenous, including 42 cryptogenic, species are listed as having been introduced since the 13th century. The majority of the species originated from the temperate Northern Pacific. They mainly arrived through both ballast and hull fouling and also are associated with shellfish farming activities. Most of them have been introduced since the 1970s, a time when maritime and aquaculture trade intensified. Despite important human-aided opportunities for species transfer between the three marine regions (for instance, via recreational boating or aquaculture transfers), only a third of these NIS are common to all regions, as expected due to their environmental specificities.

The distribution range of the American comb jelly Mnemiopsis leidyi has expanded across Europe for several decades, particularly in the eastern Atlantic and Mediterranean Sea. This study aims to assess its expansion along the French Atlantic coast, mainly in the Bay of Biscay and Iroise Sea, since the first record in 2014. Mnemiopsis leidyi is now clearly established along 500 km of coastline, from the coast of Lorient to Arcachon Bay, which is the southernmost colonised area in the eastern Atlantic to date. It will likely colonise the Spanish Gulf coast in the near future through natural dispersal via currents, as has occurred between the Gironde estuary and Arcachon Bay. We quantify that this species now colonises nearly 45% of the French coastline. The invaded area includes the main estuaries of the Seine, Loire, Gironde and Rhône rivers, where M. leidyi populations may constitute reservoirs for colonising other harbours through merchant vessel traffic via ballast water. Finally, the Marennes- Oléron Bay and Arcachon Bay are the two main spat-producing regions for the Pacific oyster Magallana gigas in France. As M. leidyi consumes bivalve larvae, the potential economic and ecological impacts on this shellfish industry are discussed.

Distributional shifts in species ranges provide critical evidence of ecological responses to climate change. Assessments of climate-driven changes typically focus on broad-scale range shifts (e.g. poleward or upward), with ecological consequences at regional and local scales commonly overlooked. While these changes are informative for species presenting continuous geographic ranges, many species have discontinuous distributions—both natural (e.g. mountain or coastal species) or human-induced (e.g. species inhabiting fragmented landscapes)—where within-range changes can be significant. Here, we use an ecosystem engineer species (Sabellaria alveolata) with a naturally fragmented distribution as a case study to assess climate-driven changes in within-range occupancy across its entire global distribution. To this end, we applied landscape ecology metrics to outputs from species distribution modelling (SDM) in a novel unified framework. SDM predicted a 27.5% overall increase in the area of potentially suitable habitat under RCP 4.5 by 2050, which taken in isolation would have led to the classification of the species as a climate change winner. SDM further revealed that the latitudinal range is predicted to shrink because of decreased habitat suitability in the equatorward part of the range, not compensated by a poleward expansion. The use of landscape ecology metrics provided additional insights by identifying regions that are predicted to become increasingly fragmented in the future, potentially increasing extirpation risk by jeopardising metapopulation dynamics. This increased range fragmentation could have dramatic consequences for ecosystem structure and functioning. Importantly, the proposed framework—which brings together SDM and landscape metrics—can be widely used to study currently overlooked climate-driven changes in species internal range structure, without requiring detailed empirical knowledge of the modelled species. This approach represents an important ad

Increasingly, ecological rehabilitation is envisioned to mitigate and revert impacts of ocean sprawl on coastal marine biodiversity. While in the past studies have demonstrated the positive effects of artificial fish habitats in port areas on fish abundance and diversity, benthic colonization of these structures has not yet been taken into consideration. This could be problematic as they may provide suitable habitat for Non-Indigenous Species (NIS) and hence facilitate their spreading. The present study aimed to examine communities developing on artificial fish habitats and to observe if the number of NIS was higher than in surrounding equivalent habitats. The structures were colonized by communities that were significantly different compared to those surrounding the control habitat, and they were home to a greater number of NIS. As NIS can cause severe ecological and economical damages, our results imply that in conjunction with the ecosystem services provided by artificial fish habitats, an ecosystem disservice in the form of facilitated NIS colonization may be present. These effects have not been shown before and need to be considered to effectively decide in which situations artificial structures may be used for fish rehabilitation.

Introduced species constitute a critical bio-security issue worldwide and the precise monitoring of their spread is crucial for their management. For species forming cryptic complexes this may remain difficult. Using integrative taxonomy, we formally report for the first time, well-established populations of the cosmopolitan introduced bryozoan Watersipora subatra in the French Mediterranean Sea and compile worldwide existing genetic data for Watersipora species alongside newly acquired data to establish the most complete phylogeny of the genus to date. This revealed pervasive erroneous identifications in Genbank, which in turn perpetrate further errors in recent studies, primarily misidentifying W. subatra as W. subtorquata. High abundance and geographic spread of W. subatra in our Mediterranean sampling sites suggest that this species has been present for some time but has been misidentified until now. We provide an updated species identification for all current reference sequences in the Watersipora genus, which may help future monitoring of W. subatra and other Watersipora species.

Seafloor litter samples were collected as part of the International Bottom Trawl Surveys in 2021 and 2022. The surfaces of 146 macrolitter items taken from benthic trawl surveys conducted in the North-East Atlantic were examined for the presence of macrofauna, including Non-Indigenous Species (NIS). A total of 145 taxa were recorded, including three NIS (the barnacles Solidobalanus fallax and Austrominius modestus and the slipper limpet Crepidula fornicata). The three NIS were found exclusively in the English Channel, on litter items likely to have been recently reclaimed from very shallow coastal waters. No NIS were found in the Bay of Biscay, however a large amount of litter from longline fisheries was found to be colonised by diverse sessile communities. Dominant litter plastic types were smooth flexible polyethylene and polyamide – found mostly in the form of monofilament fishing lines. The results from this study will be pooled with those from a sister study led by Cefas, thus bringing together into a single dataset 251 colonised seafloor litter items. The resulting broad-scale dataset will allow us to compare litter items and plastic types with fouling communities.

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium- and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a ‘very high risk’ of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate ‘rapid’ management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be r

The goal of the ICES Working Group on the Introduction and Transfers of Marine Organisms (WGITMO) is to contribute to the ICES vision and mission by addressing specific science objectives related to the introduction, spread and impacts of non-indigenous marine species (NIS). The expert working group provides information and advice on the impacts of human activities (e.g. pressures caused by invasive species, litter, aquaculture, biofouling) on marine ecosystems including the Arctic. The Terms of Reference include annual national reporting on NIS detections and research, climate change impact on the spread of NIS, the risk and impacts of NIS, vectors of spread of NIS including biofouling, marine debris and aquaculture. This report summarizes the key findings and outcomes from the 2020–2022 term. A joint meeting in (2020) with WGBOSV [Ballast Water and Other Ship Vectors] and WGHABD [Harmful Algal Bloom Dynamics] was held to discuss scientific issues of joint interest including climate change in the Arctic environment, and early detection of and response to species through the use of innovative molecular tools. The discussion on molecular tools was used by the groups to develop the framework for a targeted Molecular Tools workshop in conjunction with at the International Conference for Marine Bioinvasions (ICMB) in May 2023. National activities were presented and discussed from over 20 countries each year. Common themes included, new species introduction and monitoring, recent activities on traditional and innovative methods for detection and surveillance (including molecular tools). Science highlights include the submission of the ICES biofouling viewpoint to the International Maritime Organization (IMO) regarding biofouling guidelines, development and publication of a global scale NIS screening tool, and publication of a global review of NIS trends over 50 years. The Information system on aquatic non-indigenous and cryptogenic species AquaNIS continu

Distributional shifts in species ranges provide critical evidence of ecological responses to climate change. Assessments of climate-driven changes typically focus on broad-scale range shifts (e.g. poleward or upward), with ecological consequences at regional and local scales commonly overlooked. While these changes are informative for species presenting continuous geographic ranges, many species have discontinuous distributions—both natural (e.g. mountain or coastal species) or human-induced (e.g. species inhabiting fragmented landscapes)—where within-range changes can be significant. Here, we use an ecosystem engineer species (Sabellaria alveolata) with a naturally fragmented distribution as a case study to assess climate-driven changes in within-range occupancy across its entire global distribution. To this end, we applied landscape ecology metrics to outputs from species distribution modelling (SDM) in a novel unified framework. SDM predicted a 27.5% overall increase in the area of potentially suitable habitat under RCP 4.5 by 2050, which taken in isolation would have led to the classification of the species as a climate change winner. SDM further revealed that the latitudinal range is predicted to shrink because of decreased habitat suitability in the equatorward part of the range, not compensated by a poleward expansion. The use of landscape ecology metrics provided additional insights by identifying regions that are predicted to become increasingly fragmented in the future, potentially increasing extirpation risk by jeopardising metapopulation dynamics. This increased range fragmentation could have dramatic consequences for ecosystem structure and functioning. Importantly, the proposed framework—which brings together SDM and landscape metrics—can be widely used to study currently overlooked climate-driven changes in species internal range structure, without requiring detailed empirical knowledge of the modelled species. This approach represents an important ad

Aim To investigate some of the environmental variables underpinning the past and present distribution of an ecosystem engineer near its poleward range edge. Location >500 locations spanning >7,400 km around Ireland. Methods We collated past and present distribution records on a known climate change indicator, the reef‐forming worm Sabellaria alveolata (Linnaeus, 1767) in a biogeographic boundary region over 182 years (1836–2018). This included repeat sampling of 60 locations in the cooler 1950s and again in the warmer 2000s and 2010s. Using species distribution modelling, we identified some of the environmental drivers that likely underpin S. alveolata distribution towards the leading edge of its biogeographical range in Ireland. Results Through plotting 981 records of presence and absence, we revealed a discontinuous distribution with discretely bounded sub‐populations, and edges that coincide with the locations of tidal fronts. Repeat surveys of 60 locations across three time periods showed evidence of population increases, declines, local extirpation and recolonization events within the range, but no evidence of extensions beyond the previously identified distribution limits, despite decades of warming. At a regional scale, populations were relatively stable through time, but local populations in the cold Irish Sea appear highly dynamic and vulnerable to local extirpation risk. Contemporary distribution data (2013–2018) computed with modelled environmental data identified specific niche requirements which can explain the many distribution gaps, namely wave height, tidal amplitude, stratification index, then substrate type. Main conclusions In the face of climate warming, such specific niche requirements can create environmental barriers that may prevent species from extending beyond their leading edges. These boundaries may limit a species’ capacity to redistribute in response to global environmental change.

Uncommon fish records may reflect local or global changes of fish composition resulting from environmental changes or anthropogenic activities. Significant records of uncommon marine fishes, including migrant, non-native, cryptic, rare and threatened species, collected in French waters or by French vessels in European waters, observed by scuba divers or beachgoers, are reported for the year 2019. They include first, new, rare and unusual records for the following 33 species: Tetronarce nobiliana, Gymnothorax unicolor, Maulisia mauli, Salmo trutta, Grammonus ater, Photostomias guernei, Ijimaia loppei, Echiodon drummondii, Holocen- trus adscensionis, Nerophis lumbriciformis, Scorpaena scrofa, Lepidotrigla dieuzeidei, Eutelichthys leptochirus, Liparis montagui, Mycteroperca rubra, Serranus cabrilla, Remora remora, Caranx crysos, Naucrates ductor, Trachurus picturatus, Seriola rivoliana, Argyrosomus regius, Parablennius pilicornis, Pseudoscopelus astro- nesthidens, Deltentosteus collonianus, Didogobius schlieweni, Didogobius splechtnai, Gobius couchi, Gobius gasteveni, Lebetus guilleti, Synapturichthys kleinii, Lagocephalus lagocephalus and Mola mola, among which I. loppei, H. adscensionis and P. astronesthidens represent first records for the French waters and additions to the Checklist of the marine fishes from metropolitan France. Photostomias guernei is a first record for the Bay of Biscay, found close the French EEZ., Les signalements inhabituels de poissons peuvent témoigner de changements locaux ou globaux résultants de modifications environnementales ou d’activités anthropiques. Des signalements remarquables de poissons marins, comprenant des espèces migrantes, non natives, cryptiques, rares et menacées, collectés dans les eaux françaises ou bien par des navires français dans les eaux européennes, observées par des plongeurs sous-marins ou des promeneurs, sont mentionnés pour l’année 2019. Ils comprennent des premiers et nouveaux signalements ainsi que des signalements rares et inhabituels pour les 33 espèces suivantes : Tetronarce nobiliana, Gymnothorax unicolor, Maulisia mauli, Salmo trutta, Grammonus ater, Photostomias guernei, Ijimaia loppei, Echiodon drummondii, Holocentrus adscensionis, Nerophis lumbriciformis, Scorpaena scrofa, Lepidotrigla dieuzeidei, Eutelichthys leptochirus, Liparis montagui, Mycteroperca rubra, Serranus cabrilla, Remora remora, Caranx crysos, Naucrates ductor, Trachurus picturatus, Seriola rivoliana, Argyrosomus regius, Parablennius pilicornis, Pseudoscopelus astronesthidens, Deltentosteus collonianus, Didogobius schlieweni, Didogobius splechtnai, Gobius couchi, Gobius gasteveni, Lebetus guilleti, Synapturichthys kleinii, Lagocephalus lagocephalus et Mola mola, parmi lesquelles I. loppei, H. adscensionis et P. astronesthidens représentent des premiers signalements pour les eaux françaises et des additions à la Liste des poissons marins de France métropolitaine. Photostomias guernei est un premier signalement pour le golfe de Gascogne, trouvé proche de la ZEE française.

Le règlement européen relatif aux espèces exotiques envahissantes (EEE) (1143/20141) fournit une liste d’EEE réglementées à l’échelle européenne. A ce jour, sur les 66 EEE de cette liste, seulement deux sont des espèces non indigènes (ENI) marines. L’objectif du présent travail est de proposer une liste d’espèces à réglementation à l’échelle nationale (selon les articles L411-5 dit de Niveau 1 et L411-6 dit de Niveau 2 du Code de l’Environnement2), suivant une nouvelle procédure d’analyse de risques décrite sommairement ci-dessous.