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Aggressive, omnivorous, invasive: the Erythraean moon crab Matuta victor (Fabricius, 1781) (Crustacea: Decapoda: Matutidae) in the eastern Mediterranean sea
Journal of Natural History
Abstract
Since its first sighting in 2012 in Haifa Bay, Israel, the population of the Indo-Pacific moon crab, Matuta victor, has increased greatly along the Israeli littoral and spread to Lebanon and the Mediterranean coast of Turkey. To examine possible interactions with the Levantine nearshore psammophilic community, the crab's feeding behaviour was observed in situ and the foregut contents of 69 specimens collected in December 2015 and June 2016 were analysed. Its omnivorous diet was confirmed and previously unknown intraspecific competitive feeding behaviour is reported. The agonistic behaviour may denote behavioural flexibility that enables the crabs to colonize and persist in a depauperate novel habitat. Site-specific disturbance regimen related to human activities seems to have had a critical role in driving the rapid population increase. ARTICLE HISTORY
... M. purnama is found only in coastal areas facing the Indian Ocean (ocean coast) (Lai & Galil 2007;Hanim et al. 2021). Although the genus Matuta is generally inhabitant of tropical sandy shores (Lai & Galil 2007), M. victor is also found in the subtropical region of the Mediterranean Sea (invasive species) (Galil & Mendelson 2013;Innocenti et al. 2017). In contrast, the genus Asthoret is primarily distributed in eastern Indonesia (Galil & Clark 1994), and the genus Izanami is also found in eastern Indonesia at 27 m (this study). ...
Several species of brachyuran crabs in Indonesian waters have not been reported since almost 100 years ago. This research reports a brachyuran crab that is rarely found and one new record in Indonesian waters. This study was conducted in the waters of southern Aru Island and the Malacca Strait using trawls during a cruise held by the Research Institute for Marine Fisheries, Ministry of Marine Affairs and Fisheries, Indonesia.. Our findings were Izanami reticulata, a new record (family Matutidae) from southern Aru Island, and Cryptopadia fornicata (family Parthenopidae) from the Malacca Strait. The two locations are close to where the species were found in previous studies: the Arafura Sea, which is adjacent to the Aru Islands, and the Malacca Strait, which is adjacent to Borneo. It is suspected that the presence of these two species in Indonesia is due to their distribution through sea currents during the pelagic larval stage. This article also provides the specific habitat for both species in Indonesia, which was previously unknown. In addition, this article contributes to strengthening Indonesia as a mega-biodiversity country with an initial compilation of a database of Brachyura in its waters.
... M. victor is a voracious scavenger and an omnivorous predator, displaying interspecies nutritional competition and aggressive behavior. Although it mainly preys on mollusks and crustaceans, small individuals feed on small soft-shelled species, while larger individuals feed on slow-moving invertebrates such as gastropods , anomurans and bivalves (Innocenti et al., 2017;Galil et al., 2015). They are widely distributed in the Indo-Pacific region, including the New Hebrides, Fiji (from Southeast Asia) and the Red Sea, are caught by the local population with nets, handheld or beach purse seines (Carpenter & Niem, 2001;Hanim et al., 2021;Zviely et al., 2021). ...
Matuta species belong to the superfamily Calappoidea and are widely distributed in the Indo-Pacific region, including the New Hebrides, Fiji (from Southeast Asia) and the Red Sea. They live in sandy coastal areas and at depths between 0-20m. To date, the studies of Matuta victor have generally focused on the first record/occurrence. In addition, egg morphology and fecundity studies are limited due to the difficulty in encountering ovigerous female individuals. In this study, the number of eggs and egg morphology of an ovigerous female individual belonging to the M. victor species caught from Antalya Bay (in August 2022) were investigated. In the metric measurements, the length of the carapace was 2.53 cm, the width of the carapace was 2.62 cm, and the characteristic distance between the end points of the lateral spines on the carapace was 3.90 cm. The weight of the individual was measured as 7.380 g. The average diameter of 100 eggs was calculated as 331.75 ± 7.62 µm. The number of oil droplets observed in the eggs was 1 and the the oil drop diameter was measured as a minimum of 59.64 µm, a maximum of 73.12 µm and an average of 64.16±3.21 µm. The yolk diameter in eggs was measured as a minimum of 264.96 µm, a maximum of 299.56 µm and an average of 286.10±9.19 µm. The ratio of oil drop diameter to yolk diameter was calculated as 0.22±0.01 µm. Since there are very limited studies on M. victor in the Mediterranean, and there is no study on egg morphology and fecundity, especially in Antalya Bay, this study presents novel data that can be used for comparison in other egg morphology studies of M. victor or another species belonging to the same genus.
... The species seems to spread quite fast in the Mediterranean Sea, yet its presence to date is restricted to the south-eastern parts of the basin. Innocenti et al. (2017) characterise the species as "aggressive, omnivorous and invasive", reflecting in this way the characteristics that make the species a successful invader. The feeding habits and foraging characteristics of M. victor might affect the structure of benthic invertebrate populations, if it becomes well established and abundant (Galil & Mendelson, 2013). ...
This Collective article reports 17 introduced species and 22 new locations for these species in the Mediterranean Sea. The reports are from three different Marine Strategy Framework Directive (MSFD) subregions (Aegean-Levantine Sea, Adriatic Sea and Western Mediterranean Sea) and the Sea of Marmara and cover ten different countries. The goal of consistent and detailed reporting of introduced species is to complement the existing species inventories and serve as a basis for establishing monitoring strategies and other conservation measures. Some of the reports from this article are the first species records for the Mediterranean Sea, namely the green alga Udotea flabellum from the Aegean Sea (Turkey) and the deepbody boarfish Antigonia capros from the Balearic Sea (Spain). In addition, new records of introduced species are included for different seas, namely the moon crab Matuta victor for the Aegean Sea (Greece), the whale shark Rhincodon typus and the lionfish Pterois miles for the Alboran Sea (Spain), the almaco jack Seriola rivoliana for the Tyrrhenian Sea (Italy), and the hound needlefish Tylosurus crocodilus for the Adriatic Sea (It-aly). Furthermore, reports on first country records are included: the red alga Colaconema codicola from Slovenia, the nudibranch Melibe viridis from Bosnia and Herzegovina, the lionfish Pterois miles from Montenegro, and the goldstripe sardinella Sardinella gibbosa from Syria, which also represents a second record for the Mediterranean Sea. Furthermore, the occurrence of the sclerac-tinian coral Oculina patagonica was noted in Gulf of Lion (France). Four polychaete species, namely Leodice antennata, Timarete punctata and Branchiomma bairdi, are reported from the vermetid reef habitat and two of them (L. antennata and B. bairdi) are also recorded for the first time in Lebanon. Evidence for established populations of the Asian date mussel Arcuatula senhousia in the Sea of Marmara (Turkey) and the rayed pearl oyster Pinctada radiata around the island of Sardinia (Italy) is provided.
... Beach nourishment may also displace native biota. It was claimed [106] that beach nourishment in the Haifa Bay enhanced the introduction and dispersal of the non-indigenous, aggressive, omnivorous, invasive Lessepsian moon crab, Matuta victor. However, a recent study [107] proved that the spread and establishment of this invasive species in the Eastern Mediterranean is not associated with beach nourishment. ...
In the last 100 years, the population of the land of Israel has increased dramatically, accompanied by a very intense and accelerated economic and industrial growth. The objective of the present review is to reveal how these major changes have affected the Mediterranean marine and coastal environment. The present review analyzes the global, regional, and local factors and processes that cause substantial environmental changes affecting a variety of marine habitats and taxa. These include: (1) seawater warming that enhances the considerable introduction and establishment of non-indigenous tropical, i.e., Lessepsian, species; (2) overfishing of native biota that seems to contribute to this process; (3) sea-level rise, associated with global warming, which may threaten the sensitive intertidal abrasion platforms; (4) chemical, noise, and light pollution and marine debris; (5) massive sand mining from the beaches, which caused severe erosion in many coastal sections and was banned in Israel in 1964; (6) extensive dredging in the sea, mainly related to the construction and development of large ports, which can be detrimental for the benthic biota, especially in rocky substrates; and (7) marine structures (harbors, marinas, detached breakwaters) that interfere with the natural pattern of sand transport along the coast and cause morphological changes (sand erosion or accumulation) on nearby beaches and the seabed. Israel’s coast is presently characterized by intense anthropogenic activity and many stakeholders with considerable conflicts between them and with the marine ecosystem. A few environmental impacts have ceased, and others have been reduced considerably, but the extent of many additional types have increased significantly, and new impacts have appeared in recent years. Some environmental impacts are beyond our control, and others can be reduced by proper management, but it is predicted that certain major environmental impacts, such as Lessepsian migration, will continue in the future at enhanced rates.
... However, our results indicate that C. granulata is an omnivorous species, with crustaceans being a preferent food component, followed by fish and cephalopods. Other calappid crabs are also known for their omnivorous nature, such as Acanthocarpus alexandri [63], Hepatus pudibundus [64], Matuta lunaris [3] and Matuta victor [65]. In accordance with the crab's predatory nature, the presence of hard remains such as crustacean exoskeleton, fish otoliths and bones, was not surprising; however, observation of cephalopod beaks and sucker rings in the crab stomach was. ...
This study presents the first data on morphometry, length–weight relationship, diet, reproductive biology, epibionts and genetic identity of the shamefaced crab Calappa granulata from the central eastern Adriatic Sea. A total of 92 crabs were collected during 2011, 2014 and 2015, of which 64 were females and 28 were males. Overall, 11 morphometric characteristics were measured. Carapace length of sampled individuals ranged from 48.46 to 76.09 mm, and body weight from 47.06 to 221.39 g. The length–weight relationship showed negative allometry for males and isometric growth for females. Analysis of the stomach content revealed the crab’s preference for crustaceans (20.28%) and cephalopods (10.58%), less for fish (3.4%) and shellfish (0.28%). Size at first sexual maturity (CL50%) of 59.25 and 66.92 mm was estimated for males and females, respectively. Epibiotic serpulid polychaetes were recorded on the crab exoskeleton with an overall prevalence of 29.3%. Analyses of a partial sequence of mtCOI showed high haplotype (Hd = 0.964) and low nucleotide diversity (π = 0.00598). Phylogenetic inference and estimation of population differentiation (FST = 0.013, p = 0.271) with publicly available Mediterranean sequences currently imply one homogenous population unit. To the best of our knowledge, these are the first nucleotide sequences of C. granulata from the Adriatic Sea made publicly available.
... Beach nourishment may also displace native biota. It was claimed [106] that beach nourishment in the Haifa Bay enhanced the introduction and dispersal of the non-indigenous, aggressive, omnivorous, invasive Lessepsian moon crab, Matuta victor. However, a recent study [107] proved that the spread and establishment of this invasive species in the Eastern Mediterranean is not associated with beach nourishment. ...
Beachrock is composed of intertidal-associated sediments, rapidly cemented by calcium carbonate, and has important implications for understanding coastal morphological processes. This study focuses on the morphodynamic erosion patterns of Late Holocene beachrock outcrops along the Mediterranean coast of Israel that have formed since the sea reached its present level about 4,000 years ago. Exposed beachrock is subjected to erosion, affecting its seaward and landward facing fronts and upper surface, and creating distinct morphological features due to wave pounding and coastal currents which remove unconsolidated sediment supporting layers. The current state of beachrock morphology is presented, based on field measurements and field relation interpretations of selected sites, backed by petrographic and sedimentological data. It shows and studies selected beachrock exposures along Israel’s coast, and characterizes their morphological features in various field-relation configurations. A classification is developed of the main erosion patterns of beachrock embedded on loose, hard, partly hard and partly loose substrate.
... Matuta victor was firstly reported from the Mediterranean in 2012 from Haifa Bay and ever since has rapidly increased its population in the Levantine Sea (Galil and Mendelson 2013;Crocetta et al. 2015a;Innocenti et al. 2017). The invasive crab has exhibited intraspecific competitive behavior for food ), yet no impacts on biodiversity or ecosystem services have been reported from Mediterranean ecosystems. ...
Biological invasions have become a defining feature of marine Mediterranean ecosystems with significant impacts on biodiversity, ecosystem services, and human health. We systematically reviewed the current knowledge on the impacts of marine biological invasions in the Mediterranean Sea. We screened relevant literature and applied a standardised framework that classifies mechanisms and magnitude of impacts and type of evidence. Overall, 103 alien and cryptogenic species were analysed, 59 of which were associated with both negative and positive impacts, 17 to only negative, and 13 to only positive; no impacts were found for 14 species. Evidence for most reported impacts (52%) was of medium strength, but for 32% of impact reports evidence was weak, based solely on expert judgement. Only 16% of the reported impacts were based on experimental studies. Our assessment allowed us to create an inventory of 88 alien and cryptogenic species from 16 different phyla with reported moderate to high impacts. The ten worst invasive species in terms of reported negative impacts on biodiversity include six algae, two fishes, and two molluscs, with the green alga Caulerpa cylindracea ranking first. Negative impacts on biodiversity prevailed over positive ones. Competition for resources, the creation of novel habitat through ecosystem engineering, and predation were the primary reported mechanisms of negative effects. Most cases of combined negative and positive impacts on biodiversity referred to community-level modifications. Overall, more positive than negative impacts were reported on ecosystem services, but this varied depending on the service. For human health, only negative impacts were recorded. Substantial variation was found among Mediterranean ecoregions in terms of mechanisms of impact and the taxonomic identity of impacting species. There was no evidence that the magnitude of impact increases with residence time. Holistic approaches and experimental research constitute the way forward to better understanding and managing biological invasions.
... M. purnama is found only in coastal areas facing the Indian Ocean (ocean coast) (Lai & Galil 2007;Hanim et al. 2021). Although the genus Matuta is generally inhabitant of tropical sandy shores (Lai & Galil 2007), M. victor is also found in the subtropical region of the Mediterranean Sea (invasive species) (Galil & Mendelson 2013;Innocenti et al. 2017). In contrast, the genus Asthoret is primarily distributed in eastern Indonesia (Galil & Clark 1994), and the genus Izanami is also found in eastern Indonesia at 27 m (this study). ...
This research aimed to report two species of Brachyuran crabs that were found rarely from Indonesian waters. The latest report was more than one hundred years ago, and the study from Indonesia before was not so clear, both information about specimens and location details. We conducted our study in Southern Aru Island and Malacca Strait using trawl during the cruise research which was held by the Research Institute for Marine Fisheries, Ministry of Marine Affairs and Fisheries. Our findings were Izanami reticulata , New Record (family Matutidae) from Southern Aru Island, and Cryptopodia fornicata (family Parthenopidae) from Malacca Strait. The two locations are located close to the location where the species was found in previous studies, namely the Arafura Sea which is adjacent to the Aru Islands, and the Malacca Strait which is adjacent to Borneo. We suspect that the presence of these two species in western and eastern Indonesia was due to their distribution during the pelagic larval stage through the sea current. This article also provided the specific habitat for both species which has not been stated. In addition, this article will contribute to strengthening Indonesia as a mega biodiversity country with initiate compiling the database of Brachyura in Indonesian waters.
In this study, some biological characteristics of the invasive moon crab, Matuta victor, which has recently entered the waters of the northeastern Mediterranean, Türkiye, were investigated for the first time. The study was carried out seasonally on sandy bottoms at 0.5-3 m depths along Karataş (Adana, Türkiye) coasts between 2020 -2021. A total of 364 crabs were obtained, 93 females (27 ovigerous), 270 males and one juvenile. The carapace width of female crabs ranged between 27.49-49.30 mm with a mean of 41.55±4.01 mm. The carapace width of male crabs ranged between 21.28-66.70 mm with a mean of 49.15±8.97 mm. Mean carapace length measurements in females and males were 26.83±2.52 mm and 32.71±5.85 mm, and the mean total weights were 8.18±1.99 g and 16.27±7.30 g, respectively. The male:female ratio was 2.16:1. Morphometric relationships indicated negative allometric growth for females, males, and both sexes. Ovigerous females were obtained in all seasons except the winter. The female crabs with carapace widths that ranged between 35.31-48.84 mm and a mean of 41.97±3.29 mm had a mean fecundity of 36822.04±29745.9 eggs.
Sandy beaches are iconic interfaces that functionally link the ocean with the land via the flow of organic matter from the sea. These cross-ecosystem fluxes often comprise uprooted seagrass and dislodged macroalgae that can form substantial accumulations of detritus, termed 'wrack', on sandy beaches. In addition, the tissue of the carcasses of marine animals that regularly wash up on beaches form a rich food source ('carrion') for a diversity of scavenging animals. Here, we provide a global review of how wrack and carrion provide spatial subsidies that shape the structure and functioning of sandy-beach ecosystems (sandy beaches and adjacent surf zones), which typically have little in situ primary production. We also examine the spatial scaling of the influence of these processes across the broader land-and seascape, and identify key gaps in our knowledge to guide future research directions and priorities. Large quantities of detrital kelp and seagrass can flow into sandy-beach ecosystems, where microbial decom-posers and animals process it. The rates of wrack supply and its retention are influenced by the oceanographic processes that transport it, the geomorphology and landscape context of the recipient beaches, and the condition, life history and morphological characteristics of the macrophyte taxa that are the ultimate source of wrack. When retained in beach ecosystems, wrack often creates hotspots of microbial metabolism, secondary productivity, biodiversity, and nutrient remineralization. Nutrients are produced during wrack breakdown, and these can return to coastal waters in surface flows (swash) and aquifers discharging into the subtidal surf. Beach-cast kelp often plays a key trophic role, being an abundant and preferred food source for mobile, semi-aquatic invertebrates that channel imported algal matter to predatory invertebrates, fish, and birds. The role of beach-cast marine carrion is likely to be underestimated, as it can be consumed rapidly by highly mobile scavengers (e.g. foxes, coyotes, raptors, vultures). These consumers become important vectors in transferring marine productivity inland, thereby linking marine and terrestrial ecosystems. Whilst deposits of organic matter on sandy-beach ecosystems underpin a range of ecosystem functions and services, they can be at variance with aesthetic perceptions resulting in widespread activities, such as 'beach cleaning and grooming'. This practice diminishes the energetic base of food webs, intertidal fauna, and biodiversity. Global declines in seagrass beds and kelp forests (linked to global warming) are predicted to cause substantial reductions in the amounts of marine organic matter reaching many beach ecosystems, likely causing flow-on effects for food webs and biodiversity. Similarly, future sea-level rise and increased storm frequency are likely to alter profoundly the physical attributes of beaches, which in turn can change the rates at which beaches retain and process the influxes of wrack and animal carcasses. Conservation of the multi-faceted ecosystem services that sandy beaches provide will increasingly need to encompass a greater societal appreciation and the safeguarding of ecological functions reliant on beach-cast organic matter on innumerable ocean shores worldwide.
Globally, the spread of non-indigenous species in marine ecosystems is a major ecological and socio-economical concern. The need for long-term assessment on a large scale is a pre-requisite for
understanding the drivers associated with their establishment and expansion. Here, the patterns of invasions
of subtidal soft-bottom assemblages of shelled moluscs have been quantified based on a unique dataset
collected between 2005 and 2012 along the coast of Israel (SE Mediterranean Sea), a hotspot of bioinvasion. Overall, the number of non-indigenous species doubled between 2005 and 2012. Significant differences in terms of species richness and relative abundance were observed in space and time in both native and non-indigenous species. A combination of enduring disturbance regimes related to human activ-
ities and site-specific environmental conditions seem to have a critical role in promoting the observed
patterns. Our results emphasize the value of long term broad-scale systematic surveys to the development of
effective environmental policies for the control of bioinvasions.
This contribution forms part of a series of collective articles published regularly in Mediterranean Marine Science that report on new biodiversity records from the Mediterranean basin. The current article presents 51 geographically distinct records for 21 taxa belonging to 6 Phyla, extending from the western Mediterranean to the Levantine. The new records, per country, are as follows: Spain: the cryptogenic
calcareous sponge Paraleucilla magna is reported from a new location in the Alicante region. Algeria: the rare Atlanto-Mediterranean bivalve Cardium indicum is reported from Annaba. Tunisia: new distribution records for the Indo-Pacific lionfish Pterois miles from
Zembra Island and Cape Bon. Italy: the ark clam Anadara transversa is reported from mussel cultures in the Gulf of Naples, while the amphipod Caprella scaura and the isopods Paracerceis sculpta and Paranthura japonica are reported as associated to the –also allochthonous–bryozoan Amathia verticillata in the Adriatic Sea; in the latter region, the cosmopolitan Atlantic tripletail Lobotes surinamensisis also reported, a rare finding for the Mediterranean. Slovenia: a new record of the non-indigenous nudibranch Polycera hedgpethi in the Adriatic. Greece: several new reports of the introduced scleractinian Oculina patagonica, the fangtooth moray Enchelycore anatina, the blunthead puffer Sphoeroides pachygaster (all Atlantic), and the lionfish Pterois miles (Indo-Pacific) suggest their ongoing establishment in the Aegean Sea; the deepest bathymetric record of the invasive alga Caulerpa cylindracea in the Mediterranean Sea is also registered in the Kyklades, at depths exceeding 70 m. Turkey: new distribution records for two non indigenous crustaceans, the blue crab Callinectes sapidus (Atlantic origin) and the moon crab Matuta victor (Indo-Pacific origin) from the Bay of Izmir and Antalya, respectively; in the latter region, the Red Sea goatfish Parupeneus forsskali, is also reported. Lebanon: an array of records of 5 alien and one native Mediterranean species is reported by citizen-scientists; the Pacific jellyfish Phyllorhiza punctata and the Indo-Pacific teleosteans Tylerius spinosissimus, Ostracion cubicus, and Lutjanus argentimaculatus are reported from the Lebanese coast, the latter notably being the second record for the species in the Mediterranean Sea since 1977; the native sand snake-eel Ophisurus serpens, rare in the eastern Mediterranean, is reported for the first time from Lebanon, this being its easternmost distribution range; finally, a substantial number of sightings of the lionfish Pterois miles further confirm the current establishment of this lessepsian species in the Levantine.
In this third Collective Article, with fisheries-related data from the Mediterranean Sea, we present the historical length distribution of Lophius budegassa in the catch of commercial trawlers in the Greek seas; length-weight and length-length relationships of five flatfish species (Lepidorhombus boscii, L. whiffiagonis, Platichthys flesus, Pegusa lascaris and Solea solea) from different coastal areas of Turkey (Black Sea and Eastern Mediterranean Sea); growth of settled Polyprion americanus and length-weight relationships
of this species and of Deltentosteus quadrimaculatus, Capros aper and three commercially important groupers in the Eastern Mediterranean Sea; the age, growth and mortality of Zosterisessor ophiocephalus in the Eastern Adriatic Sea; the length-weight relationship and condition factor of Atherina boyeri in a Central Mediterranean semi-isolated lagoon, and also the length-weight and length-length relationships of three Alburnus species from different inland waters in Turkey.
While marine hermit crabs are well known for being omnivorous filter feeders, less is known about the role they may play as active carrion scavengers in intertidal ecosystems. Prior studies have revealed that intertidal hermit crabs can be attracted to chemical cues from predated gastropods. Yet their attraction is usually assumed to be driven primarily by the availability of new shells rather than by food. We conducted field experiments to assess hermit crabs’ potential role as generalist carrion scavengers on the California Coast, examining their speed of attraction and the size of the aggregations they formed in response to chemical cues from freshly smashed gastropods and mussels, both of which indicated available carrion. Compared to all other marine species, hermit crabs (Pagurus samuelis, P. hirsutiusculus, and P. granosimanus) were the fastest to arrive at the provisioning sites. Hermit crabs also dominated the provisioning sites, accumulating in the largest numbers, with aggregations of up to 20 individuals, which outcompeted all other scavengers for carrion. Notably, hermit crabs arrived equally quickly for both smashed gastropod and mussel, even though the latter does not offer suitable shells for hermit crabs and even though the former only yields shell-related chemical cues over time frames longer than our experiments. These results thus suggest that shell availability is not the only, or even the primary, reason marine intertidal hermit crabs aggregate at carrion sites; they also aggregate to forage, thereby playing an important role as active carrion scavengers in intertidal ecosystems.
Two adult specimens of Matuta victor were recently collected in Haifa Bay, Israel. A single specimen of Ashtoret lunaris, collected in 1987 from Haifa Bay, was hitherto the only record of the Matutidae in the Mediterranean Sea.
Observations of the behavioural responses of near-shore marine scavengers to fish carrion were made at two depths (1–2 m, 16–18 m). Gobies and juvenile whelks were the most numerous scavengers, but appeared to consume little biomass. The first scavengers to appear at carrion (seconds/minutes) were swimming forms, later (minutes) joined by fast-moving, crawling portunid crabs. Large scavengers (crabs/starfish/catsharks) arrived after tens of minutes/hours. Scavengers were ‘direct feeders’ on the bait (crabs and some fish) or ‘indirect feeders’ (gobies and whelks) on scraps generated by direct feeders. Scavengers spent little time in aggression. While fish spent relatively low proportions of their time feeding (e.g. Lipophrys pholis: 2.2–15.8%), crabs fed almost continuously (e.g. Carcinus maenas: 97.8–99.3%) before leaving baits. Crab presence depressed fish feeding. Crabs were wasteful feeders that macerated the baits, generating scraps for indirect feeders and attracting more scavengers. Large scavengers consumed most bait.
At 726 the number of recorded multicellular non indigenous species (NIS) in the Mediterranean Sea is far higher than in other European Seas. Of these, 614 have established populations in the sea. 384 are considered Erythraean NIS, the balance are mostly ship and culture-introductions. In order to effectively implement EU Regulation on the prevention and management of the introduction and spread of invasive NIS and the Marine Strategy Framework Directive in the Mediterranean Sea it is crucial that this priority pathway is appropriately managed. Three potential impediments – incomplete and inaccurate data; unknown impacts; policy mismatch – hinder implementation. Current geographical, taxonomical and impact data gaps will be reduced only by instituting harmonized standards and methodologies for monitoring NIS populations in all countries bordering the Mediterranean Sea, prioritizing bridgehead sites and dispersal hubs. The option of implementing European environmental policies concerning marine NIS in member states alone may seem expedient, but piecemeal protection is futile. Since only 9 of the 23 states bordering the Mediterranean are EU member states, the crucial element for an effective strategy for slowing the influx of NIS is policy coordination with the Regional Sea Convention (Barcelona Convention) to ensure consistency in legal rules, standards and institutional structures to address all major vectors/pathways.