Seeing Red : Alien species along the Mediterranean coast of Israel

An overview is presented of the metazoan alien biota recorded from the Mediterranean coast of Israel. Of the 296 alien species, 284 have been introduced from the Red Sea/Indo West-Pacific through the Suez Canal. A brief history of the research on introduced species along the Israeli coast is presented along with the list of species, and their ecological and economic impacts are discussed.


A brief history of the research on marine alien species off the Mediterranean coast of Israel
The first marine alien species from the coast of Israel was found on the beach of Jaffa (Figure 1) and described in 1891 as Cerithium levantinum by E. A. Smith (in Hart, 1891).That species was later identified as C. scabridum Philippi, 1848 (Mienis, 1992b), a species known from the Red Sea and the Indian Ocean, that had already been described from the newly excavated Suez Canal and its Mediterranean terminal at Port Said (Fuchs 1878, Keller, 1883).The first alien species identified as such was the pearl oyster Pinctada radiata (Leach, 1814) (as Meleagrina savignyi Monterosato, 1878), mentioned from Jaffa " .. c'est là une espèce de la mer Rouge, immigrée dans la Méditerranée depuis le percement de l'Isthme de Suez" (Monterosato, 1899: 392).These early findings set a pattern that holds true to this day -127 of the 297 alien Dr. med.et phil.Walter Steinitz from Breslau was among the first to recognized the scientific significance of the movement of biota through the Canal.Dr. Steinitz, published a pamphlet at his own expense, where he pointed out that the Suez Canal "…is the only place on earth where two quite different zoological provinces have come into direct touch with one another", and that the Canal "…connects two oceans having each a very different fauna from the other, which throws up a number of new problems: Does an exchange of fauna take place between the two oceans by means of this canal?Do the immigrants from the other side flourish on this or die?Has such an immigration caused important changes in the fauna of the eastern basin of the Mediterranean?" (W. Steinitz 1919: 8).Steinitz deplored the lack of faunistic research in the Levantine Basin "… at this highly important point of juncture there is no place of observation!", and forsook his flourishing medical practice to study the marine biota of Palestine in 1924 and1925.Noting 15 species of Indo-Pacific origin, he urged the creation of a Marine Station in the Levant dedicated to the study of the transformation of the Levantine biota (W.Steinitz 1929Steinitz , 1936)).In 1933 Dr. Steinitz immigrated to Israel and resumed his research in a space allotted him by the Zevulun Seafaring Society, Tel Aviv, but the need to provide for his family compelled him to join a communal village and breed poultry.However, he passed his scientific interest to his son, Heinz Steinitz, who studied with the pioneer ecologist Bodenheimer and received the first Ph.D. in zoology awarded by the Hebrew University of Jerusalem.
Munro Fox, who would later head the 'The Cambridge Expedition to the Suez Canal', outlined in 1923 "the dates of the various stages in the migration northward through the Canal of the Red Sea crab (Neptunus pelagicus) [= Portunus pelagicus (Linnaeus, 1758)], and … the apparent limits of its present distribution along the Mediterranean coast" including the fish market of Haifa (Fox, 1924).Indeed, Bodenheimer in his seminal "Animal life in Palestine" when discussing the "Indo-Pacific influx through the Suez Canal" mentioned that "Quite a number of [alien] fishes have not only reached our shores, but some of them have even increased in such numbers, that they appear regularly on the fish market" (Bodenheimer 1935: 457).He then presciently added "It is almost certain that the Indo-Pacific influx is still under way and it will be most interesting to study this process.The local increase will take considerable time, even for those organisms which thrive successfully in the new area" (Bodenheimer 1935: 460).The progress of Erythrean biota in the Levant in the early 20th century was noted in the inventories of molluscs (Monterosato 1899, Pallary 1912, 1938, Gruvel and Moazzo 1931, Haas 1937, 1948, Steuer 1939); decapod crustaceans (Gruvel 1928, 1929, 1930a,b, 1931, Monod 1930, 1931, 1932, Steuer 1938) and fish (Gruvel 1929, 1931, Liebman 1934), some of which report findings from the Israeli coast.
The intensive investigations of the biota of the continental shelf of Israel by the Sea Fisheries Research Station (SFRS) in [1946][1947][1948][1949][1950][1951][1952][1953][1954][1955][1956] resulted in a series of publications that highlighted the extent the Erythrean taxa have been established along the coast (Carmin 1946, Haas and H. Steinitz 1947, Haas 1948, 1951, Gottlieb 1953, 1960, Holthuis and Gottlieb 1958, Pérès 1958, Tebble 1959, Oren and H. Steinitz 1959, Lewinsohn and Holthuis, 1964).The earlier community studies of the continental shelf of Israel were mainly fishery research (Wirszubski 1953, Gilat-Gottlieb 1959), and it was only in the 1960s that an extensive program was undertaken by Gilat (1964) to describe the macrobenthic communities off the Israeli coast.The SFRS fisheries biologist, Ben Tuvia, a former student of H. Steinitz, published the first list of fishes from the Mediterranean coast of Israel, focusing on the Erythrean alien species (Ben-Tuvia 1953a).He observed the development of the Erythrean invasion in "a, appearance of new Erythrean species in the eastern part of the Mediterranean; b, the spreading of Erythrean species, already established in the eastern Mediterranean close to the Suez Canal, to new areas (a movement following the coast of Israel, Syria, Turkey and Rhodes); c, the increased abundance of the invading species in areas where they were formerly scarce."(Ben-Tuvia 1953b: 464).Ben Tuvia continued to update the list of Erythrean alien fish off the Israeli coast: 21 species (Ben-Tuvia 1958), 30 species (Ben-Tuvia 1971), 41 species (Ben-Tuvia 1985).The steadily increasing number of alien fish moved him to write that "[v]ery little is known about how the influx of Red Sea species has influenced the ecology of the eastern Mediterranean.Certainly these fish must play an important role in the food chain and the general biological balance of this area."(Ben-Tuvia 1971: 3).Ben Tuvia estimated, based on the catch statistics collated by the Department of Fisheries, that between 1965 and 1969 Erythrean fish made up 8% of the total landing (in weight) (Ben-Tuvia 1973), and the amount doubled to 16% between 1980and 1982(Ben-Tuvia 1985).
In 1967, a joint program by the Smithsonian Institution, the Hebrew University of Jerusalem, and the Sea Fisheries Research Station, Haifa, was established to investigate the spread of the Erythrean biota in the Levant (Israel, Cyprus, Rhodes) and its impact on the native biota.The scope of the program was expanded following the 'Six Day War' to include the Sinai coasts and the Suez Canal itself.H. Steinitz headed that program with W. Aron, Director of the Oceanography and Limnology Program, Smithsonian Institution.On the untimely death of Steinitz, his deputy, Por, assumed the position.At the end of the 3rd year of the program, with some 5300 samples collected and partially sorted and identified, Steinitz published "A critical list of immigrants via the Suez Canal" of 140 Erythrean and Indo-Pacific species known to have crossed the Suez Canal into the Mediterranean (H. Steinitz 1970).By now, it was widely perceived that the littoral and infralittoral biota of the Levantine basin has been undergoing a rapid and profound change (Por 1978).Galil and Lewinsohn (1981) noted that the shallow benthic communities along the Mediterranean coast of Israel had no known parallel outside the Levant because of the great number of Erythrean aliens.

Aliens, vectors, trends
Research papers, conference abstracts, the local Fishermen's Bulletin, unpublished M.Sc.and Ph.D. theses, and the author's own databases resulting from two decades of monitoring the benthic communities off the Israeli coast, were assembled and critically examined in order to construct an authoritative dataset tracing the origin, date and mode of introduction, current distribution, and impact of the 296 metazoan alien species recorded along the Mediterranean coast of Israel.Earlier records were reassessed and some were deleted, such as the seven sponge species and three species of hydroids listed by Por (1978) that, as tactfully suggested by Zibrowius (1992), were in need of "critical reevaluation".Por (1978) also included in his list seven species of ascidiaceans, that are either widely distributed, or of "problematic identification.The list thus provides an inexact impression of lessepsian migration among ascidians" (Zibrowius 1992: 96).
The dataset includes the date of collection (if unavailable, date of publication) of the first recorded specimens, the native range of the alien, its means of introduction, whether through the Suez Canal, vessels, or mariculture, and the current population status.The date of collection of the first specimen(s) is significant for the study of the patterns and processes of invasion, though we accept that the date of collection (or, when missing, the date of publication) may be years behind the actual entry dates, and that identification and publication may lag behind collection: the gastropod Cerithium scabridum (Philippi, 1848) collected on Jaffa beach before 1891, was misidentified as C. levantinum (see above), and only when collected again in Jaffa in 1928-9 it was correctly identified as a "forme de la mer Rouge" (Gruvel and Moazzo 1931).The pyramidellid gastropods Chrysallida maiae (Hornung and Mermod 1924) and Syrnola fasciata (Jickeli 1882) were collected off the Israeli coast in 1935and 1949and identified only in 1992(van der Linden and Eikenboom 1992), and 1995(Mienis 1995) respectively; the tube worm Hydroides brachyacantha Rijoa, 1941, was collected in Jaffa, Israel, in 1933, but identified only nearly 60 years later (Ben-Eliahu 1991).
The 296 metazoan species identified in the present work as alien off the Israeli coast are listed in the Annex.This particular list is limited to multicellular organisms because the identity of many unicellular organisms is still in doubt, as well as their native range and distribution.A taxonomic classification of the alien species (Figure 2) shows that the alien phyla most frequently recorded are Mollusca (43%), Chordata (22%), Arthropoda (16%), and Annelida (7%).Phyla not represented in the list include the little studied Porifera, Nemertea, Priapula, Nematoda, Entoprocta, Pogonophora, Sipuncula, Echiura, Brachiopoda and Phoronida.The data are presumably most accurate for large and conspicuous species, which are easily distinguished from the native biota.
A geographic classification (Figure 3) shows that the native range of the alien taxa recorded in Israel is most commonly the Indo-Pacific Ocean (48%), the Indian Ocean (24%), the Red Sea (17%), and pantropical (6%).Caution should be exercised when using these data: the true origin of the Israeli populations of a species widely distributed in the Indo-Pacific Ocean may be either its populations in the Red Sea or further in the Indian Ocean, or secondarily from other established Levantine populations.The source populations or means of introduction of alien species in Israel have not yet been successfully ascertained by molecular means (Terranova et al. 2006).But even taking into account these caveats, it is quite clear that most of the alien species off the Israeli coast are thermophilic, originating in tropical seas.
A classification according to the means of introduction shows that the great majority of aliens off the Israeli coast entered through the Suez Canal, whereas vessels and mariculture contributed only a small number of aliens.Here too, caution should be exercised when using these data: only rarely are the means and route of introduction known from direct evidence.Mostly they are deduced from the biology and ecology (if known) of the species, the habitats and locales it occupies in both the native and introduced range, and its pattern of dispersal (if known), i.e., for a fouling species frequently recorded from ports, shipping is assumed to be the most probable vector.It is has been assumed that Erythrean aliens progress through the Suez Canal and along the coasts of the Levant as a result of "natural" dispersal, by autochthonous active or passive larval or adult movements, unaided further either directly or indirectly by human activity.Indeed, a temporal succession of directional ("stepping stones") records from the Red Sea, the Suez Canal, and along the coasts of the Levant confirms a species status as a naturally dispersing Erythrean alien.However, vessel-transported dispersal is feasible as well: "It is, of course, well known that ships have in more than one instance dispersed marine organisms from one part of the world to another.This must apply equally to transport through the Suez Canal.….Possibly tugs and barges permanently employed in the Canal may take a larger share than other vessels in this transport from one end of the Canal to the other.There are coal barges, for instance, which remain for some months at one end of the Canal and then are towed through to stay for some months more at the other end.The time spent at either end would permit on the one hand of the settling of larvae on the bottom of the barges, and on the other hand of the liberation of eggs or larvae from mature individuals" (Fox 1926:20).Even where records are consistent with long-shore dispersal, there might be a degree of uncertainty where fouling organisms (such as serpulid polychaetes or mussels) are concerned, as they are more susceptible to shipping-mediated transfer.In some cases we suspect simultaneous mechanisms of transport.
Though the date of collection (or publication, see above) may lag years behind the date of introduction, the numbers of alien species recorded off the Israeli coast each decade over the past century are given in Figure 4.With the exception of few scattered early records (see above), the records begin in the 1920s with the works of W. Steinitz and the results of 'The Cambridge Expedition to the Suez Canal', whereas the 1930s saw the publication of several regional lists (see above).The smaller number of records in the 1940s probably reflects the devastation of the Second World War and the struggle for the independence of Israel.A surge in the records in the 1950s through the 1970s probably represents both an increase in introductions and an interest in their study, culminating in the publications resulting from the joint program by the Smithsonian Institution, the Hebrew University of Jerusalem, and the Sea Fisheries Research Station, Haifa.Though no concerted effort was undertaken since, the number of records in the 1980s and 1990s were 35 and 36 respectively.More introductions were recorded in the first years of the 21th century than in the 1980s and 1990s.
Since the 1950s major political, economical and societal changes have occurred in the Levant.Their impact on the rate and means of introduction is apparent (Figure 5): though the Suez Canal remained the main access route for alien species, the rate of introductions by vessels has been higher.Of the 56 alien species known in 1950, 93% entered the Mediterranean through the Suez Canal, 7% were possibly canal/vesseltransported; of the 240 alien species recorded since 1950, 80% were Erythrean aliens, 9% were canal/vessel-transported, 10% and 1 % respectively were vessel-transported and mariculture introductions.The increase in vessel-transported aliens may be attributed to the increase in shipping volume throughout the region.Since the probability of collecting a vagrant incursion in the sea is diminishingly small, most recorded alien species are considered as 'established' species that have self-maintaining  1900-1910-1920-1930-1940-1950-1960-1970-1980-1990-≥2000  populations of some duration.It is recognized that some alien species may fail to maintain populations over time and thus a single record dating back several decades may be considered an ephemeral entry.We list 36 species known from single records, most of them recorded in the last decade.The distinction between the 'established' and 'ephemeral' aliens is sometimes difficult to discern and circumscribed in large part by our ignorance of the marine environment.Even once established in the Mediterranean, the alien species differ markedly in their histories.

The parasitofauna of the alien species off the Mediterranean coast of Israel
Absence of natural enemies, be it competitors, predators, pathogens, or parasites, is one of the explanations given for the success of alien biota (Wolfe 2002, Torchin et al. 2003).Diminished parasitization of alien species may be attributed to reduced probability of infestation due to the small numbers of the founding population, its being composed of uninfected larval stages, or, in the case of heteroxenous parasites, the absence of intermediate hosts in the new locale, and on the other hand, the host-specificity of some native parasites forestalling infection of alien hosts.
The parasitofauna of the two Erythrean alien siganids were examined in the 1970s and 1980s and 11 parasite species were identified -all monoxenous parasites with direct life cycles requiring no intermediate host, including the monogenoids Glyphidohaptor plectocirra (Paperna, 1972), Tetrancistrum polymorphus (Paperna, 1972), T. suezicus (Paperna, 1972), T. strophosolenum Kritsky, Galli and Yang, 2007 (Paperna 1972, Diamant 1989, Galli et al., 2007).A study of S. rivulatus collected at the port of Ashdod, next to fish farming facilities, in the mid 1990s, revealed 7 Erythrean species of monoxenous parasites (Diamant et al. 1999). However, Fischthal (1980) identified in Siganus rivulatus (Forsskål, 1775) specimens from the Mediterranean two species of heteroxenous digenetic trematodes with complex life cycles requiring more than one host.Paperna (1972:3) suggested that endoparasitic helminthes spread into a new area only if they are not highly hostspecific or if the suitable intermediate host has arrived as well, though "in most cases the migration of the fish host does not coincide with similar migration by the intermediate invertebrate hosts".It is of interest that a recent study of S. rivulatus has shown that the prevalence of its Erythrean monogenean ectoparasite Polylabris cf.mamaevi off the Mediterranean coast is three times as high as that found in the Red Sea populations (Pasternak et al. 2007).These authors ascribe the heavier infection to "Changes in the natural environment and impact of anthropogenic factors encountered by the rabbitfish in their new Mediterranean habitats" (Pasternak et al. 724).However, the siganids are immensely successful colonizers, and it may be that the parasite high infestation levels stem from their access to much denser host populations.
Fischthal (1980) examined parasite loads of 500 fish of 59 species collected by gill-netting in 1977 off the Mediterranean coast of Israel.He found that 29 of the 43 (67%) native Mediterranean species were infected with digenetic trematodes, but only 5 of the 12 (42%) Erythrean alien species.Interestingly, many of the trematodes infecting the Erythrean hosts were of Atlanto-Mediterranean origin and were probably acquired in the Mediterranean from native hosts.These results support the 'enemy release hypothesis' -alien species generally import only a subset of their parasitofauna, thus releasing themselves from the parasites of their native habitat during introduction, and though subsequently accumulating parasites native to their new environment, they harbor fewer parasites in their new locale than in their native range (Torchin et al. 2001).
The Levantine populations of the Erythrean swimming crab Charybdis longicollis Leene, 1938 have been parasitized recently by the sacculinid rhizocephalan, Heterosaccus dollfusi Boschma, 1960 (Galil andLützen 1995).The swimming crab, can form as much as 70% of the benthic biomass on sandy-silt bottoms off the Israeli coast (Galil 1986).Release from parasites may have contributed to its success -of the thousands of C. longicollis collected off the Israeli coast in over three decades, none was parasitized until 1992, when a few specimens were discovered carrying the externae (reproductive part of the parasite) of the castrating sacculinid, itself an Erythrean alien.Along the Israeli coast infection rates of up to 77% were recorded, with up to 57.6% of the infected hosts bearing more than one externa (Galil and Innocenti 1999).The rapid spread and the high prevalence of H. dollfusi infestation may be related to the dense population of the host and the year-round reproduction of the parasite, causing recurrent infection.In its second decade in the Mediterranean, the population of H. dollfusi seems stable: despite the high prevalence of the parasite and its injurious impact on the host reproduction, there is no noticeable reduction in the host population.It is suggested that the high fecundity of the host females, the "size refuge" formed by parasite-free larger males, and the "open" recruitment dynamics of C. longicollis, keep its population density high enough for H. dollfusi, with its "closed" recruitment dynamics, to maintain its pandemic infection rates (Innocenti and Galil 2007).The Erythrean sacculinid had not been detected in any of the other portunid crabs, alien or native, inhabiting the Levantine sublittoral, including the congeneric C. helleri.

The ecological impact of alien species off the Mediterranean coast of Israel
A single local extirpation of a native species is known and several cases of sudden decline in abundance concurrent with proliferation of aliens had been recorded off the Israeli coast.But even when populations of native Mediterranean species appear to have been wholly outcompeted or partially displaced from their habitat space by an alien, the causes cannot be disentangled from potential confounding factors such as the profound anthropogenic alteration of the marine ecosystem through habitat destruction, pollution, and rising Mediterranean seawater temperature.
The Erythrean alien killifish, Aphanius dispar (Rüppell, 1829), is markedly euryhaline, occurring in freshwater, and in salinities up to 4 times as high as seawater, whereas its peri-Mediterranean endemic congener, A. fasciatus (Nardo, 1827), occurs mostly in brackish lagoons.The first Erythrean killifish was collected off Tel Aviv, Israel, in the winter of 1943/44 (Mendelssohn 1947).The last specimens of the native killifish, A. fasciatus, along the Israeli Mediterranean coast were collected on August 13, 1976 (M.Goren, pers. comm.; preserved in the National Collections, Tel Aviv University, access number 6319).Naturally occurring hybrids of the two killifish species were described as " ... common, and in some localities (Ashdod Harbour [southern coast of Israel], parts of Bardawill Lagune etc.), these populations comprise mostly hybrids" (Goren and Rychwalski, 1978: 261).Within a generation an endemic genotype appears to be locally lost through hybridization, and A. dispar and its hybrids replaced A. fasciatus along the Mediterranean coast of Israel (Goren and Galil 2005).
The two species of siganid fish, Siganus rivulatus and S. luridus (Rüppell, 1828), that entered the Mediterranean from the Red Sea through the Suez Canal, were first recorded off the coast of Israel in 1924 (Steinitz 1927) and 1955(Ben Tuvia 1964), respectively.The schooling, herbivorous fishes, able to settle in a range of habitats, comprise one third of the fish biomass in rocky habitats along the Israeli coast (Goren and Galil 2001).The multitudinous siganids have altered the community structure and the native food web along the Levantine rocky infralittoral.They replaced native herbivorous fish, such as Sarpa salpa (Linnaeus, 1758), that had been abundant in trawl catches early in the 20th century (Gruvel 1931, George and Athanassiou 1967, Bariche et al. 2004).Prior to the invasion of the siganids, there were few native herbivorous fish and invertebrates and their role in the food web off the Levantine rocky habitats had been negligible.The siganids increased the rate by which large amounts of algal material were recycled, these fish apparently accelerated the transfer of energy from the producer to the consumer levels (in hours through the fish gastrointestinal system rather than weeks or months of decomposition), and by serving as major item of prey (up to 70 %) for larger infralittoral predators such as groupers (Aronov 2002, Goren andGalil 2005).Their grazing pressure on the intertidal rocky algae may have benefited the proliferation of an alien Erytrean mussel by providing suitable substrate for its settlement (see below).A comprehensive study of the algal vegetation and the ecology of the fish community off a vermetid reef, south of Haifa Bay, Israel, provided an opportunity to compare the diets of S. rivulatus and S. luridus collected at the site with the composition of the local algal community, and examine the importance of algal spatial variability and seasonality in the dietary choices of both siganid fishes.An analysis of the siganids' gut contents, in conjunction with the spatial and seasonal composition of the local algal community, showed that their diet has a significant impact on the structure of the local algal community: it seems that by feeding selectively they have nearly eradicated some of their preferred algae locally (Lundberg et al. 2004).
A small Erythrean mytilid mussel, Brachidontes pharaonis (Fischer P., 1870), was considered in the early 1970s "c.250 times rarer" than the native mytilid Mytilaster minimus (Poli, 1795), that formed dense 'Mytilaster beds' on intertidal rocky ledges along the Israeli coastline, with up to 26 specimens per cm² (at Palmahim, Safriel et al. 1980, tab. 4).Studies conducted in the late 1970s along the Israeli coastline, while B. pharaonis was still relatively rare, predicted it would neither establish dense populations nor outcompete the native Mytilaster minimus: "B.variabilis [pharaonis] never forms 'beds' in the eastern Mediterranean, and is singly or in small groups dispersed within M. minimus", and "… it did not displace M. minimus" (Safriel et al. 1980: 39, 59).The relative rarity of B. pharaonis was attributed to the invader's low intrinsic rate of increase in comparison to that of the native species, and to strong density-independent mortality generated by exposure to either high wave action or sedimentation.By the end of the 1980s, following a series of experiments, it was determined that Brachidontes interferes with recruitment of Mytilaster, and detrimentally affects its survival and growth, yet the researchers maintained that the Erythrean mytilid was not likely to outcompete the native species: "The two species can coexist, both locally and regionally" (Safriel and Sasson-Frostig 1988: 225).In the late 1990s a survey conducted in some of the same sites have shown a rapid shift in dominance, with some dense populations of up to 300 specimens per 100 cm² on rocky platforms "where mussel beds were absent in the past" (Rilov et al. 2004: 347).More recently "the same rocks are ….completely covered with the Erythrean B. pharaonis, while M. minimus is only rarely encountered."(Mienis 2003d: 15).The establishment of massive beds of Brachidontes has had significant effects on the biota of the rocky intertidal.As the presence of algae is negatively correlated with the presence of the Erythrean mytilid, and is considered to impede the settlement of its postlarvae (Safriel and Sasson-Frostig 1988), a shift in habitat conditions that reduces algal cover might have benefited Brachidontes.As it happens, few herbivores occurred in the rocky shores of the southeastern Levant prior to the arrival of the Erythrean siganid fish (see above).During high tide schools of (mostly young) siganids feed on the intertidal platforms (Lundberg et al. 2004).It is suggested that the multitudinous siganids may have triggered the population increase by clearing the intertidal platform of algae.The displacement of the native mussel by the larger, thicker-shelled Erythrean mytilid may have changed predation patterns so that the population of the native whelk, Stramonita haemastoma (Linnaeus, 1758), that were found to preferentially prey on Brachidontes, increased greatly (Rilov et al. 2002).
An Erythrean limpet, Cellana rota (Gmelin, 1791), first collected in the Mediterranean in 1961 (Christiaens 1967), spread by 2000 along the Israeli coast, occupying the less waveexposed intertidal sites, whereas the native Mediterranean limpet, Patella caerulea Linnaeus, 1758, inhabited rocks exposed to the surf.A recent survey along the Mediterranean coast of Israel found that the alien limpet dominates the upper rocky littoral and has been replacing the native limpet when "a few years ago Patella caerulea was the only limpet inhabiting the same rocks at that locality [Ashdod]" (Mienis 2002b: 275).Along the southern coast of Israel it has already completely replaced the native limpet, along the central coast it "has taken possession of 40-50% of the available space." (Mienis 2003d: 15).Similarly, the Erythrean jewel box oyster Chama pacifica Broderip, 1834, outnumbered its native congener, C. gryphoides Linnaeus, 1758: "The local S. gaederopus and C. gryphoides are hardly even encountered as epibionts on the new immigrant species."(Mienis 2003d: 15).The native Mediterranean cerithiid gastropods, Cerithium vulgatum Bruguière, 1792 and C. lividulum Risso, 1826, respectively common and abundant in shallow water along the coast of Israel until the 1970s, were supplanted by the Erythrean cerithiids Cerithium scabridum Philippi, 1848 and Rhinoclavis kochi (Philippi, 1848) (Mienis 2003d: 15).The population of the Erythrean narrow-barred mackerel, Scomberomorus comerson Lacepède, 1800, has greatly increased in the 1980s, coincidently with the decline of the onetime common native meager, Argyrosomus regius (Asso, 1801), to the point where the latter is rarely encountered along the Israeli coast; the Erythrean dragonet, Callionymus filamentosus Valenciennes, 1837, replaced the native callionymids C. pusillus Delaroche, 1809, and C. risso LeSueur, 1814, along the Levantine upper shelf (Golani 1998).The Erythrean snapping shrimps Alpheus inopinatus Holthuis &Gottlieb, 1958, andA. audouini Coutière, 1905, are more common in the south-eastern Levantine rocky littoral than the native A. dentipes Guérin-Méneville, 1832, and on the muddy bottoms A. rapacida de Man, 1908, is much more common than the native A. glaber (Olivi, 1792) (Lewinsohn andGalil 1982, Galil 1986).The native penaeid prawn, Melicertus kerathurus (Forskål, 1775) was commonly caught by trawlers along the Israeli coastal shelf on sandy or sandy mud bottoms, and supported a commercial fishery throughout the 1950s (Holthuis and Gottlieb 1958).It has since nearly disappeared, and its habitat overrun by the Erythrean penaeid prawns.
Competitive displacement may also modify bathymetric ranges in populations of Erythrean and native species: the native red mullet, Mullus barbatus (Linnaeus, 1758) and the native hake, Merluccius merluccius (Linnaeus, 1758) were both displaced into deeper, cooler waters by their respective Erythrean competitors, Upeneus moluccensis (Bleeker, 1855) and Saurida undosquamis (Richardson, 1848).The goldband goatfish, U. moluccensis, made up 10-15% of the total mullid catches off the Israeli coast by the late 1940s (Wirszubski 1953).Following the exceptionally warm winter of 1954-55, its percentages increased to 83% of the catch, replacing the native red mullet in the commercial fisheries (Perlmutter, 1956).Both mullid species have a similar diet, and occupy muddy bottoms shallower than 75 m, but whereas the red mullet spawns from April to June with a peak in May, the goldband goatfish spawns from June to September (Wirszubski 1953).The considerably higher water temperatures may have resulted in poor survival of the red mullet spawn whereas an unusually large year class of the goldband goatfish survived.In previous years, the young red mullets would settle to the bottom during July through September, where they have had a distinct size advantage over the later-spawned goldband goatfish.The failure of the 1955 red mullet year class may have left their niche only partly occupied, to the advantage of the Erythrean species, and the unusually warm waters enhanced the latter species' survival rate (Oren 1957a, b).The native mullet has ever since been displaced into deeper, cooler waters: 87% of the mullid catch off the Israeli coast consisted of alien mullids at depth of 20 m, 50% at 55 m, but only 20% in waters deeper than 70 m (Golani and Ben Tuvia 1995).The Erythrean lizardfish, S. undosquamis, was first recorded from the Mediterranean coast of Israel in 1952 (Ben Tuvia 1953a).The "abrupt rise in catch of the lizard fish Saurida undosquamis, taken by otter trawlers with the usual gear on the regular fishing grounds" (Oren 1957b: 1) was attributed to the warm winter of 1954-55 (Ben Yami 1955, Chervinsky 1959).In 1955-56 the lizardfish became commercially important, constituting up to one fifth of the total annual trawl catch along the Mediterranean coast of Israel.This sudden increase came at the expense of the native hake, it too was displaced into deeper waters (Ben Yami and Glaser, 1974).Since the mid 1980s the lizardfish's share in catches has declined, and that of the hake augmented.Similarly, The Erythrean mantis shrimp, Erugosquilla massavensis, (Kossmann, 1880) is abundant off the Israeli coast at depths of 20-60 m.Though on occasion it is taken together with the native Spottail mantis shrimp, Squilla mantis (Linnaeus, 1758), generally the latter occurs in deeper waters than Erythrean alien.The Spottail mantis shrimp is fished commercially in shallow waters elsewhere in the Mediterranean (Lewinsohn and Manning 1980), but off the Israeli coast it is found mostly between 70 and 90 m.Lewinsohn and Manning (1980) questioned "whether temperature, bottom type, or pressure from O. massavensis, or a combination of these is responsible for its depth distribution".

The economic impact of marine alien species off the Mediterranean coast of Israel
Some Erythrean aliens have been exploited commercially almost as soon as they entered the Levant and their economic importance had been acknowledged early : "... les passages définitifs de ces espèces à travers la totalité du Canal présentent un résultat économique [sic] également très important..... pour les marchés palestiniens et syriens, un appoint non négligeable et particulièrement intéressant, par consequent, pour l'ensemble des populations de ces deux Pays" (Gruvel 1936: 228, 229).
An early Erythrean invader, the swimming crab Portunus pelagicus was on sale already by the early 1900s in the fish market of Haifa (Fox 1924, Calman 1927), and during the British Mandate the fishermen of Haifa and Acre sold 20 tons of the crab annually (Perlmutter 1956).By mid-century the Erythrean fishes were an important part of the Levantine fisheries.Insofar as the Israeli fishing grounds were concerned, the bulk of the trawler catch from 1950 to 1955, was comprised of three species -the native red bream, Pagellus erythrinus (Linnaeus, 1758), and hake, Merluccius merluccius, and the Erythrean yellow striped mullet, Upeneus moluccensis.The latter were fished commercially in the early 1940s only along the southern coast of Israel, but by 1946-1947 were found all along the coast (Gottlieb 1957), and by the late 1940s constituted an estimated 10-15% of the total mullid catch (Wirszubski 1953).In 1955 Israeli fishermen noticed greater numbers of the yellow striped mullet, and data assembled by the Sea Fisheries Research Station, Haifa, indicated that their percentage in the mullid catch rose to 20%, and to over 83% in early 1956 (Oren 1957a,b), and was considered "the most important commercial fish in the Israel trawl catches" (Gottlieb 1957:20).Since the total mullid catch had remained constant, the yellow striped mullet had in the early 1950s "almost completely replaced the Mediterranean species, the red mullet, Mullus barbatus in the trawl catch" (Perlmutter 1956:4).In 1955, another Erythrean alien, the lizardfish, Saurida undosquamis became an important part of the trawl catch (Oren 1957b).In 1953 it was first recorded from the Mediterranean coast of Israel (Ben Tuvia 1953a,b) as much rarer than the native Mediterranean lizardfish, Synodus saurus (Linnaeus, 1758).Within two years commercial catches increased steadily, in November and December 1955, 22 and 27.5 tons respectively were taken, swelling to 40 and 46.8 tons in January and February 1956 respectively, to a total of 266.5 tons for 1956 -20% of the total annual trawl catch (Oren 1957a, b).The sudden increase in the populations of the lizardfish, the yellow striped mullet, the red soldierfish, and Erythrean penaeids was attributed to a rise of 1-1.5ºC in sea temperature during the winter months of 1955 (Ben Yami 1955, Chervinsky 1959).
Examination of the Israeli fisheries statistics since the mid 1980s underscores the growing prominence of the Erythrean aliens.The Erythrean conch, Conomurex persicus Swainson, 1821, and on occasion the Erythrean spiny oyster, are served in seafood restaurants in Israel.Erythrean penaeid prawns make up most of the shrimp catches along the SE Levantine coasts.The Erythrean prawns, in particular Marsupenaeus japonicus (Bate, 1888), Metapenaeus monoceros (Fabricius, 1798) and Penaeus semisulcatus de Haan, 1844, are highly prized and beginning in the 1970s a shrimp fishery developed off the Sinai coast, and since the mid 1980s off the Israeli coast where a small fleet of coastal "mini" trawlers has specialized in shrimping, bringing in a quarter of the total trawl catch volume and a third of the trawl gross income (Pisanty and Grofit 1991, Snovsky andShapiro 1999).Nearly half of the trawl catches along the Israeli coast consist of Erythrean fish (Golani and Ben Tuvia 1995).The dominant fishes in the inshore fisheries (trammel-netting and hook-and-lining) are the siganids S. rivulatus and S. luridus, the obtuse barracuda Sphyraena chrysotaenia Klunzinger, 1884, and the Erythrean jack, Alepes djedaba (Forsskål, 1775).The above species, together with Sillago sihama (Forsskål, 1775) and S. commerson, two species that underwent population explosion in the early 1980s, are common in purse-seine landings.The annual catch of the Erythrean lizardfish which reached 400 tons in 1960 soon after its arrival (see above), declined to 100 tons in the mid 1960s, but has since increased, and catch fluctuations are correlated with CPUE.Catch statistics for mullids do not distinguish between the natives, M. barbatus and M. surmuletus Linnaeus, 1758, and the Erythrean aliens Upeneus moluccensis and U. pori, but a study of the frequency of the latter in trawl catches conducted in the mid 1980s showed they formed 87% of the mullid catch off the coast of Israel at depths of 20 m, and 50% at 55 m, whereas the native mullids are more abundant in deeper waters (Golani and Ben Tuvia 1995).The percentage of the Erythrean mullids in the total mullid catch has been increasing steadily, from 30% in 1980, 42% in 1984, to 47% in 1989(Golani and Ben Tuvia 1995).Similarly, catch statistics of sphyraenids do not separate the Red Sea obtuse barracuda from the native Mediterranean species S. sphyraena (Linnaeus, 1758) and S. viridensis Cuvier, 1829.However, examination of the landed catch showed that the Erythrean barracuda had outnumbered the native sphyraenids in inshore trawl and purse-seine catches (Grofit 1987).In addition, two of the four species of Erythrean clupeids that established populations in the Levant -Dussumieria elopsoides Bleeker, 1849, and Herklotsichthys punctatus (Rüppell, 1837) -are of importance in the inshore-pelagic fishery.The increasing exploitation of Erythrean aliens meant the shifting of the trawling grounds nearshore since their densest populations occur at depths up to 50 m.Between 1980 and1986 the Israeli trawlers doubled their activity (measured as fishing hours) in shallow waters (Pisanty and Grofit 1991).The shoreward displacement of the fishing grounds coupled with the inexorable gain of Erythrean aliens raise the ratio of alien to native taxa in the Levantine trawl landings.
But together with the commercially exploitable species, the Erythrean invasion swept ashore the scyphozoan jellyfish, Rhopilema nomadica Galil, 1990.Each summer since the mid 1980s huge swarms of the Erythrean jellyfish have appeared along the Levantine coast.These planktotrophic swarms, some stretching 100 km long, must play havoc with the limited resources of this oligotrophic sea, and when the shoals draw nearer shore, they adversely affect tourism, fisheries and coastal installations.Local municipalities report a decrease in holiday makers frequenting the beaches because of the public's concern over the painful stings inflicted by the jellyfish.The local newspapers and TV news report during the summer months the presence of jellyfish along the beaches.Coastal trawling and purse-seine fishing are disrupted for the duration of the swarming due to net clogging and inability to sort yield "It is not uncommon that fishermen, especially purse seines, discard entire hauls due to the overwhelming presence of poisonous medusae in their nets" (Golani and Ben Tuvia 1995: 287).Jellyfish-blocked water intake pipes pose a threat to cooling systems of port-bound vessels and coastal power plants: in the summer of 2001 Israel Electric removed tons of jellyfish from its seawater intake pipes at its two largest power plants, at estimated costs of 50,000 US$ (M.Cohen, pers.comm.).Yet, the jellyfish shelters among its nematocyst-laden tentacles the juveniles of the Red Sea carangid fish, Alepes djedaba (Galil et al. 1990), and may have precipitated the sudden population increase of this commercially important species (Grofit 1987).
The recent spread of the silver stripe blaasop, Lagocephalus sceleratus (Gmelin, 1789), and the striped catfish, Plotosus lineatus (Thunberg, 1787), pose severe health hazards.The blaasop's internal organs, and in particular the gonads during the spawning season, contain a strong paralytic neurotoxin.In the Suez City, on the Red Sea, eight fatalities from tetrodoxin poisoning associated with eating the fish have been described recently (Zaki 2004).Several cases of poisoning were reported from Israel, but none proved fatal.Injuries caused by the barbed and venomous first dorsal spine and pectoral spines of the striped catfish may produce pain levels requiring hospitalization -injuries have been reported by local professional and amateur fishermen.

The miners' canary
Evidence is accumulating that changes in biodiversity patterns in the Mediterranean are linked to direct drivers such as climate change and invasive species, in addition to the wellestablished drivers of habitat change, overexploitation and pollution.By the middle of the century, climate change and invasive species may be the dominant direct drivers of biodiversity loss and increased risk of extinction for many species, especially those already at risk due to low population numbers, restricted or patchy habitats, and limited climatic ranges.
The Erythrean aliens are thermophilic, originating in tropical waters.It stands to reason that rising seawater temperature enhances the reproduction, growth, and survival of the Erythrean aliens, and provides them with a distinct advantage over the native Mediterranean biota (Galil 2007).The location of the Israeli coast "downstream" of the prevailing current from the opening of the Suez Canal means that it is the first haven for the Erythrean propagules.Most of the Erythrean aliens known from the Mediterranean Sea have been first recorded from Israeli coast.
As both processes -sea surface temperature rise and influx of aliens -continue unabated, it is imperative to expand research into those issues.The likely biotic change may impact the already teetering fisheries, mariculture, and tourism through proliferation of alien parasitic, noxious and poisonous species, displacement of commercially-important native species, or through alteration of the food web and by causing phase shift in coastal ecosystems and changing seascape patterns.
The profound changes in the biota off the Israeli Mediterranean coast caused by the intrusion of Erythrean aliens should serve as a miners' canary -if unheeded and unchecked they are likely to spread beyond the easternmost Mediterranean Sea.

Figure 1 .
Figure 1.Map of the Levantine basin of the Mediterranean and the Israeli coast

Figure 3 .
Figure 2. Taxonomic classification of marine alien species along the Mediterranean coast of Israel

Figure 4 .
Figure 4. Number of marine alien species recorded per decade along the Mediterranean coast of Israel <1900-2007.