Parent document
Marine Biology I

Colloquial Meeting of Marine Biology I

 

Essay about the phenomenon of
Lessepsian Migration

Headed by: dr. A. Goldschmid

Author: Pierre Madl

Salzburg, April 1999 (revised in Nov. 2001)

Lessepsian Migration (LM) Definition: Migration across the Suez Canal (planned by Ferdinand de Lesseps); generally from the Red Sea to the Mediterranean, rarely the other way. Favored by two distinct man made events:
  • To a stronger extent by the opening of the Suez Canal,
  • and to a lower extent by the building of the Aswan dam.

For 100 years, the colonization of the Suez Canal and the movement through this passage has been going on, but surprisingly little is known of its results. The following report, compiled from numerous sources, is an attempt to show in a preliminary way, what is known today of the outcome of the 2-way migration via the Suez Canal. Verification of records has not been made at this stage, rather records have been adopted for the present purpose.
The occurrence of Atlantic or Indo-Pacific species not previously recorded in the Mediterranean Sea is not necessarily evidence of recent immigration. Such new records are usually based on only one or few specimens, indicating their rarity in the Mediterranean Sea. These are more likely to be old inhabitants of the Mediterranean that have not come to the attention of taxonomist until now.

When the Suez Canal was opened in 1869 the waters of the Mediterranean and the Red Sea, which had been separated by the Isthmus of Suez, came into direct contact. For plants and animals, elements of the Atlanto-Mediterranean and the Indo-Pacific-Erythrean flora and fauna, an opportunity was thus created to penetrate into new regions. Like many other man-made environmental changes, Lessepsian Migration is imprinted on a general pattern of historical processes.
Although, contact with the Indian Ocean has not been established until recently, fossil specimens of marine fishes found in Italian Messinian deposits reveal that episodic contacts with the Indian Ocean must have taken place previously (some 12mio years ago).
The Suez Canal - Historical Framework

Construction of the canal initiated on April 25th 1859; officially opened on April 25th 1869. Although an international agreement ratified in 1888 granted free and unhindered passage of commercial and military vessels of all countries, Egypt denied any usage of the canal for ships under Israeli banner which culminated in a 6-day war between those two states.

Fig.1 The Canal from Port Said to Suez
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Fig.2 Suez Canal
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During the occupation of the Sinai peninsula by Israel's armed forces, traffic through the canal came to a halt and did not resume for eight years. Only after the completion of the 1979 peace treaty between those two states free traffic was once again established. Today, the canal provides a rapid shortcut to/from the Indo-Pacific for container vessels up to 150E3 metric tons which can easily maneuver through the canal within 15 hours. The Isthmus of Suez bridges the Asian with the African continent and separates the Mediterranean from the Red Sea. This strait geologically represents a low-laying sand and stony desert, in which swampy terrain surrounds lake Bitter settled at its lowest depression.

There is almost no fresh water present which would otherwise alter the overall salinity of the Suez Canal. The canal is an open gate with slightly unbalanced water levels at either ends - low enough to operate the canal without appropriate gates and channels. It covers a total length of 165km, its mean depth is 14.5m and 325m in width - minimal surface width of 160m.

Effects aiding in LM:

Let us now turn to a Mediterranean crisis from the 20thcentury, which indicates what a small rise in sea level can mean. 

Aswan Dam: During the months of September to November, before the completion of the Aswan dam in 1964, Nile floodwater along with the prevailing eastwards current, spread as a surface layer off the Port Said entrance to the Canal, and acted as a barrier, thus probably forced many animals down so far below the water surface that their chances of entering the Canal, by then only 8m deep (later up to 12m), were much reduced.
Cessation of Nile floods after the completion of the Aswan Dam cut the river's freshwater flow to less than 10% of the previous level; with the concomitant effects of: 
  • Phytoplankton bloom associated with the regular Nile floods ceased, which resulted in a sharp drop of Sardine catches of Egypt from 10-20E3 tons per year to a meager 600tons of slim and lean Sardines in 1966; 
  • 100E6m3 of silty sediments per year are withheld by the dam itself, which has a degrading effect of the Nile's downstream bed as well as disrupting the dynamic equilibrium between marine coastal erosion and fluvial delta sedimentation; 
  • Increasing the mean salinity along the coast of Israel from roughly 38.8 to >39.1 (during the Nile floods from Sept.- to Nov. used to be as low as 34%0); this increase could raise productivity again of the eastern Mediterranean beyond previous levels, since heavier salty water would sink beyond the 150m mark during cold winters resulting in a thoroughly mixing of cold nutrient rich bottom waters with the upper photosynthetic layers.
Salinity: On its way through Lake Timsah (at Al Ismailia), the Canal cuts into the Great and the Small Bitter Lakes. These lakes were dry salt valleys, 13km long and 5km wide, until they became part of the Suez Canal. De Lesseps estimated the thickness of the salt bed to be 13.2m (roughly 970E6 tons of salt).
Shortly after the opening of the canal, the salty bottom of the lakes gradually dissolved over a period of 60 years. This enormous surge in salinity along the various parts of the canal (hypersaline Lake Bitter, 68%0 ) with the extra high temperature of the Canal water during the summer half-year (about 10°C warmer at the northern than at the southern end), made the passage problematic for adult animals, and probably impossible for larvae. By now, the salty bottom has probably already completely disappeared (from 52%0 in 1924 to a current average 49% 0 in the summer and 44%0 in winter - although evaporation rate should be sufficient to maintain these levels). With the deepening of the lakes and reduced salt concentrations - equalizing density differences, an exchange of water along with migrant species is further facilitated.

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Fig.3 Schematic representation of decreasing salinity and dredging events in the Suez Canal, versus gradual increase in species diversity.

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Fig.4 The Suez Canal is not in stable equilibrium with the surrounding seas and the pattern of temperature and salinity such as these are constantly changing with the seasons.
Left margin: southern end of canal
Right margin: northern end of canal
Temperature: The Mediterranean is a warm sea populated by cold species, whereas the Red Sea is a tropical water body in which temperatures do not fall below 18°C in winter. To enable Red Sea species to establish themselves north of their usual habitat, tropical species require summer temperatures high enough for the reproductive process and development of eggs, and minimum winter temperatures above their lethal limits. The change of global climate and temperature pattern could yet provide another boost to the ongoing process of northward migration by tropical species. 
Currently, lower winter temperatures are apparently the main factor preventing the spreading of the bulk of the Red Sea fishes into the Mediterranean Sea, much in the same way as they prevent the penetration of a multitude of other tropical organisms, for example the reef-building corals.
Hydrostatic Pressure: The present level of the Red Sea is about 1.2m higher than the Mediterranean; since the canal is not equipped with channel gates , the gravitational gradient pushes water unhindered northward (and even more so during prevailing winds from the south-east).
The actual dynamics of the passage of animals are boosted also by tidal currents which usually move rapidly from the Red Sea into the Bitter Lakes to spread in the large basin where animals flushed along must spend a comparatively great part of their total passage time through the Canal in hypersaline conditions.
Atmospheric Effects: Since there are many days during the year were there are no currents prevailing a north or southbound migration of species, only atmospheric influences can aid in the migrating process. In fact southern winds which facilitates a northbound migration (shorter) over the southbound migration (which takes a lot longer) of eggs and juveniles.

Fig.5 Wind directions in the Suez Canal area
Left: at Port Said (northern end)
Right: at Port Taufiq (southern end)
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Fig.6 Mechanism of the density gradient in the Gulf of Suez. Northerly flowing water suffers evaporating and cooling, and "turns under" mainly near the mouth of the Gulf of Suez where there is considerable shallowing. Returning water flows south below the thermocline. A sill in the mouth of the Gulf of Aqaba (not shown) precludes a similar effect in that Gulf. Water in the Gulf of Aqaba is also subject to less cooling, since its greater depth buffers it against sharp temperature changes. Light arrows are winds, dark arrows are currents.
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Fig.7 Left sketch shows a winter and right sketch shows a typical summer flow through the entrance into the Red Sea. Section across the sill at Bab el Mandeb showing the layers of water flow.
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The Magnitude of LM:

The colonization of the (eastern) Mediterranean by Red Sea species may be regarded as a large-scale experiment by which the processes of colonization and adaptation can be observed, and the source and colonizing populations may be compared.
The Levant Basin of the Mediterranean, delimited by Asia Minor, the Levantine coast and the shores of Egypt, is a most impoverished extension of the temperate Atlantic fauna. The northern Red sea, separated from the Mediterranean by the narrow Isthmus of Suez, contains a rich tropical fauna, an almost complete array of the highly diversified world of the Indo-Pacific coral reef. 
The biogeography of the eastern Mediterranean in general, and of the Levantine basin (defined by the annual surface isotherm of 20°C and the minimum surface isohaline of 39%0 which form an arc from the Nile Delta to the eastern part of Crete and the Dodecanese in particular) is the result of both historical and ecological factors.
Pleistocene glaciations, geographical barriers, high temperatures and salinities, low nutrient and oxygen contents, all in a synergetic effect, led to an impoverishment of the eastern Mediterranean communities. It is said that the western Mediterranean basin houses roughly twice as many species compared to the eastern basin. Such low species diversity is presently counterbalances by the immigration of well adapted (for warm and saline waters) Red Sea biota through the Suez Canal. This biota, having evolved under conditions of rapid, natural changes and out of highly diversified Indo-Pacific biota, is highly competitive.
At times when canal waters were high in salinity, especially the Bitter Lakes, it acted as a "filtrating funnel" which has hindered the northward advance of many fish corals, echinoderms and almost all planktonic species.
It is thus not surprising that once salinity fell, fish fauna successfully colonized the Bitter Lakes of the Suez Canal facilitating migration and further expansion into the Mediterranean Sea.
There is now doubt by now that Lessepsian Migrants in the Eastern Mediterranean mutated from exotic to dominating species; they often build large populations (especially certain fish and decapods). Very large commercial catches of migrant fish have been reported from the coast of Israel.
As a result, the Suez Canal is an open gate for Red Sea water to run into the Mediterranean. Every year, five to ten new species from the Red Sea, and even the Indian Ocean, are discovered in the Mediterranean. So far, at least 10% of all fauna found in the Levant basin are of Indo-Pacific origin.
Ironically, the Mediterranean may be returning to the pre-Messinian situation of millions of years ago, when the marine life was in balance. It is a test of the fragility and capacity for change of these ancient waters. Mankind has shown again that it can change the environment and create crisis conditions in a very short period of time as compared with the geological timescale.

Planktonic Migrants: While several species, perhaps all (fishes, shrimps and crabs) may have passed the canal as adults - which may take between 1 to 5 days, depending on their size - pelagic larvae would encounter difficulties. Before 1929 when hypersaline conditions existed in the Bitter Lakes planktonic migrants were eficiently blocked from threspassing, whereas, nowadays certain larval stages indeed possess the capabilities to pass this bottleneck. The shallowness of the Canal suggests that the animals passing through are possible epifaunistic forms. Pelagic larvae of bottom invertebrates will be carried back and forth by the tidal currents as well as by the changing direction of the main current system during specific seasons of the year, and so may not find suitable bottom conditions to settle or survive an extended migratory path.
Several species of fish parasites (Protozoa and Monogenea) have accompanied their hosts. Consequently an equally migrant bivalve must be mandatory to enable his nutritional survival in this new distributional area.
Invertebrates: More up to dated census extensively list migrant species of Polychaeta (Nereidae), several among the Serpulidae, species of Indo-Pacific mollusks and more un-doubtful species as new settlers; the influx of Crustacea seems to be somewhat slower than compared to the others. Increase in polychaete, mollusks, and decapods populations are significant - to a lesser extent towards the western basin of the Mediterranean. At the moment when the first census on exotic species within the east-Mediterranean was done (early 70's), some 45 Red Sea species (26 among Gastropods and 19 among Bivalves) have been identified - which amounts to about 9% of the known mollusc fauna. Among decapods, some 43 species out of 19 families (some 20% of the total fauna) have been identified as Lessepsian migrants.
Especially ship-borne expansion represents a useful means of transportation for "low probability migrants" such as juvenile stages of several organisms with bi-phasic lifecycles (pelagial larvae drifting as plankton).
Migrating fish: Of the 430 (or more) species of marine fishes identified from the Mediterranean coast of Israel and its immediate neighborhood, 100 species are circumtropical-cosmopolitan, the remaining species belong to the Atlanto-Mediterranean fauna. Many of them are found also in the Indo-Pacific and Red Sea regions. Thus summing up the Red Sea and cosmopolitan fishes in the eastern Mediterranean, there are 56 species (among 39 families) which constitute about 13% of all the ichthyofauna identified in this region;

check this detailed exotic species list (CIESM - the International
Commission for the Scientific Exploration of the Mediterranean Sea):
exotic Fishes in the Mediterranean
exotic Decapods in the Mediterranean
exotic Molluscs in the Mediterranean
The origin of Immigrants

70% of the immigrant species belong to the wide Indo-Pacific region, ranging from northern Australia and southern Japan to the eastern coast of Africa and the Red Sea. A meager 17% is known to be of western Indian origin, 4% are circumtropical, and none of the immigrants belong to endemic Red Sea species.

The following factors might expose a limiting effect upon a northward migration:

1. Families, known to be associated in the tropics with coral reefs, cannot colonize the Levant basin prior to the settlement of reef building coelenterates.
2. Both corals and coral reef fishes are thermophilic and cannot survive the low winter temperatures of the Mediterranean Sea.
3. Lack of suitable habitat prevents coral reef fishes from entering the Suez Canal.
4. Coral fishes are mostly bottom spawners with non-existing or short-lived pelagic stages; therefore, they lack sufficient opportunities of drifting with currents to the northern end of the Suez Canal.
5. The shallow Gulf of Suez contains good trawling grounds of muddy bottom depths of 20-50m. The main stream of colonizers come from this demersal stock, being able to find a similar habitat in the Mediterranean.
The conquest of new territories:

Lessepsian province: Due to the consistent influx of migrant species into the eastern basin, one can delimitate a biogeographic province within the Mediterranean. The limits of the province are, for the time being, the entrance to the Aegean Sea on hand and the Eastern coast of Sicily on the other (excluding the Adriatic). The boundaries of today will certainly expand or shrink according to the climatic evolution in our area.

The predominantly northward route of the immigration can be explained by the following factors:

  • The Red Sea contains more species than the eastern Mediterranean (about 1000 compared to 430); the densities of the populations are also greater in the Red Sea.
  • The multitude of Red Sea fishes as part of the rich western Indo-Pacific fauna evidences better, more versatile adaptation to various ecological niches; these fishes are able to compete successfully with Mediterranean species.
  • Prevailing winds and currents facilitate the passage in the South-North direction, especially of eggs and juveniles.
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Fig.8 The Lessepsian Province of the Mediterranean featuring selected species (based on ciesm, 2001).

A colonizer species is considered to be a species that has established a population in an area previously unoccupied by that species. In studying the immigration of organisms (mostly fishes) trough the Suez Canal, three zoo-ecological areas must be taken into consideration:
  • The northern Red Sea 
  • the eastern Mediterranean, and 
  • the Suez Canal itself in which many marine animals from the two neighboring areas have found a permanent habitat.
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Fig.9 Bardawil Lagoon

The prevailing hydrographic conditions differ in these areas, although the salinities and summer temperatures are to some extend similar, they are the main abiotic factors influencing the distribution of organisms over large zoo-geographical areas. Often they also have a decisive influence on the ecological distribution of species in various biotopes of an area. 
The process of immigration is highly selective. Common species of the home areas are not necessarily successful immigrants in a new region. The adaptation of a species to a new area requires adjustment of its reproductive processes, especially with regard to the correct timing of spawning in order o ensure suitable physical and ecological conditions for the development and survival of the young stages.
Species for whom settlement in the canal proper has been impossible, owing to its adverse physical conditions, and whose pelagic life is too short for a "one jump" dispersal, have probably crossed the Canal using the Bitter Lake as a stepping stone. Having higher temperatures, lower turbidity and less gelatinous mud on its bottom, the lake, despite its extraordinary characteristics, may provide a more favorable environment for settlement and reproduction, than the canal proper.
Evidently, immigration is a continuos process, and over time the probability of suitable species of fish entering the Suez Canal and colonizing the new region increases. Time also plays an essential role in the biological processes of adaptation of the species to the modified conditions of life. More resistant species, endowed with greater plasticity of genetic characters, can form local "races" within a few generations by natural selection in the new environment. But first they need a firm foothold on the other side of the Canal, geographically close to the parental stock and in places where conditions are not drastically different from their normal habitat. Many of the species that successfully colonized the eastern Mediterranean are also dominant species on the trawling grounds of the Gulf of Suez.
High percentage of Red Sea fishes found in the hypersaline Bardawil Lagoon on the northern coast of Sinai indicates that it may serve as a further stepping stone in the immigration of Red Sea fishes into the Mediterranean, especially if we regard it as a part of the system of lakes and lagoons of the Isthmus of Suez. 
It is a common feature of invading organisms that after an initial period of successful adaptation to the new and basically favorable environment, they may suddenly increase in number and spread to adjacent areas.
Coexisting with indigenous species

The impact of Lessepsian migration in the Levant basin ecosystem has been immense.
The fact that many species successfully establish themselves in the new environment indicates that the dietary requirements of many migrant species reflects the non-selective nature of their feeding habits. This adaptation is of great importance for any migrant in its new environment. It is self-evident that successful colonization can only be established where the overlap between the environmental conditions in the source and target areas is within colonizer tolerance. Since these environments are not identical, the colonizing population will respond to the new selective pressures by diverging from its mother population, thus becoming better adapted to its new habitat.
The successful establishment of about 500 Lessepsian Migrants in the Mediterranean (today's estimate), to whom low productivity did not act as a barrier (probably because of the existence of under-exploited niches), poses the question of complex interactions with local species. This high number is mainly determined, however, by a migrants ability to occupy a niche in the new ecosystem, maintaining itself by means of successful reproduction when oceanographic conditions are optimal for the development of the young stages.

Inter- and Intraspecific Competition:

The ecological process occasioned by spatial and temporal overlap in the use of resources, is considered in important force in organizing fish communities. Competition can mediate adaptations which may include habitat selection and/or resource allocation or extinction; however, it is not very common in natural communities, since resources (renewable or non-renewable) usually provide more ecological niches than there are specialists to fill them. In regards to ecological times, many resources remain under-exploited even when species exist that are specialized on these resources. Yet, predation and environmental harshness/variability are known to moderate the effect of competition. Local extinction by means of competition are probably restricted to habitats that occur in patches and in islands.
Considering just fishes, they are ecologically flexible with habitat switching as a common and predictable event. Fishes clearly alter their behavior in the presence of competitors in order to reduce the utilization of similar resources. There is no record of total replacement of an indigenous species by a Lessepsian migrant. Outcompeted local species would experience a vertical habitat displacement by usually maintaining themselves in deeper and cooler waters. So far, no misplacement has been yet reported, which clearly indicates the under-exploitation of niches in the eastern Mediterranean communities.
In few cases it seems more probable that, with the arrival of new competitors, interfering competition led to a narrowing of trophic niche of the indigenous species. This scenario implies that the new species is superior to the native one. It is also in agreement with studies which have indicated that the diet breadth of individual species decreases when interspecific competition increases (e.g. introduction of a new competitor), accompanied by a reduction of the total biomass of the original species assemblage largely due to the reduction in the number of individuals, that biomass being replaced by the invading competitor. Conversely, both diet breadth and biomass of the original species assemblage increase when competition is reduced.


Trophic Characterization of migrant fish:

The feeding habits are divided into four categories, i.e. piscivorous, benthic invertebrates feeders, planktivorous, and herbivirous (both benthic and pelagic feeders were split equally between piscivorous and benthic invertebrate feeders). As can bee seen in the scan on the right, a strong similarity between the trophic composition of source ichthyofauna of the Red Sea and the recipient ichthyofauna of the Levant, the main difference being the expected paucity of herbivorous fishes in the temperate-derived Mediterranean. The relatively high proportion of planktivorous species among the migrants may not necessarily indicate a vulnerable and penetrable site for invasion, but rather the result of their transient behavior and their subsequent experience of a wide range of hydrographic conditions, enabling them to acclimate rapidly to new environments.

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Fig.10 Food of Lessepsian fishes as compared to that of the source ichthyofauna (Red Sea) and recipient ichthyofauna (Mediterranean).

In addition, these species from medium- to large-sized schools, reducing the probability of random extinction, especially during the founding stage. It is commonly agreed upon that bathymetrical distribution of goatfishes (family Mullidae) is the most important mechanism for maintaining coexistence amongst migrant and native species (e.g. the migrating species Upeneus moluccensis dominates the 10-30m range while U.pori as a demersal invader is most common at 40-55m). This bathymetrical distribution is indirectly supported by the fact that significantly higher average Hg-concentration in bottom dwelling fish species closer to the surface, which coincides with the heavier polluted depths by human activity. In a study of a non coevolved assemblage of estaurine fishes in California, a stable coexistence of recently encountered species suggests that in an ecosystem vulnerable to invasion, coevolution plays a minor role in determining the interspecific relationships.
  • Bathymetrics: It is important to stress, however, that the bathymetrical segregation is not a result of displacement of some species to shallower or deeper waters, but rather to limitation posed on many researchers who did not find those species in their traditional trawl ground. This phenomenon of bathymetrical partitioning especially among lizardfishes (family Synodontidae) contradicts the pattern established for most Lessepsian-confamilial native species; namely, the inhabiting of shallow water by the invader species, as was the case in Mullidae, Sphyraenidae, and various crustaceans. It is interesting to note that different feeding habits, such as ambush (frontal attack) or chasing (caudal attack), diurnal or nocturnal activities may be utilized by different species which increases their chances to find their proper niches in an appropriate thropic level.
  • Partitioning: A high tropic selectivity amongst some herbivorous fish species Siganus luridus, S. rivulatus (both Lessepsian migrants of the family Siganidae) could be observed amongst the mother colony remaining in the Gulf of Suez and offsprings migrating into the Mediterranean. Although partitioning between the diet resources in the Gulf was previously evident, it was broken once the fish reached the south-eastern Mediterranean (horizontal platforms at about sea-level with a low tidal motion inhibit grazing). Both siganids fed on a similar diet of available algal species, diet overlap became greater, and niche partitioning weaker. It was shown that partitioning became greater again, once there was a higher diversity and abundance of vegetation (rocky shore versus sandy bottom). There, these siganids tend to choose its own specific diet by grazing on one or few plant species which are rejected or less grazed upon by the other. Thus, again reducing competition and increasing resource partitioning.
Several authors have suggested that successful colonization of the Mediterranean by Lessepsian Migrants was facilitated by an unsaturated niche in their new habitat (as shown with the siganids - above). The origin of the Mediterranean fish fauna is the temperate Atlantic. Temperate regions are characterized by a lower diversity and abundance of herbivorous fish than tropical regions; this is mainly due to a constrained digestive physiology, which is affected by temperature. The occurrence of a single species of herbivorous indigenous fish Sarpa salpa in the subtropical environment of the Eastern Mediterranean strongly suggests an impoverished niche of herbivorous fish.
Although no precise surveys about indigenous species and successful colonizers have been made until recently (compared with terrestrial ecology), it is generally assumed that the massive invasion of the Levant basin with Red Sea species do not seem to influence the abundance of native species (observations based primarily upon commercial fishing). So far, the greater number of immigrant species enrich the catch considerably. Although, recent piscivore immigrants reduced some of the flourishing populations of earlier migrants.
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Fig.11 El Bilaiyim

Anti Lessepsians:

It seems that there are very few species which migrated from the Mediterranean to the Red Sea. This fact cannot be simply ascribed to the circumstance that the number of autochthonous species is so much higher in the Red Sea than in the Mediterranean. As the biota of the Red Sea is several times richer than that of the Mediterranean, these facts and figures indicate that the number of Lessepsian migrants could be three (or more) orders of magnitude higher than of the anti-Lessepsians.

As stated above, many factors facilitates the transport of organisms through the canal in a predominantly northward direction. The discovery of Mediterranean species Sphaerodiscus placenta (a sea star) in the lagoon of El Bilaiyim, situated 180km south of the entrance to the Suez Canal, is one of the few indisputable evidences of the anti-Lessepsian migration.
However, we have to bear in mind that the conditions of El Bilaiyim differ considerably from those of the Gulf proper (salinity is much higher, 60-60%0 and most probably the seasonal and diurnal fluctuations are greater than those of surrounding waters. In this particular biotope, less competition is expected than in the open coastal waters).

Conclusion:

The invasion of the eastern Mediterranean by Red Sea species enables an investigations regarding the processes of migration and colonization. Although this invasion of the Mediterranean received scientific attention almost from its outset, until the last two decades most studies were of an inventory or monitoring nature.

In general the lack of knowledge about the faunistics of the Suez Canal system in the last three decades is very unfortunate.

With all the justified willingness to approach the aspects of strategies and the dynamics of Lessepsian Migration, in most of the cases the taxonomic information or even the taxonomic resolution is still insufficient. De facto potential migrants are "R-strategists" (quick populators in which the structure of organism focused on reproduction rather than complexity) involves a smooth gene-flow between con-specific populations on both sides of the canal. This likely possibility has to be taken into account when differentiating between Lessepsian Migrants and indigenous species; e.g. comparative advantages between different reproductive strategists can be established only between strictly congeneric species. Comparison between the autochthonous and migrant populations too, have to be performed by using all the parameters which can be mustered by both classical and modern taxonomy.

For a better understanding of Suez Canal immigration, additional taxonomic and biological investigations are required. Comparison of racial characteristics of immigrant organisms could help to clarify the question of the origin and relationship between the Red Sea and the Mediterranean populations. It is expected that in some cases, exchange of fauna and flora may have taken place before the opening of the Suez Canal as a result of the elevation of seal levels and undulations of the Isthmus during the Pleistocene.

Knowledge of the comparative life histories of the immigrant species in the two areas is essential for understanding the selective mechanisms controlling passage through the Suez Canal and evaluating extensive ecological changes that the invading species may produce in the new areas of their distribution.

Whether the success of the Lessepsian migrants is the result of their occupation of an "unsaturated niche" or whether it is due to an efficient competition with local species on the same resources is yet to be determined. Regardless of the cause, it is anticipated that the number of Red Sea fish species which will successfully colonize the (benthic) Levantine habitat will increase in the coming years rather than flatten asymptotically. It seems that the eastern Mediterranean ecosystem allows additional links in the food web. This indicates that communities are loosely packed and competition at present plays an important role (as compared to predation and/or environmental harshness/variability) in shaping the eastern Mediterranean communities and will continue to do so until equilibrium in terms of resident species is reached (immigration balances extinction) and communities become tightly packed with a regular spacing between species (refering to Huntchinsonian distances).
Expectations suggest that Lessepsian Migration should eventually reach a plateau; current census do not indicate that such a flattening trend is initiated. Indications suggest that the flux of Indo-Pacific migrant species into the Mediterranean Sea is locked at the current rate of five to ten new species per year. The current level of Lessepsian Migrants is thought to be at least 10% of the species inventory of the Levantine Basin.

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  • Some Sites on the WWWeb:
    Exotic Species in the Mediterranean Sea
         http://www.ciesm.org/atlas/
         http://www.springerlink.com/
    The Mediterranean Crises
         http://www.unu.edu/unupress/lecture16-17.html
         http://reports.eea.eu.int
    A Case Study of the Maltese Islands
         http://www.science.plymouth.ac.uk/departments/learn/malta/Malta.htm
         http://www.science.plymouth.ac.uk/departments/learn/malta/Eco5.htm
    Jellyfish Sting Newsletter
         http://www.jcu.edu.au/school/phtm/PHTM/ACTM/JFN/jfn14.htm
    School of Biological Sciences
         http://l00.bio.bris.ac.uk/research/markwilk/pjm.htm
    Israel Journal of Zoology
         http://www.tau.ac.il/zoology/
    De Lesseps Lives
         http://www.unu.edu/unupress/lecture16.html
         http://www.unu.edu/hq/ginfo/wip/wip%2Dwin98.html
    Lessepsian Migration
         http://www.ciesm.org/atlas/
         http://www.com.univ-mrs.fr/DIMAR/THESEBARICHE.htm
    Marine Bioinvasion
         http://www.iucn.org/places/medoffice/Documentos/Invasive2.pdf
         http://www.yale.edu/environment/publications/bulletin/103pdfs/103golani.pdf
    The Introductions Table 
         http://www.cgiar.org/ICLARM/fishbase/manual/FishbaseThe_INTRODUCTIONS_Table.htm
    Role of the Mediterranean in the Global Change system
         http://w3medias.meteo.fr/www/anglais/lettre/09/Mediterr/GrIV/GrIV.html