Every year, many more species of fish and invertebrates of Indo-Pacific origin are discovered in the eastern basin of the Mediterranean Sea, right off the coast of the State of Israel, meaning that they came from the Pacific and Indian Oceans up the Red Sea to the Gulf of Suez at its end, and through the canal to the Mediterranean Sea. The count today stands at 300 species of animals that migrated this wayThe
"Nemo, pack your bag, we're leaving"
"But father, I don't want to leave. All my friends are here at the coral reef"
"We're getting too crowded on the coral reef son, we're going to try our luck in the Mediterranean"
It sounds like an imaginary dialogue from the cartoon "Finding Nemo", and indeed in reality the shoshanon fish ("clown fish"), the heroes of the film, have not yet left the reef and have not migrated anywhere. But sea urchins, grizzinons, spearfish, jellyfish, corals, sea worms, and many other good ones found their way from the Red Sea to the Mediterranean Sea, through the Suez Canal of course. And the arm is still tilted - every year many more species of fish and invertebrates of Indo-Pacific origin are discovered in the eastern basin of the Mediterranean Sea, right off the coast of the State of Israel, meaning that they came from the Pacific and Indian Oceans up the Red Sea to the Gulf of Suez at its end, and through the canal to the Mediterranean Sea. The count today stands at 300 species of animals that migrated this way and it is clear that this is only part of the list.
Man's influence on his environment is evident in many areas. Reduction and fragmentation of the living areas of animals, pollution of areas, uncontrolled hunting and overfishing, drying up of watercourses, deforestation - all these are only a small part of the list of the destructive effects of man on nature. And in the marine environment - along with sea pollution and overfishing, the introduction of foreign species is at the top of the list of negative effects. In some cases the introduction of the species was active and intentional, such as the Nile princess fish that were deliberately brought to the Nile basins to form a basis for the fishing spoils and in a short time eliminated every other fish in their area. However, in other cases the introduction of species is a byproduct of human activity, which by its very nature changes nature and adapts it to its needs. The same is true in the case of the mass migration through the Suez Canal.
Until 5 million years ago, the Mediterranean Sea was a closed sea. The vast Tethys Ocean, which separated the 2 supercontinents at the time, became smaller with the migration of the continents and the formation of Europe, Asia and Africa as they are known today. Between these, a closed water basin was formed, a kind of vast lake, which, following the processes of evaporation and drying, became salted. About 5 million years ago, an opening opened in the west of Hima, known today as the Strait of Gibraltar, which added the Mediterranean Sea to the world ocean map. Through the opening that opened in Gibraltar, the cool ocean waters, rich in nutrients that support a wide variety of fish and invertebrate species, flow into the western Mediterranean.
With the entry of ocean water the western Mediterranean lost its salinity, was enriched with nutrients and many Atlantic species that migrated from the ocean. The topographical structure of the Mediterranean Sea is such that the eastern basin reaches but little of all this. The Strait of Marsella, which separates Sicily from Tunisia, is relatively shallow and narrow and therefore constitutes a sort of threshold separating the western basin from the eastern basin of the Mediterranean Sea. The currents of water penetrating from the ocean move east along the coast of North Africa and north along the Italian shelf, but only a minority of them penetrate the eastern basin. Thus, the eastern basin remains relatively high in salinity (3.9-4% compared to 3.5% in the oceans or 3.6-3.7% in the western basin), has high temperatures (up to 30 degrees in the summer, compared to 24 in the western Mediterranean) and is a poor sea and low in nutrients that enrich the the water. Also in terms of the variety of species in which it is quite scarce. Less than 200 species of fish, for example, are known in the Levant Basin (the eastern part of the Eastern Basin) compared to about 600 species in the Western Basin. In addition to this, there is a phenomenon known as "Mediterranean dwarfism": fish of certain species that maintain populations in both the eastern and western basins, will reach much more impressive dimensions in the western sea. For example, the Japanese stingray, which despite its local name exists all over the Mediterranean Sea, reaches a length of 80 cm at maturity, while on the coasts of France and Spain individuals of this species can reach a length of about 140 cm.
These conditions of salinity, temperatures and water composition allowed the successful migration of animals from the Red Sea to the eastern Mediterranean. The Red Sea is also a poor sea. Especially in its northern part, there is no flow of fresh water into it at all. It is a blue and clear sea - which indicates a shallow sea. Only in the coral reef areas is wealth maintained, mainly thanks to the primary production process, photosynthesis, which occurs in the coral. Due to the scarcity of fresh water flowing into it and due to the increased evaporation in the desert climate that surrounds it, the Red Sea is also one of the saltiest seas in the world, with a salinity of about 4.1%. And in addition, of course, it also has warm water, as befits a tropical sea in a desert climate. A fish that will move from the Gulf of Suez in the northern Red Sea to the eastern Mediterranean "will feel at home", in terms of environmental conditions. What's more: due to the overexploitation of species populations in the eastern Mediterranean and other human influences, the animal society is diluted and migratory species can easily occupy ecological niches in the northern Red Sea subject to heavy competition with other species.
Along with all this, it is clear that such a massive migration would not have been possible without the direct mediation of man.
The Suez Canal is not the first attempt in human history to connect the seas, and to open convenient and fast trade routes between them. The first recorded attempt was made by King Ramses II in the 14th century BC. The canal that was built then connected the north of the Gulf of Suez to the Mediterranean Sea through one of the Nile's branches. Other passages were opened and the last of them survived until the eighth century AD, but none of them lasted long and they were not known to have a decisive effect on the animal society of the two days.
In 1869, the Suez Canal was opened, designed by the French architect Ferdinand Marie de Lesseps. Unlike previous canals, this canal maintained the level of the sea and did not include level changes and dams, thus allowing a continuous and relatively fast passage of animals. The length of the canal is 163 km, its depth is quite shallow and during it it passes through a series of shallow lakes with different salinities.
So far, as mentioned, about 300 species are known to have migrated from the Red Sea to the Mediterranean Sea, and the phenomenon was given the name "Laspesian migration", after the architect who designed the canal, of course. Migration in the opposite direction ("anti-Lessepsian migration") is almost non-existent and its ecological impact is negligible.
Among the old immigrants, those who have already managed to settle, prosper, push out local species and also influence the fishing industry, the dangerous fish that passed through the canal more than a century ago can be praised. Apparently these swallowed the road in the form of planktonic eggs carried with the current. Today they are found on almost all the shores of the eastern Mediterranean and every diver or swimmer who puts his head in the water will come across them. Another fish that has found a warm and loving home in the eastern Mediterranean is the garzinon, that small, flamboyant fish with a shape reminiscent of an ax blade. This fish now inhabits almost every rock crevice or cave, and these are abundant on the rocky shores of the Mediterranean.
Another migrant, even better known but much less loved, is the dreaded wandering filamentous jellyfish that swarms our shores every summer. This jellyfish is of Indo-Pacific origin and in the past it was believed that it arrived on our shores in ballast water (huge water tanks used to stabilize vessels) of merchant ships. This possibility is still valid, but today it is more common to think that, like many other migrants, the jellyfish also migrated through the channel that opened and under the protection of the currents. Their life cycle is such that in the winter they spend in larval form (a tiny caterpillar), the early life stage of their life, and with the arrival of summer they undergo a radical change to the adult form, equipped with terrible burning cells that most of us have experienced first hand, simply put.
One cheeky fish, which is used to "swim against the current" and also to migrate between changing sea conditions is the golden kipon (a species of mullet) which migrated precisely in an anti-Lespesian migration, to the Red Sea. In its native land in the middle of the Middle East, the kipon was used to climbing up the mouths of rivers, despite the currents and despite the extreme drop in salinity, and inhabiting ponds and streams. The adaptability he developed also stood him in good stead during the transition from the Mediterranean to the Red Sea and today he is common in both seas and of commercial importance both here and there.
Contrary to popular belief, there are indeed corals in the Mediterranean Sea as well and not only in the Red Sea and the tropical areas. But these corals are scattered and flat colonies that do not form a massive coral reef like the one we know from the Gulf of Eilat. The common coral on our shores, which is very common in rocky areas such as Ashkelon, Palmahim Beach, Bonim-Dor and especially in the north of the country - is another immigrant that came to our area from somewhere. But ironically, this immigrant is not part of that highly influential phenomenon of Red Sea migration and he apparently came to us from really far away regions. The coral Oculina patagonica apparently arrived in the cargo tanks of merchant ships, which unloaded them in the eastern Mediterranean at the end of the voyage from Tierra del Fuego in South America, it is patagonica and hence the name of the coral.
When it comes to sapsian migrants such as snails, sea cucumbers and oysters, which do not excel in excessive mobility, the story can sound a bit strange: could it be that slow creatures and even sedentary and stationary creatures used their legs the whole long way??? To answer this question it is important to understand that almost all marine animals, and fish in general, have a young life stage that is often called a larva (larva, or pupa) and this stage is carried with the plankton wherever the current takes them. Those whose larval stage is long enough can spend days and weeks wandering with the current, and in this way qualify for the eastern Mediterranean and even further away. Let's return for a moment to our friend the Shoshones, who recently became famous in "Finding Nemo" as no small nomads, even though in reality they rarely go beyond the borders of the home Shoshana. It is not impossible, however, that in their larval stage the shoshannon fish (and even the shoshanon itself) will find themselves migrating as migrants to the Sepsians. Imagine a colorful goldfish with a large flowerhead with red and twisting arms, clinging to a rock on the beach in Bat Yam. Not far today...
Although the Helaspesian migration also has apparently positive sides, which enriched our scarce sea with a variety of species and tropical colors, it is important to remember that it is fundamentally a large-scale phenomenon that affects the local fauna and we need to study it in depth so that we will be able to monitor its negative effects in the future.
Nemo in the Mediterranean Sea is nice, but swarms of poisonous jellyfish, for example, is less nice and what is being done - cannot be answered.
About the author
Amir Gur is a graduate of a master's degree in marine biology, and the author of the book "Underwater - 44 diving sites in Israel"