32
The HistoricaI Background
We come now to a very small group among the presumed pre-Lessepsians:
Pirenella conica, Liza carinata, and Aphanius dispar, which are characteristically
euryhaline and high-salinity resistant species. Pirenella conica is a species restricted to the Southern Mediterranean shores and is probably identical with the
Red Sea Pirenella cailliaudi. The case of Aphanius dispar has already been discussed above: this fish is capable of withstanding salinities of around 100%. It is,
therefore, much more reasonable to consider it to be a more recent migrant into
the Mediterranean rather than a Tethys re1ict. The grey mullet Liza carinata may
also be able to resist high salinities but there is no reason not to inc1ude it also
among the many recent Lessepsian migrants.
Whereas in the case of Pirenella and Aphanius, their wide distribution in the
Mediterranean prior to 1869 makes it necessary to consider them pre-Lessepsians, there is a certain number of species, besides Liza carinata, which might have
come from the Red Sea and settled restricted lagoon areas along the Mediterranean even before the opening ofthe Suez Canal. The fauna of the hypersaline
Sirbonic Lagoon (Sabkhat el Bardawil, Sinus Sirbonicus of the c1assical authors)
gives some good examples of Red Sea species which can survive salinities such as
probably existed in the lakes and pools of the Isthmus of Suez before the building
of the Suez Canal. To our knowledge some of these species are still restricted to
the Sirbonic Lagoon. The Sirbonic Lagoon will be treated in more detail below.
There is, of course, a slight possibility that some species might have migrated
into the Mediterranean during interglacial high eustatic levels and subsequently
disappeared. This was suggested by some authors inc1uding Kosswig (1956) and
Por (1971 b). However, there are no fossil proofs for this and every passing year of
intensive research fails to supply any convincing evidence.
At least for the period since the last Interglacial, some 100,000 years ago, there
was no stenohaline marine contact through the Isthmus. There were short per iods
of contact through the freshwaters of the Eastern branches of the Nile Delta.
More frequent probably were the cases in which isolated hypersaline pools, left
behind by a retreating sea-tongue or aspring flood or else an abundant Nile
flood, could carry a certain fauna to survive till the next flood. In such short
jumps some very euryhaline species could have spread over the chain of Isthmus
lakes: the Bitter Lake, Lake Timsah, Lake Ballah, Lake Menzaleh, and the Sirbonic Lagoon. These basins have probably carried waters of some degree of
hypersalinityall the time (see Seetzen's and Schleiden's information above). Lake
Menzaleh was probably reduced to a few small salt pools until invaded by the sea
in the Middle Ages, when it turned into a brackish basin. The Sirbonic Lagoon
shows considerable changes of salinity if the bar-openings to the Mediterranean
are open or silted. Both lagoons are indicative of the pre-Lessepsian conditions of
the Isthmus water-bodies.
Even when the c1assical shipping canals were functioning, shallow and narrow
as they were (see above), they could not change the prevailing hydrographic
conditions of the Isthmus lakes: hypersalinity in normal years and occasional
flooding by Nile waters. The shipping canals,- with a possible short exception
during the Ptolemy per iod, always led through the Tumilat-Pelusium way, i.e.
through the freshwaters ofthe Nile.
The HistoricaI Background
We come now to a very small group among the presumed pre-Lessepsians:
Pirenella conica, Liza carinata, and Aphanius dispar, which are characteristically
euryhaline and high-salinity resistant species. Pirenella conica is a species restricted to the Southern Mediterranean shores and is probably identical with the
Red Sea Pirenella cailliaudi. The case of Aphanius dispar has already been discussed above: this fish is capable of withstanding salinities of around 100%. It is,
therefore, much more reasonable to consider it to be a more recent migrant into
the Mediterranean rather than a Tethys re1ict. The grey mullet Liza carinata may
also be able to resist high salinities but there is no reason not to inc1ude it also
among the many recent Lessepsian migrants.
Whereas in the case of Pirenella and Aphanius, their wide distribution in the
Mediterranean prior to 1869 makes it necessary to consider them pre-Lessepsians, there is a certain number of species, besides Liza carinata, which might have
come from the Red Sea and settled restricted lagoon areas along the Mediterranean even before the opening ofthe Suez Canal. The fauna of the hypersaline
Sirbonic Lagoon (Sabkhat el Bardawil, Sinus Sirbonicus of the c1assical authors)
gives some good examples of Red Sea species which can survive salinities such as
probably existed in the lakes and pools of the Isthmus of Suez before the building
of the Suez Canal. To our knowledge some of these species are still restricted to
the Sirbonic Lagoon. The Sirbonic Lagoon will be treated in more detail below.
There is, of course, a slight possibility that some species might have migrated
into the Mediterranean during interglacial high eustatic levels and subsequently
disappeared. This was suggested by some authors inc1uding Kosswig (1956) and
Por (1971 b). However, there are no fossil proofs for this and every passing year of
intensive research fails to supply any convincing evidence.
At least for the period since the last Interglacial, some 100,000 years ago, there
was no stenohaline marine contact through the Isthmus. There were short per iods
of contact through the freshwaters of the Eastern branches of the Nile Delta.
More frequent probably were the cases in which isolated hypersaline pools, left
behind by a retreating sea-tongue or aspring flood or else an abundant Nile
flood, could carry a certain fauna to survive till the next flood. In such short
jumps some very euryhaline species could have spread over the chain of Isthmus
lakes: the Bitter Lake, Lake Timsah, Lake Ballah, Lake Menzaleh, and the Sirbonic Lagoon. These basins have probably carried waters of some degree of
hypersalinityall the time (see Seetzen's and Schleiden's information above). Lake
Menzaleh was probably reduced to a few small salt pools until invaded by the sea
in the Middle Ages, when it turned into a brackish basin. The Sirbonic Lagoon
shows considerable changes of salinity if the bar-openings to the Mediterranean
are open or silted. Both lagoons are indicative of the pre-Lessepsian conditions of
the Isthmus water-bodies.
Even when the c1assical shipping canals were functioning, shallow and narrow
as they were (see above), they could not change the prevailing hydrographic
conditions of the Isthmus lakes: hypersalinity in normal years and occasional
flooding by Nile waters. The shipping canals,- with a possible short exception
during the Ptolemy per iod, always led through the Tumilat-Pelusium way, i.e.
through the freshwaters ofthe Nile.