158
The Migrant Biota
in the Mediterranean. Bänärescu and Bo~caiu (1973) see the reason in the greater
competitive and expansion capacities of the Red Sea fauna. Recently, Briggs
(1974 b) asserted that the one-sided faunal movement results from the fact that the
Ind
sought in the fact that the currents from Lake Timsah to the north flow northward during most ofthe year. However, one cannot dismiss the fact that there is a
considerable admixture of Mediterranean species in the Canal itself despite the
fact that the migration through the Suez Canal is unidirectional in its results (Por,
1971 b). The reasons I saw were on one hand the preadaptation of the Red Sea
biota to the conditions of the Suez Canal and of the Levant Basin and on the
other hand the competitive "vacuum" in the Eastern Mediterranean.
No such favorable preconditions exist for the Atlantic-Mediterranean fauna,
which is already impoverished and near its pessimal conditions in the Levant
Basin. To migrate even farther along an increasing salinity and temperature
gradient is hardly possible. Moreover, the Red Sea fauna is not impoverished, but
a fauna in which many endemie species have evolved in answer to the local
conditions. In a later paper (Por, 1975a) I have attempted to place the process of
Lessepsian migration into the more general framework of the Pleistocene faunal
movements within and into the Mediterranean: the Red Sea migrants thus correspond to a subtropical invasion in response to interglacial subtropical conditions
in the Eastern Mediterranean.
Since 1969 when I first used it, the term "Lessepsian Migration" has become
synonymous with migration from the Red Sea into the Mediterranean. At that
time the most up-to-date listing of the species which migrated the opposite way,
i.e. from the Mediterranean to the Red Sea, comprised 16 species (H. Steinitz,
1968), at least half of which were cases of dubious merit. Even for the fish the
above-mentioned listing contained only old records (Tillier, 1902), or uncontrolled data (Gohar, 1954) regarding their presence outside the Canal outlet at
Suez.
Recently, however, several publications have appeared, which put the exclusive unidirectional nature of the Suez Canal migration in a somewhat changed
perspective. Ben-Tuvia (1971 b, 1975b) mentioned the capture of two AtlantoMediterranean fish in the Gulf of Suez; Fishelson and Rullier (1969) listed Mediterranean Polychaeta which allegedly migrated into the Red Sea; and Ben-Eliahu
(1972d) commented favorably on this, giving a few further cases from among the
Polychaeta. Schmidt (1971, 1972) while analyzing the Hydrozoa of the Gulf of
Elat assumed the possibility of transport from the Mediterranean. Glynn (1972)
assumed the same for two species of Isopoda.
A total of 53 species listed below (Table 10) have been at different times and by
different authors considered to be Mediterranean immigrants to the Red Sea.
Some outright erroneous data such as by Russo (1935), on a whole list of wouldbe Mediterranean echinoderms, have been deleted from the list. However, as seen
below and in the remarks added to the list, most of the cases are of dubious value.
The only convincing cases are found among lhe 13 species of fish, most of which
are known only from the Port of Suez or the lagoons of Suez, but their presence in
the open Gulf is doubtful. The bulk is formed of 32 species of Polychaeta and 11
The Migrant Biota
in the Mediterranean. Bänärescu and Bo~caiu (1973) see the reason in the greater
competitive and expansion capacities of the Red Sea fauna. Recently, Briggs
(1974 b) asserted that the one-sided faunal movement results from the fact that the
Ind
sought in the fact that the currents from Lake Timsah to the north flow northward during most ofthe year. However, one cannot dismiss the fact that there is a
considerable admixture of Mediterranean species in the Canal itself despite the
fact that the migration through the Suez Canal is unidirectional in its results (Por,
1971 b). The reasons I saw were on one hand the preadaptation of the Red Sea
biota to the conditions of the Suez Canal and of the Levant Basin and on the
other hand the competitive "vacuum" in the Eastern Mediterranean.
No such favorable preconditions exist for the Atlantic-Mediterranean fauna,
which is already impoverished and near its pessimal conditions in the Levant
Basin. To migrate even farther along an increasing salinity and temperature
gradient is hardly possible. Moreover, the Red Sea fauna is not impoverished, but
a fauna in which many endemie species have evolved in answer to the local
conditions. In a later paper (Por, 1975a) I have attempted to place the process of
Lessepsian migration into the more general framework of the Pleistocene faunal
movements within and into the Mediterranean: the Red Sea migrants thus correspond to a subtropical invasion in response to interglacial subtropical conditions
in the Eastern Mediterranean.
Since 1969 when I first used it, the term "Lessepsian Migration" has become
synonymous with migration from the Red Sea into the Mediterranean. At that
time the most up-to-date listing of the species which migrated the opposite way,
i.e. from the Mediterranean to the Red Sea, comprised 16 species (H. Steinitz,
1968), at least half of which were cases of dubious merit. Even for the fish the
above-mentioned listing contained only old records (Tillier, 1902), or uncontrolled data (Gohar, 1954) regarding their presence outside the Canal outlet at
Suez.
Recently, however, several publications have appeared, which put the exclusive unidirectional nature of the Suez Canal migration in a somewhat changed
perspective. Ben-Tuvia (1971 b, 1975b) mentioned the capture of two AtlantoMediterranean fish in the Gulf of Suez; Fishelson and Rullier (1969) listed Mediterranean Polychaeta which allegedly migrated into the Red Sea; and Ben-Eliahu
(1972d) commented favorably on this, giving a few further cases from among the
Polychaeta. Schmidt (1971, 1972) while analyzing the Hydrozoa of the Gulf of
Elat assumed the possibility of transport from the Mediterranean. Glynn (1972)
assumed the same for two species of Isopoda.
A total of 53 species listed below (Table 10) have been at different times and by
different authors considered to be Mediterranean immigrants to the Red Sea.
Some outright erroneous data such as by Russo (1935), on a whole list of wouldbe Mediterranean echinoderms, have been deleted from the list. However, as seen
below and in the remarks added to the list, most of the cases are of dubious value.
The only convincing cases are found among lhe 13 species of fish, most of which
are known only from the Port of Suez or the lagoons of Suez, but their presence in
the open Gulf is doubtful. The bulk is formed of 32 species of Polychaeta and 11