90
The Migrant Biota
2. Species known from the Red Sea and the Canal, but still confined to "take
off' areas otIPort Said or in the Sirboniclagoon.
3. Indo-Pacific species known from the Red Sea, reported also in the Eastern
Mediterranean, but not found in the Suez Canal.
A special category is formed by the parasitic species, where for instance, the
proof for the migration of the fish species, served also as proof for its parasite.
The question may rightly be posed as to why the above listing of proven
Lessepsian migrants considers only a certain unidirectional movement from the Red
Sea to the Mediterranean. There are only a few instances of proven migration in
the opposite direction, i.e. from the Mediterranean to the Red Sea.
For the sake of clarity the name "Lessepsian migrants" refers to the bulk of
species which migrated northward, while the very few species which moved south
are called here "Anti-Lessepsian migrants". A special chapter will deal with the
analysis of the overwhelming unidirectionality of the migration through the
Canal.
H. Steinitz (1967) published a list of migrants called A Tentative List. In a
research report of the Hebrew University-Smithsonian Institution Joint Program Biota ofthe Red Sea and the Eastern Mediterranean (1970), H.Steinitz compiled a revised list entitled Comprehensive List of Immigrant Animals. In the same
report he started another type of list called A Critical List of Immigrants via the
Suez Canal of which only the tables for Porifera, Polychaeta, and Echinodermata
were completed. I have consulted some of the notes for the other taxa, left by
Steinitz, for the list below.
The following list will deal with plants and animals, and presents separately
the evident and doubtful cases ofLessepsian migrants.
A third list of accidental or highly improbable cases is listed in succinct form
(Table4).
FinaIly, an approach which does not seem to' be evenhanded has to be justified: in weIl investigated taxa, such as fishes, moIluscs, echinoderms, I have taken
less care in including a species among the certain Lessepsian migrants. Yet the
critical selection has been much more severe among the ascidians, decapods and
algae, and most emphatically among polychaetes, bryozoans, sponges, and copepods.
The first two lists contain 128 species considered to be certain Lessepsian
migrants and 76 species considered to be uncertain. Dowidar (1973, 1974) speaks
of four species of phytoplankton and seven species of Tintinnida which have
migrated into the Mediterranean. There are several species of migrant fish parasites under study (Paperna, personal communication). No less than five species of
fish have been added to the list of migrants in the last few years. Even if this does
not necessarily indicate an ongoing immigration it certainly points to the fact that
even in the well-investigated taxa, many migrants are still undetected. Finally, one
has to add that in many animal groups, such as Platyhelminthes, Nematoda,
Acarina, and Hydrozoa, the Eastern Mediterranean is still a "terra incognita".
The list of H. Steinitz (1967) contained 114 species of Lessepsian migrants, some
ten of them uncritically included. One may thus say that in less than ten years,
the list has doubled due in most part to new reports of migrants.
The Migrant Biota
2. Species known from the Red Sea and the Canal, but still confined to "take
off' areas otIPort Said or in the Sirboniclagoon.
3. Indo-Pacific species known from the Red Sea, reported also in the Eastern
Mediterranean, but not found in the Suez Canal.
A special category is formed by the parasitic species, where for instance, the
proof for the migration of the fish species, served also as proof for its parasite.
The question may rightly be posed as to why the above listing of proven
Lessepsian migrants considers only a certain unidirectional movement from the Red
Sea to the Mediterranean. There are only a few instances of proven migration in
the opposite direction, i.e. from the Mediterranean to the Red Sea.
For the sake of clarity the name "Lessepsian migrants" refers to the bulk of
species which migrated northward, while the very few species which moved south
are called here "Anti-Lessepsian migrants". A special chapter will deal with the
analysis of the overwhelming unidirectionality of the migration through the
Canal.
H. Steinitz (1967) published a list of migrants called A Tentative List. In a
research report of the Hebrew University-Smithsonian Institution Joint Program Biota ofthe Red Sea and the Eastern Mediterranean (1970), H.Steinitz compiled a revised list entitled Comprehensive List of Immigrant Animals. In the same
report he started another type of list called A Critical List of Immigrants via the
Suez Canal of which only the tables for Porifera, Polychaeta, and Echinodermata
were completed. I have consulted some of the notes for the other taxa, left by
Steinitz, for the list below.
The following list will deal with plants and animals, and presents separately
the evident and doubtful cases ofLessepsian migrants.
A third list of accidental or highly improbable cases is listed in succinct form
(Table4).
FinaIly, an approach which does not seem to' be evenhanded has to be justified: in weIl investigated taxa, such as fishes, moIluscs, echinoderms, I have taken
less care in including a species among the certain Lessepsian migrants. Yet the
critical selection has been much more severe among the ascidians, decapods and
algae, and most emphatically among polychaetes, bryozoans, sponges, and copepods.
The first two lists contain 128 species considered to be certain Lessepsian
migrants and 76 species considered to be uncertain. Dowidar (1973, 1974) speaks
of four species of phytoplankton and seven species of Tintinnida which have
migrated into the Mediterranean. There are several species of migrant fish parasites under study (Paperna, personal communication). No less than five species of
fish have been added to the list of migrants in the last few years. Even if this does
not necessarily indicate an ongoing immigration it certainly points to the fact that
even in the well-investigated taxa, many migrants are still undetected. Finally, one
has to add that in many animal groups, such as Platyhelminthes, Nematoda,
Acarina, and Hydrozoa, the Eastern Mediterranean is still a "terra incognita".
The list of H. Steinitz (1967) contained 114 species of Lessepsian migrants, some
ten of them uncritically included. One may thus say that in less than ten years,
the list has doubled due in most part to new reports of migrants.