168
The Migrant Biota
opportunities for passive transport. However, the Panama Canal has existed
hardly more than half a century while the classical Suez waterway has existed for
centuries. Comparing it with the Panama freshwater canal it appears reasonable
to assume that among the species which are suspected to be "Pre-Lessepsian"
migrants there may be some extremely euryhaline species, still confined to the
Isthmus and its immediate surroundings, as weIl as several passively transported
species, as in the case of the Panama Canal.
There is a last group of phenomena to which it is interesting to compare
Lessepsian migration: these are the faunal movements into the Baltic Sea, the
Black Sea and the Caspian Sea, movements which started several thousand years
ago and are still going on. In the case of the first two seas these are natural
contacts with the adjacent sea; however, these natural contacts are by means of
narrow and shallow straits perfectly comparable to the Suez Canal. In the case of
the Caspian Sea, the new contact with the Black Sea is through an artificial
freshwater passageway. However, here again the Volga-Don Canal is somewhat
of an artificial replica of the Pleistocene Manych straits (Zenkevitch, 1963) which
also had very close to freshwater salinity values. Some of the faunal movements
into these three seas have been reviewed in a previous paper (Por, 1975a). Suffice
it to say here that in all these cases we are witnessing the advance of a warm and
salt-water faunal element, against a cold-water low salinity element: briefly, an
advance of an interglacial fauna. In the case of the landlocked Caspian Sea, the
Volga-Don Canal supplied an artificial waterway for a faunal progress for which
the potential prerequisites were there.
The same happened in the case of the Suez Canal: it enabled the entrance of a
subtropical interglacial faunal element into the Levant Basin which was isolated
from any other supply of warmwater fauna. The Lessepsian migration has
reached its impressive and unique dimensions only since it is a replica of natural
phenomena, an artifact which was unknowingly made in the right place and at the
right time.
Much has been written and discussed recently on the ecological impact of a
projected sea-Ievel Panama Canal-enabling free intermixing of the Atlantic and
Pacific waters. The scientific community was justly alarmed by the possible uncontrolled changes which would occur at both ends because of the penetration of
new species. What was especially alarming was the fact that, on one hand, the
fisheries (fish and shrimp) on both sides of the Isthmus could have been deleteriously influenced and that current knowledge on the marine biota of both coasts
was extremely poor. Previsions ranged, therefore, from catastrophic (Briggs, 1969)
to less worried, but by and large, scientists admitted the possibility of harmful
effects. These focused almost exclusively on the possible penetration into the
Caribbean of the poisonous sea-snake (Pelamys platurus) and the coral devouring crown-of-thorns sea star (Acanthaster plan ci) (Rubinoff, 1968; 1970; Topp,
1969, etc.). In 1969, the American National Academy of Sciences appointed a
Committee of Ecological Research for the Interoceanic Canal (CERIC). The recommendations ofthis Committee were summarized by Newman (1972). The need
for detailed surveying and investigation of die biota on both sides of the Isthmus
has been urged, in order to minimize the potential threats. CERIC considered
The Migrant Biota
opportunities for passive transport. However, the Panama Canal has existed
hardly more than half a century while the classical Suez waterway has existed for
centuries. Comparing it with the Panama freshwater canal it appears reasonable
to assume that among the species which are suspected to be "Pre-Lessepsian"
migrants there may be some extremely euryhaline species, still confined to the
Isthmus and its immediate surroundings, as weIl as several passively transported
species, as in the case of the Panama Canal.
There is a last group of phenomena to which it is interesting to compare
Lessepsian migration: these are the faunal movements into the Baltic Sea, the
Black Sea and the Caspian Sea, movements which started several thousand years
ago and are still going on. In the case of the first two seas these are natural
contacts with the adjacent sea; however, these natural contacts are by means of
narrow and shallow straits perfectly comparable to the Suez Canal. In the case of
the Caspian Sea, the new contact with the Black Sea is through an artificial
freshwater passageway. However, here again the Volga-Don Canal is somewhat
of an artificial replica of the Pleistocene Manych straits (Zenkevitch, 1963) which
also had very close to freshwater salinity values. Some of the faunal movements
into these three seas have been reviewed in a previous paper (Por, 1975a). Suffice
it to say here that in all these cases we are witnessing the advance of a warm and
salt-water faunal element, against a cold-water low salinity element: briefly, an
advance of an interglacial fauna. In the case of the landlocked Caspian Sea, the
Volga-Don Canal supplied an artificial waterway for a faunal progress for which
the potential prerequisites were there.
The same happened in the case of the Suez Canal: it enabled the entrance of a
subtropical interglacial faunal element into the Levant Basin which was isolated
from any other supply of warmwater fauna. The Lessepsian migration has
reached its impressive and unique dimensions only since it is a replica of natural
phenomena, an artifact which was unknowingly made in the right place and at the
right time.
Much has been written and discussed recently on the ecological impact of a
projected sea-Ievel Panama Canal-enabling free intermixing of the Atlantic and
Pacific waters. The scientific community was justly alarmed by the possible uncontrolled changes which would occur at both ends because of the penetration of
new species. What was especially alarming was the fact that, on one hand, the
fisheries (fish and shrimp) on both sides of the Isthmus could have been deleteriously influenced and that current knowledge on the marine biota of both coasts
was extremely poor. Previsions ranged, therefore, from catastrophic (Briggs, 1969)
to less worried, but by and large, scientists admitted the possibility of harmful
effects. These focused almost exclusively on the possible penetration into the
Caribbean of the poisonous sea-snake (Pelamys platurus) and the coral devouring crown-of-thorns sea star (Acanthaster plan ci) (Rubinoff, 1968; 1970; Topp,
1969, etc.). In 1969, the American National Academy of Sciences appointed a
Committee of Ecological Research for the Interoceanic Canal (CERIC). The recommendations ofthis Committee were summarized by Newman (1972). The need
for detailed surveying and investigation of die biota on both sides of the Isthmus
has been urged, in order to minimize the potential threats. CERIC considered