Materials and methods
Publications recording the presence of introduced species along the Mediterranean coast
of Israel were re-examined, validated, expanded to capture both previously overlooked
records and recently published ones (to June, 2022), while some records were deleted
following reevaluation). With the exception of documented intentional introductions,
the means and route of introduction are seldom known from direct evidence. These are
inferred from the biology and ecology of the species, the habitats and locales it occupies
in both native and introduced ranges, and its pattern of dispersal. The Suez Canal is
recognized both as a pathway, through which biota may cross naturally, and a corridor
for shipping-introduced biota. We document the spread of Erythraean aliens to regions
within the Mediterranean Sea. It is recognized that data varies greatly, and even better
studied regions experience geographic, temporal and taxonomical lacunae.
Results
A total of 440 multicellular species were recorded thus far off the Israeli coast, more
than anywhere in the Mediterranean Sea (Galil et al., 2021), and when reckoned per
coastline length the number is of calamitous proportions. The cumulative number of
recorded introductions has been rising inexorably, the number tripled between 1970
(147 species) and 2022 (440 species). The most speciose taxa are molluscs, fish,
crustaceans comprising 35%, 22%, 14%, respectively. The rate of reporting new records
varied among taxa, reflecting the temporal irregularity of research efforts and dearth of
expertise. The overwhelming majority of Israeli and Levanitine introductions are
considered to have been entered through the Suez Canal. The geographic spread pattern
of the Erythraean molluscs, fish and crustaceans is roughly similar: their number decline
with distance. This pattern is amplified among these species which populations along
the Israeli coastline are ‘common’ and ‘abundant’: larger populations ensure higher
percentage of successful establishement. Examination of the major taxa of Erythraean
aliens reveals a distinctive pattern: a high percentage of species recorded before 1960
have established large populations, whereas, for species recorded in the past three
decades, rare species, or those known from single records, comprise an important
portion. The geographic spread pattern of the major taxa of Erythraean aliens reveals a
distinct temporal pattern as well. A high percentage of species recorded in the Southeast
Levant before 1960 have spread westwards in the Mediterranean Sea (e.g., 84%, 32% in
the Greater Levant and Central Mediterranean, respectively). For species recorded in the
past three decades the percentages are distinctly lower (51%, 18%, respectively, despite
the great enlargement of the Suez Canal and the rising sea water temperature in the
Mediterranean Sea during this time period. It has long been assumed that populations of
Erythraean aliens will be restricted to the upper shelf as the shallow depth of the Suez
Canal would exclude deeper living organisms. Indeed, until the 1980s Erythraean biota
along the Israeli shelf, with few exceptions, was confined to habitats shallower than 50
m. But post-millenium, Erythraean species, some newly arrived, some long-established,
were collected on the Levantine lower shelf and upper slope: Erythraean fish and a
brachyuran crustacean were collected beyond the shelf edge (Innocenti et al., 2017;
Galil et al., 2019). The occurrence of aggressive, carnivorous and highly fecund lionfish
Pterois miles and swimming crab Charybdis longicollis in mesophotic habitats likely
interferes with the native biodiversity of these sensitive and geographically
circumscribed communities.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
35
Publications recording the presence of introduced species along the Mediterranean coast
of Israel were re-examined, validated, expanded to capture both previously overlooked
records and recently published ones (to June, 2022), while some records were deleted
following reevaluation). With the exception of documented intentional introductions,
the means and route of introduction are seldom known from direct evidence. These are
inferred from the biology and ecology of the species, the habitats and locales it occupies
in both native and introduced ranges, and its pattern of dispersal. The Suez Canal is
recognized both as a pathway, through which biota may cross naturally, and a corridor
for shipping-introduced biota. We document the spread of Erythraean aliens to regions
within the Mediterranean Sea. It is recognized that data varies greatly, and even better
studied regions experience geographic, temporal and taxonomical lacunae.
Results
A total of 440 multicellular species were recorded thus far off the Israeli coast, more
than anywhere in the Mediterranean Sea (Galil et al., 2021), and when reckoned per
coastline length the number is of calamitous proportions. The cumulative number of
recorded introductions has been rising inexorably, the number tripled between 1970
(147 species) and 2022 (440 species). The most speciose taxa are molluscs, fish,
crustaceans comprising 35%, 22%, 14%, respectively. The rate of reporting new records
varied among taxa, reflecting the temporal irregularity of research efforts and dearth of
expertise. The overwhelming majority of Israeli and Levanitine introductions are
considered to have been entered through the Suez Canal. The geographic spread pattern
of the Erythraean molluscs, fish and crustaceans is roughly similar: their number decline
with distance. This pattern is amplified among these species which populations along
the Israeli coastline are ‘common’ and ‘abundant’: larger populations ensure higher
percentage of successful establishement. Examination of the major taxa of Erythraean
aliens reveals a distinctive pattern: a high percentage of species recorded before 1960
have established large populations, whereas, for species recorded in the past three
decades, rare species, or those known from single records, comprise an important
portion. The geographic spread pattern of the major taxa of Erythraean aliens reveals a
distinct temporal pattern as well. A high percentage of species recorded in the Southeast
Levant before 1960 have spread westwards in the Mediterranean Sea (e.g., 84%, 32% in
the Greater Levant and Central Mediterranean, respectively). For species recorded in the
past three decades the percentages are distinctly lower (51%, 18%, respectively, despite
the great enlargement of the Suez Canal and the rising sea water temperature in the
Mediterranean Sea during this time period. It has long been assumed that populations of
Erythraean aliens will be restricted to the upper shelf as the shallow depth of the Suez
Canal would exclude deeper living organisms. Indeed, until the 1980s Erythraean biota
along the Israeli shelf, with few exceptions, was confined to habitats shallower than 50
m. But post-millenium, Erythraean species, some newly arrived, some long-established,
were collected on the Levantine lower shelf and upper slope: Erythraean fish and a
brachyuran crustacean were collected beyond the shelf edge (Innocenti et al., 2017;
Galil et al., 2019). The occurrence of aggressive, carnivorous and highly fecund lionfish
Pterois miles and swimming crab Charybdis longicollis in mesophotic habitats likely
interferes with the native biodiversity of these sensitive and geographically
circumscribed communities.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
35