5.4
Fish Ecology of the Red Sea and Persian Gulf*
H. STEINITZ
Among the important factors of Red Sea and Persian Gulf ecology are the following:
A. The Red Sea is a deep basin with warm surface-to-bottom water; it has an
extremely shallow sill at the narrow southern entrance allowing very little exchange
of water and creating, therefore, a largely separate water body; its geographical position
and extension cause in a northward direction a declining temperature and an ascending
salinity gradient in the surface water.
B. The Persian Gulf is a shallow basin with no sill separating it from the open ocean;
it has high temperature maxima and high salinities, but no prominent gradients have
been observed.
Neither sea has been thoroughly explored biologically, and certainly not with regard to
fishes, but the Persian Gulf even less than the Red Sea. Consequently, it is difficult to
compare the ecological characterization of their respective fish faunas. Nonetheless, it
can be said that the Persian Gulf is probably considerably poorer in fish species than
the Red Rea. What is certain is that bathypelagic and abyssal species are (largely or
completely) absent and endemic littoral species, if they exist at all, are much less numerous
than in the Red Sea. The Red Sea, on the other hand, has bathypelagic as well as abyssal
fish which are, however, adapted to warm-water conditions.
Among the littoral fishes (the largest eco-group of fishes in the Indian Ocean), the
coral fishes play a central role. The endemics of the Red Sea are found among these.
The coral fishes seem to be poorly represented in the Persian Gulf.
From the point of view of productivity, the Red Sea falls into 2 parts with the dividing
line between the richer south and the poorer north at about 20
0
N. Phytoplankton and
associated flora, the basic links of food chains, are more amply developed in the south.
The higher yield of fishes corresponds with old and new records of observations. There
are more sharks, more turtles, more sea birds and more porpoises in the southern areas
of the Red Sea than in its north.
The Red Sea seems to promote speciation tendencies in numerous invertebrate groups
and fish. But much more data than we have at present, and a critical evaluation of these
data, are required to conform this conclusion. One of the urgent problems of future
research is to explain how the interplay of environmental parameters accelerates intrinsic
speciation tendencies. Temperature (possibly combined with salinity) may be one of the
chief factors influencing the fauna in the Red Sea. The temperature gradient of the
littoral waters, which ascends along the coast line of the Red Sea, turns these waters
into an ideal natural laboratory; it could be studied extensively to supplement the field
* Abstract of the paper delivered by the late Prof. H. STEINITZ at the Kiel Symposium.
Fish Ecology of the Red Sea and Persian Gulf*
H. STEINITZ
Among the important factors of Red Sea and Persian Gulf ecology are the following:
A. The Red Sea is a deep basin with warm surface-to-bottom water; it has an
extremely shallow sill at the narrow southern entrance allowing very little exchange
of water and creating, therefore, a largely separate water body; its geographical position
and extension cause in a northward direction a declining temperature and an ascending
salinity gradient in the surface water.
B. The Persian Gulf is a shallow basin with no sill separating it from the open ocean;
it has high temperature maxima and high salinities, but no prominent gradients have
been observed.
Neither sea has been thoroughly explored biologically, and certainly not with regard to
fishes, but the Persian Gulf even less than the Red Sea. Consequently, it is difficult to
compare the ecological characterization of their respective fish faunas. Nonetheless, it
can be said that the Persian Gulf is probably considerably poorer in fish species than
the Red Rea. What is certain is that bathypelagic and abyssal species are (largely or
completely) absent and endemic littoral species, if they exist at all, are much less numerous
than in the Red Sea. The Red Sea, on the other hand, has bathypelagic as well as abyssal
fish which are, however, adapted to warm-water conditions.
Among the littoral fishes (the largest eco-group of fishes in the Indian Ocean), the
coral fishes play a central role. The endemics of the Red Sea are found among these.
The coral fishes seem to be poorly represented in the Persian Gulf.
From the point of view of productivity, the Red Sea falls into 2 parts with the dividing
line between the richer south and the poorer north at about 20
0
N. Phytoplankton and
associated flora, the basic links of food chains, are more amply developed in the south.
The higher yield of fishes corresponds with old and new records of observations. There
are more sharks, more turtles, more sea birds and more porpoises in the southern areas
of the Red Sea than in its north.
The Red Sea seems to promote speciation tendencies in numerous invertebrate groups
and fish. But much more data than we have at present, and a critical evaluation of these
data, are required to conform this conclusion. One of the urgent problems of future
research is to explain how the interplay of environmental parameters accelerates intrinsic
speciation tendencies. Temperature (possibly combined with salinity) may be one of the
chief factors influencing the fauna in the Red Sea. The temperature gradient of the
littoral waters, which ascends along the coast line of the Red Sea, turns these waters
into an ideal natural laboratory; it could be studied extensively to supplement the field
* Abstract of the paper delivered by the late Prof. H. STEINITZ at the Kiel Symposium.