Zoogeography of the Fishes of the Indian Ocean
463
(COHEN, 1966); 4, in 3 genera are South African; 2, in 2 genera, are Australian; neither
the same species nor genera are found in both areas.
The small tidepool fishes of the family Clinidae are particularly abundant in South
Africa and their distribution has been studied by PENRITH (1970) who found 28 species.
None of these is conspecific or congeneric with the handful of species recorded from
western Australia (MILWARD, 1967).
IV. Conclusions
The data given above for Indian Ocean shore and benthic deep-sea fishes generally
confirm statements by MYERS; there is a large element of the fauna that is widespread in
the Indo-Pacific. Furthermore, the Indian Ocean itself does not appear to be a natural
zoogeographic unit, as there are very few species found both in the western and eastern
parts that do not live in the Pacific. There are, however, some distinct areas of endemism,
certainly the Red Sea and the western Indian Ocean. Regarding the latter, although I have
presented no documentation, it seems probable that the Arabian Sea and the southwestern part of the Indian Ocean are local centers. The eastern Indian Ocean fauna
probably is best considered as part of the fauna of the western Pacific, as there are few
species in the eastern Indian Ocean that are not shared.
It is generally accepted that the Indo-Australian region has the greatest number of
shallow water species, and with this I agree. Furthermore, it has been postulated that the
number of species decreases in a gradient to the west (see for example TALBOT, 1970).
However, the limited data that I have compiled above does not substantiate such a
decrease. For the groups covered we find 91 species in the eastern Indian Ocean and
91 in the western Indian Ocean. True, there are only 30 in the Red Sea, but special
reasons may exist to explain this situation.
For pelagic fishes, more widespread species seem to be the rule, although exceptions
do exist. At least some of the deep-water species are distributed roughly according to
water mass distribution.
Few reliable data exist on which to assess distributional patterns of temperate water
shore fishes, but there seem to be few, if any, widely distributed species.
There are no well-documented quantitative studies on the characterization and
distribution of species complexes, although RASS (1965) has given preliminary qualitative
data on assemblages of commercially useful fishes, and HIDA and PEREYRA (1966) have
discussed trawl catches at the family level. Although regional guides for identification
are available, thorough and well-documented world-wide taxonomic revisions are much
needed for such commercially important groups as the clupeoids, flatfishes, sciaenids,
lutjanids, lethrinids, sparids and serranids, to name but a few. Until adequate classifications are available, it will be difficult to properly characterize species complexes or study
their distribution.
463
(COHEN, 1966); 4, in 3 genera are South African; 2, in 2 genera, are Australian; neither
the same species nor genera are found in both areas.
The small tidepool fishes of the family Clinidae are particularly abundant in South
Africa and their distribution has been studied by PENRITH (1970) who found 28 species.
None of these is conspecific or congeneric with the handful of species recorded from
western Australia (MILWARD, 1967).
IV. Conclusions
The data given above for Indian Ocean shore and benthic deep-sea fishes generally
confirm statements by MYERS; there is a large element of the fauna that is widespread in
the Indo-Pacific. Furthermore, the Indian Ocean itself does not appear to be a natural
zoogeographic unit, as there are very few species found both in the western and eastern
parts that do not live in the Pacific. There are, however, some distinct areas of endemism,
certainly the Red Sea and the western Indian Ocean. Regarding the latter, although I have
presented no documentation, it seems probable that the Arabian Sea and the southwestern part of the Indian Ocean are local centers. The eastern Indian Ocean fauna
probably is best considered as part of the fauna of the western Pacific, as there are few
species in the eastern Indian Ocean that are not shared.
It is generally accepted that the Indo-Australian region has the greatest number of
shallow water species, and with this I agree. Furthermore, it has been postulated that the
number of species decreases in a gradient to the west (see for example TALBOT, 1970).
However, the limited data that I have compiled above does not substantiate such a
decrease. For the groups covered we find 91 species in the eastern Indian Ocean and
91 in the western Indian Ocean. True, there are only 30 in the Red Sea, but special
reasons may exist to explain this situation.
For pelagic fishes, more widespread species seem to be the rule, although exceptions
do exist. At least some of the deep-water species are distributed roughly according to
water mass distribution.
Few reliable data exist on which to assess distributional patterns of temperate water
shore fishes, but there seem to be few, if any, widely distributed species.
There are no well-documented quantitative studies on the characterization and
distribution of species complexes, although RASS (1965) has given preliminary qualitative
data on assemblages of commercially useful fishes, and HIDA and PEREYRA (1966) have
discussed trawl catches at the family level. Although regional guides for identification
are available, thorough and well-documented world-wide taxonomic revisions are much
needed for such commercially important groups as the clupeoids, flatfishes, sciaenids,
lutjanids, lethrinids, sparids and serranids, to name but a few. Until adequate classifications are available, it will be difficult to properly characterize species complexes or study
their distribution.