462
D. M. COHEN:
Stomiatoids are predatory bathypelagic fishes averaging about 20 cm in length. Two
species of Chauliodus are found in the Indian Ocean; 1, which is worldwide, lives in
the central water mass and in equatorial water as well, but only to about 10 0 N, where
it is replaced by a second species which is endemic to the Arabian Sea and Bay of Bengal.
GIBBS and HURWITZ (1967) find the distribution of the second species correlated with an
oxygen poor layer, high productivity at relatively shallow depths and the influence of
warm, high-salinity water from Red Sea and Persian Gulf. A somewhat similar situation
has been reported by GOODYEAR and GIBBS (1969) for 2 species of Astronesthes. Both
live in the equatorial water mass of the Indian Ocean; however, 1 which is found in the
south part lives also in the Pacific; the other, an endemic, is distributed in the Arabian
Sea and Bay of Bengal. The authors suggest that oxygen is a determining factor. The
genus Stomias has 4 Indian Ocean species, all of which are found in other oceans. Two
species are typically taken in equatorial and 1 in central water; another is characteristic
of the region of the subtropical convergence. A unique convergence stomiatoid fauna
has been suggested by GIBBS (1969), which is similar in concept to the postulated ecotone
fauna inhabiting the boundary between north central and subarctic water in the North
Pacific (BEKLEMISHEV and PARIN, 1960).
For deep-water pelagic fishes the boundaries of temperature-salinity defined water
masses appear to function as boundaries for some but not all species.
Family Myctophidae, the lanternfishes, is the largest family of oceanic fishes with
300 to 500 species found around the world. Apparently most species perform diel vertical
migrations which may place a population in one water mass at night and in a different
one during the day. I have examined the areal distribution of 50 species, most of which
are not restricted to the Indian Ocean, based on data from taxonomic papers by BEKKER
(1964) and NAFPAKTITIS and NAFPAKTITIS (1969) on part of the Indian Ocean fauna.
Eighteen species appear to live in the region of the equatorial water mass; 8 are found in
equatorial and central water areas; 6 are in the central water area; 11 live in the central
and subantarctic regions; 5 are restricted to the subantarctic; and 2 are latitudinally
widespread, living from the Arabian Sea to the subantarctic. Approximately 42% of the
species of lanternfishes probably transcend water mass boundaries. Whatever the reason,
however, latitude does demark myctophid ranges in the Indian Ocean.
6. Temperate Shore
The temperate-water shore fauna of South Africa and southwest Australia are quite
distinct from their northern tropical neighbors and probably from each other as well,
although some common genera are present. In general, the cool-water Indian Ocean fishes
of South Africa are part of a fauna that extends north along the Atlantic coast of Africa
to southern Angola. The western Australian cool-water fishes are part of a fauna that
ranges along the south coast of Australia to Tasmania and New Zealand. The South
African fauna is fairly well known; the Australian one is so poorly studied and described
that few precise comparisons are possible.
Several groups of shorefishes can be mentioned. Of the temperate Indian Ocean gobiesocids, 4 species in as many genera are known from South Africa; 2 species in 2 genera
are cool-water Australian; no species but 1 genus is common to both regions (BRIGGS,
1955). A similar pattern is present in the 6 species of shallow-water viviparous ophidioids
D. M. COHEN:
Stomiatoids are predatory bathypelagic fishes averaging about 20 cm in length. Two
species of Chauliodus are found in the Indian Ocean; 1, which is worldwide, lives in
the central water mass and in equatorial water as well, but only to about 10 0 N, where
it is replaced by a second species which is endemic to the Arabian Sea and Bay of Bengal.
GIBBS and HURWITZ (1967) find the distribution of the second species correlated with an
oxygen poor layer, high productivity at relatively shallow depths and the influence of
warm, high-salinity water from Red Sea and Persian Gulf. A somewhat similar situation
has been reported by GOODYEAR and GIBBS (1969) for 2 species of Astronesthes. Both
live in the equatorial water mass of the Indian Ocean; however, 1 which is found in the
south part lives also in the Pacific; the other, an endemic, is distributed in the Arabian
Sea and Bay of Bengal. The authors suggest that oxygen is a determining factor. The
genus Stomias has 4 Indian Ocean species, all of which are found in other oceans. Two
species are typically taken in equatorial and 1 in central water; another is characteristic
of the region of the subtropical convergence. A unique convergence stomiatoid fauna
has been suggested by GIBBS (1969), which is similar in concept to the postulated ecotone
fauna inhabiting the boundary between north central and subarctic water in the North
Pacific (BEKLEMISHEV and PARIN, 1960).
For deep-water pelagic fishes the boundaries of temperature-salinity defined water
masses appear to function as boundaries for some but not all species.
Family Myctophidae, the lanternfishes, is the largest family of oceanic fishes with
300 to 500 species found around the world. Apparently most species perform diel vertical
migrations which may place a population in one water mass at night and in a different
one during the day. I have examined the areal distribution of 50 species, most of which
are not restricted to the Indian Ocean, based on data from taxonomic papers by BEKKER
(1964) and NAFPAKTITIS and NAFPAKTITIS (1969) on part of the Indian Ocean fauna.
Eighteen species appear to live in the region of the equatorial water mass; 8 are found in
equatorial and central water areas; 6 are in the central water area; 11 live in the central
and subantarctic regions; 5 are restricted to the subantarctic; and 2 are latitudinally
widespread, living from the Arabian Sea to the subantarctic. Approximately 42% of the
species of lanternfishes probably transcend water mass boundaries. Whatever the reason,
however, latitude does demark myctophid ranges in the Indian Ocean.
6. Temperate Shore
The temperate-water shore fauna of South Africa and southwest Australia are quite
distinct from their northern tropical neighbors and probably from each other as well,
although some common genera are present. In general, the cool-water Indian Ocean fishes
of South Africa are part of a fauna that extends north along the Atlantic coast of Africa
to southern Angola. The western Australian cool-water fishes are part of a fauna that
ranges along the south coast of Australia to Tasmania and New Zealand. The South
African fauna is fairly well known; the Australian one is so poorly studied and described
that few precise comparisons are possible.
Several groups of shorefishes can be mentioned. Of the temperate Indian Ocean gobiesocids, 4 species in as many genera are known from South Africa; 2 species in 2 genera
are cool-water Australian; no species but 1 genus is common to both regions (BRIGGS,
1955). A similar pattern is present in the 6 species of shallow-water viviparous ophidioids