Zoogeography of the Fishes of the Indian Ocean
461
pseudoceanic, is characteristically found around islands; another pseudoceanic species
is often found far out at sea. PARIN (1968) also mentions 2 other widely distributed
species the young of which are found at sea among drifting algae.
Genus Sardinella, Family Clupeidae has 15 Indo-Pacific species, of which 12 have
been reported from the Indian Ocean (CHAN, 1965); 11 of these are widespread and
range into the Pacific; 1 is found in the eastern and western Indian Ocean but not in the
Pacific. Although in general Sardinella adults are less oceanic than needlefish adults, the
belonids have a lower proportion of widespread species.
Among the permanent truly oceanic epipelagic fishes PARIN (1968) lists examples of
the larger carcharinid sharks, flying fishes, sauries, tunas, marlins, bramids, stromateoids,
and ocean sunfishes. Most of the species are widely distributed throughout the tropics
and the zoogeographer is less concerned with presence or absence and more with local
centers of abundance, which are often separated in time and space and represent feeding
grounds and breeding areas. This topic will most certainly be covered in greater detail by
other authors and I will not pursue it here at greater length.
5. Deep-water Pelagic
The deep-water pelagic fishes of the Indian Ocean number about 300 species (based
on midwater trawling catches during cruises 3 and 6 or the RV "Anton Bruun" during
the nOEl, many of which appear to be widely distributed. EBELING (1962) and others
have proposed that an important guide to delimiting the distribution patterns of the deep
midwater fauna is the concept of water masses as defined by the relationship between
temperature and salinity. He has surveyed the distribution of 135 species of bathypelagic
fishes throughout the world and finds that species living in the Indian central and Indian
equatorial water masses (combined) have a 45% overlap with the fauna of the South
Atlantic central water and a 75% overlap with the Indonesian fauna. He further states,
"The central water masses of the South Atlantic, Indian Ocean and western South Pacific
resemble each other in the physico-chemical and biological properties and, perhaps,
should· be considered for our purpose as one. All 3 are broadly interconnected, even
around the tip of Africa, and have almost a common bathypelagic fish fauna." It seems
reasonable to conclude from the above that the boundaries between the 3 major Indian
Ocean water masses: equatorial, central and subantarctic (Fig. 1), function as zoogeographic boundaries. The distribution of several groups is examined in light of this idea.
Melamphaids are the only deep-water Indian Ocean fishes for which temperaturesalinity data have been published. For several other groups data is available for areal and
in some instances probable depth distribution, so that a rough attempt can be made to
assign species to water mass.
Family Melarnphaidae is a group of about 35 species of bathypelagic fishes which
average approximately 7 cm in length. Although small, they are apparently actively
swimming predators. Most of the species are widespread in occurrence and some are
found in all 3 oceans. Three recently revised genera, Melamphaes (EBELING, 1962),
Sio (Moss, 1962) and Scopelogadus (EBELING and WEED, 1963) have 11 species or
subspecies in the Indian Ocean, none of which is endemic. Six species appear to have
their centers of abundance in the equatorial water mass; 3 appear to be characteristic of
the central water mass; 1 might be considered to transcend the boundary, and 1 species
lives south of the central water mass in subantarctic water.
461
pseudoceanic, is characteristically found around islands; another pseudoceanic species
is often found far out at sea. PARIN (1968) also mentions 2 other widely distributed
species the young of which are found at sea among drifting algae.
Genus Sardinella, Family Clupeidae has 15 Indo-Pacific species, of which 12 have
been reported from the Indian Ocean (CHAN, 1965); 11 of these are widespread and
range into the Pacific; 1 is found in the eastern and western Indian Ocean but not in the
Pacific. Although in general Sardinella adults are less oceanic than needlefish adults, the
belonids have a lower proportion of widespread species.
Among the permanent truly oceanic epipelagic fishes PARIN (1968) lists examples of
the larger carcharinid sharks, flying fishes, sauries, tunas, marlins, bramids, stromateoids,
and ocean sunfishes. Most of the species are widely distributed throughout the tropics
and the zoogeographer is less concerned with presence or absence and more with local
centers of abundance, which are often separated in time and space and represent feeding
grounds and breeding areas. This topic will most certainly be covered in greater detail by
other authors and I will not pursue it here at greater length.
5. Deep-water Pelagic
The deep-water pelagic fishes of the Indian Ocean number about 300 species (based
on midwater trawling catches during cruises 3 and 6 or the RV "Anton Bruun" during
the nOEl, many of which appear to be widely distributed. EBELING (1962) and others
have proposed that an important guide to delimiting the distribution patterns of the deep
midwater fauna is the concept of water masses as defined by the relationship between
temperature and salinity. He has surveyed the distribution of 135 species of bathypelagic
fishes throughout the world and finds that species living in the Indian central and Indian
equatorial water masses (combined) have a 45% overlap with the fauna of the South
Atlantic central water and a 75% overlap with the Indonesian fauna. He further states,
"The central water masses of the South Atlantic, Indian Ocean and western South Pacific
resemble each other in the physico-chemical and biological properties and, perhaps,
should· be considered for our purpose as one. All 3 are broadly interconnected, even
around the tip of Africa, and have almost a common bathypelagic fish fauna." It seems
reasonable to conclude from the above that the boundaries between the 3 major Indian
Ocean water masses: equatorial, central and subantarctic (Fig. 1), function as zoogeographic boundaries. The distribution of several groups is examined in light of this idea.
Melamphaids are the only deep-water Indian Ocean fishes for which temperaturesalinity data have been published. For several other groups data is available for areal and
in some instances probable depth distribution, so that a rough attempt can be made to
assign species to water mass.
Family Melarnphaidae is a group of about 35 species of bathypelagic fishes which
average approximately 7 cm in length. Although small, they are apparently actively
swimming predators. Most of the species are widespread in occurrence and some are
found in all 3 oceans. Three recently revised genera, Melamphaes (EBELING, 1962),
Sio (Moss, 1962) and Scopelogadus (EBELING and WEED, 1963) have 11 species or
subspecies in the Indian Ocean, none of which is endemic. Six species appear to have
their centers of abundance in the equatorial water mass; 3 appear to be characteristic of
the central water mass; 1 might be considered to transcend the boundary, and 1 species
lives south of the central water mass in subantarctic water.