5. The Distribution and Ecology of Fish Larvae, Fish and Benthic
Organisms
5.1
Kinds and Abundance of Fish Larvae in the Arabian Sea
and the Persian Gulf
W.NELLEN
During cruise I of the RV "Meteor" to the Arabian Sea and the Persian Gulf, fish
larvae were caught routinely from December 1964 to April 1965 (Fig. 1 in BABENERD
et aI., 1973 this volume). Following the ichthyogeographical classification of LAGLER,
BARDACH and MILLER (1967), the zones fished for larvae were: the neritic zone (water
mass over the shelf), the epipelagic zone (oceanic surface water down to 200 m), and the
mesopelagic zone (water between 200 and 1000 m). The larval stages of mesopelagic
fish species are found mainly in the epipelagic zone, therefore faunistic elements of the
third zone were probably over represented.
I. Material and Methods
1. Nets Used
The plankton nets used for these investigations were: 1. Heligoland larvae net (HLN),
mouth opening 144 cm diameter, equivalent to 1.63 m 2 , length of filtering net bag 2.2 m,
2. Ringtrawl net (RT), mouth opening 125 cm in diameter, equivalent to 1.23 m 2 , length
of net bag 4 m, and 3. Vertical Ringtrawl net (VRN), same size as the RT but with a net
bag 6 m long. The VRN, like the HLN, was towed only vertically after all Heligoland
larvae nets had been lost. The filtration efficiency was considered equal to that of the
HLN. The RT was brought down obliquely at a ship's speed of 2 knots and was hauled
in short horizontal steps; these tows were considered as oblique tows. Since the flow
meters did not work well, the amount of water filtered was calculated very roughly
according to ship's speed, time of haul, and size of net. All nets had a mesh aperture
of 500 f.l.
2. Station Work
Generally, one HLN and one RT sample or two HLN samples of different depths were
made at each station. A total of 231 stations (Table 1) were covered with 227 HLN and
99 RT hauls. The standard HLN haul fished the upper 100 m of water; a second HLN
haul at the same station was usually made from a depth of 200 m to the surface. With
the RT, catches were done only down to 40-70 m. The samples were preserved in 4%
formalin buffered with 100 g hexamethylene-tetramine to 1 1 of 40% formalin. Off the
Organisms
5.1
Kinds and Abundance of Fish Larvae in the Arabian Sea
and the Persian Gulf
W.NELLEN
During cruise I of the RV "Meteor" to the Arabian Sea and the Persian Gulf, fish
larvae were caught routinely from December 1964 to April 1965 (Fig. 1 in BABENERD
et aI., 1973 this volume). Following the ichthyogeographical classification of LAGLER,
BARDACH and MILLER (1967), the zones fished for larvae were: the neritic zone (water
mass over the shelf), the epipelagic zone (oceanic surface water down to 200 m), and the
mesopelagic zone (water between 200 and 1000 m). The larval stages of mesopelagic
fish species are found mainly in the epipelagic zone, therefore faunistic elements of the
third zone were probably over represented.
I. Material and Methods
1. Nets Used
The plankton nets used for these investigations were: 1. Heligoland larvae net (HLN),
mouth opening 144 cm diameter, equivalent to 1.63 m 2 , length of filtering net bag 2.2 m,
2. Ringtrawl net (RT), mouth opening 125 cm in diameter, equivalent to 1.23 m 2 , length
of net bag 4 m, and 3. Vertical Ringtrawl net (VRN), same size as the RT but with a net
bag 6 m long. The VRN, like the HLN, was towed only vertically after all Heligoland
larvae nets had been lost. The filtration efficiency was considered equal to that of the
HLN. The RT was brought down obliquely at a ship's speed of 2 knots and was hauled
in short horizontal steps; these tows were considered as oblique tows. Since the flow
meters did not work well, the amount of water filtered was calculated very roughly
according to ship's speed, time of haul, and size of net. All nets had a mesh aperture
of 500 f.l.
2. Station Work
Generally, one HLN and one RT sample or two HLN samples of different depths were
made at each station. A total of 231 stations (Table 1) were covered with 227 HLN and
99 RT hauls. The standard HLN haul fished the upper 100 m of water; a second HLN
haul at the same station was usually made from a depth of 200 m to the surface. With
the RT, catches were done only down to 40-70 m. The samples were preserved in 4%
formalin buffered with 100 g hexamethylene-tetramine to 1 1 of 40% formalin. Off the