The Distribution and Abundance of Zooplankton during Postmonsoon and Premonsoon Periods 269
most abundant in the slope water region at all stations except station 62/4, and in March
in the western sector near Astola Island where a reduced surface isothermal layer was
present. An almost similar picture was obtained for Euchaeta wolfendeni except that
numbers were much less than of P. indica.
The distribution of Sagitta decipiens is shown in Fig. 16. This species is essentially
mesopelagic and is reported in the Indian Ocean below 200 m (ALVARINO, 1965; RAo
and GANAPATI, 1958). Large concentrations of this species were found during November
•
PAKISTAN
D
nmriM
• ..
D •
•
ARABIAN
SEA
0 1
" \ ' .,
o '
/"-;' 0 "
, 6 . , "J ' . "
. ./ " \
. . . . ~/ :!, . ~
"'.
. (,~
• :1
"
o
•
100-299 No per m2
• ... • 1- 99 1
•
300-499
'
•
~500
E
Fig. 16. Distribution and numerical abundance of Sagitta decipiens (cruise I - IV and "Machera"
cruise)
along the continental margin as well as in the area of the Swatch, even at the shallow
(21 m) station 64112 where the bottom temperature was 23.9° C. It was probably
transported by ascent of oceanic water into the shallow region of the shelf. This species
and the others referred to above seem to provide biological evidence of subsurface water
upwelling in the area.
III. Discussion
The observations reported in this paper for the area adjoining the coast of Pakistan
are confined to the postmonsoon (October through December) and premonsoon (March)
most abundant in the slope water region at all stations except station 62/4, and in March
in the western sector near Astola Island where a reduced surface isothermal layer was
present. An almost similar picture was obtained for Euchaeta wolfendeni except that
numbers were much less than of P. indica.
The distribution of Sagitta decipiens is shown in Fig. 16. This species is essentially
mesopelagic and is reported in the Indian Ocean below 200 m (ALVARINO, 1965; RAo
and GANAPATI, 1958). Large concentrations of this species were found during November
•
PAKISTAN
D
nmriM
• ..
D •
•
ARABIAN
SEA
0 1
" \ ' .,
o '
/"-;' 0 "
, 6 . , "J ' . "
. ./ " \
. . . . ~/ :!, . ~
"'.
. (,~
• :1
"
o
•
100-299 No per m2
• ... • 1- 99 1
•
300-499
'
•
~500
E
Fig. 16. Distribution and numerical abundance of Sagitta decipiens (cruise I - IV and "Machera"
cruise)
along the continental margin as well as in the area of the Swatch, even at the shallow
(21 m) station 64112 where the bottom temperature was 23.9° C. It was probably
transported by ascent of oceanic water into the shallow region of the shelf. This species
and the others referred to above seem to provide biological evidence of subsurface water
upwelling in the area.
III. Discussion
The observations reported in this paper for the area adjoining the coast of Pakistan
are confined to the postmonsoon (October through December) and premonsoon (March)