SEA FD E C /SC S. 73: S-31
R esearch o n D em ersal F ishes on th e C o n tin en tal Slope in th e N o rth e rn P art o f th e S o u th C hina Sea
T he cruise resu lt o f R /V K A IY O -M A R U b y
T suneo A o yam a
Seikai R egional Fisheries R esearch L ab o rato ry Nagasaki, Jap an
1. IN T R O D U C T IO N
D uring th e p erio d fro m M ay 16 th ro u g h J u n e 2, 1971, th e research cruise fo r th e tra w l fishing gro u n d w as carried o u t b y R /V K aiyo-m aru (2 5 3 9 G T) o f th e Japanese F isheries A gency in th e n o rth e rn area o f th e S o u th C hina Sea b e tw e e n th e m argin o f m ain lan d C hina c o n tin e n ta l sh elf and c o n tin e n ta l slope. E x p erim e n ta l traw l fishing o p e ra tio n w as d o n e 33 tim es, an d th re e ocean o g rap h ic o b serv atio n lines vertical to th e co astal line. T h o u g h th is cruise w as d o n e ra th e r o n a sm all scale, th e resu lt m ight have som e valuable suggestions fo r th e f u tu re o p era tio n s o f trawling, since th e tra w l o p era tio n s in such area as c o n tin e n ta l slope has b ee n scarce.
T h e areas A, B and C in th e E ast C hina Sea w ere in c lu d ed in th is research cruise f o r tw o p u rp o ses : (1 ) to o b ta in som e id e a o f th e d ifferen ce in sto c k assessm ent b e tw e e n th e s o u th C hina Sea an d th e E ast C hina Sea and (2 ) to co m p are th e fishing efficien cy o f Jap an ese co m m er
cial traw lers.
T he sea d e p th a t th e sta tio n s and n u m b e r o f hauls by area are su m m arized b riefly as follow s:
A rea Sea d e p th N u m b er o f hauls
E ast C hina Sea A 1 0 5 - 1 1 8 3
B 5 3 - 7 6 2
C 94 2 T o ta l 7
S o u th C hina Sea D 8 7 - 1 5 8 8 3 2 0 - 3 2 8 2
6 9 5 - 8 6 0 2 T o ta l 12
E 1 2 0 - 1 5 8 5
1 7 0 - 2 4 0 2 T o ta l 7
F 9 8 - 1 2 7 5
1 6 5 - 1 8 6 2 T o ta l 7
2. R ESU LTS
I) In th e S o u th C hina Sea, th e a m o u n t o f dissolved o x y g en w as less th a n 3.5 m l/ l a t th e d e p th b etw e en 100 an d 150 m e tres an d less th a n 3 .0 m l/ l a t th e d e p th o f m o re th a n 3 0 0 m etres. This suggests th a t th e re w o u ld be less e x p e c ta tio n fo r th e large la te n t fish resources in th e d e p th g re a te r th a n 3 0 0 m e ters w ere com p o sed o f abyssal fish species fo r th e m o st p a rt, in d icatin g th e
sim ilar resu lts a t th e c o n tin e n ta l slope in th e E ast C hina Sea.
2) T o p o g rap h ical survey b y echo so u n d e r ind icates th a t in th e areas D and E th e co n tin e n ta l slope is fairly w eak in g rad ien t and fo rm s tw o o r th re e steps o f deep sea terraces. T h e tra w l fishery w o u ld b e su itab le geographical
ly a t th e fla t p lane p o rtio n , b u t n o t possible a t th e sh o u ld e r p a r t o f te rrac e w here it is fairly ro ck y .
In th e area F , th e to p o g ra p h ic survey show ed ra th e r steep g rad ie n t o f th e slope.
3) A bundance o f th e fish was b est a t th e sh o u ld e r p a rt o f th e c o n tin e n ta l shelf.
4 ) T he catches o f th is cruise was com prised o f larger individuals th a n th o se in th e E ast China Sea. T he fish w ere classified an d to ta le d up to 170 species. T h e m ain fishing resu lts b y area are :
A rea D .... fairly good c a tc h w ith large sized porgy,*
Isaki, ru d d erfish , an d sea bass in th e w a te r shallow er th a n 200 m etres. O n th e c o n tra ry , very p o o r fishing was n o te d in th e d ee p er w aters w ith sm all a m o u n t o f abyssal fish
species.
A rea E ... p o o r fishing w ith sm all am o u n t o f Jap an ese th re a d fin b ream , ru d d erfish , big eye sn ap p er an d sea bass.
A rea F ... P o o r fishing w ith large sized porgy, h airtail, big eye snap p er, N agasaki sn a p p er and lizard fish.
5) T he p ro d u c tiv ity o f th e sea area d ee p er th a n 3 5 0 m etres seem s to b e p o o r, fo r th e follow ing reasons: 1) th e cu rren t is n o t distinguished, 2) th e re is n o stro n g upw elling, 3 ) vertical m ixing in w in te r is w eak, 4 ) th e th e rm o c lin e is developed w ell in general and 5) th e re fo re , th e dissolved o x y g en is very little in c o n te n t. T he ca tc h in th e area w ere abyssal fishes th a t seem to b e n o t valuable com m ercially, only.
In th e area o f 2 0 0 — 350 m etres in d e p th , w e caught som e large size com m ercially im p o rta n t fishes, alth o u g h th e a m o u n t w ere n o t large. As m a n y traces o f fishes w ere observed o n th e echo sounder, it w as su p p o sed th a t th e re
*p o r g y C h r y s o p h r y s m a j o r
i s a k i P a r a p r is tip o m a s p p .
r u d d e r f i s h S e r i o la s p .
s e a b a s s m a n y s p p .
J a p a n e s e t h r e a d f i n b r e a m N e m i p t e r u s sp . b ig e y e s n a p p e r P r ia c a n t h u s sp .
h a i r t a i l T r ic h i u r u s l e p t u r u s
r e d s n a p p e r L u t ja n u s s p p .
N a g a s a k i s n a p p e r P r i s t i p o m o i d e s sp
l iz a r d f is h S a u r id a s p p
99
were considerably large amount of small fishes which might have escaped through mesh of the net (as the stretched mesh size was 90 mm).
Large sized valuable fishes were caught considerably at the area situated near the edge of the continental shelf, the depth of which was shallower than 200 metres.
Especially good catch was encountered at Area D.
The catch per 30 minutes trawling are shown as under:
Area No. of
hauls
Catch per 30 min. haul
in ton.
East China Sea A 3 0.11
B 2 0.09
C 2 0.06
Total 7 0.09
South China Sea D (deep) 9 0.07
D (shallow) 4 0
E (d) 6 0.06
E (s) 1 0.34
F (s) 5 0.06
Sub total (d) 20 0.11
" (s) 5 0.07
Total 25 0.10
The fishing efficiency of the R/V Kaiyo-maru was rather low compared to the Japanese commercial pair trawlers, as shown below: the value of catch per 80 minuts’ trawling which is the standard trawling duration of pair trawlers.
Area
Commercial pair trawler
May 1970 June 1970 Kaiyo-maru
H CPH H CPH H CPH
A 1156 ton
0.30 463 ton
0.30 3 ton
0.26
B 4156 0.32 1853 0.44 2 0.25
C 16 0.37 7 0.32 2 0.15
H, number of hauls; CPH, catch per 80 minutes’ trawling.
THE FISHERIES OCEANOGRAPHY SEAFDEC/SCS.73: S-4
Fishing Condition and its Oceanographic Interpretation in Bottom Long Line Fishing Grounds
by Otohiko Suzuki
Marine Fisheries Research Department Southeast Asian Fisheries Development Center Abstract
During the experimental bottom long line fishing conducted in June and September, 1972, near the Gulf of Thailand and off Kuching, Sarawak respectively, simul
taneous oceanographic surveys were also carried out. The analysis of the data suggested possible relation between oceanographic and fishing conditions. Throughout the two trips it was a common feature that good catches were often obtained near the boundary between the nearshore warm water and the deeper cold water.
Through oceanographical consideration of the data obtained, the following conclusion was deduced. There is a possibility that good fishing grounds are located along the canyon off Kuching throughout all seasons. However, their locations may be altered with the change of oceanographic conditions. In the area off the Gulf of Thailand, good fishing grounds may be formed only in certain specific seasons.
INTRODUCTION
Studies on the feasibility of bottom long lining in the South China Sea were conducted by the research vessels CHANGI in June and September, 1972. One of the two survey cruises was made near the Gulf of Thailand during
17—25 June, and the other off Kuching, Sarawak between 16 and 27 September. Systematic surveys on oceano
graphic condition were also carried out simultaneously with the experimental bottom long line fishing.
The purpose of these studies was to investigate the existence o f possible relationship between oceanographic and fishing conditions.
SURVEYS
During the June trip, the experimental bottom long linings were made at six different locations within the area enclosed by 6°20'N and 8°15'N in latitude, and 102°20'E and 103°45'E in longitude. Except for one operation at the final location, two operations using different types of long line were made repeatedly at each location. The number of units used in each operation ranged from 14 to 21. Twenty oceanographic stations were arranged at almost regular intervals to cover this area, while six other stations outside the area were arranged at intervals of about 30 nautical miles along the east coast of the Malay Peninsula. At each station serial and BT observations were made.
During the trip in September, bottom long line opera- 100
