DEMERSAL FISH RESOURCES RESULT OF MV . SEAFDEC 2 SURVEY IN THE SOUTH CHINA SEA OF INDONESIA Wudiantol

The South China Sea is belonging to western part of Sunda shelf which consisted of shallow water in the southern part and deep water in the northern part area. The area of Indonesian water in the South China Sea is estimated 595,000 km2 including exclusive economic zone waters. Some fisheries activities are concentrated in coastal area especially to exploit small pelagic and demersal fish. During 2005 to 2006, a survey on estimation of demersal fish resources has been conducted in the South China Sea by using MV. SEAFDEC 2. These surveys are a collaboration research between Research Center for Capture Fisheries-lndonesia and SEAFDEC. Bottom trawl net was used as sampling equipment and swept area method was applied for estimation demersal fish abundance. During 2005, survey was carried out in the southern part area composting of 20 trawl stations which onetrawl stationwasfails.Thecatchrateswerevariedbetweenll .27 and 131.6kgperhour. In2006, the location of survey shifted to the northern part area composting of 11 trawl stations. The catch rate in this cruise was found higher than that of the 2005 cruise. The lowest catch rate recorded was 37.79 kg per hour and the highest one was 507.71 kg per hour. The catch composition caught during both cruises was dominated by demersal fish species such as Lutjanidae, Ariidae, Nemipteridae, Synodontidae, Priacanthidae, and Mullidae.


INTRODUCTION
The South China Sea is a continental shelf belongs tothewestern partof the Sunda Shelf with theaverage depth of 70 m, flat bottom, and with stratification of water mass by seasons (Wyrtki, 1961).As part of the Sunda Shelf, the South China Sea is shallows water and has no plain base topography, so it is not enable to divide the column waters according to the depth.The area of South China Sea belong to lndonesia is estimated 595,000 km2 (South China   Sea, 1979;Cholik ef a/., 1995).
Recently, the development of fisheries resources exploitation leads to a competition, since the hitech vessels allowed to operate in the Indonesian exclusive economic zone of South China Sea, whereas the fisheries activities are concentrated in the coastal area and in surrounding waters of several small islands.
Consequently, both fishing pressure and competition among fishers forthe resource in the area will increase and may accelerate conflicts among them.
were dominated by small pelagic fish resources which were exploited by purse seine fishery.The contribution of the pelagic catch is approximately at around 45o/o of total landed (Anon., 2002).A previous acoustic study carried out by Johanesson & Mitson (1985)   showed that the estimated densities as an indicator of abundance fluctuated by the season.

Recent study based on landing sites around South
China Sea on all groups of demersal, small pelagic and crustacean species and estimated trough surplus production models showed that the resources has already heavily exploited (Anon., 2006).To clarify and updating these phenomenon as a part of national program on fish stock assessment, the information seems to be reevaluated through in situ on board observation.The recent and modern research equipment installed on M. V. SEAFDEC 2 was available to be used as a platform on this program.This paper presented the demersalfish resources as results of M. V. SEAFDEC 2 survey which were conducted in 2005 and 2006.The global environmental condition in this area is The objectives of this study were as follows 1) to governed by monsoonalchanges.Previous research identify tf," Oi.trinrtion and abundance of demersal carried out in 1978, 1985, 1994, and 2002 showed fisfr resourcesi 2) to identify the catch composition of that the fish resources consrsted of typical tropicat ;;il*"; fish; and 3) to observe some biotogical shallow oceanic waters species i.e. demersalr,s,lall ;;r;;;i;r of some demersat fish with emphasize on pelagic and shrimp resources.A few existing fishery iir" "f i1, n.Map of survey area by M. V. SEAFDEC 2 in South China Sea, Indonesia, 10 to 23 June '10- 13,2006.

Research Vessel and Equipments
The cruises were carried out using the research vessel M. V. SEAFDEC 2, with specification is a207 gross tonnage, 32.5 m in length, and 7 .2m in wide.
The gearand equipments used were fisheries acoustic instruments, bottom trawlfishing, squid jigging, bongo paired plankton net and oceanographic equipments.
Bottom trawl net of 17.30 m in head rope was used, with mesh size for cod end of 60 mm as shown in Appendix 1.

Methodology
The position of sampling stations were set up systematically along the latitude on the hydro acoustic transect lines.Prior to each trawling station an oceanographic surveywas carried out.ln 2005, a total of 20 trawl fishing, 20 oceanographic sampling stations, and20 larval stations have been completed.
From total of 20 trawling stations, one trawl fishing should be considered unsuccessful due to some technical problems.The otter boards were upside down during the towing of the nets, which resulted in the improper opening at trawl mouth.During 2006 the survey has been carried out on 11 trawling stations, 30 oceanographic stations, and 30 larvae sampling stations.
Trawl net was towed in one hour duration at the vessel speed of 3 knots.Fish catches were sorted and weighted.Sorting of fish were carried outwhenever possible until species level, genus or family (Fisher  & Whitehead,1974; Tarp & Kailola, 1984; Mansoor   Table 1.et at., 1998; Carpenter & Volker,1998, Grey &   Dall,1 983; Holthuis, 1991 ).Catch data in the form of weight and numberwere filled into a fishing log sheet.
The length and weight frequency measurements were done to some relatively dominant species.
Swept area method was applied to estimate demersalfish abundance which is indicated by catch per unit effort (catch per hour trawling) (Shindo , 1973;   Saeger et a\.,1976).

RESULTSAND DISGUSSION Catch Rate
Catch rate cou!d provide as indicator for the index of abundance of fish resources.During cruise 2005, the lowest catch rate of about 11.27 kg per hour was occurred at the station number 7, while the highest catch rate was occurred at the station number 13.The summary of the catch rates during 2005 cruise is presented in Table 1, and the distribution of catch rates are illustrated in Figure 3.
The relatively high variation in catch rate indicate that the distribution of demersal fish resource in this area during the survey periods was somewhat forming cluster.This was likely due to the occurring differences in bottom substrate.In the central area of the southern part of South China Sea, the bottom substrate was dominated by giant cup sponges (Poterion sp.) mix with some life corals.This was indicated by the occurrences of the butterfly fish, Coradion sp. of the fam ily Chaetodontidae.
Summary of the catch rates of demersal fish caught using bottom trawl in the South China Sea-lndonesia, June 13 -July 2,2405  2. Spatial distribution of catch rates are illustrated in Figure 4.
Figure 4 show that the high abundance of fish was found in the southeast part of South China Sea where this area is shallower than the northern part area.

Catch Composition
A total of approximately 149 species of bony fish and elasmobranch, three species of cephalopod, five species of crustacean including shrimp, and lobsters has been recorded.Some fish groups which were considered as trash fish and number of sea snakes were also counted.The dominant fish family caught during 2005 and 2006 cruises are listed in the Table    During 2005 cruise, most of fish caught was dominated by sharks and rays.Within this group the species of Dasyatis kuhlii and Himantura gerrardi provide the most dominant.The second dominant fish groupwas catfish (Ariidae) and snappers (Lutjanidae).
Some of pelag'ic fish of the family Carangidae such as round scad (Decapterus maruadsi and Decapterus akaadsi),yellow strip trevallies (Se/aroides /eptolepis) and big eyed scad (Se/ar chromenopthalmus)were found in a very small quantity.Other pelagic fish such as chub mackerels (Rastrelliger kanagurta) was also found in very small quantity.
Other non fish biota which was caught in substantial quantity was the squids and cuttle fish group.Squids were dominated by Loligo edulis and Loligo srnghalensis, while cuttle fish group by Sepia aculeata.ltwas very few number of penaeid shrimp were caught in this area that are only three specimens of shrimp i. e. endeavour shrimp (Metapenaeus endeavourl), coarse shrimp (Trachypenaeus granulosus and Trachypenaeus asper) were found.
Crustaceans group was dominated by flathead lobster (Thenus oientalis) and two specimens of ornate spiny lobster (Pa n ul iru s orn atu s).
Similar result was also found during 2006 survey as shown in     3. Some of demersalfish caught in smallsizes, this phenomenon indicated that the fish resources have been fully exploited.

ACKNOWLEGMENT
We would like to thank to all the team members of M.
lnd.Fish Res.J. Vol.14 No.2 December-2O)7: 67-74MATERIALS DAN METHODSSurvey Area and CruiseGeographic location of the research area is shown in Figure1for cruise in 2005 and Figure2for cruise in 2006.The main survey area is characterized by inshore and offshore waters.Several small islands with there surrounding area were belonging to untrawlable grounds.The cruises were designed as a standard parallel transect for acoustic and bottom trawl survey.

Figure 1
Figure 1 and2 show that during 2005 survey the site of study located in the southern part area, whereas during 2006 survey the area of study shifted to the northern part area.In 2005 and 2006, the duration of surveywas 20 days (from 12 June to 3 July 2005) and 13 days (from '10 June to 23 June 2006) including bunkering and replenishment, respectively.

Figure 3
Figure 3 Distribution of catch rate (kg per hour) in the survey area during 2005 V. SEAFDEC 2 survey during 2005 and 2006 cruise for helping to collect the data.This survey was conducted based on the research collaboration between Research Center for Capture Fisheries and SEAFDEC.lnd.Fish Res.J. Vol.l4 No.2 December-2008: 67-74 Appendix 1. Design of bottom trawl used for demersal fish sampling tlft; 5l{B Sr4 Ll : (F* {S1O fiL: CSR St* fiL; &rH,h-6lE fr,t;fr; {Sf, *Sanrn 8*: {F|? idtrun MAT n

Table 2 .
1 DE" 'lIu" 70 Distribution of catch rate (kg per hour) in the survey area during 2006

Table 3 .
The dominant fish caught using trawl during survey in 2005 During 2005 survey, the third dominant group i.e.,

Table 5 .
4, the dominant catch were occupied by families of Lutjanidae, Nemipteridae, Priacantidae, Synodontidae, Carangidae, and Total length of some demersal fish during survey in 2005

Table 6 .
Total length of some demersal fish during survey in 2006 A total of 3,188 individual fish from 35 species has been measured.The ten most dominant measured fish are listed in the following Table.

Table 5
and 6 indicated that most of demersal fish species caught by trawl net during those cruises were found in small size.From this phenomenon could roughly conclude that some demersal fish species in the South China Sea were already fully exploited.