The abundance of fisheries resources and their structure off shore of Sarawak, Sabah and Brunei Darussalam were investigated under the SEAFDEC Collaborative Research Survey. Hydro-acoustic surveying by using a scientific echo sounder model FQ-70 was conducted for estimating the fish abundance and biomass. Two survey cruises were carried out by M.V. SEAFDEC during 10 July to 2 August 1996 and 1 to 24 May 1997 for pre and post-northeast monsoon seasons, respectively. The scientific echo-sounder was equipped with an echo-integrator and two quasi-ideal beam transducers with operating frequencies of 50 and 200 kHz. For pre and post-northeast monsoon season was 1,717,852 tons and 956,397 tons, respectively. The maximum fish abundance were found at the water depth between 100 to 200 m was 92.4% and 49.8% of total abundance for pre and post-northeast monsoon season, respectively

Theparoonrat, Yuttana

Southeast Asian Fisheries Development Center, Training Department Institutional Repository

S2/FR3<YUTTANA>-362-Biomass Estimation by Hydro-acoustic Methods in the South China Sea,Area II : Sarawak, Sabah and Brunei Darussalam.Yuttana  TheparoonratTraining Department, Southest Asian Fisheries Development Center.ABSTRACTThe abundance of fisheries resources and their structure off shore of Sarawak, Sabah and BruneiDarussalam were investigated under the SEAFDEC Collaborative Research Survey. Hydro-acousticsurveying by using a scientific echo sounder model FQ-70 was conducted for estimating the fishabundance and biomass. Two survey cruises were carried out by M.V. SEAFDEC during 10 July to 2August 1996 and 1 to 24 May 1997 for pre and post-northeast monsoon seasons, respectively. Thescientific echo-sounder was equipped with an echo-integrator and two quasi-ideal beam transducerswith operating frequencies of 50 and 200 kHz. For pre and post-northeast monsoon season was1,717,852 tons and 956,397 tons, respectively. The maximum fish abundance were found at the waterdepth between 100 to 200 m was 92.4% and 49.8% of total abundance for pre and post-northeastmonsoon season, respectively.Key words: Biomass estimation, Acoustic survey, South China Sea, Sarawak, Sabah, BruneiDarussalam.IntroductionMarine fisheries resources are migrate according to the change of seasonal and maturity state.The abundance estimation of such migratory species are need to design the survey with cover all thatparticular area. Southeast Asian Fisheries Development Center (SEAFDEC) was proposed to conductthe Collaborative Research Survey on the marine fisheries resources and the environmental factors inthe South China Sea of SEAFDEC member country’s waters. Two survey cruise were performed byM.V. SEAFDEC during pre-northeast monsoon season from 10 July to 2 August 1996 and post-northeast monsoon season from 1 to 24 May 1997. The objective of the survey is to estimate theabundance of fisheries resources and their structures at the off shore of Sarawak, Sabah and BruneiDarussalam waters, and to study on the variation of the abundance during pre-northeast monsoon andpost-northeast monsoon season.Materials and MethodsThe survey area was divided into 79 oceanographic survey stations (Fig 1). Each station werelocated at 30 nautical miles apart. The hydro-acoustic survey by using scientific echo-sounder modelFQ- 70 are carried out along the parallel cruise track of 30 nautical mile. Scientific echo-sounder wasequipped with dual frequency by using two quasi-ideal beam transducers with operated on 50 kHzand 200 kHz. This acoustic survey system were equipped with echo integrator, calibration system anddata recorder. The system is designed so that a vast amount of data can be stored onto the floppy diskmemory and processed by the data analyzer. The raw data from Furuno FQ-70 software in form of K3ASCII code are using for the calculation. The volume back scattering strength (SV) of high frequency(200 kHz) was calculated from data recorded from 10 to 200 m.The calibration of FQ-70 is conducted before the survey cruise is performed at the surveystation number 1. M.V. SEAFDEC is anchored at the water depth of 36 meter where the clam sea andweak current of 0.4 knot. The calibration is performed by using standard hydrophone model TW-9103-S attached at 1 meter under the transducer sound beam axis. Both low (50 kHz) and high fre-S2/FR3<YUTTANA>-363-quency (200 Attenuation and Gain, Transmitting Sensitivity of Transducer, and Receiving Sensitivityof Transducer.Hydro-acoustic Data CollectionThe hydro-acoustic data of fish school in the area of Sarawak, Sabah and Brunei Darussalamare recorded by using scientific echo sounder (FQ-70). The data of means volume back scattering wasrecorded by high frequency (200 kHz.) with the transmission rate of 123 ping/min. The ship constantcruising speed is 10 knots. During the survey cruise, the raw data of reflected echo signal from fishschool also recorded on to VHS Video tape for data bank reservation. The processed echo informationfrom echo integrator with the distance interval of 0.1 nautical mile were calculated by echo integratorand data analyzer. The integration of volume back scattering strength (SV) of fish school were calcu-lated from the water depth layer of 10 m to 200 m for 8 integration layers. Two bottom integrationlayers were calculated at 1 m to 5 m to 10 m above the sea bottom. The integrated of SV and densityof fish were recorded on the floppy disk as well as printed out on printer and also plotted on theechogram. The recorded data was recalculation for biomass estimation of fisheries resources and theirdistribution in the survey area. The parameters setting for echo integrator unit are showing below:The Parameter Setting for Echo Integrator UnitRange Sonar parameter1. REC RANGE 0 - 200 m 1. Calculation SV-H SV-L2. LAYER 1 10 - 20 m 2. SL 220.00 215.102 20 - 40 m 3. ME -194.90 -185.603 40 - 60 m 4. Absorption 92.70 9.904 60 - 80 m 5. 10 log y -16.10 -14.505 80 - 100 m 6. AMP Gain 50.30 49.006 100 - 130 m 7. Pulse Length 1.20 1.207 130 - 160 m 8. Sound Velocity 1500.008 160 - 200 m9 B10 -B5 m10 B5 - B1 mCalculation of Volume Back Scattering Strength (SV)The volume back scattering strength (SV) of fish school is obtained from the following equa-tion;SV = 20 log Vsv – (SL + ME) + 20 log r + (2αr/1000) – 10 log ( log (cτ/2) – 10 logψwhereSV : Volume Back scattering Strength, (dB) α : Absorption Coefficient (dB/km)Vsv : Voltage output (Vrms) c : Underwater Sound speed (m/sec)SL : Source Level, (dB) τ : Pulse duration (ms)ME : Receiving Sensitivity, (dB) ψ : Equivalent beam widthS2/FR3<YUTTANA>-364-r : Range of target (m)The scientific echo sounder FQ-70 can be automatically calculated the means volume backscattering strength (SVavg) in particular layer width and log interval of ship cruising. The calculationcan be perform with pre-setting parameter by the following equation;SVavg = ( Σ∆r Σ1 svi)/∆r1where     ∆r   : Layer width 1        :        Log intervalDuring the survey cruise, the layer width and log interval was set at 0.1 nautical mile. Thefish density can be calculated as the following formula;N = 10(SV-BSV)/10where N       :  Density of fish in the integrating layer (n/m3)BSV  :  Back scattering strength of a single fish per unit volume (=TS)The calculation of SV was performed by average the SV from 1st layer with started at 10 mdepth down to 200 m layer. The layer at with sea bottom appear was excluded from the calculation butwill be substituted by two bottom layer of layer 9 and 10Averaging the SV Value in Sections of the Distance RunThe average of SV value in section of distance run can be calculated by using the followingequation :       Σ 10 (svi/10)SVavg:  = 10 log (—-———————)            Kwhere SVavg: SV value after averagingSvi :  SV value of each sectionK :  Number of integral per section of distance runThe integrated average SV from FQ-70 were check and eliminated the high SV value causedby the interference from the ship electronic equipmentBiomass estimationBiomass is defined as the density of fish (Tones per square nautical mile) in the area surveyed,derived from the integrated echoes. The biomass estimation can be perform by using Algebraic Method(Johannesson and Mitson, 1983). The basic principle is schematically illustrated in Fig. 2.  Eachsample observation (ai) is assigned to a corresponding rectangular area, here call “Elementary Statis-tical Sampling Rectangle” (ESSR). For a parallel survey grid with equidistant inter-transect spacing(Dt) (30 nautical mile) all ESSR’s will  have equal area sizes given byESSR = Dt x (ESDU) mile2where ESDU is the selected “Elementary Sampling Distance Unit”. When the inter-transect spacingequal one ESDU, it follow that the ESSR becomes a square of size (ESDU)2S2/FR3<YUTTANA>-365-The estimation of biomass was calculated by using algebraic Method with estimated the meansSV of each Elementary Statistical Sampling Interval (ESSR) with cover area is 30x30 nautical miles.The population density (fish/m2) was calculated by using the parameter of means SV in each ESSRand fish target strength (TS). The average TS of fish was calculated by the equation (Miyanohana etal, 1987; Furusawa, 1990 as following ;TS = 20 log 1-66  (dB)Where   1 is fish length in cm.Since, the maximum catch of pelagic species in Sarawak, Sabah and Labuan of Malaysia con-tributed from sardine with annual catch ranging from 16,907 tons to 19,958 tons from 1994 to 1995(Table.1 (D.O.F. Malaysia, 1994, 1995, 1996), then sardine was selected as the representative speciesfor determine TS of single fish for biomass estimation. The target strength (TS) of sardine (Sadinellagibbosa) with the first capture at body length of 10 cm and weight of 10 gm (Somjaiwong, 1991) is –46.0 dB was using for the calculation. The abundance of biomass in each ESSR in obtained by mul-tiplying the population density in the ESSR to the means weight of sardine.Table 1 Landing of marine fish by year and species of Sarawak, Sabah and Labuan.                Fish Species 1993 1994 1995Round Scad 11,650 13,779 15,833Sadine 7,802 16,907 19,958Tuna 20,028 14,548 18,050Mackerel 18,249 15,106 13,092Spanish Mackerel 12,077 6,871 8,393Total 69,806 67,211 75,326Result and DiscussionFig 3 shows the echogram of pelagic and demersal fish school detected by 200 kHz. And 50kHz. The echogram also showing the vertical distribution curve (VDC) with scale ranging from –80dB to –30 dB. The VDC detected by 50 kHz Shows the high reverberation level from surface tobottom. Where as VDC detected by 200 kHz. Showing the less values. The sample of average volumeback scattering strength (SV) and density of fish (N) in each depth layer with integrated for each 0.1nautical mile of 200 kHz  And 50 kHz.Fig. 4 and Fig. 5 showed the biomass distribution presented by means SV at each 0.1 nauticalmile measured during pre and post-northeast monsoon season, respectively. The SV showing highvalue of both season at the shallow water and around the station numbers 25, 26, 27, 36, 41, 42 and 50where, the stations are between the contour line of 100 m to 200 m. During the survey cruise, theechogram can be recorded a lot of big pelagic fish school.The summary of biomass estimation by frequency of 200 kHz. During pre-northeast monsoonand post-northeast monsoon season are showing in Table 2 and 3. The total estimated biomass duringpre-northeast monsoon season are 1,717,852.38 tons and 956,396.88 tons, respectively. The biomassdistribution are showing in Fig. 6 and 7 for pre and post-northeast monsoon season, respectively.During the post-northeast monsoon season, the maximum biomass is presented between sta-tion number 50 to 51 with the water depth of 160 m. in the amount of 1,384,550.oo tons. The mini-mum biomass is presented between station number 63  to 64 in the amount of 93.06 tons Where thewater depth is 1600 m. The total biomass presented at the water depth of <100m, 100 to 200m andS2/FR3<YUTTANA>-366-Fig. 2. Elementary statistical sampling interval(ESSR) along the cruise track when theinter-transect (Dt) equals one elementarysampling distance unit (ESDU).  Tatalbiomass estimation is the summation ofall the abundance of the ESSR area.SARAWAKSABAH108                                   110                                   112                                   114                                  116  ˚EKUCHINGBINTULUMIRIMUARAKOTAKINABARUBRUNEI8642˚N12345678911121314151617181920212223242526272829303134333235363738394041424344454649484750515556575859606162636466656768697170727374757678777910525354Fig. 1    The survey areaESDUFig. 3 The echogram of pelagic and demersal fish schools superimposed with Vertical Distribu-tion Curve (VDC) detected by 50 kHz. and 200 kHz.Fish SchoolS2/FR3<YUTTANA>-367-Table 2 Summary of biomass estimation by high frequency (200kHz)during premonsoon season offshore Sarawak, Sabah and Brunei Darussalam. The table show estimation for each station(ESSR) with cover area is 30x30 nuatical mileStation Means SV Weight Depth Station Means SV Weight Depth(dB) (tons) (m) (dB) (tons) (m)1-2 -72.87 2953.02 46.5 40-41 -90.47 220.47 200.02-3 -82.83 424.48 66.2 41-42 -68.77 29489.90 180.63-4 -84.37 322.92 71.9 42-43 -68.54 20559.98 119.54-5 -76.97 1730.17 70.1 43-44 -76.13 2845.26 95.05-6 -74.45 1715.50 38.9 44-45 -83.41 429.57 76.76-7 -71.83 2906.67 36.0 45-46 -75.92 1383.76 44.07-8 -68.52 5892.31 34.1 46-47 -64.81 10314.61 25.48-9 -74.26 2305.88 50.0 47-48 -72.19 4179.90 56.39-10 -85.74 260.51 79.5 48-49 -79.40 1314.43 93.210-11 -88.88 152.36 95.7 49-50 -72.03 10834.45 140.711-12 -68.60 18238.01 107.6 50-51 -51.55 1384550.00 160.912-13 -86.25 328.15 112.7 51-52 -86.56 542.54 199.913-14 -87.82 204.31 100.6 52-53 -85.01 775.07 200.014-15 -82.52 548.99 79.8 53-54 -81.55 1719.86 200.015-16 -72.96 3542.96 57.0 54-55 -87.06 484.22 200.016-17 -66.01 12012.21 39.0 55-56 -84.98 780.03 200.017-18 -71.11 3734.24 39.2 56-57 -93.03 122.22 200.018-19 -76.06 1846.91 60.6 57-58 -79.87 2531.68 200.019-20 -78.41 1433.26 80.8 58-59 -82.76 1206.11 185.220-21 -76.10 3087.13 102.2 59-60 -77.14 4087.36 172.121-22 -74.13 6201.32 130.7 60-61 -92.49 138.60 200.022-23 -77.60 3106.12 145.4 61-62 -90.41 223.86 200.023-24 -77.15 4128.30 174.4 62-63 -81.88 1594.94 200.024-25 -82.68 1325.05 200.0 63-64 -94.22 93.06 200.025-26 -70.05 18492.92 152.3 64-65 -84.43 886.63 200.026-27 -69.11 16483.74 109.4 65-66 -86.44 557.56 200.027-28 -67.22 20153.80 86.4 66-67 -78.45 3510.98 200.028-29 -76.94 1662.97 66.8 67-68 -90.78 205.45 200.029-30 -71.24 4104.37 44.5 68-69 -82.11 1373.12 181.830-31 -70.79 2680.09 26.1 69-70 -76.52 2852.94 104.331-32 -65.88 9762.12 30.7 70-71 -70.21 23020.09 196.732-33 -74.45 1937.49 43.9 71-72 -85.60 677.37 200.033-34 -80.59 643.74 60.0 72-73 -81.09 1913.19 200.034-35 -80.45 873.43 78.8 73-74 -87.01 489.67 200.035-36 -78.06 1882.09 98.0 74-75 -80.63 2126.18 200.036-37 -70.29 15615.09 135.7 75-76 -75.11 7235.07 191.037-38 -82.76 1300.35 200.0 76-77 -73.94 4985.01 100.538-39 -88.99 310.04 200.0 77-78 -80.05 2202.20 181.239-40 -80.24 2324.37 200.0 78-79 -74.02 8767.69 180.0Total = 1717852S2/FR3<YUTTANA>-368-Station Means SV Weight Depth Station Means SV Weight Depth(dB) (tons) (m) (dB) (tons) (m)1-2 -62.73 30475.03 46.5 40-41 -73.28 11544.31 199.92-3 -73.22 3901.30 66.6 41-42 -70.87 18149.18 180.53-4 -71.76 5959.60 72.8 42-43 -68.17 22378.88 119.44-5 -68.99 10906.12 70.3 43-44 -74.53 4107.04 94.95-6 -69.81 4966.83 38.6 44-45 -74.11 3672.33 76.96-7 -67.90 7283.08 36.5 45-46 -65.60 15003.80 44.37-8 -72.96 2165.15 34.7 46-47 -63.93 12804.26 25.78-9 -68.89 8018.83 50.5 47-48 -65.69 18732.57 56.49-10 -80.16 937.97 79.1 48-49 -75.17 3499.58 93.510-11 -77.95 1895.55 96.1 49-50 -68.02 27524.18 142.111-12 -65.37 38629.55 108.1 50-51 -69.68 21489.75 162.412-13 -74.30 5163.92 113.1 51-52 -69.93 25005.21 200.013-14 -76.81 2548.95 99.5 52-53 -76.69 5271.18 200.014-15 -72.81 5170.71 80.2 53-54 -68.85 32017.28 200.015-16 -74.39 2563.12 57.2 54-55 -80.44 2220.10 200.016-17 -62.22 29410.04 39.9 55-56 -82.99 1235.54 200.017-18 -68.77 6329.70 38.7 56-57 -75.35 7175.69 200.018-19 -69.57 8302.24 61.2 57-58 -71.03 19359.08 200.019-20 -75.64 2742.49 81.7 58-59 -71.71 15065.28 181.620-21 -74.41 4566.07 102.5 59-60 -66.50 44562.34 162.021-22 -74.64 5474.31 129.7 60-61 -82.39 1418.77 200.022-23 -67.81 29603.82 145.4 61-62 -71.05 19278.31 200.023-24 -76.23 5012.40 171.3 62-63 -78.92 3150.28 200.024-25 -72.20 14823.12 199.9 63-64 -83.83 1016.37 200.025-26 -68.33 27626.06 152.9 64-65 -89.80 256.87 200.026-27 -81.99 850.65 109.5 65-66 -77.60 4274.07 200.027-28 -73.48 4784.12 86.8 66-67 -75.46 6992.36 200.028-29 -69.23 9861.52 67.2 67-68 -78.56 3421.60 200.029-30 -70.61 4755.88 44.5 68-69 -68.36 32650.16 181.930-31 -61.99 23392.87 26.1 69-70 -69.69 13898.91 105.431-32 -58.10 58311.63 30.7 70-71 -77.63 4185.10 197.532-33 -65.59 14907.20 43.9 71-72 -80.30 2295.99 200.033-34 -75.17 2253.92 60.2 72-73 -73.85 10120.98 200.034-35 -83.11 474.30 78.9 73-74 -78.49 3482.21 200.035-36 -78.10 1864.24 97.8 74-75 -85.13 753.75 200.036-37 -62.34 95461.97 133.1 75-76 -83.43 1066.63 191.337-38 -75.60 6768.21 200.0 76-77 -76.45 2744.86 98.738-39 -80.05 2427.10 200.0 77-78 -68.00 35457.60 182.039-40 -75.30 7258.02 200.0 78-79 -82.41 1266.92 179.7Total = 956397Table 3.    Summary of biomass estimation by high frequency (200 kHz) during post-northeast mon-soon season off shore of Sarawak, Sabah and Brunei Darussalam.  The table  show estima-tion for each station (ESSR) with cover area is 30 x 30 nautical mile.S2/FR3<YUTTANA>-369-Fig. 4  Distribution of back scattering volume (SV) of fish biomass measured during the pre mon-soon season in Sarawak , Sabah and Brunei Darussalam waters.Fig. 5  Distribution of back scattering volume (SV) of fish biomass measured during the post mon-soon season in Sarawak , Sabah and Brunei Darussalam waters.8642˚N108                                   110                                   112                                   114                                  116  ˚ESARAWAKSABAHKUCHINGBINTULUMIRIMUARAKOTAKINABARUBRUNEI-95-90-85-80-75-70-65-60-55-50dB8642˚N108                                   110                                   112                                   114                                  116  ˚ESARAWAKSABAHKUCHINGBINTULUMIRIMUARAKOTAKINABARUBRUNEI-95-90-85-80-75-70-65-60-55-50dBS2/FR3<YUTTANA>-370-Fig. 6  Distribution of average fish biomass (ton x 900nm) during the pre monsoon season inSarawak , Sabah and Brunei Darussalam waters.Fig. 7  Distribution  of average  fish biomass  (ton x 900nm)  during the post monsoon season inSarawak , Sabah and Brunei Darussalam waters.8642˚N108                                   110                                   112                                   114                                  116  ˚ESARAWAKSABAHKUCHINGBINTULUMIRIMUARAKOTAKINABARUBRUNEIdB5015005030005045005060005075005090005010500501200050135005015000508642˚N108                                   110                                   112                                   114                                  116  ˚ESARAWAKSABAHKUCHINGBINTULUMIRIMUARAKOTAKINABARUBRUNEItons250102502025030250402505025060250702508025090250100250

Biomass Estimation by Hydro-acoustic Methods in the South China Sea, Area II: Sarawak, Sabah and Brunei Darussalam

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