CANADA FUNDS-IN-TRUST FI: GCP /INS /056 / C.AJ.'1 Field Document 3 August 1985
INDONESIA
REPORT ON 1982-1983 ACOUSTIC SURVEYS OF PELAGIC FISH RESOURCES IN THE COASTAL WATERS OF SANGIHE AND TALAUD ARCHIPELAGOS NORTH OF NORTH SULAWESI
A report prepared for the Indonesia Fisheries Development Project (INFIDEP)
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 1985
W/R 5917 This is one of a series of reports prepared during the course of the project identified on the title page. The conclusions and the recommendations given in the report are those considered appropriate at the time of its preparation. They may be modified in the light of further knowledge gained at subsequent stages of the project.
The designations employed and the presentation of the material and maps in this document do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. iii
ABSTRACT
Three acoustic survey cruises were carried out in the Sangihe and Talaud Archipelagos of the North Sulawesi Province from April 1982 to May 1983. Standing fish biomass for the area around Sangihe was estimated at maximum 58 539 metric tonnes and for the Talaud shelf area at 17 881 tonnes during the relatively strong southeast monsoon. Estimates obtained for the same areas during the calm monsoon (April-May) were extremely low, i.e.,1 463 and 169 tonnes, respectively. Corresponding measurements of biomass densities ranged from about 5 to 50 tin mi 2 • There is strong evidence in the data to suggest that the observed variability in the obtained estimates is caused by natural factors, such as changes in fish behaviour and migratory movements of the fish in and out from the area covered by the survey. Apparently, the most useful measurements of the target stocks can be achieved during the strong monsoon, when relatively large fish concentrations are detected and the biomass is mostly distributed in midwater and thus well exposed for acou9tic measurements. The report also describes the survey methods, discusses the results and emphasizes the need for further research effort, in particular to (a) study in greater detail the causes and characteristics of the seasonal/ annual fluctuations in observed biomass, and (b) develop more effective means and methods for identification of the fish species of the surveyed biomass.
v
TABLE OF CONTENTS
1. PREFACE
2. INTRODUCTION 2
3. SURVEY AREA AND CRUISES 3
3.1 General Conditions of Survey Area 3 3.2 Survey Cruises 3
4. RESEARCH VESSELS AND EQUIPMENT 3
4. 1 R/V TENGGIRI 3 4.2 Acoustic Survey Equipment 4 4.3 Temperature Measurement Equipment 6
5. SURVEY METHODS 6
5.1 Survey Design and Coverage 6 5.2 Data Collection and Processing 7
5 .2. 1 Data collection 7 5.2.2 Data handling and processing 7
5.3 Equipment Calibrations 8
5. 3. 1 Standard target 8 5.3.2 Inter-transducer calibration 9 5.3.3 Live fish calibration 10
5.4 Fishery Data Collection 11
6. RESULTS 11
6.1 Summary of Cruises 11 6.2 Calibration Results 13
6.2.1 Standard target 13 6.2.2 Inter-transducer calibration 14 6.2.3 Live fish calibration 15
6.3 Distribution and Abundance 19
6.3.1 Biomass distribution 19 6.3.2 Abundance estimation 21
6.4 Temperature Measurements 22 6.5 The State of Fishery Resource Exploitation 22
7. DISCUSSION AND CONCLUSIONS 23
7.1 Main Findings of the Survey 23 7.2 Possible Bias in the Estimates 24 7.3 Identification of Species 25 7.4 Implications and Future Research 25
8. ACKNOWLEDGEMENTS 26 Vl
REFERENCES 27
Appendix 1a: VESSEL SPECIFICATIONS 28
Appendix 1b: FISF.ERIES SURVEY .~'ID EXPLORATORY VESSEL TENGGIRI GENERAL ARRANGEMENT 29
Appendix 2: EXAMPLE OF ACOUSTIC LOG SHEET 30
Appendix 3: EXAMPLE OF PRINTOUT OF DATA FROM QD DIGITAL INTEGRATOR 31
LIST OF FIGURES
1. Geographic Location of Survey Area 32 2. Outline of System for Data Handling and Processing 33 3. General arrangement for Calibration on Standard Target 34 4. General arrangement for suspension of calibration cage and transducer together with keep-net for experimental live fish 35 s. Geometric view of calibration cage location in the water column 36
6. Location of Site for Live Fish Calibration 37 7. Graphs showing variations in integrator readings during (a) calibration of live fish and (b) length distribution of the experimental fish targets 38
8. Measured vs. theoretical TVG for TENGGIRI's EK-S120 sounder 39
9. Survey Track and biomass distribution chart also showing positions of BT stations made 40
10. Survey Track covering the Sangihe Area 41
11. Distribution and abundance of pelagic fish biomass in the Sangihe area, based on integrator data 42
12. Survey Track covering the Sangihe Area 43 13. Distribution and Abundance of Pelagic Fish biomass in the Sangihe Area based on Integrator Data 44 14. Echo-recordings made with two echosounders (EK400/EK-1-20S) at different ranges and frequencies over same transect sections during CR.02/8208-09, Leg I, showing large fish concentrations on the NE bank of Sangihe island 45 15. Echo-recordings made with two echosounders (EK400/EK-120S) at different ranges and frequencies over same transect sections during CR. 02/8208-09, Leg I, showing typical fish traces on the shelf area (littoral) around Sangihe 46 16. Survey Track covering Sangihe Area 47 17. Distribution and abundance of pelagic fish biomass in the Sangihe area, based on integrator data 48 18. Echo-recordings made with two echosounders (EK400/EK-120S) at different ranges and frequencies over same transect sections during CR.02/8208-09, Leg II, showing typical fish traces in the littoral of Sangihe island 49 Vll
Page 19. Survey Track covering the Talaud Area 50 20. Distribution and abundance of pelagic fish biomass in the Talaud area, based on integrator data 51 21. Echo-recordings made with two echosounders (EK400/EK-120) at different ranges and frequencies over same transect sections during CR.02/8208-09, Leg III, showing typical fish traces on the shelf area of the Talaud Archipelago 52 22. Echo-recordings made with two echosounders (EK400/EK-120) at different ranges and frequencies over same transect sections during CR.02/8208-09, Leg III, showing typical fish traces on the shelf area of the Talaud Archipelago 53 23. Echo-recordings of selected transect sections made with two echosounders (EK400/EK-120S) at different ranges and frequencies during CR.02/8208-09, Leg III, showing relatively large concentrations of fish, found in the depth range from about. 20-30 m, at the shelf area of the Talaud Archipelago 54 24. Survey Track covering the Sangihe Area 55 25. Echo-recordings made with EK-120 (Range: 0-100 m) during CR.02/8208-09} Leg IV, Sangihe, showing large concentration of pelagic fish (a-b) just south off Dhago, (c-d) 3 miles north from Kalama, aE.d (e-f) miles SW from Para island 56 26. Echo-recordings made with EK-120 (Range: 0-100 m) during CR.02/8208-09, Leg IV, Sangihe, showing large pelagic fish schools and layers (a-b) 5 miles west from Para, (c-d) 3 miles NW from Kahakitang, and ·(e-f) 10 miles south off Sangihe 57 27. Distribution and abundance of pelagic fish biomass in the Sangihe .rea, based on integrator data 58 28. Survey Track covering the Sangihe Area 59 29. Distribution and abundance of pelagic Area biomass in the Sangihe Area, based on integrator data 60
30. Echo-recordings made with EK400/38 kHz (Range. 0-300 m) during cruise 01/8304-05, Leg I, showing typical biomass and seabed characteristics on the narrow shelf area around Sangihe 61 31. Echo-recordings made with EK400/38 kHz (Range: 0-300 m) during cruise 01/8304-05, Leg I, near the west coast of Karakelong island, 12 miles south of Sangihe. These were the only fish traces detected during this part of the cruise 62 32. Survey Track covering the Talaud Area 63
33. Distribution and abundance of pelagic fish biomass in the ~alaud Area, based on integrator data 64 34. Survey Track covering the Talaud Area 65 35. Echo-recordings made with EK400/38 kHz (Range: 0-300 m) during cruise 01/8304-05, Leg III, showing (a-b) fish traces in deep waters about 10 miles NE from Karakelong island, (c-d) deep fish traces close to the west coast of Karakelong, and (e) large pelagic schools at about 170 m depth, west off Salibu island 66 36. Survey Track covering the area between Sangihe and North Sulawesi 67 Vlll
37. Echo-recordings made with EK400/38 kHz (Range: 0-250 m) during cruise 01/8304-05, Leg IV, showing unidentified traces (a) south of Siau island, (b) south of Tagulandang island, (c-d) north and south of Biaro island, respectively 68 38. Measured Temperature Profiles 69 39. Measured Temperature Profiles 70 40. Measured Temperature Profiles 71 41. Measured Temperature Profiles 72 42. Measured Temperature Profiles 73 43. Measured Temperature Profiles 74 44. Measured Temperature Profiles 75 45. Catch Fluctuations 1978-1982 in the Sangihe-Talaud Archipelagos 76 46. The Increases of Fishing Efforts in the Sangihe-Talaud Area, 1977-1981 77
LIST OF TABLES
1. RESULTS OF INTER-TRANSDUCER CALIBRATION 78 2. AREA BACK-SCATTERING STRENGTH AND RESULTANT INTEGRATOR CONVERSION CONSTANTS USED FOR SURVEY 78
3. SMALL PELAGIC SPECIES~ ESTIMATED ABUNDANCE BASED ON INTEGRATOR DATA FROM CRUISE 02/8204-05. (a) WHOLE SURVEY AREA AND (b) SANGIHE LITTORAL AND NE BANK 79 4. SMALL PELAGIC SPECIES: ESTIMATED ABUNDANCE BASED ON INTEGRATOR DATA FROM-CRUISE 02/8208-09 80 5. SMALL PELAGIC SPECIES: ESTIMATED ABUNDANCE BASED ON INTEGRATOR DATA FROM CRUISE 01 /8304-05 81 6. SUMMARY OF ABUNDANCE ESTIMATION IN THE SANGIHE-TALAUD ARCHIPELAGOS (See page 23 for in-text table) 7. FISHERIES DATA OF SANGIR-TALAUD DISTRICT 1977-1981 82 8. CATCH (LANDING) COMPOSITIONS (t) IN SANGIHE-TALAUD 1979-1981 83 9. CATCH AND FISHING TRIP DATA IN SANGIHE-TALAUD, 1981 84 10. AVERAGE FISH DENSITIES WITHIN VARIOUS AREAS OF TIIE SHELF (AT 10-200 m DEPTH) ALONG THE INDIAN OCEAN AND SOUTH CHINA SEA, ESTIMATED DURING CRUISES WITH R/V DR. FRIDTJOF NANSEN 85 11. AVERAGE PELAGIC FISH DENSITIES WITHIN VARIOUS SURVEY AREAS, ESTIMATED DURING INFIDEP CRUISES WITH R/V TENGGIRI MADE OVER THE PERIOD FROM MAY 1981 TO DECEMBER 1983. 85 1. PREFACE
This report is the result of the collective effort of the following persons, who participated in the survey cruises through field observations, data collection, processing and analysis and contributed individually and collectively (either part-time, or full-time) to the preparation of the various parts of the report.
Project Team Leader and Counterparts
K. Johannessen FAO Team Leader, INFIDEP 2_/
T. Sujastani Co-Manager/Scientific Coordinator, INFIDEP
M. Badrudin Biologist, MFRI, Semarang 3./
B. Soekarso Electronic Engineer, MFRI, Jakarta
D. Nugroho Acoustic Biologist, MFRI, Semarang
B. Gafa Acoustic Biologist, MFRI, Semarang s. Marzuki Acoustic Biologist, MFRI, Semarang s. Budihardjo Acoustic Biologist, MFRI, Semarang
H. Wahyuono Acoustic Biologist, MFRI, Semarang 3/ E. Mulyadi Acoustics/Exploratory Fishing, FTDC - ' Semarang Suwito Acoustics/Exploratory Fishing, FTDC Semarang
Masterfisherman P. Fjeldstad was on the project team from April 19S1 to Decemoer 1982 and participated in some of the cruises. He also assisted with the construction of calibration net-cages and keep nets for live fish calibrations of the acoustic survey equipment. Consultant Masterfisherman T. Gestsson joined the project in May 1983 and during a period of six months assisted the project in training the captain and ~rew of the research vessel TENGGIRI in purse seining and carrying out fishing trials with light attraction.
During the course of the survey programme, several observers and students from universities in Semarang and Bogor participated actively in the collection of the data and were introduced to modern acoustic research methods. In addition, the UNDP/FAO South China Sea Fisheries Development and Coordinating Programme (SCSP) arranged for two researchers 'from the Philippines to participate in one· cruise to familiarize themselves with the equipment and survey procedures.
1/ INFIDEP = Indonesia Fisheries Development Project 2.! MFRI =Marine Fisheries Research Institute l_i FTDC = Fisheries Techniques Development Centre 2
2. INTRODUCTION
The Government of Indonesia, assisted by the Food and Agriculture Organization of the United Nations, are involved in operating the CIDA/FAO Indonesia Fisheries Development Project (INFIDEP) (GCP/INS/056/CAN), with financial assistance provided by the Government of Canada through the Canadian International Development Age~cy (CIDA). The project included as an essential part of its objectives the evaluation of the pelagic resources base, in two specific project areas using echo-integration techniques, using both analog and digital echo-integrators. The present report relates to the survey area which is located in the boundary zone between the Celebes Sea to the west, Molucca Sea to the south and the Pacific Ocean to the east. Surveys in this area focused mainly on the littoral zones of the Sangihe and Talaud Islands, plus nearby banks, northeast of North Sulawesi.
The total area of reference ( ~ 49 000 n mi2 ) was defined approximately as the area between 00_5o latitude north and 125°-128° longitude east. Between 00-20 latitude north, the eastward extent of the area is determined by the west coast of Halmahera, while to the west its limit is set by the east coast of North Sulawesi. Administratively the area falls under the jurisdiction of the North Sulawesi Province.
A total of three acoustic survey cruises were ma~e in the area with the Directorate General of Fisheries project survey vessel TENGGIRI.
This effort was supplemented by one experimental fishing cruise from 14 August to 24 November 1982 carried out on the project's chartered boatF/V KERANG III, which was fitted with small-scale fishing gear, such as 240 x 20 m purse seine, bottom longlines and trolling lines, as well as handlines.
The timing of the surveys was planned so that the first and the third cruise coincided with the calm northeast monsoon (wind force generally 1-2 on the Beaufort scale) during April-May in 1982 and 1983, respectively, while the second cruise, made during August-September 1982, fell in with a strong southeast monsoon recording-wind velocities in the range from 3-6 on the Beaufort scale.
Because of the almost nonexistence of background information on principal factors such as: presence of fish, geographic distribution, identity, behaviour, etc., as a basis for the design of a survey plan for the whole area of reference, it was necessary to first conduct a large-scale preliminary survey (covering an area the size of 50 000 n mi 2 ) to determine the best strategy and design for future surveys.
During the first cruise (April-May 1982) practically no fish concentrations were encountered in·the large open sea areas. In contrast, fish were detected on the acoustic instruments in limited areas along the coast of Halmahera and North Sulawesi and also in the area between Sangihe and the northern tip of North Sulawesi. Further occurrence of fish schools was noted by eye in the coastal waters of Sangihe and Talaud _Islands.
Based on these preliminary findings, and taking into account the pre-established geographical priorities, it was decided to concentrate subsequent survey efforts around the islands of Sangihe and Talaud, including nearby banks.
This report describes the methods applied and presents the results of these surveys, based on summary evaluation of all data material collected. The derivation of figures for absolute biomass of pelagic fish in this report is based on a number of assumptions, the validity of which need to be varified in future research. Consequently, the biomass estimates are only preliminary and the figures presented need to be treated with caution. 3. SURVEY AREA AND CRUISES
3. 1 GENERAL CONDITIONS OF SURVEY AREA
The geographic location of the project area is shown in Figure 1, where the dashed lines demark the total area of reference. Geographically, the main survey area is characterized by the two distinct archipelagos named Sangihe and Talaud, which administratively form one district. By far the largest islands of the two archipelagos are Sangihe and Karakelong. The most important islands adjacent to Karakelong are Salebaboe and Kaboeroeang, which are located close to the southern tip of the main island. Among the larger islands that make up the Sangihe Archipelago are Manipe and Boekide close to the northeast coast of Sangihe, Beng Dara near the southeast coast, Kalama, Kahakitang and Para about 10-15 mi off the south coast and then the larger islands, such as Siau, Tagulandang, Ruang and Biaro, which are located much further south (30-70 n mi). All the islands are surrounded by a very narrow shelf, characterized by uneven and/or rocky bottom conditions. For Sangihe, the width of the shelf varies from one half to six mi and for Talaud, only between one half and two n mi. In some places, especially in. the Sangihe survey area, there are coral heads extending almost to the surface. This was a hindrance to safe navigation in certain areas and often prohibited the relatively large survey vessel to survey some waters of interest close inshore. The edge of the shelf is usually sharply defined and beyond the edge, seaward, the slope of the seabed is very steep (40-60 degrees angle ref. surface), a fact that makes bottom longlining difficult in many places.
The Sangihe and Talaud area has a tropical climate which is strongly influenced by the prevailing .monsoon wind system in which the direction of the wind flow reverses so as to produce wet or dry seasons.
The area is typified by year round sea surface temperatures of between 28.50C and 3ooc. Vertical temperature profiles are characterized by an average negative gradient of 0 .9°c per 10 m depth increase in the depth range from about 40 250 m. The upper 40 m have reasonably homogeneous temperature distribution.
During the strong monsoons, there is a relative standstill in fishery activities and acoustic surveys become more difficult to carry out due to noise problems associated with water turbulence and heavy vessel movements.
3.2 SURVEY CRUISES A total of four cruises were carried out in the area, i.e., three acoustic surveys and one experimental small-scale fishing survey. A summary of these surveys is given below.
4. RESEARCH VESSELS AND EQUIPMENT
4 . 1 R/V TENGGIRI
The R/V TENGGIRI, delivered in 1979, is an all-steel, 39mpurse seiner with longlining and squid jigging facilities. She is owned by the Directorate General of Fisheries (DGF) and was assigned to INFIDEP for carrying out the planned bio-acoustic surveys. For this purpose, the project, supported by the Canadian International Development Agency (CIDA), installed two echo-integrator systems on the TENGGIRI, i.e., one analog system and one modern digital system.
For test fishing (sampling) purposes, the TENGGIRI was alternatively carrying a 640 x 109 m deep-sea purse seine net or a 514 x 60 m net for seining in relatively shallow waters. Also available were equipment and a small boat for light fishing.
The vessel's main specifications and an arrangement plan are presented in Appendix 1a and 1b. 4
Cruise No. Vessel Dates Survey-Area Remarks
Acoustic Research Cruises
01/8204-05 TENGGIRI 6 Apr.-18 May 1982 Whole area around NE Sangihe monsoon - Leg I - Leg II calm
02/8208-09 TENGGIRI 18 Aug.- 6 Oct.1982 - Leg I Around Sangihe + SE bailks monsoon - Leg II Around Sangihe strong - Leg III Around Talaud winds - Leg IV Off south Sangihe
01/8304-05 TENGGIRI 16 Apr.-23 May 1983 - Leg I Around Sangihe + banks - Leg II Littoral of Talaud - Leg III LST J_/ around Talaud - Leg IV Between Tahuna/Bitung
Experimental Fishing Cruise 01A/8208-11 KE RANG III 14 Aug.-24 Nov.1982 around Sangihe
4.2 ACOUSTIC SURVEY EQUIPMENT
The TENGGIRI is equipped with two echo-integrator systems: a Simrad QM-:MK-II, a two channel analog integrator, which works in conjunction with a Simrad EK-S120 (120 kHz) scientific sounder; the second system consists of the QD multichannel digital integrator, connected to the Simrad EK-400, dual frequency (120/38 kHz) scientific echo-sounder. It was originally planned to collect data simultaneously with both systems for certain comparative studies but technical problems with the QD computerized system prevented this. Digital data were obtained only during one survey cruise (CR.02/8306-07), which was conducted in the Natuna area.
To facilitate interpretation of echo-recordings the TENGGIRI was also fitted with a Simrad color display, Model CF100, which could be switched alternatively to the EKS or EK400 sounder. Additional survey equipment was the JRC omni-directional scanning sonar Hodel JFS 688. This sonar was operated during the entire large-scale, preliminary survey without detecting a ~ingle target. It was then used occasionally during subsequent surveys, but also with negative results. Consequently, no sonar data are presented in this report.
Control settings of the various equipment were as follows:
.1/ Large scale track 5
Analog System
Sounder: Simrad EK-S120 and 120-25-E transducer with 10° beam angle and 1C cm diameter radiating surface.
Output power 1/1 (maximum)
Receiver gain 0 dB
TVG function 20 log R/O dB
Pulse duration 0.3 ms
Receiver bandwidth 10 kHz
Recorder gain 6
Mode WL (white line)
Discriminator 6 (variable)
Range 0-1 00 m
Sounding rate 125 soundings/min
Echo-Integrator: Simrad QM-MK-II and Hewlett Packard recorder 7702 B.
Gain 20 dB
Scale Expander x 10
Threshold 2
Speed Compensator 10 knots (fixed)
Bottom Stop ON/manual reg.
Integrator Channels A 3-50 m B 50-100m/3-100 m
Reset manually every 2 mi during first survey and every 1 mi during second and third survey
Digital System
Sounder: Simrad EK400 working with QD echo-integrator automatic print-out of details is given below. 6
R/V TENGGIRI CRUISE 02/8306-07 o,{ -H'- - -E•'" ANAMBAS SURVEY AREA C):>MMENTS:
So•-•t-n:•EP. Na. : 2 FP.EG!UENCY: • :;::::. 0 1-<:Hz :~:auP.•=E LEVEL; 11 ·::i. 4 r·B t'uLSE D1_1P.AT I ON: 0.35 MS TP.ANSDUCEF! 1 -21. 0 r•B \•'OL TA•:o;E RESPONSE: :~~. 5 r• B ruLSE REP.FREI;!. : 12:3 p/11 T'./G: f.:.4. 6 nB GAIN: o. I) i::•B IJ\,"'1::(. RANGE: :314 M Sv-SuPPF!Ess: :-70 DB C:-E•=HOSOl_li"U•ER: -31"5 DB ------~------~------!..AYER 0 I I I I I I I'./ ''... \·'I \·'I I \.'I I I I:='~ ·.· IJF·f"ER-LIM 2. I) 1 (!. I) 20:0 30.0 40. I) .s (I. 0 6 0. 0 70. OB+ 1.S. .SB+ ._I•r: ·-=; Lm· Sector from -90° to +90° Tilt Angle 3° down Display PPI/CRT plus recorder Range 0-800 m Frequency 88 kHz 4.3 TE1'1PERATURE MEASUREMENT EQUIPMENT- _A bathythermograph (BT) model TSK (10-1979) with computer facilities was used for observations on vertical temperature profiles and surface temperatures along the survey tracks were recorded on an M-type Electric Resistance Thermometer manufactured by Murayama Denki Ltd. 5. SURVEY METHODS Essentially the theoretical and practical details of the survey methods as well as ___the methods of data processing and analysis, are described in Johannes son and Mitson (1983) and Burczynski (1982). In summary the methods can be described as follows: 5. 1 SURVEY DESIGN AND COVERAGE The preliminary survey (CR.01/8204~05), which covered the whole area, was designed as a parallel grid pattern with transects running in due east-west direction and reverse. Transect lengths and inter-spacing was fixed at 180 and 30 n mi, respectively. An illustration of the survey grid· and the area covered can be seen in Figure 9. The transect patterns of the subsequent surveys were of mixed design, i.e., a combination of zig-zag and parallel legs, or either zig-zag or parallel transects. Such designs were primarily governed by the shapes of the respective shelf areas surveyed, also taking into account the navigational security of the TENGGIRI~ ~ I 5.2 DATA COLLECTION A...'ID PROCESSING 5.2.1 Data collection For survey purposes, the cruisin~ speed of the vessel was maintained practically constant at 10 knots. The continuous log of acoustic data from the analog integrator and EK-S120 sounder was recorded on a log sheet as shown in Appendix 2. Data were recorded for each 2 mi or 0 mi) sections of the survey track, depending on the scale of the surveys. Hence, the elementary sampling distance unit (ESDU) corresponded normally to a 12 min time unit (at 10 knots) and contained a train of 1 500 echo soundings but, when 1 mi data logging was preferred, the resulting ESDU corresponded to 6 min and 750 sound transmissions. During surveys with the QD digital integrator system, the relevant data were printed out automatically in a format as shown in Appendix 3. 5.2.2 Data handling and processing An outline of the general system is illustrated diagrammatically in Figure 2. The most critical procedures included visual evaluation of the data material, mapping and interpretation of echo recordings. Visual evaluation : The purpose of this type of evaluation was twofold, namely (1) to carry out corrections for false echo integrations attributed to various sources of noise and ·bottom integration, and (2) to compare biomass trace characteristics with the graphic integrator output in order to separate recorded biomass into nekton (fish biomass) and plankton. . In practice, this was done by unfolding the echograms and the corresponding integrator chart paper side-by-side (on a long table) so that about 20-30 mile sections of the cruise track recordings could be scrutinized in one overview. This offered better possibilities to detect significant trends in the echo-trace characteristics and to judge the proportion of plankton v. nekton biomass in mixed recordings where only a given fraction of the observed integrator readings could be assigned to fish biomass. Data mapping : All millimetre readings for echo-intensities (M) were normalized so as to give correct matching to the established calibration constant (C=0.28), irrespective of changes in equipment performance or control settings. (e.g pulse duration). Hence, the biomass distribution maps are all directly comparable in terms of relative abundance given by millimetre readings on the analog integrator. The following abundance categories were established. Category mm-readings Abundance rating ,. 10-100 very scattered 2 101-500 scattered 3 501-1 000 dense 4 >1 000 very dense Interpretation of echo recordings : Following the simultaneous evaluation of the echo grams and integrams, the following steps were carried out. (1) Each section of the recorded biomass along the survey tracklines was classified into types of traces and given the following coding: 8 PT pelagic fish traces PS pelagic fish schools DT demersal fish traces DS demersal fish schools SLF scattering layer of fish SLP scattering layer of plankton In establishing the above subjective coding system, the project team could draw on considerable experience in this type of interpretation of echo recordings. Also, as far as possible, information from sample fishing was taken into account. (2) A special large-scale chart was produced with the established codes plotted along the survey routes. (3) Contour lines were then drawn on the chart to delimit areas of biomass distribution, exclusively encompassing fish biomass, or a mixture of fish and plankton biomass. Hence, the portion of the survey area which recorded only plankton, or plankton mixed with faint fish traces, was ignored in the estimation procedure. 5.3 EQUIPMENT CALIBRATIONS 5.3.1 Standard target The principle of placing a known target, with an accurate and reliable target strength on the axis of the beam at a specified distance from the transducer can be used to obtain a combined figure for SL + VR, Le·., the source level and voltage receiving response, respectively. This method avoids the use of calibration hydrophones or relying on electrical measurements, then calculating SL and VR from formulae. It does requize very accurate alignment of the target on the acoustic axis of the beam and the calibration only refers to this axis unless the beam pattern is known. The following expression is used to obtain SL + VR when a standard target is available. SL +VR V + 40 log R + 2 a R - TS rms o o or SL +VR V + 2 TL - rms TS where SL source level in dB/1pPa/1 m VR receiver sensitivity at end of TVG range in dB/1V/1jU'a V voltage at the receiver output due to standard target echo in dB/ volt rms = TL transmission loss in dB, i.e., 20 log R + aR 0 0 R distance between transducer face and target TS target strength of calibration sphere in dB R range at which the TVG function ends (m) 0 9 Apart from the echo-sounder and a standard target, only an oscilloscope is needed to complete the equipment needed for this form of calibration, However, when an overall survey precision to = 0.5 dB is necessary, great care must be taken to ensure that no error is introduced into the calibration experiment. The difficulty lies mainly in the suspension and the alignment of the standard target on the axis of the beam in the far-field. In the present work this problem was minimized by using a specially designed transducer/target suspension rig to calibrate the 120 kHz sounder first on spare transducer and then, through inter-transducer calibrations, to transfer results to the hull-mounted survey transducer. The general arrangement for the standard target calibration is shown in Figure 3. The standar4 target used for the calibration was a copper sphere with an optimal diameter of 30-. 05 mm, giving a nominal target strength of : TS = -3 7. 0 dB. The purpose of determining the combined parameter (SL+ VR) is twofold , i.e. (1) to check that the system is working according to performance specifications, and (2) to enable calculations of absolute fish densities for species of known target strength. The relevant results are presented in Section 6.2 below. 5.3.2 Inter-transducer calibration The purpose of this particular calibration was to compare the accurately calibrated spare (external) transducer with the ship's transducer and thus establish the required parameter for the actual survey transducer. The principal approach is simple, namely to use an integrator system which integrates the echo-intensity (M) from a target with constant density ce) and the two transducers are then alternatively switched to it. The mathematical basis for the intercalibration is Transducer A : f A Transducer B : f B where {° given target density C equipment constant (Lumped) T transmit/receiving response of the transducer M integrator reading in mm Given the assumption that transducer A and B are on average sounding on equal target density, i.e.,(? A =eB' it follows .that: C TA MA C TB~ Hence, by rearranging we obtain In other words, the performance factor for transducer A is equal to that of transducer B, multiplied by the ratio of the mean integrator values. 10 Based on this relationship, a successful intercalibration was carried out in the harbour of Bitung, North Sulawesi, on 29 April 1982. The target used was the seabed in the range.interval from 23-27 m,which exhibited a target scrength similar to a very dense fish school. The results are also given in Section 6.2. 5.3.3 Live fish calibration Before quantitative,results can be obtained from acoustic surveys of fish abundance it is necessary to determine: either the parameters of the acoustic system, then use previous knowledge of fish target strength; or alternatively make a collective calibration of equipment with numbers of fish having known length/weight relationships. A direct method of calibration, similar to that described by Johannesson and Losse (1977), was used to convert the observed readings from an echo-integrator, into fish densities, following the relationship f = CM given by Midttun and Nakken (1971). In this way, the constant of integration 'C' can be determined experimentally in units of tonnes per square nautical mile per millimetre of integrator reading 'M' in mm, results in an estimate of absolute density, expressed in tonnes per square nautical mile of sea surface area. An estimate of calibration constant 'C' can be obtained, depending on the availability of experimental data, either from a regression analysis, or as a point va-hi-e--from a single set of observations. In the latter case the constant is obtaiBed from the formula: C 3.43 NwLiRc 2 c = --- (tonnes/mile /mm) ••• ( 1) M,.V where: N number of fish within the calibratiQn cage V effective volume of cage (m3) LiR integrator range gate (m) c w mean weight of fish in the cage (or keep-net) 3,43= conversion factor to raise km2 to n mi2 and M = is the integrator scale reading in mm as before The above expression can be written in a more general form as follows: s p µv c C c c ••• (2) cc-) c-) s· s . p s s or in a logarithmic form: s p LiG. LG .•. (3) 10 log Cs= 10 log Cc+ 10 log C-i3-) +log (pc) i e c s where: C = constant related to actual equipment control setting during survey s s ( ~) ratio of the number of soundings chosen for calibration to the number vsc used for survey 11 p use~ ( ____::_ ) numerical ratio between pulse duration during p calibration and survey, respectively s LIG. (G - G ) difference (dB) in integrator gain used during 1. s c- calibration and survey, respectively LIG (G - G ) difference (dB) in echo-sounder gain used during e s c calibration and survey, respectively, and c and R as above c c While constant C (equation 1) must be used for derivation of fish target strength from the calibration c data, the survey constant Cs (equation 2), i.e., Cc normalized to survey standard, is used for density estimates. A schematic illustration of the general arrangement for the live fish calibration experiment is shown in Figures 4 and 5. During the later surveys the R/V TENGGIRI was carrying all necessary equipment for ad hoc live fish calibrations but, on two occasions, all attempts to carry out calibrations had to be abandoned due to adverse weather condition and/or non-availability of suitable fish. However, a successful calibration experiment was carried out in the Bay of Tahuna during the period from 10-13 May, 1983. The results obtained are presented in Section 6.2 below. 5.4 FISHERY DATA COLLECTION The fishery data were acquired from the District Fishery Service Office of North Sulawesi and -its Sub-District Office in the Sangihe-Talaud area, which have been collected through the National Fishery Production Survey implemented in 1976. The method does not cover detailed information required for stock assessment wherein the catch data are broken down to groups of species by types of fishing gear and the effort data do not include features of the fishing units affecting fishing power as well as the time units used in the fishing trip measures. 6. RESULTS 6.1 SUMMARY OF CRUISES Cruise 01/8204-04 1/ Leg I : This was a preliminary cruise, covering the whole area of reference, for familiarization with the area in general. This was a large-scale survey covering a total· area of approximately 49 000 ri mi 2 , with a total distance sailed of 2 536 mi. This cruise also included a visit to the Government's Fisheries Office in·Manado, North Sulawesi, and visits to chiefs of two fishing villages on the Manipe and Kahakitang islands, located northeast and south of Sangihe. The purpose of these visits was to obtain information about the fisheries in the area. In addition, good contacts were established with the Government's Fisheries Service in Tahuna and the Chief of the Government's Terminal in Dhago, located on the west and south coast of Sangihe, respectively. Acoustic data were collected continously with the 120 kHz integrator system in the depth range from 3-100m. The TENGGIRI was carrying its large purse seine net (640 x 109 m) for sample fishing and this was shot twice on fast moving surface schools of tuna-like species but no catch resulted. Trolling lines were also used during the whole cruise track, resulting in successful catches in six separate areas, mostly spread in the region between North Sulawesi and Halmahera The species caught were: skipj ack tuna (500-600 g), albacore tuna (5-6 kg), dolphin fish (5-6 kg) and rainbow runner (2-3 kg). This cruise also provided surface temperature recordings and 22 BT stations for observations on vertical temperature profiles down to maximum depths of 250 m. 1_/ (key) (-) sequential cruise numbers for the vessel or project (=) the year (1982) 01 I 82 04 - 05 (::) the month(s) (April-C-Iay) - - - 12 Leg II : This survey was concentrated in the coastal waters and nearby fish banks of Sangihe. The main emphasis was on the collection of integrator data but also a close eye-watch was kept for detecting possible occurrence of surface schools. A few schools were sighted but were not considered catchable and so no attempt was made to encircle them with the vessel's large purse seine. Cruise 02/8208-09 Leg I : Before the actual work of Leg I of this cruise started, the TENGGIRI was used to assist a mariculture survey around Sangihe. A survey team, headed by a project consultant, Dr William Chan, undertook to carry out a preliminary survey of the potential for sea-farming in Sangihe during the period from 10to13 September 198 2 • The TENGGIRI was used as a mother vessel from which an inflatable rubber boat was launched to take the t·eam to their observation sites close inshore. On conclurion of the survey, a meeting was held with the Government Authorities (BUPATI) in Tahuna in order to discuss project activities and exchange information on the fisheries situation. After completion of the mariculture survey, the vessel connnenced an integrator survey covering the littoral zone of Sangihe and the nearby fish banks south and northeast of the main island. Four steps were taken to improve the acoustic sampling. These were: (a) new 120 kHz transducer was side-mounted in an "acoustic shadow" from the 38 kHz transducer, (b) vessel speed was reduced to 6 knots, (c) pulse duration was increased from 0.3-0.6 ms-, and (d) the EK400 sounder (38 kHz) and EK120 sounder were·operated simultaneously but with ranges at 100 and 300m,respectively. This arrangement eliminated previo~sly existing interference between the two sounders and also, because the side-mounted transducer was positioned only 1 .5 mbelow the surface (vs. the hull-mounted at 4 m depth), provided for more efficient sampling in the uppermost water column. Continuous integrator data were logged and constant watch kept on possible schooling activities at surface levels. Leg II : The priority here was to repeat the survey of Sangihe's littoral zone to provide an idea of the inter-survey variability in integrated echo intensities. Leg III : A preliminary survey of Talaud's coastal waters with particular emphasis on the narrow shelf area. Methods and survey instrument operated as described above. Leg IV : A very detailed parallel grid survey of the fish banks off the south coast of Sangihe. Cruise 01/8304-05 Leg I :Re_petitionof the survey made during Cruise 02·/8208-09 (Leg I), covering the littoral zone of Sangihe and the nearby fish banks south and northeast of the island. Leg II : Repetition of the survey grid worked in the littoral zone of Talaud during Cruise 02/8208-09 (Leg III). Upon completion of the survey track, the vessel called at Lirung, the main town of Talaud, where a meeting was held with the authorities both to explain the project activities and to discuss the status of the fisheries in the different islands. Leg III : A relatively large-scale survey around Talaud. Parallel transects were run in. due east-west (and reverse) direction with interspacing of 5 n mi and lengths varying from 10-20 n mi. Collection of integrator data was made throughout the survey and 18 BT stations were carried out. 13 Leg IV : Following eight days of calibration efforts on live fish inside the Bay of Tahuna, the Leg IV survey was commenced on 13 May 1983. This survey covered more or less a rectangular area (30 x 110 n mi) between the southern part of Sangihe and the northern tip of North Sulawesi. Integrator data were collected and routine visual scouting of the sea surface for possible pelagic schooling activities was maintained. 6.2 CALIBRATION RESULTS 6.2.1 Standard target Using the method described in Section 5.3.1 above, the EK-S120 sounder was calibrated on a standard target (copper sphere 30.05Cmdiameter and target strength specified as TS= -37.0 dB) at a location inside the Bay of Tahuna on the Island of Sangihe under excellent environmental conditions. The target's alignment on the centre of the acoustic axis of the transducer beam was accurate and the geometrical stability of the suspension rig (Fig. 3) was almost ideal, as evidenced by the fact that practically no fluctuations could be observed in the echo amplitude of the target. Thus, the sphere echo as observed on an oscilloscope was "clean" and remained at constant amplitude. The echo voltage of the sphere, with 40 log R TVG, was first observed for full transmitting power as during actual survey and then observed for reduced transmitter power. The results were as follows: Full transmitter power (1/1) Observed peak-to-peak echo voltage V = 0.26 volt p-p 0.26 v = v I (2 V2) 0.092 volt rms p-p 2V2 Equation for combined parameter (SL + VR) = 20 log V + 40 log R + 2a:R - TS rms o o sphere For the EK-S120 we have R 100 m and a: 0,038 dB/m. 0 Inserting all relevant values in the above equation for (SL+ VR), we obtain (SL + VR) 20 log 0~092 + 40 log 100 +2 x 0.038 x 100 - (-37.0) -20.7 + 80 + 7.6 + 37 103.9 dB Reduced transmitter power (1/10) v 0 .152 volt p-p (0.152/2V2) 0.0537 vrms Hence, (SL + VR) 1/10=20 log 0.0537 + 80 + 7 .6 + 37 -25.4 +'80 + 7.6 +37 99.2 dB 14 6.2.2 Inter-transducer calibration Place Bitung Harbour, North Sulawesi Vessel R/V TENGGIRI Date 29 April 1982 Target Seabed echo from 23-27 m Essential equipment control settings: EKS-120 Sounder QM-MK-II Integrator Gain -20 dB/20 log R Gain 20 dB Pulse 1 .0 ms Expander x 10 Power 1 I 1 Range gate 23-27 m Range O:...SQ m Others as proper and convenient- The external transducer was suspended on a nylon rope and lowered into the water column close to the front of the hull-mounted transducer so as to give exactly the same depth sounding. These transducers were alternatively switched to the echo integrator system to obtain comparative integrator values corresponding to 500 soundings as controlled by an electronic counter. The results are shown in Table below: Table 1 RESULTS OF INTER-TRANSDUCER CALIBRATION External Transducer Ship's Transducer (120 kHz, 10 cm p) ( 120 kHz,_ 10 cm 9)) Cb.a:nnel A Cb.a:nnel B Obs. M Obs. M Obs. M Obs. i·l (No.) (mn) (No.) (mm) (No.) ( rrim) (No.) (mm) i 516 9 5o8 1 306 9 350 2 515 10 562 2 375 10 348 3 437 11 472 3 327 11 348 4 467 12 480 4 332 12 334 5 443 13 512 5 337 13 315 6 479 14 473 6 354 14 310 7 523 15 503 7 408 15 369 8 494 8 364 Mean value : - Mean value : M1 = 492.3 i 2 = 345.1 Coeff. of variation: C.V.= 6.6% Coeff. of variation: C.V. = 7.8% 15 It.should be noted that during the measurements the vessel was slowly moving over. the bottom about its anchor chain, so for practical purposes, the assumption can be made that the two transducers were sounding on the same target. The ratio between the transducers was estimated as A = f1 /f1 = 492.6/345.1 = 1.426 R 1 2 and confidence interval for the ratio was calculated from CI R.. ~ t "~'VVar (R) where: t 2.15 corresponding to 95% confidence probability and 14 degrees of freedom, and Var (R) is calculated from Var (~) =--2 x ~ M;i - 2 R=M1i M2i + R2Z..MzJ n-1 n '112 Thus yielding the confidence limits Upper limit R 1.497 u Lower limit R. 1.355 l. corresponding to± 5% deviation from R = 1.462 and hence suggesting that inter-transducer calibration can be- carried out on the seabed with fairly high degree of precision. This type of calibration was repeated on several occasions and gave consistent results. Experience from these calibrations suggests that because of the relatively low coefficient of variation (say, 8-16%) associated with bottom echo integration in selected places, the seabed is a suitable target. 6.2.3 Live fish calibration This work was carried out inside the Bay of Tahuna, the main town of Sangihe Island, which is about 100 n mi north of North Sulawesi. The location of the calibration site is shown in Figure 6. Earlier attempts to calibrate in the Anambas survey area had failed due tonon-availabilityof experimental fish. Since, the principal species are largely the same in both project areas of investigation, it was decided to select Tahuna for the calibration. The fish were supplied by the local fishermen who operate their small purse seiners (8-10m) both inside and in the vicinity of the mouth of the bay. The time of the calibration, which took place from 10-13 May 1983, coincided with the peak fishing season for round scad (Decapterus spp.), so this was the only species available for calibration purposes. Five series of measurements were carried out, each series comprising 16 individual integrator readings and each reading determined as the accumulated M-value per 1 000 soundings as counted by an electronic counter._ Observed integrator readings were obtained with equipment control settings as follows: 16 EK-S120 Sounder QM-~fK-II Integrator Ch A Output power 1 I 1 Gain/Expander -20 dB/x 10 Receiver gain -20 dB Threshold 2 TVG function 20 log R Speed compensation 10 knots Pulse length 0.3 ms Depth 4m Range 0-100 m Interval m It should be explained that the nominal settings of "depth" and "interval" did not correspond to actual range limits. This is so because for calibration purposes a special circuit adjustment was made to allow the sound beam to sample a maximum range interval within the cage volume. With the .echo-pattern of the cage displayed on an oscilloscope together with the range-gate pulse, it was possible to obtain optimum adjustment so as to eliminate the strong echoes of the cage's two steel frames in a way that resulted in a maximum range interval LiR = 1 .54 m and this was used in subsequent calculations. Before the target fish was introduced into the cage, the empty-cage echo was integrated to determine the actual contribution of the cage-net echo to the total integrated values. Hence, the appropriate correction is given as follows: =M -M Mfish observed (IIDn) cage or, in the ~resent case = M -8 .9 Mfish observed (IIDn) where the quantity 8.9 represents the mean millimetre reading for the empty cage. Following the above preparations the experimental fish were fed into the cage. The total number was 1 281 fish, giving a mean density of : ($= 213.5 fish/m3 • However, observations by divers showed a total mortality of 170 dead fish at the end of the experiment. Hence, the actual density, assuming linear mortality, was calculated from: ~ = 0 281 + 111)/2/6 = 199.3 fish/m3 • A total of five measurement series were made over a three day time span. The relevant results are presented graphically in Figures7a and 7b, which show a histogram of the length frequency of the experimental fish targets. While the graphs show small intraseries variability , some schooling tendencies and changes in the · orientation distribution pattern of the fish was evident from diving observations, but did not offer unambiguous explanations. Consequently, the mean of the four serieA (No. 1,2,4 and 5) was taken as the most representative value and this gave: M b = 451 mm, resulting in net value 0 s Mfish = 451-8.9 ,,...__/ 442 mm Given the above information and a mean weight: W = 17.49 for the calibration fish, the calibration constant C for conversion of integrator readings into absolute fish densities was calculated from equation No. 1 (Section 5.3.3). Hence, c 3 • 43 N . w •t.'R c V • Mfish 1196 x 17.4 x 1.54 3 •43 6.442 41 .45 17 The above constant was then adjusted to survey conditions using equation No.2 (Section 5 .3.3) above. p s liG ) (~) (~) 10-0.1(.tiGi + e cs c c s p s s 1 000 0.3 . 41. 45 1 500 0 • 3 10 -O . 1 ( 0 + 20) 0.276 Finally, taking a rounded value C 0.28 tonnes/n mi 2 per mm and ref. 2-mile ESDU s The above constant was used for estimation of nekton biomass from all survey data. It should be noted that the TVG function of the system was checked (see Fig.8) but the measured deviations from theoretical values were so small that corrections were not necessary to be introduced. Determination of target strength Estimation of target strength in decibels for the fish (Decapterus·spp.) used for the experiment was made on the basis of the relationship: TS = (SL+VR) + (20logR + 2aR ) - 10log(c T) - n - G. 10log( f v) - 10logC 0 0 -- 0 1. s where: 2 fA SL source level (dB// 1 Bar ref. 1m) VR maximum voltage receiving response (dB//IV per Bar) R maximum TVG range (here 100 m) 0 attenuation coefficient (here 0.046 dB/m) c sound velocity 0 542 m/s) T pulse duration (0.3 m/s) equivalent ideal beam cone (-18 dB) G. gain of integrator (dB//1 mm per unit of time ref. 1 mrange) 1. interval and 1 volt average input voltage) volume fish density (number/m3 ) area fish density (tonnes/n mi 2 ) Individual terms of the above equation can be calculated, or are determined as follows: 18 (SL+ VR) = 103.9 (from 6.2.1) (20 log R + 2aR) = 20 log 100 + 20.038.100 = 47.6 0 10 log (Tc/2) = 10 log (0.0003.1542/2) = -6.4 n -17.6 (value given by manufacturer) 0 G. 37 .9 l. 10 log Cfv/~) = 10 log (199.3/11897) -17 .8 10 log C = 10 log 0.276 = -5.6 s Inserting the above values in the corresponding equation gives TS= -103.9 + 47.6 + 6.4 + 17.6 - 36.1 + 17.8 + 5.6 = -45.0 So, for a round scad of 13.6 cm mean length, the mean target strength is TS = -45.0 dB The above conventional TS expression is then readily converted into TS per kilogramme from the' formula TSkg = TS - 10 log Wkg Hence·, -~5.0 - 10 log (17.4/1 000) -45.0 - (-17.6) -27.4 dB/kg Comparison with results elsewhere Similar calibrations and target strength estimates were carried out by the UNDP/FAO Regional Fishery Survey and Development Project in the Gulf and the Gulf of Oman (Lamboeuf and Simmonds, 1981). The relevant results are summarized and presented in Table 2. A target strength of -28.8 dB/kg was obtained from a mixture of Decapterus (45%) and Selar (55%). This figure is 1.4 dB lower than the present estimates of -27.4 dB, but this can be explained as an expected difference because the former TS-value is derived from a frequency of 38 kHz, while in the present work a 120 kHz system was used. Several workers, e.g.,Saetersdal et al. (1983) have reported about two decibel higher target strength for 120 kHz in comparison with a frequency of 38 kHz. Consequently, the two independent results show reasonable agreement. Species/length dependence of C5 The nuinerical value of the integrator conversion constant (Cs) may or may not depend significantly on species, but usually it depends on their length parameters, especially for the smaller pelagics. For the latter, it is sufficient for the purpose of the present report to assume the constant to be porportional to fish length. Hence, the Cs value obtained experifuentally on fish, having a mean langth 'J: = 13.6 cm (Fig.7b) will, within a given range, be' length dependent as follows: 19 c .0.28 T s = 13.6 or 0.021 c s I From the work.done in the Gulfs (see Table 2) it appears that Cs is practically species independent for the seven species enlisted. Since five of these species groups (Sardinella, Decapterus, Selar, Rastrelliger and Stolephorus) are also likely to make up the bulk of the observed nekton in the Indonesian survey, according to existing catch statistics, it seems reasonable to assume that the established constant (Cs = 0.021 t) will be relatively free of species related bias. However, it is clearly subjected td a potential length-dependent bias , given that its numerical value is approximately proportional to fish length. Hence, to establish a properly weighted survey constant, a. knowledge of the proportional magnitude and length classes that characterize the surveyed biomass is required. Given such information, the density estimator (~ = CM in a simple case) would take the form M (tonnes/n mi2) p eA p1 p2 p3 n -+ +- + .... + c c1 c2 c3 n where P is the weighted proportion of the relevant length-determined biomass component n and Cn is the length-corrected constant for that same component and M denotes the observed integrator reading .. For the present survey, neither the available catch statistics, nor the samples from the TENGGIRI fishing operations, were considered suff icientiy reliable to supply the required information on Pn and en and therefore, the same constant (Cs = 0.28) was used for all survey estimates. 6.3 DISTRIBUTION AND ABUNDANCE 6.3.1 Biomass distribution Cruise 01/8204-05 The main characteristics of the apparent geographical distribution pattern of the acoustically observed fish biomass, together with the corresponding survey tracks, as well as photos of echograms, are mapped and illustrated in Figures 9-37. The large-scale track (Fig.9) of the preliminary survey cruise (Leg I) produced a distribution map for the depth range 0-100 m,as also shown in Figure 9. As evidenced by the map, traces of pelagic fish were found only in very limited areas and the echo-integrator measured constantly low biomass densities. To complement the acoustic observations, trolling lines were used to provide information on possible occurrence of fish at the surface water levels. These ·resulted in apparently random catches taken along transects Nos.6-10 (2°30'-0°30' Lat.north). The predominant species in the catches appeared to be skipjack tuna in the size range 0.5-0.7 kg. Other species included two albacore tunas (5.5 and 3.8 kg) one dolphin fish (5 .8 kg) and a few rainbow runners. The use of trolling lines was thus useful as a means to confirm the presence of the above species in the area, however their catch efficiency was clearly reduced significantly due to the relatively high vessel speed of about 10 knots. The second part of the cruise (Leg II) concentrated in the area around Sangihe and nearby islands as illustrated by the corresponding survey track pattern in Figure 10. This survey produced a distribution map shown in Figure 11, which indicates a very low 20 biomass abundance, mostly distributed as a narrow band along the east and west coast of the main island. It is particularly noteworthy that no fish were detected on this occasion around the smaller islands south of Sangihe. Cruise 02/8208-09 The survey track of the Leg I is shown in Figure 12 and the resulting distribution map in Figure 13. Comparison with the previous map (Fig.11) indicates considerable changes in the diptribution pattern, notably in the area northeast of Sangihe, which was scarcely populated before, but now showed relatively large concentration of biomass distributed over the entire bank area. Photographs of echo-recordings made with two sounders (38 & 120 kHz) on this occasion are presented in Figure 14. As shown by the EK-400 echo grams (a & b), there are fish traces located well below the 100 m depth range, which corresponds to maximum integration interval. The fact that the present map also· shows somewhat higher densities in the littoral zone of Sangihe (see Fig.15), suggests that during the period between the two cruises there has been a significant influx of biomass into the area covered by the survey. The survey around Sangihe was repeated after two days with a transect pattern shown in Figure 16, which produced a distribution chart presented in Figure 17. Typical echo traces from this survey are shown in Figure 18. Comparison between Figures 13 and 17 suggest that significant shifts in biomass distribution may occur within a time interval of only a few days, or even from one day to the next. A subsequent survey of the narrow shelf area around the Talaud Archipelago was conducted in the form of a wide-angle oblique grid pattern (Fig.19), which yielded a biomass distribution map shown in Figure 20. Some very dense layers and schools of pelagic biomass were detected during this Leg III of the cruise. Samples of photographs showing typical echograms are presented in Figures 21-23, which are self-explanatory. The last part of the cruise (Leg IV) covered a well known fishing area around the smaller islands south of Sangihe (see Fig.24), which during Cruise 01/8204-0~ (Leg II) had appeared to be devoid of fish. In sharp contrast, the present survey recorded practically continuous traces of pelagic biomass, including some concentrations on a commercial scale, as can be shown by a sample of the photographed echograms presented in Figures 25 and 26. The dis~ribution pattern is shown in Figure 27. It should be noted that the geographical boundary of the distribution, beyond the actual transect coverage, was determined arbitrarily. Cruise 01/8304-05 The first leg covered again the area around Sangihe and nearby fish banks south and northeast of the island (Fig. 28) The resulting distribution map (Fig.29) shows occurrence of pelagic biomass only in the southern part of the east and west coast of Sangihe, while the banks south and northeast of the island appear remarkably devoid of fish. A comparison with the acoustic observations made during Cruise 02/8208-09 (Leg I and IV), which covered the same areas, shows a remarkable difference, as clearly illustrated by comparison between Figure 29 and Figures 13 and 27. Echograms obtained from the acoustic equipment within the area of fish distribution were mostly of the type as illustrated in Figure 30. In the area south of Sangihe, where no valid integrator readings were obtained, the only fish echo-traces detected were those shown in Figure 31. A subsequent replicate survey (Leg II) of the Talaud Archipelago's shelf area (Fig.32) produced similar results, i.e.,with the pelagic fish biomass practically absent from the area, as shown by the observed distribution map in Figure 33. Here again, the difference is striking when compared with previous results shown in Figure 20. 21 The third leg of the present cruise was conducted in the form of a relatively large scale parallel grid survey covering the near-shore waters of the Talaud. area, .extending up to 20 n mi from the coastline. The area track pattern is illustrated in Figure 34. While no echo-traces were detected on the 120 kHz sounder during the entire survey (hence, no distribution map), some large pelagic schools were detected in deeper waters (150-250 m)on the powerful 39 kHz sounder. This is illustrated by a series of echograms shown in Figure 35. The last part of the cruise (Leg IV) was designed as a parallel grid survey to cover a 30 mi wide band extending from Sangihe in the north to North Sulawesi in the south (see Fig.36). No integrator data resulted from this survey track and only a few unidentified echo-traces were recorded by the EK400 (38 kHz) scientific sounder (see Fig.37). 6.3.2 Abundance estimation Estimates of absolute fish biomass were derived from the acoustic data on the basis of the methods described in Section 5.2 on data processing, as well as Section 5.3.3, which details the method for establishing the required integrator constant (C) to convert the analog integrator readings into absolute biomass densities. The calculation of total biomass within a given area is then achieved by first plotting the integrator readings (M) along 2 mi sectors of the track chart. The resulting set of data is then post stratified as follows: Stratum (h) M-values (nun) Abundance 10-100 very scattered 2 101-500 scattered 3 501-1 000 dense 4 >1 000 very dense Subsequently, the corresponding isolines are drawn, usually resulting in several sub areas within stratum, the sizes of which are determined by a planimeter. The echo abundance (Eh.) within the ith sub-area, in the hth stratum is then estimated from 1. iL M. ) J. 1. i = 1 where: i index for sub-area n number of M Values within the jth sub-area A· area size of the jth sub-area (n mi2 ) 1. M. ith sample of M within the jth sub-area Ji The total echo abundance within stratum is found by summation: j = m Eh > j = 1 where : m = number of sub-areas within stratum. Further, the total echo abundance in the area surveyed (Et). is found by the summation: h = 4 Et ~ Eh h = 1 22 Finally, the conversion into total biomass (Wt) is obtained from the product where: C is the experimentally determined calibration constant. Details of the calculations and the figures obtained for fish biomass (expressed in metric. tonnes) resulting from the individual cruises are presented in Tables 3-5. A summary of the essential results is given in Table 6 below. Table 6 SUMMARY OF AEUNDANCE ESTIMATION IN THE SANGIHE-T.ALAUD ARCHIPELAGOS Survey Area Month/Year Biomass Estimate (t) Sangihe + nearby banks May 1982 947 " September 1982 58 539 " April 1983 1 463 Talaud shelf area September 1982 17 881 " April 1983 169 These estimates are discuss~d in Section 7 below. 6.4 TEMPERATURE MEASUREMENTS Cruise 01/8204-05 (Leg I) A total of 22 BT stations were made during this cruise at locations indicated in Figure 9. The results are presented graphically in Figures 38-41. Depth coverage of the measurements was generally from 0-250 m, While the temperature profiles do not show any pronounced thermoclines, they indicate a typical average gradient of approximately 0.08°C/m in the depth range from 50-100 m,with relatively homogeneous temperature distribution in the upper 50-m depth column. Cruise 01/8304-05 (Leg III) A total of 18 BT stations were worked in the waters around the Talaud Archipelago, the position of which is shown in Figure 34. The results are given in Figures 42-44, which are largely self-explanatory. 6.5 THE STATE OF FISHERY RESOURCE EXPLOITATION The Sangir-Talaud District (abbreviated as SAT.AL) is administrated by the North Sulawes i Province and consists of two main islands, Sangihe and Karakelong. The number of fishermen in the SAT.AL in the four years (1977-1981) did not show a marked increase; there were over 32 000 fishermen in 1981, corresponding to approximately 10 600 fisheries households (Table 7). The catch (landings) in 1981 was approaching 11 000 t, showing an average increase during 1978-1981 of over 10 percent per year (Table 8). However, it has shown a relatively small increase from 1980-1981 of only about 2.5 percent. The catch composition during 1978-1981 (Table 8) shows 16 identified species (or group of species) wherein the pelagic fish species composed almost 75 percent, which could be divided into large pelagics of 29 percent and the small pelagics, which are dominated by scad (Decapterus) and garfishes (Hemirhampus), which account for over 45 percent. The demersals account for only about 10 percent of the total and these mostly consist of coral fish species, dominated by fusiliers, caught by muro-ami, handlines, and traps (Table 8). The large pelagics are those species mainly caught by lines (handlines and trolling) and these consist mostly of eastern-little-tuna (Auxis and Euthynnus), skipjack (Katsuwonus pelamis) and tunas (Thunnus). The catch statistics for these species show relatively steady landings of around 3 000 t per year during 1978-1981 (Table 8). The small pelagics, caught by seine nets (beach seine,mini purse seine and lampara), gillnets (drift and encircling) and also traps~ (weirs), consist chiefly of scads, flying fish, garfishes and trevallies, plus some other species of little commercial importance. The landings during 1978-1981 show a marked increase, averaging almost 30 percent per year. This increase is most probably linked to the increase in outboard motor utilization (Table 8, Fig.45), which has made the fleet more productive. The fishing gear used in the Sangir-Talaud waters is dominated by lines and gillnets (rables 7 and 9). During 1977-1981, the use of handlines showed an average increase of 18.8 percent per year, whereas the use of gillnets increased by 33 percent. These increases were matched to the increase in numbers of outboard motors at a rate of 43 percent per year. However, the total numbers of nonpowered boats are fairly stable, with a declining tendency in 1980-1981 of 0.5 percent (Table 7, Fig.46). 7~ DISCUSSION AND CONCLUSIONS 7. 1 MAIN FINDINGS OF THE SURVEY The main survey effort provided charts of the geographical distribution pattern of pelagic fish biomass in the coastal waters of the Sangihe-Talaud_Archipelagos. Three independent estimates of standing biomass weights for the resources of small pelagic species in the Sangihe area were obtained. Also, two estimates were obtained from the Talaud surveys. The most striking feature of these estimates (Table 6) is their large variability. In this respect it should be pointed out that the performance of the equipment was carefully monitored during the sequential surveys and no changes made in the survey routines in order to minimize the component of variability associated with the actual equipment and methods used. It is, therefore, reasonable to conclude that the two estimates (in September 1982 a total of 76 420 t and then in May 1983 totalling only 1 632 t for Sangihe + Talaud) represent real .differences, i.e. ,variability, which is largely governed by natural factors such as changes in fish behaviour patterns and migratory movements of the fish in and out from the area covered by the survey. It is noteworthy that the situation in both survey areas (Sangihe and Talaud) was strikingly different in May 1983 compared with September 1982 when large concentrations of fish schools and layers were detected. A visual example of this is given by comparing the observed distribution patterns of the biomass in the Sangihe area as shown in Figures 13 and 29 or by comparing Figures20 and 33 for the Talaud survey coverage. Also, the acoustic observations in April 1982 indicated total absence of fish from the area south of Sangihe, while in September of the same year the same area was observed to be densely populated with ~ome fish concentrations on a commercial scale (e.g.~ig.25). The estimated biomass for the area on this occasion gave a figure of approximately 45 000 t. Then again in April 1983, a replicate survey of the same area showed it to be comp1etely devoid of fish. Similarly, the area northeast of Sangihe, where relatively large concentrations of fish were 24 observed in September 1982 (Fig.14), was also practically devoid of pelagic fish in May 1983. The importance of these observations, as it relates to possible migration of the fish, is strengthened by the fact that the same type of variability occurs in the Talaud survey ·results. This was clearly brought out by visual comparison between Figure 20 and Figure 33. The former corresponds to a biomass estimate of 17 881 t (Table 5), whereas the latter only resulted in a total estimate of 169 t. The suggestion that migratory movement of the target fish is the principal source of the large fluctuations in obtained biomass estimated is supported by observations made with the powerful (38 kHz) EK-400 sounder. At the time (Apr{l 1983), the 120 kHz integrator system produced extremely low biomass estimates in the range interval from 3-100 m,within the survey area, the EK-400 recorded significant concentration of pelagic traces outside the area at depths of 150-250m (see Figs.35 and 37). 7.2 POSSIBLE BIAS IN THE ESTIMATES The survey procedures and the acoustic measurement methods applied, may give rise to bias in either the negative (underestimation) or positive (overestimation) direction. For the present survey, the following sources of possible biases can be readily identified: Negative bias limited area coverage too low integrator conversion constant tuna-like species excluded from estimates Positive bias insufficient correction for plankton inflated integrator conversion constant inclusion of demersal species.in estimates An evaluation of the above factors, based on various check calculations and an overall logical examination, does not permit a conclusive answer as to the question of whether the estimates obtained are too low or too high. For example, it is difficult to assess the lev--e1 of A bias, which clearly can vary from one survey to another. This can 1 be seen by comparison between Figure 25 and 29, the former suggesting that significant quantities of biomass were distrib~ted outside the survey boundaries (notably to the south) whereas the distribution pattern in Figure 29 for the same area does not indicate a major bias of the A type. The A and B sources of biases also remain difficult to evaluate 1 2 2 in the absence of adequate oiological samples. As for tuna-like species, which in 1981 accounted for about 33percent (Table 8) of the annual pelagic fish land.ings, these. are almost totally excluded from the· present estimates. Part of the reason is the fact that these species are often found at surface levels above the detection zone of the acoustic beam (notably during the calm monsoon seasons) and, therefore, cannot be measured. However, the main reason relates to the way in which the numerical value of the integrator conversion constant C = 0.28 t/n mi 2 per mm is established, i.e, for species with swim.bladder, which normally account for about 90 p~rcent of the backscattered sound energy, and thus exhibit relatively high target strength. The tuna-like species in question either have no swimbladder or only a rudimentary one, which means that their target strength is likely to be about 8-10 dB lower than typical values for the sardines and mackerels. Consequently, the appropriate constant for the estimation of the biomass weight of tuna-like species probably should have a numerical value in the range from 3-6 instead of C = 0.28. In other words, if the measured biomass includes as a large component the smaller tuna-like species, then the biomass component would have been underestimated by a factor of 10 or more. In regard to the 25 B -type bias, which is theorectically positive, an FP correction factor (based on the 1 ratio between the daytime-to-nighttime mean millimetre readings) was applied. It should be stressed that this approach was adopted because visual evaluation of echograms and colour scope displays to evaluate the proportional contribution of planktonic, demersal species, and possibly squid, to the total echo-integration, tended to agree with the FP ratios. However, this was not the case during cruise 03/8311-12, which yielded a value FP = 1.04, "Whereas the subjective evaluation suggested strongly to use the previous ratio (FP = 0.69, see Table 6) for the data from this survey, which recorded exceptionally high biomass abundance. It should be further emphasized that the above method was adopted only as a preliminary approach to a complicated problem which should be specifically addressed in future research surveys. Specifically, now that both the analog and digital integrator systems are working well, they can be operated simultaneously and thus give two sets of data (38 and 120 kHz) with potential use for establishing more ccurate FP ratios. Such an approach should be complemented by improved biological sampling and ~11 relevant data subjected to detailed statistical analysis to deduce the most efficient weighing factor. Otherwise, the general estimates of mean biomass densities from the surveys seem reasonable when, for example, they are compared with density estimates obtained during cruises with the R/V DR. FRIDTJOF NANSEN in some neighbouring countries. A comparison is facilitated byTables 10 and 11. Also, Table 11 enables comparison between density estimates obtained from both project areas. It is particularly noteworthy that the density ranges (5.0-57.7) measured in the Sangihe and Talaud Archipelagos are very similar to those obtained from the Anambas and Natuna Archipelagos More interesting though is the fact that, in both areas, very low densities were observed during the calm monsoon periods, whereas during the strong monsoons, large concentrations of pelagic fish were detected, consequently yielding high density estimates. 7.3 IDENTIFICATION OF SPECIES Complementary information from sample fishing concerningweight/length distribution of the various species as well as their proportional representation in the total biomass estimate, is required for accurate interpretation of the survey results. This applies both to the conversion constant "C" as discussed in Section 6.2.3 and, to a greater extent, to the yield aspect, i.e.,to determine the sustainable annual potential yield from the total biomass assessment. Apart from inadequate seasonal coverage, the main limitations of the present survey was its inability to catch and directly identify the acoustic targ~ts. Experience from the survey brought out three particular factors which impeded successful use of the TENGGIRI's large purse seine as a sampling gear. These were : (a) schools sighted at the surface levels are difficult to catch due to their rapid movements and tendencies to dive out of sight before the vessel can be manoeuvered into shooting position, (b) larger schools were often detected in waters too shallow for shooting the net, and (c) unfamiliarity of the captain and crew with purse seine operations. In regard to the last factor is should be noted that, following a special six months training programme, this problem was largely eliminated in the last phase of project field operations. 7.4 IMPLICATIONS AND FUTURE RESEARCH An assessment of the above results brings out a number of complications with respect to their scientific interpretation as well as their practical meaning as an input for future development planning of the fisheries. Large seasonal variability in the obtained biomass estimates, apparently related to migratory movements of the fish, as well as the lack of adequate biological sampling data, are all factors that impede the formulation of clear concepts about the pelagic resources in the area. Hence, it is difficult to evaluate the significance of the maximum estimate of 76 420 tyielded by cruise 02/8208-09. At the same time, the survey has raised questions as to the general availability of these resources and their accessibility to the traditional fishing units, which can operate only under good weather conditions (or in sheltered waters.) with relatively simple fishing gear. 26 Because tuna-like fish species are largely excluded in the acoustic estimates, these actually represent additional pelagic resources found in the area. In terms of biomass level and given the present annual catch rate of only about 5 000 t it would appear that relatively large, unexploited pelagic resources exist in the area on a seasonal basis. While the project's resources survey has achieved one of its principal objectives, i.e.,to quantify the level of the pelagic fish biomass, it is clear from the foregoing discussion of the results that further data are needed before a realistic assessment of the resources potential can be attempted. To achieve this would require further research efforts, in particular (a) to study in greater detail the cruises and characteristics of the seasonal/annual fluctuations in biomass, and (b) to develop more effective means and methods in order to identify the fish species of the surveyed biomass • Morever, it is important to be aware that the survey does not provide accurate information on the species composition of these resources, nor does it provide explanations of the biological relationship between the bulk of the measured resources and the actual species that are normally caught by the traditional fishermen in the close inshore waters. Also, the fact that some part of the observed pelagic resources are distributed outside the geographic extent of the traditional fishery coupled with apparent migratory movements of the resources, which again appears to be linked to the monsoon seasons, are all factors that must be duly considered in any attempt to determine the harvestable fraction of these resources. Hence, the near future development of the resources may depend more on factors related to their availability and accessibility rather than on biological limitations. The present acoustic surveys have demonstrated that they represent one potential approach to provide first estimates ~f the pelagic resources in the area of investigation and to advance-the general knowledge about the seasonal and/or annual changes in distribution and abundance of these resources. They have also generated new knowledge which can serve as a base-line for future research in the area. 8 . ACKNOWLEDGE1:1ENTS FAO is greatly indebted to the many people who assisted the Indonesia Fisheries Development Project to carry out these surveys. Special thanks are due to the Director General of Fisheries, Adm. Abdu Rachman, for his support to the project. Thanks. are also due to Messrs. Soewito, Director of the Directorate of Resources Manamenent, DGF, and M. Wibisono, Chief of the Fisheries Technique Development Centre in Semarang, for their excellent cooperation and coordinating role in relation to all vessel operations. Special mentio.n should also be made of the late Mr. Unar, Director, Research Institute for Marine Fisheries, Jakarta, who always gave his full support to the project. Finally, thanks are due to the heads of the various District and Sub-District Government Fisheries Service Offices who provided valuable data and information on the local fisheries, and to Mr. Baithur S., Captain of R/V TENGGIRI and his crew without whom these surveys could not have been made. 27 REFERENCES Aglen, A. ,L. F~yn, 0. R God~, S. Myklevoll and O.J. 0stvedt. Surveys of the marine 1981a fish resources of Peninsular Malaysia, June-July 1980. Reports on Surveys with the R/V Dr. Fridtjof Nansen. Institute of ~arine Research, Bergen Aglen, A.,L. F~yn, O.R. God~, S. Myklevoll and O.J. 0stvedt A survey of the marine fish 1981b resources of the west coast of Thailand, July 1980. Reports on Surveys with the R/V Dr. Fridtjof Nansen. Institute of Marine Research, Bergen Aglen, A. ,L. F~yn, O.R. God~, S. Myklevoll and O.J. 0stvedt. A survey of the marine fish 1981c resources of the north and west coast of Sumatra, August 1980. Reports on Surveys with the R/V Dr. Fridtjof Nansen. Institute of Marine Research, Bergen Burczynski, J. Introduction to the use of sonar systems for estimating fish biomass.FAQ Fish.Tech.Pap. (191) Rev. 1:89 p.(Issued also in French and Spanish)~- FAO Report on 1981-1983 acoustic fishery resources surveys in the·southern 1985a part of the South China Sea, with special reference to the waters around Natuna, Anambas. Serasan and Tambelan Island groups. A report prepared for the CIDA/FAO Indonesian Fisheries Development Project. Rome. FI: GCP/INS/056/CAN, Field Document 2 Johannessen, K.A. and G.F. Losse. Methodology of acoustic estimation of fish abundance 1977 in some UNDP/FAO resource survey projects. Rapp.P.V.CIEM, 170: 296-318 Johannessen, K.A. and R.B. Mitson. Fisheries acoustics: A practical manual for aquatic 19ip biomass estimation. FAQ Fish.Tech.Pap. .(240):249 p. Lamboeuf, M. and E.J. Simmonds. Acoustic estimation of the biomass of the stocks of small 1981 pelagic species in the Gulf and the Gulf of Oman (September 1977- 0ctober 1978). Regional Fishery Survey and Development Project, FAO, Rome; FI:/DP/RAB/71/278/11 Midttun, L. and O.Nakken On acoustic identification, sizing and abundance estimation of 1971 fish. Fiskeridir.Skr. (Havunders.), 16(1): 36-48 Saetersdal, G., T.Str~mme, B. Bakken and L. Piekutowski. Some observations on frequency 1982 dependent back scattering strength. FAO Fish.Rep., (300):150-6 28 Appendix 1a VESSEL SPECIFICATIONS Name TENGGIRI Owner Directorate General of Fisheries Type Purse seiner with longlining and squid jigging facilities Delivered December 19 79 Length Over All 39.2 m Breadth 8.5 m Depth 4.0 m Gross Tonnage 303 .5 t Fish Hold 40.6 m3 Freezing Room 12. 9 m3 Cooling Room 8 .3 m Complement 6 officers; 12 crew, 2 instructors; 5 scientists, 4 technicians Main Engine Niigata, 800 HP at 900 rev/min Propeller Controllable pitch Speed 12.5 knots Bow Thruster Kamone, 1.2 tf thrust Purse Seine Winch Kawasak.i, 3 tf at 40 m/min Line Hauler Ifui Skiff 6.2 x 2.8 x 0.9 m Working Boat FRP, 4.5 x 1.7 x 1.0 -m Acoustic Equipment 2 fishfinders; portable sounder; 1 scanning sonar; 1 catch meter (all Japan Radio); SIMRAD scientific sounder equipment Navigational Aids Gyro compass; 2 radars; loran; radio direction finder 29 Appendix 1b FISHERIES SURVEY AND EXPLORATORY VESSEL TENGGIRI GENERAL ARRANGEMENT f9-E OECX: W.CPASS DEC)< Appendix 2 EXAMPLE OF ACOUSTIC LOO SHEET CRUISE: VESSEL: DATE: PLACE: SHEET NO.: Time Log Depth Leg Course Roll Station QM-reading QM-intervals H Surface (hr) (No.) (m) (No, ) (degr} (No,) (No.) Stop Start RE HA R K S Corr. REMARKS (TDC) (m4) I n\\i) lm"i lm~ A/B 00 12 21t 36 , 110 00 12 211 36 L» 0 ltB 00 12 21t 36 118 00 12 24 36 IJS Echosounder Control Settings: Echointegrator Control Settings: Channel A Channel B Gain/Tvg: Pulse: Speed comp. Gain/Exp1 Power: Bandwidth: Range Comp. Threshold: Range: lleo.BRin: Reset: Model 31 Appendix 3 EXANPLE OF PRINTOUT OF DATA FROi-f QD DIGIT.AL INTEGRATOR ------ './ESSEL: R/Y TENGGIRI CRUISE 02/8306-07 PAGE 5 PLACE: AtiAMBA-S: S:UR\.'EY AREA DATE: 83.6.15 COMMENTS: START 22.48 ------~------~------~- ::;:ouNr•ER No.: 2 FREG!UENCY: 38. (I 1-<:Hz :SOURCE LEVEL: 119. 4 D PULSE DURATION!. 0.35 MS TRFtNSD•JCEP.- 1 -21.0 DB 'v°CLTFt<5E RESPCNse: 3.5 D F't_ILS:E F.'.EP. F REG!. : 128 P/M rv1:;: 64-. 6 DB GAIN: I). (I D Mt=i::<. RAN•:::E: :314 M S:v-;5:1_1PPRESS: -70 DB C-EcHcscuNDEP.-: :-31. 5 D LAYER I) I I I III IV '·I VI VII VIII IX UF·PER-LIM 2. (I . 1 o. 0 20. 0 30.0 40.0 50.0 60. 0 70.0B+ 15.5B+ 5. LCJf-.IER-LIM 1 0. I) 2 o. 0 30.0 40. I) 50.0 60.0 70.0 80.0B+ 5.5B+ o. THRES. M'•/P 10 f O 10 10 10 10 10 10 F.:Ec. CH. 1 ·;j.... ::;:•=ALE 10.00 1.00 Lo•:::...-·ToTAL 7:?.. 0 0. 12 o. 06 ••••• .... I). 01 I). 01 ...... •.++->>»>» o. 01 o. 0 -E.O. 7 -54.'4 -6.:.• 4 -65.0 -63.4 -63.1 -64.6 -61.8>»>>>> -63.4 -58. 66.2 8.0 1 o. ·o 10.0 1 o. I) 1 o. 0 9.9 3. 3>>»>>> 10. 0 5. :::o.o 0. 1r::. 0. 06 ...... I). 03 0. 03 •·• ..>>>>>>> o. 01 o. 0 -5·:-:t. 8 -54.4 -65.'3 -64.1 -59.2 -59.0 -63.6 -62.6>>»>>> -62.9 -60. 69.8 8.0 10.0 10. 0 10.0 1 o. 0 ··-10.0 6.8>>>>>>> 1 o. 0 s .. :=:2. I) (I. 13 0.06 ...... o. 01 0.01 o. 01 O. Ol>>>»» 0.02 .. .•. -60.7 -54.5 -66.2 -65.8 -62G5 -62.1 -63.0 -61...,. ?>>>>>» -61.5 -60. 70. 8 8. 0 1 o. I) 1 o. I) 1 0. 0 1 o. I) 10. 0 . • 8>>»>» 10."o 5. 84. I) 0. 13 o. 06 •••• 0. 01 (I. 02>>»»> 0.02 ..... -60. 9 -54.5 -66.9 -66.1··- -63.7··- -62.7 -64.2··- -60.2>>>>>>> -60. 4 -61. 71.4 :::. 0 1 I). I) 10. 0 1 o. 0 1 o. 0 10. 0 8. 4>>»>>> 1 o. 0 5. :::6. 0 0. 12 O. OE...... 0.02 0.02 ..... -61. 2 -54.5 -66. '3 -67.6 -65.0 -63. 7 -64.2··- -60. 4 -55.8··- -60.4 -61. 72.4 8. I) 1 I). I) 1 o. 0 1 o. 0 1 o. 0 1 o. 0 9.3 o. 1 1 o. 0 5. 8:fl· 0 i 0. 12 0. 01$...... o. 01 I). 02 ..... I). 02 ...... -i:.1.1 -54.5 -~6. '? -67.6 -65.9··- -64.4··- -63.0 -60.5 -54.9 -60. 4 -61. ?2.6 :?, • 0 10.1) 1 I). I) 1 0. 0 10. 0 1 o. 0 9.5 . 0."1 1 0. 0 5. 90.0 0. 13 O. OE...... •·.- 0. 01 o. 01 0.02 0.02 o. 0 -60. :?, -54.6 -66.0 -66.7 -65.7 -63.2 -61.8 -60.7 -51.8··- -60.5 -60. 72.4 8.0 1 0. I) 1 I). 0 1 0. 0 1 0. 0 1 o. 0 9.4 o. 0 1 0. I) 5. :;rp 32 E -- 122° 12 4 ° 126° 127° LO KASI KABUPATEN KEPULAUAN SANGI HE DAN TALAUT Skalci = 1 : L..500.000 u -M.AS_ Fig. 1. Geographic Location of Survey Area (shaded area) 33 BIOLOGICAL SPECIES AND ..------,I SAMPLES SIZE- OISTRI BUTION .------...-!"""'1DISTRIBUTION : CHARTS I I I I CHART I ACOUSTIC ABUNDANCE I PLOTTING CALCULAT!ONr----""' ESTIMATE LOG-SHEET 1 I (M, VAL.UES) I i I L _R_!S~LT~ _J ECHOGRAM STATISTICAL MOOEL ----- r------, :osCILLOSCOPE t------COMPARISON JN TE GRAM Fig. 2 Outline of System for Data Handling and Processi_ng 34 (a). 0 Sm. SOUND SEAM. l CALIBRATION BALL OSCILLOSCOPE DISPLAY. ( b). SPHEnE ECHO VOLTAGE\ I""'~--- t = 5. 2 ms.-----'=-- Fig. 3 General arrangement for Calibration on Standard Target w lJ1 \\ I \ 'I. i General arrangement.for suspension of calibration cage and transducer together with keep-net for experimental live fish 36 WIRE TO .-BOOM \ \- \ 1 . \ I \ \_ 3.50m \ \\ I I \/ 'v _.L. Fig. 5 Geometric view of calibrat]on cage location in the water column 37 125° 20' t.O' SO' 1.• 1· I .·-······. ~-·-...... so' ··-- \:. ~-".-.... -:._ ,...... <~ ,. ·~-,~·-.J '-) ::_ __ •""• .· ·-: ..- .. __. ( ...... ·--...... :. :: {:~-- \ \ ,. '1)Torao...0..t$:;..=:t1 ': ~-· .. ___,\_.. - _.·- ·--;_7 30' ' ~- '--'/ ) v-- __ .. /-..J \~ '... _/-J '\ \ .. .. ·-···20o1K··-·""} ...... ;: .·•· : ·. \ 20' ··.. <.. ... ~ ..... // __,,' .•• J ·--.--- ·o~.L_____ ... 10' __,. 0 . .. .. --·· Fig. 6 Location of Site for Live Fi~h Ca1fbration 38 .'\ / \ 800 , ' , \ .. ----4' \ (a) 600 E.xp. 2 E.xp. t. 400 E.xp. 1 E. ~ p.S" E.xp.1 :11-05-83, 0800 -1000 hrs. 200 Exp. 2 : 11-05-83, 1145 - 1345 hrs. E.xP. 3 : 11-05-83, 1840 - 2000 hrs. Exp_ 4 : 12-05- 83. 1745 · - 1945 hrs. E.xp.5: 13-05-83, 0650 - OSSO hrs. 3 5 7 9 11 13 15 16 NUMB Er< Of READINGS ( 1000 Soundings/reading) LT= 13- 6 cm ( b) :r:. 50 (.{) Li.. n: 113 Li.. 0 30 c:: w C!J 2: ::J z 10 12 14 16 18 20 TOTAL LENGTH CM Fig. 7 Graphs showing variations in intesrator readings during (a) calibration of live fish and (b) length distribution of the experimental fish targets 39 65 ECHOSOUNDEf< EK - S 120 .r I I ..,' ,.J / 60 Theoretical TV G. I / / Measured TV G. / SS so 45 40 JS 30 / / ZS 20 2 3 4 s 7 10 15 20 30 40 so 70 90 f"?ANGE (metres). Fig. 8 Measured vs. theoreti ca 1 TVG for "TENGGI RI 11 's EK-S120 sounder 40 .» .. ..• ~ oo 22 "(! h l A U T "'MA lUKU .. · CR. 011a·2 04- OS (Leg I) ·a~f:1~ ~1' Abundance Categories (mm) 10 ~ 10 - 100 - ! c::, 11 ~.~ l) Cee~ALIABU ~ANGOLI . r- C> zo .:l. 8. T. STATION Fig. 9 Survey track and biomass distribution chart also showing positions of BT stations made 41 CR. 01I8204- 05 - LEG II 50' ~o· 30' 20' 10' Fig. 10 Sur~ey Track covering the Sangihe Area 42 Fig. 11 Distribution and abundance of pelagic fish biomass in the Sangihe area, based on integrator data so· 40' P. S A N G 30' 20' O ... ~. CR. 01 I 8204 - 05 - LEG II 10' Abundance Category (mm) ~ 10 - 100 43 CR. 0 2 I 82 0 o - 0 9 - LEG I 50' 40' 30 20' O•A 10' Fig. 12 Survey Track covering the Sangihe Area 44 125°20' JO' <:O' 50' l.()' S A N G E ))' 20' LEG I CR. 02/8208-09 iO' Abundance Categories (mm) ~ 10 100 101 500 ~f' (a) (b) (c) (e)_ --- ~ ------~-·- - --"·-·------ (NC-120S 7 120 kHz) Echo-recordings ma.de with two echosounders (NC400/NC-120S) a.t different ranges and freqo_encies over same transect sections during CR.02/8208-09, Leg I, showing la.rge fish concentrations on the NE bank of Sangihe island 46 (b) (c) (d) (e) ( f) - -, ';)'> :·; ... :;:••1;;;0 .. ~, ,;,,.-1;·;•,", •7,-.,y,;":"'J':}'.·.:·:-:·;·;··':":~;;·,~~;;,-T':°;;.:. ....,._r.•- =:;;;....,.;;;::;;;;;;;;;;;;~~~~~~~:;;:;;:=:~;;:;;;;~---~------o;;;;-;;;=-;::;;;;;;::;;;:;;;;;f:::;::;===::::::;;::;;=;;;::;::::~~;:;;:;::;::;=;::;;=.:;;;;;;;;;:;:;;;:;;;:=;:~;:;:;~::::;;~;:;;:; ·-·--·. ,§,\::::~g ~31~£~~j?.i~i~1~0~~~f~~lsM::·I{';:>;; _·1' , :; '. ::';;: ,.. '. ·.: , ·· ·. ·.·: · . .' '··. (.EK 400, 38 kHz) (.EK-120S, 120 kHz) Fig. 15" Echo-recordings ma.de with two echos0tmders (EK400/EK-120S) at different ranges and frequencies over same transect sections during CR.02/82o8-o9, Leg I, showing typical fish traces on the shelf area. (littoral) around Sangihe 47 so· CR 0218208 - C9 - so· I.JANG II ~All.OHAHf. 0POA (7.S?. 8.AL0Nf0HE,.. ~ t.o' 20' ~HA CJMAMENGETANG NENUINVC:JL. I) Fig. 16 Survey Track covering Sangihe Area 48 CR..02182 08 - 09_ - Ll:G II Abundance Categories (mm). ~ 10 - 100 illIIIl1 101 - 500 m > 1000 so' t.l.Lf'IG ~ ~All011AHE SPO• OS? ,BAl.OllTQtE;.. &. 30 20' Fig. 17 Distribution and abundance of pelagic fish biomass in the Sangihe area, based on integrator data L.~~~~~~~~~~~~-'-~~~~~~~~~~~~--I~~~~~~~~~~-:-:--:-::-~..._~__.30 _MA$_ 49 (a) (b) l 11" "I· (c) (d) (e) (EK 400, 38 kHz) (EK-120St 120 kHz) Fig. 18 Echo-recordings made with two echosounders (EK400/EK-120S) at different ranges and frequencies over same transect sections during CR .. 02/8208-09, Leg II, showing typical fish traces in the littoral of Sangihe island .SC CR.0218208 - 09 - SEG III zo' KAl1AKELONG STAnr. SALE BASU so' Fig. 19 Survey Track covering the Talaud Area 51 Fig. 20 Distribution and abunda..,ce of pelagic fish biomass in the Talaud area, based on integrator data 20' KAl1AKELO NG t."' LEG III CR.D2/8208 - 09 so' Abundance Categories (mm). ~ 10 - 100 rrmm 101 - 500 ~ 501 - 1000 ~ > 1000 52 (a) (b) .... "'"" vp•p 1, 1 *'. ~~ 10~1- I~ ml-~ I 1~ ( c) (d) I j' 'T.''"". "' • •''"! ·r ·~t "'¥"''" 1w.. " .• , ! I- (e) (f) Fig.. .2.1 Echo-recordings ma.de with two echosounders (:EK.400/EK-120) a.t di:fferent ranges and frequencies over same transect sections during CR.,02/8208-o9, Leg III, show.ing typical :fish traces on the shel:f area o:f the Talaud Archipelago 53 (Cl) (b) ~ : .. '~" ,... '"" .. ~ "*'"""" "'" '"' 1"' -·'"'""""] .,,p $ (c) {d) (e) ( f) J05" ------~e> . ...•. ·-·· =~- ~~[-:- ______···-· £K4oo ___3a-kHz. f ·· · · Fig.2. 2. Echo-recordings made with two echosounders (EX.400/EK-120) at different ranges and frequencies over same transect sections during CR .. 02/8208-09. Leg III, showing typical fish traces on the shelf area. of the Talaud Archipelago 54 (a) (c) (d) (l!K 400, 38 kHz) (:EX-120S, 120 kHz) Fig. 2.3 Echo-recordings of selected transect sections ma.de with two echosounders (l!X.4.00/:EX-120S) a.t different ranges and frequencies dnring CR.02/8208-09, Leg III, showing relatively la.rge concentrations of fish, :found in th.e dep-th range from about 2Q..230 m, at the shelf area. of the 'l'alaud Archipelago 55 ~G ~l CR.02/8208 :.. 09 :!ICEL.IJGAIOG so' \All ..... ICll SAt.000'1'0C... r.o' • "'"""" ,...... (]...... OAftU 20' 10' ~.... 56 (a) ( b) (c) (d) (e) ( f) Fig. 2. 5 Echo-recordings made with EK-120 (Range : 0-100 m) during CR.02/8208-09 1 Leg IV, Sangihe, showing large concentration of pelagic fish (a.-b) just south off Dhago 7 ( o-d) 3 miles north from Ka.I.a.ma., and ( e-f) 3 miles SW from Para island 57 (a) (b) ( c) (d) ( (? ) ( f ) Fig. 26 Echo-reoordings ma.de with EK-120 (Range : 0-100 m) during CR.02/8208-09, Leg IV 1 Sangihe, showing large pelagic f'ish schools and layers ( a.-b) 5 miles west f'rom Para, (c-d) 3 miles NW f'rom Kahakitang, and (e-f) 10 miles south off Sangihe 58 LEG IV CR.0218208 - 09 Abundance Categories (mm) 100 n 101 _ 500 ~ 501-1000 m > 1000 so' l..IAlllG ,,..,.0 (7.S?. ~ 'llNIS t.o' S A N G E ...e t:f;JllENG L.AUV ..().• ..,,, O•n•r .. i'r (fl 20' J ! 111 i Fig. 27 Iistribution and abundance of pelagic fish biomass in the Sangihe area, based on integrator data· 59 125°20' 30' !JJ' 50' CR. 01/8304-05 - LEG I '...... 50' 30' 20' ... 10' Fig. 28 Survey Track covering, the Sangihe Area _,.,As_ 60 Fig. 29 Distribution and abundance of pelagic fish biomass in the Sangihe area, based an integrator data so' 40' 30' 20· CR.01 /8304-05 - LEG I 10' Abundance Categories (mm) ~ 10 - 100 • 101 - 500 61 (a) (b) (c) (d) (e) ( f) Fig. 30 Echo-recordings ma.de with JiK400/38 kHz (range : 0-300 m) d:aring cruise 01/8304-05, Leg I, showing typical biomass and sea.bed characteristics on the narrow shelf area. a.round Sa.ngihe 62 (a) (b) (c) (d) Fig. 3 I Echo-recordings made with EX400/38 kHz (range : 0-300 m) during cruise 01/8304-05, Leg I, near the west coast of Karakelong island, 12 miles south of Sangihe. 'lhese were the only fish traces detected during thi~ pa.rt of the cruise 63 CR.01/8304 - 05 - LEG II I 30 20' KAf START. so· KASUflUANG. Fig. 32 Survey Track covering the Talaud Area 64 CR.01/8304 - 05 - LEG II Abundance Category ( mrn)_ ~ 10 - 100 zo' KAf SALESASU so' KASUr Fig; 33 Distribution and abundance of pelagic fish biomass in the Talaud area, based on integrator data _M ~S - 65 20 3 0 0 0 ~~·------~~-·------~~~~·------~s~o--· ______,12_1______"110' 40, 10 9 30' 12 7 2o' 13 6 s 3 16 so· 17 18 2 CRUISE 01/8304 - 05 (Leg III) 6. 8. T. STATION. Survey Track covering the Talaud Area 66 (a) !~·-1·· ·..... ,.;:.< ..... ;: ! I I I i I I r·, _\ ··-: ' (c) (d) -======'=!=I======~ _.. ; (e) (f) 1f I ! .' -- ,_: -· .. ·--"~_:-~------~~~ ··~_:.:_;· 3Qvn~"~- Fig.3 5 Echo-recordings made with EK.400/38 kHz (range : 0-300 m) during cruise 01/8304-05, Leg !II, showing (a,..b) fish traces in deep waters a.bottt 10 miles NE from Ka.rakelong island, (c-d) deep fish tra.oes close to the west coast of Ka.rakelong, and (e) large pelagic schools a.t a.bout 170 m depth, west off Salibu island 67 125 ° E 20' so KAHAKITANG ....------...0------ ~Al10_ zo en_ 0118301. - OS (le ;fl.' ALISE! Fig. 36 ,i '~BANGKA Survey track covering the area between Sangihe and North Sulawesi 68 (a) (b) (c) (d) Fig.. .3 7 Echo-recordings ma.de with ]1{400/38 kHz (range : o-250 m) during cruise 01/8304-05, Leg TIT, showing unidentified traces (a) south of Si~ island., (b) south of Tagulandang island, (o,d) north and south of Bia.ro island, respectively 69 CR.01/8204 - 05 - LEG I Temperature (°C) 15 20 25 50 so 100 150 1. 200 2. x 3. E 4. .c 411 s . Q... 0 'il 6. 250 Fig. 38 Measured Temperature Profiles 70 CR. 01/ 82 04 - 05. - LEG I TempHatur,. { °C J. 15 20 2S so SO 00 ISO !::. BT Station no. 7. 200 0 8. x 9 . ...: E + 10. e 11. =..c. Q \J 12. 250 . "Fig~ 39 Measured Temperature Profiles 71 CR.0118204-05.- L:SG I Temperature {" C ). 15 20 25 JO so 100 ISO !:; BT Station no 13 200 0 14 x 15 E 10 .c Q... • 17 Q 250 Fig; 40 Measured Temperature Profiles 7'2 CR.01/8204-05. - LEG I Temperature (°C J. 1S 20 ZS JO so 100 1SO 15. ST Station no. 18 200 0 19 x 20 .....; E + 21 .<: 22 "'-.. • Q 2sa Fig. 41 Measured Temperature Profiles 73 CR. 01I83 OL. - 05 (Leg III). 0 Temperature ( C ). 12 14 16 18 20 22 24 26 28 30 0 10 so 100 :c l-o... w a 150 /:; = st. 1 · 0 : St. 2 X : St. 3 + = st. 4 st. 5 200 /,:r- • = / v = st. 7 / / / / / / cl 250 Fig. 42 Measured Temperature Profiles 74 CR.01/8304 - 05 (leg Ill)_ 0 Temperature ( C )_ 11 12 14 16 18 20 22 2£. 26 is 0 9l I I 10 I ' I I I I I I so 100 E ::c: l a.. w a 150 f, =st. 8 0 =st_ 9 ·X : St.10 + = st_ 11 0 = SL 12 \J = s \_ 1 :3 200 , , , , p' I I I I I / / / ,F / / / 150 ,.,-· -.e Fig. 43 Measured Temperature Profiles 75 CR. 01/8304-0S(Leg III). 0 Temperature ( C ). 11 12 14 1 6 18 20 22 21. 26 28 0 ,9 f 10 / I /'I I I -1- I II I I I I / ,' I I : ff I I I I i / . I i / / I i / / I j 50 _,/,/ l y I , I I . I p-' ; i I I I i 11· f I I / I I I Ji. I I • I _I ,9 i I _I /, ,. I .' , ; I _I 100 , / : / _j ,,I , ./ /./,, , , / ..i / / / // / // / l( I ii // i I ii 0 = s t. 14 t:. = st 15 x = st. 16 + = st. 17 t = st. 18 200 /' / 250 "'' Fig. 44 Measured Temperature Profiles 13 L Al 11 SMALL PELAGICS )( )( )( x xx CJ x x x x x )( x )( )( lJ) 10 )I x )( )( x )( w )( x )( x xx DE ME l 2 1978 ·J979 1960 1981 1982 Fig'. 45 Catch Fluctuations 1978-1982 in the Sangihe-Talaud Archipelagos ..,- 1 I UNIT GILL NETS. 17 (UNIT: X 200). , 16 ______..,..------,.-;: ______FISHEnMEN · (UNIT: X 2.000) 15. - OUT BOAno MOTOns. 14 (UNIT: X 20) 13 12 .11 ~J---__,1--/---;( - NON - POWERED BOATS. 10 (UNIT: X 1.000) 9 8 7 6 _.. - LINES. 5 (UNIT: .X 1.000) 4 3 2 1977 1978 1979 19130 1981 19132 Fig. 46 The Increases of Fishing Efforts in the Sangihe-Talaud cArea, 1977-1981 78 Table 1 RESULTS OF INTER-TRANSDUCER CALIBRATION (See page 15 for in-text table) Table 2 AREA BACK-SCATTERING STRENGTH AND RESULTANT INTEGRATOR CONVERSION CONSTANTS USED FOR SURVEY ..Y Measured Values Area Back-Scattering Integrator Conversion . Species Strength (dB/kg/m2) Constants .. (t/mm2 /mm ref. 1 n mi) 1. Sardinella sindensis -30 5.3 2. Decapterus kiliche (45%) -28.8 4.0 3. Selar crumenophthalmus (55%) Assumed Values Area Back-Scattering Integrator Conversion Species Strength (dB/kg/m2) Constants (t/n mi2 mm ref. 1 mm) 4. Trachurus indicus -28.8 4.0 5. Rastrelliger kanagurta -28.8 4.0 6. Myctophidae (5.2cm, average length) -28.4 3.7 7. Stolephorus (6cm, average length) -28 .8 4.0 1/ from Lamboeuf and Simmonds, 1981 Table. 3 SMALL PELAGIC SPECIES. ESTIMATED ABUNDANCE BASED ON INTEGRATOR DATA FROM CRUISE 02/8204-05. (a) WHOLE SURVEY AREA AND (b) SANGIHE LITTORAL AND NE BANK c A T E G 0 R ) M-value Area Conv. Constant Survey Area Mean Density Echo Abundance Observ. Est. Biomass M(mm) ;~ A(n mi 2) C(t/n mi2/mm) pA(t/n mi2) (M x A) .No. (n) (t) No. (mm) mm;n ml (a) Whole I 1 - 100 17.1 5260 0,28 4.8 89,946 74 25' 185 (Fig.9') (b) Sangihe I 1 - 100 17.9 189 0.28 5,0 3,383 69 9117 ( F i gs .1 0 , 1 1) Table 4 SMALL PELAGIC SPECIES: ESTIMATED ABUNDANCE BASED ON INTEGRATOR DATA FROM CRUISE 02/8208-09 Survey Area s t r a t u m M-value Area Conv. Constant Mean Density Echo Abundance Observ. Est. Biomass No. (mm) M(mm) A(n .mi 2) C(t/n.mi2/mm) j)A(t/n.mi2}· (M x A) , No. (n) (metric tonnes) Sangi he I 1 - 100 32.6 343 0,28 9,1 11,182 87 3' 131 Littoral II 101 - 500 221. 7 63 0,28 62,1 13,967 23 3,911 +'NE Banks III 501 - 1000 682.5 13 0.28 191,1 8,872 4 2, 8lJ 2 IV > 1000 1,545.0 8 0,28 432.6 12,360 4 3,461 TOTAL : 111.6 427 31. 3 46,381 118 13 '31J5. ·sangihe I 1 - 100. 32.6 175 0,28 9.1 5,705 32 1,597 Littoral II 101 - 500 219.0 48 0,28 61. 3 10, 512 19 2, 9Lt3 TOTAL : 72.7 223 20.4 16,217 51 4. 5110 .'. Sangi he I 1 - 100 57.4 1ll3 0,28 15.9 8, 1119 33 2,282 Littoral II 101 - 500 215.7. 91 0,28 60.4 19,631 37 5' 1197 (repeated) III 501 - 1000 690,0 2 0.28 193, 0 1,380 2 386 CJJ TOTAL : 123,6 236 34,6 29,160 72 8,165 0 Littoral I 1 - 100 33,0 249 0,28 9.2 8,214 72 2,300 of Talaud II 101 - 500 232.2 159 0,28 65.0 36,920 65 10. 338 Archipelago III 501 - 1000 736,6 16 0,28 206, 2 11, 786 8 3,300 IV > 1000 1387,5 5 0,28 388,6 6 '938 4 1 '9113 TOTAL : 148,9 429 41. 7 63. 8 58 149 17,881 Fish Banks I 1 - 100 35.7 123 0,28 9,9 4,370 49 1,225 south off II 101 - 500 251. 3 414 0.28 70.4 104,034 122 29,130 Sangi he III 501 - 1000 659.1 25 0,28 184.6 16,1177 11 4. 6 llf IV > 1000 2028.7 18 0,28 568,1 36,518 8 10 '225 TOTAL : 278.2 580 77.9 161, 399 190 lf5 '191J SMALL PELAGIC SPECIES~ ESTIMATED ABUNDANCE BASED ON INTEGRATOR DATA FROM CRUISE 01/8304-05. s t r a t u m M-value Area Conv. Constant Mean Density Survey Area Echo Abundance Observ. Est. Biomss M(mm) 2 2/mm). - ( . • 2) No. (mm) . A(n.mi ) C(t/n.mi . pA t/n.n11. CM x A) No. (n) (metric tonnes) Sangihe Litt, I 1 - 100 23.7 111 0.28 6.7 2,684 22 7112 + NE banks II 101 - 500 257.7 10 0,28 72.1 2 ,577 3 721 TOTAL : 43.2 121 12.1 5, 261 25 1,1163 -- Ta laud I 1 - 100 9,6 63 0.28 2.7 603 11i 169 TOTAL : 9.6 63 2.7 603 14 169 - Table 6 SUMMARY OF ABUNDANCE ESTIMATION IN THE S:ANGIHE-TALAUD ARCHIPELAGOS (See page 23 for in-text ·table) .1..c1U1-t:! I' FISHERIES DATA OF SANGIR-TALAUD DISTRICT 1977-1981. 1977 1978 1979 1980 1981 Remarks 1. 1. Fishery Households 10.473 10.545 10.608 10.673 Units 2. Fishermen 31.419 31.635 31 .824 32.019 2. Fishing Boats 2.1 Non powered 8.402 (~.300) 10.230 10.408 10.352 Tonnes 2. 1. 1 dugouts 8 .150 (9.000) 9.915 (10.151) 9.940 Units 2.2.2 sailing boats 252 309 315 (257) 412 2.2 Outboard motors 73 75 110 182 287 2.3 Others 3. Fishing Gear 3.1 Seines 3. 1 . 1 Beach 267 252 254 . 169 3. 1. 2 Mini purse seine 232 224 266 262 1982, 1983 3.1.3 Others (lampara) data are not (JJ yet available. I<> 3.2 Gillnets 1.517 1. 780 1.789 3.241 3.2.1 Drift 3.2.2 Set 3.3.3 Others 3.3 Lines 3 .3.1 Hand 2.934 (3.800) 3.375 4. 769 3.3.2 Troll 1.865 (5.000) 3.951 3.465 3.3.3 Long lines 3.3.4 Pole & lines 26 3.4 Muro - ami 173 (120) 173 195 3.5 Traps 281 188 124 103 3.6 Others 281 120 433 405 ---Sout~e: Fisheries Offices of the North Sulawesi Province and the Sangir-Talaud District, 1983 (Figu~es in.brackets represent best estimates of the Provincial Fisheries Officer.) Table 8 CATCH (LANDING) COMPOSITIONS (t) IN SANGIUE- TALAUD 1979 1981 1978 1979 1980 1981 REMARKS 1. Tuna and Similar 2391 ~ 112l 2712 1982, 1983 data not 1. eastern little tune 1550 2348 2739 1844 available 2. akipjaok 473 227 249 389 3. tuna 368 286 207 479 2. Small J!elagioa 2632 il!§. .421§. ~ 1. so ad 1059 1872 2547 2755 2. barracuda 127 295 221 336 3. flying fish 494 963 954 1007 4. garfishea 211 233 320 520 5. trevallies- 494 486 541 527 6. hard-tail 106 236 185 167 (I) 7. i101f-herring 141 221 148 157 w 3. ~niersals ! ino · oora:l fiahe~l 902 1083 lli .1Ql.1 1. red snapper 353 450 235 63 2. groUper 282 257 199 110 3. emperor 211 62 51 76 4. kakap 411 5. fusilier. 261 142 183 224 6. aha.rks 56 172 106 147 4. Mi:x:ed /. o·therf! illA .!fil 183q J112. 5. TOTAL .ill2 .ml 1Qlli 10982 Source 3 Distriot Fisheries Office of Sangihe-Talaud 198J Table 9 CATCH A.t'ID FISHING TRIP DATA IN SA.t'JGIHE-TALAUD, 1981 Ca.tch Number of (t) trips 1.. Seine 1.1 Bea.ch 1,106.6 22, 138 1.. 2 Mini purse seine 987 .. 8 29,824 1.3 ~hers (lampara) 395.2 14,399 2 .. Gillnets 2 .. 1 drift 1,336.. 6 234,581 2 .. 2 set 923.3 164,529 2.. 3 others (encircling) 121 .. 9 16, 174 3.. Lines 3 .. 1 hand 2,213.9 293,352 3.. 2 troll 2,393.. 5 266,615 3.. 3 longlines 3.. 4 pole & lines 3.,5 others 4 .. 11Iuro-am:i 1,658.. 1 33,301 5.. Traps 5.. 1 weirs 3.,3 176 5 .. 2 others 59 .. 9 9,780 6.. Others (spears, etc.. ) 240 .. 5 37,352 Total: 10,982.. 6 1;122,221 Source : Distric-t Fisheries Office1 Sangihe-Talaud1983 85 Table 10 AVERAGE FISH DENSITIES WITHIN VARIOUS AREAS OF THE SHELF (AT 10 -200 m DEPTH) ALONG THE INDIAN OCEAN Al.'ID SOUTH CHINA SEA, ESTIMATED DURING CRUISES WITH R/V DR; FRIDTJOF NANSEN Average fish Area Time density References (tin mi 2 ) Peninsular Malaysia East June 1980 12 Aglen et al., 1981a West Jun-Jul 1980 19 Aglen et al., 1981a Sumatra Aglen et al., 1981c North and West Aug 1980 15 (TableS)- Thailand West Jul 1980 15 Aglen et al., 1981b Burma Sep-Nov 1979 17 Str~mme et al., 1981 Har-Apr 1980 34 S tr~mme et al. , 1981 Bangladesh Nov-Dec 1979 16 Saetre, 1981 Hay 1980 19 Saetre, 1981 Sri Lanka Aug-Sep 1978 84 Saetersdal and De Bruin, 1979 Apr-Jun 1979 60 Blindheim et al., 1979 Jan-Feb 1980 58 Blindheim and"Jf~yn, 1980 Pakistan Jan-Feb 1977 83 Anon, 1978 May-Jun 1977 20 Anon, 1978 Source: Aglen et al., 1981c, Table 7, p.81 Table 11 AVERAGE PELAGIC FISH DENSITIES WITHIN VARIOUS SURVEY AREAS, ESTIMATED DURING INFIDEP CRUISES WITH R/V TENGGIRI MADE OVER THE PERIOD FROM MAY 1981 to DECEMEER 1983. Average density Area Time (t/n mi2) References Anambas Jun-Jul 1981 5.5 FAO, 1985a Na tuna Jun-Jul 1981 10.6 " Anambas Nov-Dec 1982 5.4 " Na tuna Nov-Dec 1982 4.4 " Anambas Jun-Jul 1983 2.9 " Na tuna Jun-Jul 1983 1.2 " Anambas Nov-Dec 1983 48.8 " Na tuna Nov-Dec 1983 59.3 " Sangihe Apr-Hay 1982 5.0 Table 3 Sangihe Aug-Sep 1982 57.7 Table 4 Ta laud Aug-Sep 1982 41. 7 Table 4