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.