FISHERIES RESOURCE SURVEYS
MARINE EQUIPMENT & SURVEYS
We offer a one-week course in fisheries acoustics covering basic principles of sound propagation and reflection underwater, surveying equipment and density estimation (see course outline below) which can be given anywhere in the Southern African region. To date, two such courses have been given in Swakopmund, Namibia, to fisheries scientists and technicians from the region. Both included practical calibration exercises at sea on a local research vessel (below). The course can be tailored to your special needs to include, for example, survey design and error analysis, and to give greater emphasis on specialized topics such as the estimation of target strength and acoustic methods of target identification and classification.
In addition, we offer practical hands-on training in fisheries acoustics during surveys and experimental cruises, with emphasis on one-on-one interaction. We are also able to assist and train researchers in the planning and design of surveys and associated experimental work, and in the processing of the data and the analysis and reporting of the results.
FRS Acoustic Course: Outline
| 1. Introduction and basic principles of sound | 2. Generation of sound – the transmitter |
| Introduction | The transmitter |
| Basic principles of sound | Choice of operating frequency |
| Echo-sounder considerations | Pulse duration and receiver bandwidth considerations |
| Decibel units | Ping interval |
| 3. Generation of sound – transducers | 4. Propagation of sound underwater |
| Magnetostrictive transducers | Attenuation |
| Ceramic transducers | Refraction |
| Source level | Reflection |
| Intensity and beam patterns | |
| Efficiency | |
| Transducer bandwidth and Q factor | |
| Nearfield and farfield | |
| Directivity factor and directivity index | |
| The equivalent ideal beam angle |
| 5. Factors affecting target detectability | 6. Echo-sounders, sonars and netsounders |
| Noise | Echo-sounders |
| Sources of acoustic noise | Sonars |
| Hydrodynamic noise | Side-scan sonars |
| Machinery noise | Net sounders |
| Reverberation | |
| Ambient noise | |
| Refraction | |
| Reflection from other targets | |
| Noise reduction |
| 7. Introduction to fish target strength | 8. Determination of fish target strength |
| Target strength | Measurements on single dead or captive fish |
| Fish size and target strength dependence | Cage experiments |
| The effects of fish tilt angle | In-situ methods |
| Single target detectors |
| 9. Determination of fish density | 10. Calibration |
| Echo integration theory | The on-axis sensitivity |
| The area back-scattering coefficient | The reciprocity technique |
| Echo integrators | The calibrated hydrophone |
| The standard sphere method | |
| The TVG function | |
| The equivalent beam angle |
Practical work sessions to introduce participants to:
| 1. General Operation Of SIMRAD Echo Sounders | 2. Echo Integration Analysis Software |
| The menu system | SONARDATA ECHOVIEW |
| What you should touch | |
| What you shouldn’t touch |