Fishing and Gear Technology (2+1) copy 1

Unit 16 - Electronic equipments for fishing

16.6.Different types of Echo sounders

Different types of Echo sounders
Different types of echo sounders are now produced for different purpose and requirements. They are available in the following specifications

• Low frequency sounders 10 – 40 KHz: This gives good ground discrimination and can detect the schools of fishes without air bladders. Eg. Tuna, mackerel, squids etc. This is usually used for bottom trawling operations.
• Mid frequency sounders 40 – 80 KHz: The performance in between the previous two and is preferred by the gill netter and hand liners.
• High frequency sounders 80 – 200 KHz: These are very good for determination of fishes without air bladder but they do not give good ground discrimination. This is suitable/chosen for detecting Tuna and Mackerel. Mainly used in purse seiners, squid jigging vessels and liners.
• Dual frequency sounders 50 – 200 KHz: This combines low and high frequency and is very popular in fishing vessels.