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Amos advises fishermen not to buy 

 more depth equipment than they need. 

 "Fishermen who spend $5000 on a 

 piece of equipment want a $5000 

 return on their investment," Amos 

 says. "That's why it is important for 

 fishermen to get as much information 

 as they can about the equipment 

 before they buy." 



Fishermen should consider these fac- 

 tors before choosing a recorder: the 

 water depths at which fishing will take 

 place, the fish being caught and the 

 place on the boat where the transducer 



will be mounted. Amos has written a 

 68-page booklet, published by the Uni- 

 versity of Rhode Island Sea Grant 

 Program, that will help fishermen 

 choose a depth recorder based on their 

 particular needs. The booklet, A 

 Fisherman 's Guide to Echo 

 Sounding and Sonar Equipment : 

 Acoustic Fish Detection 

 Instruments, is available for $2 from 

 the University of Rhode Island Marine 

 Advisory Service, Publications Unit, 

 Bay Campus, Narragansett, RI 02882. 

 Fishermen should also consider 



several features when selecting a depth 

 machine. Amos says the most impor- 

 tant features are frequency, transducer 

 beam angle and pulse length. The right 

 combination of these features can 

 mean a more accurate picture of the 

 area beneath the boat and a better 

 chance of finding fish. 



For fishermen fishing shallow waters 

 (less than 50 fathoms), a high- 

 frequency depth recorder can be con- 

 sidered. But lower frequency recorders 

 should be used for fishing in deeper 

 waters and when fishermen need to 

 determine the composition of the bot- 

 tom. Many machines are now fitted 

 with both a low and a high frequency, 

 an ideal choice for the multi-purpose 

 fisherman. 



The beam angle of the transducer is 

 one feature many fishermen overlook 

 when selecting a depth recorder. Beam 

 angles can range from 9° to 25° and 

 affect the shape of the fish echoes on 

 the recorder, the ability of the recorder 

 to determine seabed composition and 

 the ability to locate smaller fish at 

 greater depths. Amos suggests 

 selecting a wide beam angle for shallow 

 fishing and a narrow beam angle for 

 deep-water fishing. A wide angle for 

 deep waters will show many more fish 

 targets than a trawl could catch during 

 a single tow; a narrow angle at shallow 

 depths would limit the fish displayed. 



Pulse length, the thickness of the 

 sound wave transmitted by the 

 transducer, can help a fisherman deter- 

 mine the size of the fish or schools of 



