limitations in that the fishing vessel must pass directly over the 

 school before receiving any indication of its presence. The depth 

 recorders now in common use are primarily designed for navigational 

 purposes and probably do not have the best frequency and wave 

 characteristics for locating fish. Research along these lines should 

 greatly benefit the fishing industry. 



The development of echo-ranging equipment similar to war-time 

 sonar(used for locating enemy submarines) but especially designed for 

 locating schools of fish and reduced to a convenient size and reasonable 

 cost for use on fishing vessels would increase efficiency of operations. 

 It is known that certain fishes make characteristics noises, and this 

 condition may well pertain to tuna. The development of listening 

 devices for receiving these sounds and thereby establishing the presence 

 of subsurface schools of tuna in an area would materially reduce the 

 time required to find fish. 



It is well established that fish will respond to an electrical 

 stimulus, and varying current densities can be used to influence the 

 reactions of fish in different size ranges. Such equipment is now used 

 in fresh water for scientific purposes, Bxperiments now being con- 

 ducted in Europe have demonstrated the possibility of controlling the 

 movements of cod and herring in the open sea. The high conductivity 

 of sea water requires far greater amounts of electrical power than 

 fresh water to control the reaction of fish. Pulsating, rather than 

 continuous, current will materially reduce the electrical power require- 

 ments and offers promise of practical electrical fishing methods at sea. 

 Extensive basic research is required to establish proper pulsation 

 patterns, to design proper and safe equipment and to test the equipment 

 under actual operating conditions. The successful development of 

 electrical fishing devices may revolutionize the fishing industry as 

 selected species and sizes of fish could be attracted to a net for 

 capture or even pumped aboard the vessel. 



Fishing Gear 



The various types of tuna fishing gear have attained their present 

 state of effectiveness throtigh the concerted efforts and ideas of many 

 thousands of practical fishermen over a period of many years, to best 

 suit the species of tuna and the area exploited. Furthermore, the 

 fishermen have become highly skilled in the operation of the gear and 

 in studying the habits of tuna to use the gear most effectively. Any 



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