42 



Two sizes of trawl hav^e been constructed - a 10 foot trawl and a 15 foot 

 trawl. The smaller-sized trawl, of which several models have been built, has 

 been extensively tested. The vane of this model, made of 1/8 inch steel plate, 

 weighs only about 150 pounds, has a spread of 10 feet, and an area of Zl square 

 feet. The net, especially designed for use with the divang vane, is about 31 feet 

 (182 meshes) long, with a mouth opening of approxinnately 87 square feet. The 

 mesh used has been 2j inch stretch, with smaller-sized netting used as liner. 

 The towing bridle has three points of attachment - at either end of the vane it is 

 attached to short, hinged side arms, and at the top of the net it is attached to a 

 6j foot spreader bar. For handling the trawl, an A frame has been used on one 

 of the Scripps' vessels, the HORIZON. With the aid of this frame, the trawl 

 can be used in heavier weather than would otherwise be possible. The trawl has 

 been very successful in taking a variety of bathpelagic animals, many of which 

 previously had been unreported for the eastern Pacific. It is being used on the 

 current Scripps expedition into equatorial waters. 



Electrical Fishing - The possibility of using electrical methods in the collection 

 of fish is being investigated in several countries. Fish respond to a pulsating 

 direct electric current by orienting to face the anode and swimming toward that 

 pole in a forced manner. By this means it may be possible to lead fish into nets 

 or traps, or to capture them by pumps. As large fish react more \T.gorously 

 than small fish, selective fishing should be possible. 



Research on electrical methods of fish collection is still in the develop- 

 mental stage. There have been a number of reports of electrical fishing experi- 

 ments being conducted by German and Russian investigators. A Russian inves- 

 tigator, N. F. Chernigin, claims to have taken 2500 pounds of salmon in 1 1 hours 

 by using a combination of an electrical field and a pump. This experiment was 

 conducted in a river, however. The German engineers, Kreutzer and Peglow, 

 have been trying to perfect a technique for using electric methods in conjunction 

 with otter trawls in marine fisheries. My knowledge of these experiments is 

 confined to several press releases, and I can't state how successful they have 

 proven. 



Groody, Loukashkin and Grant (1952) have recently issued a preliminary 

 report on the behavior of the Pacific sardine in an electrical field. Their re- 

 search thus far has been conducted on a laboratory scale, but it is felt by the 

 workers that the application of the principles involved to electrical fishing meth- 

 ods in marine fisheries miay prove of considerable value. However, they indi- 

 cate that the problems of instrumentation in this field will be challengingly dif- 

 ficult. It should be noted that some investigators are sceptical whether electri- 

 cal fishing methods can ever be adapted to marine situations. 



SAMPLING BENTHIC ORGANISMS 



Bottom animals are sampled by various types of dredges, grabs, snap- 

 pers, and coring devices such as the Petersen and Ekman grabs, the Ross snap- 

 per, or the Kullenberg piston corer. Dredges and grabs are used for the quan- 

 titative or qualitative sampling of the larger benthic organisms; small snappers 

 and coring devices are quantitative only for microscopic organisms such as 

 foraminifera and bacteria. Some of these instruments are designed primarily 

 for taking specimens of the sea-bottom sediments, and as such will be discussed 

 in another part of this symposium. Others, like the Ekman and Petersen grabs, 

 have been widely accepted for many years. 



A new type of deep-water dredge has been developed at Scripps. This 

 instrument is a logical adaption of the principle of the Isaacs-Kidd midwater 



