44 



of schooling fish - such as sprat, herring, mackerel and cod. Hashimoto (1951) 

 reports the use of echo-ranging gear for determining the speed of swimming 

 fish schools and the sinking rate of nets. Both echo-ranging and echo-sounding 

 gear have been employed in studying the probleni of "availiability" of the Pacific 

 sardine. Even so, not nearly enough use has been made of sonic gear in bio- 

 logical investigations. 



Underwater Photography - Underwater camera equipment is usually built around 

 a camera of conventional design which is enclosed in a water-tight box with a 

 glass window. There are now several commercially built underwater cameras 

 on the market. The Benthograph, designed at the University of Southern Cali- 

 fornia, and the Bathygraf, engineered by Cousteau, are recent developments in 

 submarine photographic instruments. 



Ewing, Vine and Worzel (1946) have pointed out that the principal prob- 

 lems in underwater photography are not optical in character, nor of camera de- 

 sign. Rather, the problems concern the use of the equipment: finding an in- 

 teresting subject, putting the camera in focus with it, keeping the camera rea- 

 sonably steady while the exposure is made, and providing adequate illumination. 

 Except in the littoral zone, where the investigator may accompany his equipment 

 the problems noted above can best be solved when taking photographs of the 

 ocean floor. 



Pictures made of the ocean bottom usually are found to contain interest- 

 ing information on the animal life present on and immediately above the bottom. 

 Over much of the ocean floor, photography is the only simple method of observ- 

 ing and taking a census of the benthic fauna. However, I have been assured by 

 persons who have examined large numbers of such photographs that although 

 some are excellent, many others are tantalizingly inadequate - just about, but 

 not quite good enough for identification of the organisms present. A further 

 limitation of this technique is that it can reveal only those animals which are 

 exposed on the surface. The vast assemblage of animals hidden beneath the 

 surface cannot be assessed by underwater photography. 



There is considerably more trouble finding suitable subjects for photo- 

 graphy in the oceanic province. Pictures made at random in mid-depths are al- 

 most certain to be blank. Hence, photography in this zone may prove of most 

 value in places where organisms are concentrated - such as in fish schools. 

 Investigators have experimented with manned devices, such as the Bathysphere 

 and the Benthoscope, but these have proven to be more spectacular than suc- 

 cessful. 



Underwater television equipment may become an aid in underwater ob- 

 servation of marine animals. A pioneer use of such equipment was made in 

 1947 at Bikini Atoll in depths of about 100 feet. More recently further develop- 

 ment of underwater television is being engineered in Great Britain, supported 

 by a grant from The Treasury. This project is still in the developmental stage, 

 since the grant was authorized only last year. If such gear can be perfected it 

 should be an invaluable aid in determining the kinds of schooling fish, etc. 



Self-Contained Diving Units - A time honored technique of biologists has been 

 the visual observation of animal populations in situ. The development of self- 

 contained diving gear has put an invaluable tool into the hands of ecologists wish- 

 ing to study animals in their natural environment. The Aqualung, one of the 

 more popular units, employs compressed air bottled at 200 atnnospheres. It is 

 strapped to the swimmer's back, and allows swimming about unhampered by 



