FOOD SHORTAGES AND THE SEA — MERRIMAN 379 



layer occurs are only about one-tenth as great as those in the surface 

 layers. Furthermore, ordinary echo-sounders are not sufficiently sen- 

 sitive to distinguish between plankton and fishes, and the oscilloscope, 

 which might reveal the constitution of the layer, could hardly be 

 adapted for use on commercial vessels. All in all, the deeper waters 

 are not likely to contribute greatly to the world's fish landings; fisher- 

 men will always get the bulk of their catch from the upper hundred 

 fathoms, the layer in which at least 90 percent of the ocean's living 

 populations exist. 



During the war the underwater noises made by marine animals 

 became a matter of great importance to those operating listening 

 devices for the detection of surface vessels, submarines, or other enemy 

 activity. The instruments were developed to a high degree of per- 

 fection, but animal noises interfered with accurate interpretation to 

 such an extent that investigations were carried on in the British Isles, 

 America, and also Japan to identify particular sounds with the species 

 that made them. A considerable body of literature on the subject is 

 now available; indeed, certain investigators, instead of sending out 

 the customary scientific reprints, produce actual recordings of their 

 findings; only the other day there came to my desk a record (78 

 revolutions per minute) of the underwater calls of Delphina'pterus 

 Jcucas^ the white porpoise — a form of crepitation unrivaled in the 

 annals of phonography. 



The underwater soundmakers are of many kinds, such as shrimps, 

 all sorts of fishes, whales, and porpoises. The character of the sound 

 is highly variable, and a recent United States Navy publication on 

 sonic fishes of the Pacific lists the types as follows : Breathing, click, 

 croak, crunch, drum-tap, growl, grunt-groan, hum, rasp-grate-spit, 

 squeak, toot-whistle, and whine-pipe. This same publication states 

 that "subsurface listeners described unidentifiable contacts running 

 the gamut of sound from mild beeping, clicking, creaking, harsh 

 croaking, crackling, whistling, grunting, hammering, moaning and 

 mewing, to the staccato tapping as of a stick rapidly and steadily 

 drawn along a picket fence, of coal rolling down a metal chute, the 

 dragging of heavy chains, fat frying in a pan, simulated propeller 

 noises and the pings of echo ranging." It has been suggested that the 

 identification and association of particular sounds with definite species 

 might be of practical significance to the industry in detecting schools 

 or concentrations of commercial fishes. There appears to be little 

 justification for this optimistic view; it is not likely that the sounds 

 made by fishes will be used by commercial fishermen to any greater 

 advantage in the future than in the past. There is, however, some 

 possibility that certain shrimps, which make a characteristic crack- 

 ling noise, may be of utility in the commercial sponge industry. These 

 shrimps live in the pores and channels of important sponges, some- 



