86. What is the DSL? 



The deep scattering layer (DSL) is a widespread layer of living 

 organisms that scatter or reflect sound pulses. During the day, this 

 layer has been reported at depths of 700 to 2,400 feet, but most often 

 between depths of 1,000 and 1,500 feet; at night, the layer moves to or 

 near the surface. 



Existence of the DSL has been reported from almost all deep ocean 

 areas, except the Arctic, Antarctic, and some areas of the Central South 

 Pacific. The types of organisms making up the deep scattering layer are 

 still not definitely known. They may be fish, shrimplike crustaceans, 

 or squid. Attempts to collect and photograph the organisms have been 

 inconclusive. 



The DSL produces a phantom bottom on echograms, which probably 

 accounts for the charting of nonexistent shoals in the early days of 

 echo sounders. 



Dietz, Robert S. 



"The Sea's Deep Scattering Layer," Scientific American, Vol. 207, 



No. 2, Aug. 1962. 

 Soule, Gardner 



The Ocean Adventure, Appleton-Century, 1966. 

 U. S. Naval Oceanographic Office 



Science and the Sea, Washington, D. C, 1967. 



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