ABSTRACT 



Since 1964 the Acoustical Oceanography Branch of the U. S. Naval 

 Oceanographic Office has conducted bioacoustic investigations of 

 deep scattering layers (DSL) in the Atlantic Ocean. The initial invest- 

 igations before May 1967 were conducted primarily in three regions: 

 the Gulf of Mexico, the southwestern Sargasso Sea, and the Gulf 

 Stream. Biological collections at discrete depths were attempted 

 with a six foot Isaacs-Kidd Midwater Trawl and a Be Multiple Plank- 

 ton Sampler. 



The biological collections were sorted and identified to species (fish 

 and some invertebrates) or to major groups (most invertebrates). 

 The most abundant kinds of fishes collected belong to the families 

 Myctophidae (lanternfishes) and Gonostomatidae (bristlemouths). 

 In general, 2 or 3 species of fishes in a collection were found to be 

 more abundant than the rest, often making up the majority of fish 

 in a sample. 



Investigation of the night surface scattering layers in the Gulf of 

 Mexico in March 1967 indicates that the fish in these layers tend to 

 be concentrated in a narrow depth range. Measurements in the 

 Sargasso Sea in November 1965 show some correlation between 

 the depth of occurrence of a deep scattering layer, an oxygen defi- 

 cient layer, and an abundance of organisms. Collections from both 

 areas as well as in the Gulf Stream agree with the concept that all 

 three are regions of low productivity. Although a strong correlation 

 was not established between DSL occurrence and the biological col- 

 lections, these initial investigations suggest several findings that 

 merit more intensive study, 



BERNARD J. ZAHURANEC 



W. LAWRENCE PUGH 



G. BROOKE FARQUHAR 



Acoustical Oceanography Branch 



Exploratory Oceanography Division x 5^_g ^ 



Si 



Research and Development Department j^^B ""^ 



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