copepods Ctenocalanus vanus , Oithon a simills , and a species of Corycaeus 

 also, euphausid larvae, amphipods, polychaetes, pteropods ( Llmaclna 

 helicina), and siphonophores. Off Mt. Siple the copepods Calanoides 

 acutus and Calanus propinquus , the euphausid ThyT;3noesEa macrura , and 

 some appendicularians and pteropods ( Limacina helicin a) were obtajjied. 

 Off Peter I Island, the tow contained large nmbers of Calanoides acutus 

 and Oithona similis , plus euphausid juveniles and pteropods ( Limacina 

 helicina ), A tow taken off Deception Island contained large numbers of 

 the copepods Oithona simil is and Ctenocalanus vanus , plus Calanoides 

 acutus, Calanus propinquus , the hyperiid amphipod Parathemis to 

 gaudichaudl , and euphausid juveniles. In the center of Bransfield 

 Strait a plankton tow contained moderate nxanbers of Oithona simili.s 

 and Ctenocalanus vanus, a species of Calanus (possibly C. propinquus ) , 

 the euphausid Thysanoessa macrura , and one salp. In the eastern end of 

 Bransfield Strait a tov; contained numerous diatoms plus fairly large 

 numbers of the copepods Oithona similis and large numbers of nai:plii, 

 probably belonging to Calgnoides acutus . 



F. Deep Scattering Layer 



1. Introduction 



During the cruise the EDO-type fathometer of the ATKA was almost 

 continaously in operation while underway. The resulting fathograms 

 have been ana3.yzed for the presence of the deep scattering layer (DSL) 

 along with notations of geographic location, dates of occurrence, 

 times of descent and ascent, daytime and nighttime levels, extent 

 in miles, and related miscellaneous notes. Aural observations by 

 personnel who supervised the operation of the fathometer contributed 

 pertinent inf orma-tion ' on the occurrence of the layer. 



2, Frequency of Occurrence 



The layer appeared on the fathograms of the ATKA daring all or 

 part of 36 days — 11 out of h9 days in the South Pacific Ocean, 13 out 

 of 35 days in the South Atlantic Ocean, and 12 out of 33 days in the 

 North Atlantic Ocean (see figure 19). In the South Pacific Ocean the 

 layer was not recorded south of about 56° S, or after 10 January, It 

 did not appear at any time while steaming along the entire coast of 

 Antarctica, but reappeared on the fathometer trace on 23 February in 

 the South Atlantic at approximately 62° S, Although the layer was not 

 always recorded on the fathogram in the Atlantic and Pacific Oceans, 

 its presence was evident by listening on most days. The DSL was 

 neither audibly nor visibly present when operating in the Antarctic 

 waters . 



57 



