METHODS 



Field Operations 



Midwater dives were made with the Johnson Sea-Link II , 

 equipped with a 24-canister suction collector, 8 detritus - 

 samplers, a color video camera with dual laser-beam size scale, a 

 U-matic videocassete recorder, and a 35 mm Benthos camera and 

 strobe. Details of the design and operation of this equipment 

 are given by Youngbluth (1984). Collected specimens were 

 maintained in refrigerated aquaria on deck or in the lab for 

 observation and photography, then preserved in formalin. 



Observational Data 



All dives (except 1419) were made with observers in both the 

 front and rear compartments of the submersible. Their 

 observations on the occurrence, abundance and behavior of 

 organisms were recorded on individual audio recorders. These 

 were subsequently transcribed and combined into a database to 

 facilitate sorting of observational data according to location, 

 depth or type of animal . On each dive we made stops during the 

 descent at 30, 150, 300, 450, 600, and 780 m, for a 5 minute 

 transect to count and identify the animals present. The 

 itinerary for the rest of the dive depended on what was seen, but 

 all dives went to the bottom at some point. 



RESULTS 



Dives Accomplished 



We were able to make only 11 of the planned 21 dives, due to 

 weather limitations and damage to the Sea-Link which occurred on 

 recovery of dive 1422. The twelfth dive (1429) was used to film 

 shark-baiting by the Pisces VI . Dates, times, depths and 

 positions of these dives are given in Table 1. 



Design and Operation of the Midwater Platform 



The purpose of the midwater platform was to provide a 

 station moored in the water column to which the sub could return 

 on successive dives, and which would support lights, bait 

 packages, and other experimental apparatus for the duration of 

 the field season. The mooring was designed and built at W. H.O.I, 

 by Madin and Russ Peters, with engineering consultation with 

 members of the W. H.O.I. Department of Ocean Engineering. 



The platform was constructed on a fiberglass framework 

 previously used for a bottom- landing tripod (Fig. 1). For 

 midwater mooring, the pyramid was inverted to provide an 

 attachment point at the bottom vertex for the anchor, and a flat 

 top surface of about 1.5 m 2 . Glass spheres for flotation were 



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