QUANTITATIVE ANALYSIS OF THE ABUNDANCE, 

 SWIMMING BEHAVIOR, AND INTERACTIONS OF MIDWATER ORGANISMS 



W. M. Hamner 1 , C. T. Prewitt 2 , and E. Kristof 3 



■'■Department of Biology 



University of California 



Los Angeles, CA 90024 



^Geophysical Laboratory 



2801 Upton St. N.W. 

 Washington, D.C. 20008 



^National Geographic Society 

 Washington, D.C. 20036 



ABSTRACT 



Prior efforts to record spatial and temporal distributions 

 of animals in situ from submersibles have been based on visual 

 counts or limited to two-dimensional video or photographic 

 records, but 2-D optics are inadeguate for guantitative 

 investigations of objects in a 3-D medium. We describe here the 

 3-D stereo-videogrammetric system that we used aboard the Pisces 

 VI submersible off Bermuda in 1987 to record and measure the 

 behavior of midwater organisms and deep-water sharks and compare 

 it with a diver-operated system for shallow water. We discuss 

 some of the laboratory eguipment needed to obtain guantitative 

 measurements from these video tapes of the abundance, movements, 

 and interactions of large numbers of animals in a volume of tens 

 of cubic meters. The basic components of a complete underwater 

 image analysis facility are reviewed. 



INTRODUCTION 



In oceanic research the need to measure distances, shapes 

 and volumes in three-dimensional (3-D) space is critical, whether 

 it be for behavioral studies or for investigations associated 

 with the measurement of physical objects. For many years 

 distance and objects beneath the surface of the sea have been 

 measured and mapped acoustically, but for short range 

 measurements underwater, optical technigues are far more accurate 

 than acoustics. Optical measurement of underwater objects 

 reguires that one obtain high guality underwater images in a form 

 that will permit subseguent extraction of point locations in 3- 

 dimensional space. This essay describes the rationale behind the 

 approach that we have taken to record and view the behavior of 

 marine animals at sea. 



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