Lutcavage and Kraus: Feasibility of photographic assessment of Thunnus thynnus 



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good light levels, minimal glare) when schools were 

 photographed. Altitude varied among spotters but 

 seemed to be less important in producing good records 

 than were sea state and light condition. However, 

 spotters photographing large schools at low altitude 

 were occasionally unable to include the entire school 



within the frame. We enumerated only clearly dis- 

 cernible individuals in schools and in some circum- 

 stances were able to count fish in at least one tier 

 below the surface tier. With smaller schools, particu- 

 larly in "soldier formation" or in surface-oriented 

 groups, we were able to count all members of the school. 



