Diving Behavior 



During 160 whale-track days, summary data were recorded on 92,963 dives (12,209 

 in 1989 and 80,754 in 1990). The only two summary items recorded in like fashion for 1989 

 and 1990 were the number of dives and the average dive duration during 4 and 6-hour 

 summary periods, respectively. This section will: 1) review these data; 2) discuss two subsets 

 of the data: zero duration "dives" (surface resting behavior) and the time spent submerged; 

 and 3) examine the relationship between speed of travel and dive patterns. 



Number of dives 



1989 



The number of dives in a 4-hour summary period for PTT #843 varied from 117 to 

 403 with an average of 182 ±57 (45.2/hr. see Figure 39). Allowing for a 3 s surface time, 

 this provided an average dive duration of 75 s compared to an average of 74 s for discrete 

 dive information from the same animal. 



The average number of dives was generally consistent for all areas and periods 

 (Figure 40). The highest average number of dives (227 ±_ 84) occurred east of Jeffrey's 

 Ledge between 0400 - 0800 GMT (2300 to 0300 EST), during darkness. The second highest 

 average number of dives (204 ±_ 64) occurred on Brown's Bank between 2000 and 2400 

 GMT (1500 - 1900 EST) and is 40% higher than all other periods of the day for that region. 

 This period includes dusk, which is when the deep scattering layer (DSL) first appears near 

 the surface and may, therefore, be the start of more active shallow feeding. 



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