This represents the maximum average dive duration if the entire 6-hour period were divided 

 by varying numbers of dives. In this figure, the vertical divergence of points from the 

 theoretical upper limit describes the amount of time the animal spends at the surface. 

 Higher travel speeds tend to be close to the upper limit of the curve, implying minimum 

 surface time, and are also clustered in the central portion of the curve suggesting an optimal 

 aerobic strategy. However, there apparently is not a single optimal dive (respiration) pattern 

 for right whales. The difference in respiratory strategies is apparent by comparing Figure 

 84b (adult male, PTT #823: larger numbers of short duration dives) and Figure 85b (female 

 with calf, PTT #839: smaller numbers of longer duration dives). From these figures, speed 

 does not appear to be directly related to either average dive duration or numbers of dives, 

 and average duration does not appear to be a direct inverse proportion to number of dives. 

 The high speed data, although close to one another, do not overlap. Figures 86 and 87 

 depict similar relationships for juvenile PTT #833 and adult female PTT #840. Both more 

 closely resemble PTT #839. It is impossible to say, at the present time, whether these 

 differences are due to age, sex, reproductive status or individual variability. 



Oceanographic Factors 



Temperature Profiling 



1989 



The temperature sensor in 1989 was located outside the transmitter. The transmitter 

 recorded the temperature of the water at the maximum depth of dive. Thus, we used data 

 from dives to varying depths and from several days to compile composite temperature/depth 

 profiles for PTT #843 east and northeast of Jeffrey's Ledge (Figure 88). Both profiles are 

 similar and do not show sufficient detail to discern a sharp thermocline. 



1990 



Right whale tags in 1990 were equipped with a temperature sensor inside the tags. 

 When whales returned from longer dives, the reported transmitter temperature was often 

 lower than the surface water, suggesting deep dives into temperature-stratified waters. 

 Without temperature profiles for these areas, we are presently unable to interpret the 

 specific dive depths accomplished. In the future we hope to obtain temperature profile 

 information from oceanographers maintaining offshore buoys in the areas. 



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