Grusha and Patterson: Quantification of the drag and lift of pop-up satellite archival tags 



69 



also changes. At some velocity greater than 0.60 m/s, 

 9 will approach 0°, and at that point S and C D would 

 remain constant for higher velocities. After that veloc- 

 ity is reached, then for higher velocities, drag would 

 increase proportionately to the square of velocity and 

 power would increase proportionately to the cube of ve- 

 locity. In other words, between 0.00 m/s and 0.60 m/s, 

 the changes in S and C D mask the parabolic relation- 

 ship of drag with velocity. Because the velocity at which 

 S and C D become constant is not known, extrapolations 

 far beyond the maximum velocity for which drag was 

 measured would be risky. 



The effect of the changing values of S and C D is evi- 

 dent in this data set. For example in Table 1, as velocity 

 doubles from 0.30 m/s to 0.60 m/s, drag increases by 

 only 2.09 and 2.52 for the Wildlife Computers PAT and 

 the Microwave Telemetry PTT-100, respectively, rather 

 than by a factor of four. Similarly, power increases by 

 4.13 and 5.00 for the two PSATs and not by a factor of 

 eight. For both these tags, d decreases with increasing 

 velocity resulting in a smaller value for S and a differ- 

 ent value for C D . 



By examining the forces exerted by a PSAT at various 

 velocities, insights regarding the impact of these forces 

 on a study animal can be gained. The combined forces 

 of lift and drag act chronically on the anchor site of the 

 PSAT. Although this study does not specifically address 

 attachment methods, the forces of lift and drag exerted 

 by a PSAT are not negligible and cannot be ignored 

 when evaluating an attachment technique. A PSAT 

 also imposes an energetic cost to the study animal. If 

 that energy cost compromises the animal's behavior or 

 survival, the information gained from the tag is not rep- 

 resentative of an untagged animal. By estimating the 

 energetic cost to an intended study animal, a researcher 

 can make a more informed decision regarding the suit- 

 ability of the animal for this type of tagging. Although 

 direct extrapolation to higher swimming speeds is not 

 possible with our data, the principles outlined in this 

 study can be applied to faster swimming species such 

 as tunas and billfishes that are frequently tagged. 



Acknowledgments 



We would like to thank T. Nelson, S. Wilson, W. Reisner 

 and R. Gammisch for their assistance in running and 

 setting up the flume, T. Mathes for his enthusiastic sup- 

 port, and R. Brill, D. Kersetter, and J. Hoenig for helpful 

 discussions. Financial support was provided by NOAA 

 Office of Sea Grant. 



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