READ and GASKIN: RADIO TRACKING HARBOR PORPOISES 



of 20-60 ms pulses at intervals of 0.4 s. Lithium bat- 

 teries provided a maximum power output of 0.75 

 mW and an expected transmitting life of 1.6-6.0 mo. 

 The maximum transmitting range across open water 

 was about 15-20 km. 



We used a Telonics TR-2 telemetry receiver with 

 a two-element, hand-held directional antenna. The 

 approximate direction of the transmitter was deter- 

 mined by rotating the antenna and noting the 



strongest signal. A digital data processor (Telonics 

 TDP-2) provided a visual display of signal strength. 

 The position of a tagged porpoise was determined 

 either by tracking the animal until visual contact was 

 established, or by triangulation from shore. In the 

 latter method, the receiving system was moved 

 along the shore, and signal bearings at two or more 

 locations were noted. The intersection point of these 

 bearings was then used to approximate the position 



BOLT 



— ANTENNA 



PLATE 



TRANSMITTER 



NEOPRENE 



NUT 



DORSAL FIN 



Figure 2.— The transmitter package used in radio-tracking studies of harbor porpoises in the Bay of Fundy. 

 The bolts attaching the transmitter to the dorsal fin were covered by thin teflon sleeves. 



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