threaded with a stainless steel lock-tight nut. On the opposite side of the fin, 

 the bolts were threaded with a fabricated magnesiun\ alloy nut. The 

 magnesium alloy was supplied by Metal Supply Co., Philadelphia, 

 Pennsylvania. The magnesium nuts were backed by 3.5-cm-aluminum 

 washers, also fitted with neoprene against the skin surface. Between the 

 magnesium nut and the aluminum washer was a 3.5-cm-metal washer to 

 interact electrolytically with the magnesium and salt water. The magnesium 

 nuts were designed to corrode to disappearance within about 4 wk in water 

 25-30 °C ai>d about 20-30 ppt salinity. The magnesium nuts were 2.6 cm in 

 diameter and approximately l.(>-1.3-cm thick, with the rear nut slightly 

 thinner (by 0.1 cm) than the front nut, so that the front bolt would tend to 

 hold the package a few hours longer than the rear bolt, and not cause an 

 adverse tiuming and increased drag of the radio package, likely if the rear bolt 

 held longer. 



Package Mounting 



The radio was mounted to the dorsal fin by the Teflon bolt and 

 aluminum/stainless steel/magnesium nut assemblies. Two 0.60-cm-bolt 

 holes were punched through the fin with a standard stainless steel laboratory 

 cork borer disinfected with Betadine. Prior to hole punching, a veterinarian 

 examined the chosen location for absence of major arteries v^rith an 18-gauge 

 needle, sterilized the site with alcohol, and administered a local anesthetic of 

 1.8 cc Lidocaine (Sweeney 1992). Slight bleeding occurred about one-half of the 

 time and always stopped upon insertion of the tight-fitting Teflon bolts. The 

 bolts were custom-fit to each dorsal fin by siupping off excess bolt material 

 with wire cutters. The magnesium alloy nuts were finger-tightened and then 

 pressure-crimped with a vice-grip. 



Si gnal Reception System 



Dolphin radio-transmitter signals were received with Telonics TR-2 

 hand-held receivers and Telonics TS-1 hand-held automatic frequency 

 scanning receivers. These were used with antennas ranging from hand-held 

 "H" or two-element antennas (± 20° directional accuracy) to five-element 

 Yagi-Uda antennas (± 5° directional accuracy) on aluminum poles up to 8-m 

 high (Fig. 3). Receiving systems were used from each of two 5.5-7 m outboard 

 vessels, a pick-up truck, several secondary lemd-based stations, and two five- 

 element antennas on the second story balcony of a house (Home Base) in Port 

 O'Connor, at the southern end of Matagorda Bay (28°27.05'N, 96°25.12'W). 

 Total height of the Home Base antennas was approximately 14 m above sea 

 level, and approximate range of reception varied from 10-20 km. Twin "H" 

 antennas also were mounted on the wing struts of Cessna 172 and Piper Cub 

 aircraft and on the footsteps of a Cessna 177 for aerial tracking. Usual range 



