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Following capture, fish to be implanted with transmitters were <br />anesthetized with tticain methane sulfonate (approximately 200 mg/L). The <br />surgical implantation procedure used was similar to Bidgood (1980) except for <br />these departures: a) sutures were individually tied off (usually five rather <br />than a continuous suture) and, h) the incision was made laterally, immediately <br />anterior and slightly dorsal to the insertion of the right pelvic fin. Weight <br />and total length (TL) were taken for each fish. <br />Four different radiotranemitter modules were used in this study. <br />Transmitters were manufactured by Smith-Root and AVM companies. All radio <br />modules were dipped in melted beeswax, as recommended by the AVM company, <br />before implanting. The modules varied in weight, ranging from approximately <br />11 g to 33 g, and were powered by mercury and lithium batteries {theoretical <br />life from about 6 to 18 months). The units transmitted in the 40.660- <br />40.700 MHz frequency range, and each transmitter had a unique signal <br />(frequency and pulse rate) so that individual fish could be identified. Radio <br />receiver sets used were Smith-Root RF-40 and SR-40 models. The RF type <br />enabled the investigator to precisely identify any specific frequency <br />transmitted within the frequency band. The SR receiver was a "search" type <br />and all emitted frequencies within the range could be identified with this <br />unit. <br />Omnidirectional whip and bi-directional loop antennas were employed. A <br />Larson-Rulrod Whip antenna (0.25 wavelength) was used to search for implanted <br />fish. This antenna was mounted on a 20 cm square steel plate elevated about <br />4 m above the water on boats, or mounted directly to an airplane wing or <br />landing strut of a helicopter. Smith-Root bi-directional loop antennas were <br />used to triangulate fish locations from boat or shore. <br />13 <br />