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. DRAFT . although some slightly smaller fish were used that were judged suffi ciently robust to accept a transmitter. No size restriction was placed on adult razorback suckers for implanting transmitters. 3.1.2.3 Radiotracking . Six 10-day tracking trips were conducted during each of the 2 years of this investigation (Table 1). The fish were located on the first day of each trip by aerial tracking with fixed-wing aircraft. The location of each fish was provided to ground crews to facilitate locating the fish for habitat analyses. 3.1.2.3.1 Aerial Telemetry . Aerial tracking was conducted from a Cessna 182 RG fixed-wing aircraft owned by BIO/WEST. The same pilot and observer conducted most of the tracking using uniform procedures to maximize the number of fish contacted. The plane was equipped with one Larsen Kulrod NMO-40 omnidirectional whip antenna attached to the underside of each wing strut. The lead from the antenna under the right wing was attached to the search receiver, SR-40, while the left antenna lead (pilot's side) was attached to the locator receiver, RF-40. This enabled the pilot to help the observer more closely pinpoint a fish location. . . The antenna leads were connected directly to the receivers while the headphone leads were routed through a switch box that allowed the observer to quickly switch back and forth between the audio from each receiver. Both pilot and observer had earphone sets that received the same signal. Typically, a signal was received on the search receiver (SR-40), and the observer would set the RF- 40 receiver to the frequency of the fish most likely to be in the area. By switching back and forth between receivers, and setting the RF-40 to the most probable frequencies, the identity of a fish could generally be determined with one or two aerial passes. Locations provided through aerial telemetry were generally wi thin 0.1 mile of the point subsequently located by boat. Generally, aerial telemetry was conducted at ground speeds of 70-160 mph at above-ground elevations of 50-1000 feet. . 3.1.2.3.2 Ground Telemetry . Radiotracking on the river was done primarily from jonboats, although ice cover during January and February, 1988, prevented thei r use through most of the study area. When the river was ice-covered, the fish were located by vehicle or by scanning suspect areas from cross-country skis. . Search areas were initially limited to those locations determined by aerial tracking. If a fish was not found in this high-suspect area, the search was expanded. The SR-40 receiver was used in the initial search for the signal. To obtain maximum reception, the omnidirectional whip antenna was mounted to a metal base plate about 8 feet above the water level. The receiver was continuously monitored through headphones while in transi t on the river. Resistor sparkplugs were used in the outboard motors to reduce static from the receivers. Once a radio signal was received, the RF-40 receiver and a loop antenna were used to locate the fish. . 8 .