| 摘要 |
Two half sections of bamboo defining three chambers contain a pre-inflated helium gas balloon with a radio beacon, two bags of surface dye, and bait fish. The sections are secured together by multiple wrappings of line ending in hooks or lures. When the associated probe is deployed, the windings unravel in free-fall-separating the half sections and dispersing the bait. The balloon is released and descends to the water surface, where the line hooks and the bait submerge. An aquatic nibble causes the balloon to bob. A more forceful bite separates the bags of dye-creating a surface marker. If a hook is set, the line also extracts a pin from the balloon-activating the radio beacon and freeing it to rise to an altitude where an induced leak soon results in the balloon redescending to the surface of the water. Upon reaching the surface, normal wave propagation forces out the residual gas and the balloon, being no longer buoyant under the weight of the radio beacon, sinks to the ocean bottom. Aircraft flying in various flight line patterns and deploying a given number of devices at intervals can obtain an accurate estimate of the presence of fish in any sized area. A small sinker may be added to the line to facilitate the unwinding of the device as it floats on the surface of the water. If no fish bite, the device floats until recovered for reuse.
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