8.4 Case Study No. 4Reference: Roithmayr, C.M., 1970,Airborne low-light sensor detects luminescing fish schools at night. Commer. Fish. Rev., 32(12):42–51Remote Sensing Technique: Airborne Remote Sensing: Platform - Aircraft; Sensors - Aerial Camera, Spectrometers.Objective: To assess fish stocks at night using low-light sensors.Experimental Rationale: Bioluminescence is light produced by living animals and plants including plankton. The responsible light- emitting substance, luciferin, when disturbed absorbs energy and emits light. When fish schools disturb the water, many of these organisms emit light by which the presence of fish can be detected.Method: During 1968, tests were conducted in waters off Florida aboard a commercial seiner. A starlight scope was used to detect bioluminescence associated with Spanish mackerel schools. With the use of a scope coupled to a closed circuit television camera, the image of luminescing schools was recorded on video tape. During dark nights luminescing fish schools were recorded on video tape with a SANOS (Stabilization Airborne Night Observation System) scope and closed- circuit television. Luminescing schools at the surface could be detected by a low-light detector at an altitude of 1,600 m (5,000 feet).Results and Conclusion: Low-light detectors proved to be efficient in detecting fish schools on moonless nights (refer to Figure 8.10). This can be of great assistance to fishermen in reducing their search time. It also will give scientists an opportunity to study the behaviour of fish schools at night. The airborne sensor could greatly assist in resource assessment by providing “real time” observations on the number and size of fish schools.
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