Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Skin effect wikipedia , lookup
Sound recording and reproduction wikipedia , lookup
Public address system wikipedia , lookup
Electromagnetic compatibility wikipedia , lookup
Sound reinforcement system wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Electric machine wikipedia , lookup
Alternating current wikipedia , lookup
Loudspeaker wikipedia , lookup
Sound level meter wikipedia , lookup
[:61-10-_11.VE FISHERIES RESEARCH BOARD OF CANADA Translation Series No. 1358 THE EFFECT OF SOUND AND OF ELECTROMAGNETIC FIELDS ON THE BEHAVIOUR OFCASPIAN KILKA . By I. V. Nikonorov and A. Kh. Pateev Original title: Vliyanie zvukovogo i elektromagnitnogo polei na povedenie Kaspiiskoi From: Rybnoe Khozyaistvo, Vol. 44, No. 9, p. 11-12, 1968. Preliminary translation by W. E. Ricker Fisheries Research Board of Canada Biological Station, Nanaimo, B. C. •1 1970 This is a preliminary translation prepared for the use of Fisheries the Research Board of Canada. It is not a definitive English version of the article, and it has not been checked or approved by the author. The effect of sound and of electromagnetic fields on the behaviour of Caspian kilka By I. V. Nikonorov and A. Kh..Pateev- In searching for new stimuli that might be used to help catch fish or to increase the effectiveness of present fishing gear, we have investigated the effect of sound, ultrasound and electromagnetic fields on the behaviour of kilka. Observations were made in May on the Caspian Sea in the region of the kilka fishery, on board a ship at night during quiet weather. The anchovy kilka (Clupeonella engrauliformis) was used in the experiments; they , were obtained from catches made at the light of a cone net. The kilka were placed in a thick-walled aquarium made of rubber, 2000 x 1600 x 500 mm. The rubber minimized dispersion of sound in the water coming from reflections off the walls and bottom. The source of the sound was an electromagnetic vibrator of the VSP type, to the rotor of which was attached a round membrane 120 mm in diameter. At a current frequency of 50 hertz the emitter required 30 watts and emitted sound at a frequency of 100 hertz. In our experiments a transformer was used that made it possible to-obtain currents of a frequency of 20 to 50 hertz to be fed into this emitter. The frequency of the sound, controlled by a frequency meter, accordingly varied between the limits 40-100 hertz. For the production of ultrasound we used a fourcore nickel magnitostriktsionnyi vibrator with a working frequency of 23.5 kilohertz, placed on the bottom of the aquarium with its emission surface directed either upward or to the side. The vibrator worked on an impulse regime, the microsecond?], length of each impulse being about 1 mm•sec and their frequency varied from 1 to 185 impulses per minute. Impulses were produced by the discharge into the windings of the vibrator of a condenser of 2 microfarads capacity charged to a potential of 600 volts. The average computed power of an impulse was about 300 watts. Magnetic fields were produced by two cored magnets and one interrupted [razorvannyi] annular magnet. The length of the cores of the former was 200 mm; the mean radius of the centre of the ring magnet was 200 mm, the distance between the -2-- faces [tortsy] was 200 mm. The cores, of 30 mm diameter, were made of tempered steel wire. The coils for the cores were made of copper wire size PBD-0.64 and had insulation sufficient for underwater work. The m.d.s, of each coil when the current was on for a prolonged period was about 1000 av; for short intervals it could be raised to 8,000-10,000 av. The cored electromagnets were set up for observations the behaviour of kilka in a dispersed magnetic field and in a field of opposed types [vstrechnoodnorodnoe pole], when the magnets were placed with like poles (north or south) opposite each other at a distance of 50-100 mm. qn •The ring electromagnet was used for observations on the behaviour of kilka when these moved through the magnetic field between the poles. For this purpose the magnet was placed so that only its poles were submerged in the water. The electromagnets were supplied with either direct current, or alternating current of 50 hertz. The experiments were conducted when there was weak light on deck. For observations on the behaviour of kilka in sound and magnetic fields in conjunction with light, we used a small-sized 25-watt electric lamp (voltage 26 volts) with a reflector. The lamp was suspended over the middle of the aquarium, and the radius of the circle of illumination on the surface of the water was 250-600 mm, depending on the height of suspension. The aquarium was filled with water from overboard at a temperature of about 20°C. For each experiment 50-100 of the liveliest kilka were selected. When the non-working VSP emitter was placed under the [page 12] surface of the water the kilka moved away from it approximately 10 cm. Probably the cause was the • dark colour of the emitter. After turning on the current at a sound frequency of 100 hertz the kilka moved away from the emitter, forming an empty zone around it of a radius 43-44 cm. Reducing the frequency of the sound to 40 hertz weakened the effect of the sound on the kilka. When the deck •illumination was turned off a large part of the fish gathered in the zone illuminated by the lamp suspended above the aquarium. When the emitter was switched on, the fish moved away from it, as before. No reaction of the kilka to the electromagnetic field was observed. Kilka which were in the fields of the electro- -3- magnets, or near the electromagnets themselves, did not change their behaviour either when the current in the windings of the magnet was turned on, or when it was turned off. Kilka which had assembled in the illuminated zone of the aquarium likewise did not react to the action of the electromagnetic field. Thus sound of frequency of 100 hertz frightens kilka, even when they are in an illuminated zone. It is possible that a frequency can be found to which the kilka will have a positive reaction. Utilization of acoustic excitation is an alluring prospect, in view of the low power and weak current required for sound under water, especially in the low-frequency range. À