RU2010263C1 - Method of determination of parameters of fish shoals in water - Google Patents

Abstract

FIELD: underwater acoustics. SUBSTANCE: in accordance with method receiver is located on floor. Noises of broadband source of acoustic oscillations passed through fish shoals are received within directivity diagram. Resonance frequency of fish sounds and time of crossing of directivity diagram by shoals are measured at depth of receiver. By these data size of fish and depth of their swimming are determined. EFFECT: expanded application field, gaining of information on size of fish in shoal and depth of its swimming under real sea conditions. 5 dwg

Description

 The invention relates to hydroacoustics and can be used to register fish clusters and determine their parameters.

 Known methods and devices for detecting fish, fish schools by sensing the water volume with sonar pulses of ultrasonic frequencies.

 Also known are devices that use a method for registering fish clusters and determining some of their parameters "in the light", a tomographic method.

 A known method is that they carry out continuous emission of acoustic vibrations in a wide frequency band, receiving them at a certain distance from the emitter and measuring the integral value of the received signal. If there is a fish cluster containing juveniles in the water between the emitter and the receiver, the density of fish accumulation is judged by the change in the magnitude of the received signal, i.e., by the degree of shadowing, and the number of fish passing through the device is judged by the signal duration.

 The disadvantages of this method are as follows: the inability to determine the size of the fish in the cluster and its spatial coordinates relative to the receiver and emitter; the impossibility of application in real marine conditions, for example, for recording jambs passing through the strait, and determining the depth of the jamb in this case.

 The aim of the invention is to expand the scope and obtain information about the size of the fish in the school and its depth of navigation in real marine conditions.

 This is achieved by the fact that the reception of a broadband signal passing through the jamb is carried out using a fixed spatial pattern with known geometric parameters, the signal is processed in narrow frequency bands, the spectrum components that are most obscured by the jamb are fixed, thereby determining the resonant frequency of the fish bubbles on corresponding to the depth of the joint. At the same time, the transit time of the jamb at this depth is measured. The measured time is compared with the estimated time interval for a school to cross a horizontal section of the radiation pattern by fish of different sizes. By the belonging of the measured time to a particular interval, the size of the fish and the depth of swimming of the school are determined.

 In FIG. 1 schematically shows how the jamb is detected, where 1 is the receiver (hydrophone); 2 - radiation pattern; 3 - broadband emitter; 4 - cable; 5 - processing equipment; 6 - buoy; 7 - a school of fish.

 In FIG. 2 shows a structural diagram of a device for implementing the method, where 1 is a receiver (hydrophone); 8 - broadband amplifier; 9 - decoder; 10 - a comparator; 11 - time meter; 12 - frequency spectrum analyzer.

 In FIG. 3 shows the radiation pattern 2 of receiver 1 (hydrophone), where 13 is the horizontal section of the radiation pattern.

 In FIG. Figure 4 shows graphs of the dependence of the resonant frequency of fish bubbles of different sizes on the depth of their swimming.

 In FIG. 5 shows timing diagrams calculated from the raw data of the graphs in FIG. 4 by the formula (2).

 The receiver (hydrophone) 1 is installed at the bottom of the strait. It has a radiation pattern 2. Broadband emitter 3 is installed, for example, on the buoy 6. The receiver 1 is connected by cable 4 to the processing equipment 5, located, as a rule, on the shore. The emitter 3, receiver 1 and the subsequent processing path 5 are designed for a wide range of frequencies corresponding to the resonant frequencies of fish bubbles floating at different depths.

 The signals of the emitter 3 passing through the jamb 7 are received by the receiver 1, amplified by a broadband amplifier 8, integrated by the detector 9 and fed to the comparator 10, which operates at the set leading edge levels of the integrated pulse and generates a start and stop pulse for the time meter 11, for example, an electronic stopwatch. At the same time, the broadband noise from the amplifier 8 goes to the frequency spectrum analyzer 12. The amplitude of the frequency of the spectrum corresponding to the resonant frequency of the fish bubble, due to the greatest reflection from the jamb at this frequency, will be the smallest.

, (1) где F_p - резонансная частота, кГц;
Н_р - глубина косяка, м;
L - полная длина рыбы, см.In FIG. Figure 4 shows graphs of the dependence of the resonant frequency of fish bubbles of different sizes on their swimming depth, calculated by the formula
F _p =

, (1) where F _p is the resonant frequency, kHz;
N _p - the depth of the joint, m;
L is the full length of the fish, see

 Formula (1) is obtained by converting the known formula by replacing the hydrostatic pressure parameter with depth.

 From those shown in FIG. 4 plots, it follows that in a certain range of frequencies and depths it is impossible to unambiguously determine the fish size and depth from the resonant frequency. So at a frequency of 2 kHz there corresponds a fish size of 10 cm, at a depth of 75 m and 15 cm at a depth of 230 m. With a decrease in the resonance frequency (increase in fish size), the number of uncertainties increases.

 To reveal the uncertainty, we use the features of the geometry of the radiation pattern and the property of fish of different sizes to move at their inherent speed.

, (2) где Н_в - глубина водоема, м;
Н_р - глубина косяка, м;
α - половина ула раствора диаграммы направленности;
v_p - скорость рыб соответствующего размера, м/с.The radiation pattern 2 (see Figs. 1 and 3) can be implemented in a shape close to a pyramidal base facing the sea surface. Its horizontal section 13 at different depths will have different lengths. The transit time of this section by a jamb (from entering it into the diagram to reaching its opposite edge) is calculated by the formula
t =

, (2) where N _in - the depth of the reservoir, m;
N _p - the depth of the joint, m;
α - half of the ul solution of the radiation pattern;
v _p is the speed of fish of the corresponding size, m / s.

In FIG. 5 shows timing diagrams calculated from the raw data of the graphs in FIG. 4 by the formula (2). As the value of the speeds v _p in the formula (2), the minimum and maximum "cruising" speeds of the fish of the corresponding size were used. From the time diagrams, it follows that for resonant frequencies above 0.5 kHz (fish size less than 25 cm), the calculated time intervals t do not intersect, and from them it is possible to unambiguously determine the fish size and the depth of swimming of the school. For fish sizes greater than 25 cm (resonance frequencies below 0.5 kHz), the calculated time intervals partially overlap and, therefore, the fish size and depth can be determined (for intersecting intervals) in the form of integral estimates. For example, an interval of 140-160 s corresponds to a fish length of 35-40 cm at a depth of 77-100 m.

 Thus, this method determines the size of the fish and the swimming depth of the school using the measured resonant frequency and the duration of the shading signal (its leading edge).

 Using the method allows you to register fish schools in real marine conditions; to assess the size of fish in the school and the depth of their swimming. (56) A.I. Gikunov. Search instruments and systems. L.: Shipbuilding, 1989, p. 195-226, 271-273.

 Fisheries, N 8, 1977, p. 64-66.

Claims (1)

 The METHOD FOR DETERMINING THE PARAMETERS OF FISH CLINDS IN WATER, which consists in continuous emission of a wide-band acoustic signal into the water volume, using it with a receiver allocated from the emitter and measuring the magnitude of the signal change when the receiver is shaded by the fish, which differs most in that the measurement the fish of the area of space limited by the diagrammatic direction of the receiver at the depth of finding the school of fish, compare the measured time with the calculated time interval Using a school of fish for this area of space at the possible swimming speeds of a fish of various sizes and according to the measured time for one or another interval, the size of the fish and the swimming depth of the school are determined.

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