Communications – electrical: acoustic wave systems and devices – Echo systems – Speed determination
Patent
1997-08-19
1999-11-02
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Echo systems
Speed determination
367 89, 367 94, A01K 6102, G01S 1596
Patent
active
059783150
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method and a device for detecting fodder loss and waste in connection with the breeding of fish.
Fodder loss and waste represent great losses of value in the breeding of fish and, moreover, fodder loss and waste result in pollution. It is important to the breeder to utilize the growth potential of the fish as good as possible, and to achieve this, the allottment of fodder must be close to maximum. External environmental changes, e.g. the seeping in of colder water, may rapidly reduce the appetite of the fish, thus causing excess feeding, resulting in fodder loss and waste, especially when automatic feeding machines are used. It is known to control the feeding in relation to water temperature and other factors, but these measures have not been sufficient to avoid waste and loss of fodder. One has tried to measure the appetite of the fish as a function of its activity and reaction to feeding, but this approach has not given a satisfactory result either. Therefore, a need for a device capable of detecting fodder loss and waste directly in order to reduce the supply of fodder, has existed since a long time ago.
Several devices for detecting waste and loss of fodder have been tried out. A known detecting device utilizes an echo sounder principle combined with a computer analyzing a relatively complex echo sounder image, but this device has not spread, firstly because it is too expensive and secondly because it does not give a reliable detection. The pollution problem was reduced upon the arrival of devices collecting fodder not eaten. Such devices for collecting fodder comprises a bag which is attached beneath the "fence" enclosing the fish. Also, it is known to dispose risers with gas lift or other form of pumping for transferring the fodder from the collecting bag to the surface. The equipment makes it difficult to work with the enclosure in connection with the daily operation of the breeding plant. Moreover, the collecting bags are less efficient in areas where currents are frequent. Due to the loss of the nutritive value arisen when the fodder has been staying in water for some time, this collected fodder was seldom used a second time and, thus, the fodder loss and waste still represent an economic loss for the breeder, even in cases where pollution is reduced.
The object of the invention is to provide a method and a device for detecting loss and waste of fodder.
The object is obtained through features as defined in the following claims.
An exemplary embodiment of the invention is described in the following with reference to the attached drawing. In the FIGURE, reference numeral 1 denotes a floating enclosure for fish, fodder being supplied from above. In the bottom or close to the bottom of the enclosure 1, possibly beneath the enclosure if it has a net bottom, a sound transmitter 4 and a hydrophone 6 have been disposed, both connected to an electronic measuring unit 8 and an electronic analyzing unit 10.
The measuring unit 8 is adapted to drive the sound transmitter 4, such that sound waves are transmitted in a similar way as known from echo sounders. The sound waves are substantially directed upwardly. The hydrophone 6 is adapted to pick up sound waves within a frequency band comprising the sound frequency transmitted from the sound transmitter 4. The measuring unit 8 is adapted to separate the sound received by the hydrophone 6 into different frequencies and to transfer information concerning existing frequencies to the analyzing unit 10.
Fodder, fish and other objects occupying positions above the sound transmitter 4, will reflect some of the transmitted sound energy picked up by the hydrophone 6 in a manner corresponding to that of an echo sounder. Objects moving in a direction towards or away from the sound transmitter 4, i.e. vertically, will additionally cause a change of frequency, the socalled Doppler effect. Thus, the frequency distribution of the received sound signal becomes a measure of vertical movement of objects located above the sound transmitter 4.
Fish fodder
REFERENCES:
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patent: 3231852 (1966-01-01), Kritz
patent: 3757286 (1973-09-01), Richard
patent: 3761909 (1973-09-01), Schweitzer et al.
patent: 3805224 (1974-04-01), Wenz
patent: 3867719 (1975-02-01), Perrin
patent: 3879697 (1975-04-01), Richard
patent: 4901245 (1990-02-01), Olson et al.
Akustisk Malning Av Fiskefor, Tone Berg, Bentech A/S, pp. 4, 6, 24, 34, 36.
Akva AS
Christensen Douglas J.
Lobo Ian J.
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