GB2203540A

GB2203540A - Measuring, counting & classifying fish

Info

Publication number: GB2203540A
Application number: GB08807691A
Authority: GB
Inventors: Hermann Kristjansson; Olafur Skulason
Original assignee: Birtingur H F
Current assignee: Birtingur H F
Priority date: 1987-04-01
Filing date: 1988-03-31
Publication date: 1988-10-19
Also published as: DK177788D0; DE3811376A1; IS3253A7; NO881434L; SE8801196L; SE8801196D0; DK177788A; GB8807691D0; NO881434D0

Description

METHOD AND APPARATUS FOR COUNTING, MEASURII9G SIZE, SEPARATING AND CLASSIFICATION EF FISH.

TECHNICAL FIELD The invention relates to a method and apparatus for counting, measuring sizes and classification of moving objects, specifically live fishes, such as salmon and trout.

BACKGROUND ART Fish farming is a rapidly growing industry, not only in Iceland but, in many other countries all over the world. Counting, measuring the size of the fish and classification according to size is a very important step in the process of fish farming.

Smolts are usually sold by number, and as several hundred thousands or million smolts are often sold at one time, it is very important to know the exact number and size of the smolts which are sold. In fish farming one factor which is very important in order to gain optimal rate of growth, is to have the right number of -smolts all of the same size in the same tank or pond. This is due to the fact that some fish grow more rapidly than others and that smaller fish grow slower when surrounded by bigger fish.

Several methods are known for the counting, measuring sizes and classification of live fishes, such as salmon smolt. The counting has first and foremost been undertaken in such a manner that each individual fish is counted and marked down, e.g.

by means of a simple manual counter. The measuring of the sizes of the fishes is performed either by weighing each individual fish or measuring its length by meats of a tape measure. A sort of roller apparatus exists for the mechanical classification of the sizes of live fishes.

Thereupon the fish slides in a practically horizontal platform in between two cylinders which revolve one against the other. The cylinders slant slightly outward from the horizontal position in the direction into which the fish is shifting, but the intercept between the cylinders increases at the same time. Through the revolving of the cylinders, the fish shifts forward and falls down between these at a specific position when the intercept between the cylinders has become equal to the width of the fish.

It is clear that these methods entail numerous disadvantages. The fish must be taken out of the water for a longer period which cannot be considered desirable. This specifically applies to the case of live fish, such as smolts and small salmon which need frequently be counted and classified in the course of their breeding. Allappitus which may cause friction and which may bruise fish must be considered unsuitable and undesirable in the production and handling of live fish. This affects stress to the fish. And it is perhaps a greater disadvantage that these methods function very slowly and are manpower demanding.

SUMMARY OF THE INVENTION The object of the invention is to provide a method and apparatus of the aforementioned type which is both simple, safe and quick working and would have the least possible effect on the fish and in addition thereto the fish will be out of the water for very limited time.

-kssording to-the invention: there is provided method and apparatus wherein the fish is movea past measuring apparatus where one, two or more rays of light are directed between transmitting and receiving apparatus, practically normal to a specific direction of movement of the fish, and the apparatus is connected to a microcomputer, where all measurements are feeded into, the rays being thus positioned at a fixed intercept, so that when the fish passes the apparatus and interrupts the rays, the time "tl" it takes the fish to travel a fixed intercept "S" between the rays, is measured so that it is possible to calculate its speed "V", and at the same time measurement is made of the time "at2", it takes the fish to pass by one of the rays, at the speed "V" which has previously been calculated so that it is possible to calculate its length 11L'1 by the micro-computer and direct it on a fixed course according to its size.

The method is based on the measurement of the 1,moving speed?? of the fish and from this, its length is computed from the time it takes to move the fish past one of the lightrays. Fig. 7 shows this very well. When the fish interrupts the first ray an alteration is presented in the receiver, where the intensity of light accepted by the receiver has been reduced or disappeared, and the alteration remains until the fish has passed the ray. In the selfsame manner there appears an alteration which likewise remains until the fish has passed the second ray. This is indicated in fig. 7 as "at2" at the line A2. By measuring the time which passes from the event when the fish interrupts the first ray and until it interrupts the second one, it is possible to compute its speed.This time is indicated as "tl" in fig. 7.

By measuring the time during which the ray remains interrupted (the time it takes the fish to pass the ray) it is possible to calculate its length "L" as previously stated.

V = moving speed.

S = distance between rays.

Ptl = the time it takes to move the fish between rays.

V= S otl L = the length of the fish.

ot2 = the time it takes to move the fish past the ray.

t = V x At2.

The biomass of fish (salmon) can be approximated by M = K x L3 100 By determining K it is therefore possible to calculate the biomass of the fish.

1 ' K < 1.4.

K may be evaluated by means of simple measurement while it is first and foremost subject to the species and condition of fishes, The light-receivers of the apparatus are thereupon connected to a micro-computer which measures and registers the time otl and At2 from the alteration of the volume of light which comes to the receivers. At the same time the computer counts and records the number of deflections from either one or both receivers which corresponds to the number of fishes which have passed the apparatus.

The length of each fish and classification of each fish is also recorded. Due to the speed at which the computer can work, it is possible to give a command to open appropriate gates in order to let the fish into a specific channel according to its classification.

In rearing salmon as well as other species of fish, it is also of importance to know the accurate number of fishes and size of all fishes in each tank or pond. In this manner it is possible to achieve the most favourable feeding, oxygen feed, water exchanges, correct temperature and correct feed of pharmaceuticals in each individual tank or pond, and thereby achieving the maximum utilization in the rearing. This becomes possible when one may in a simple and quick manner count the fish, measure their individual sizes and classify them.

Counting and classifying are also of much importance upon the purchase and sale of live smolts and particularly so in the case of small fish which is frequently sold by hundreds of thousands. This is a case of valuable goods and it is of major importance both for the buyer and the seller to have accurate knowledge about the number, size and weight of the fish being contracted.

A feature of t tus of fry irv,tion is tat te bm* te fish is moved in, is in cross section normal to longitudinal direction, practically V-shaped, and so laid at a fixed incline in its longitudinal direction, that the fish is kept wedged in the track and when it slides past a measuring apparatus it becomes possible to count each individual fish as well as measure its size. The fact that the track is practically V-shaped in cross-section as shown in fig. 1, 3 and 5 has the effect, particularly on live fish which is laid in the track, that it is practically unable to move by its own force.

The walls of the track support the fishs entire length, and due to the coordination of the V-shape of the track and the physical form of the fish, it lies either on its back or belly and whereas the ability of live fish to move is particularly to the sides this is largely restricted by the walls of the track; The bottom of the track thereupon also gives support and obstructs the vertical movement of the fish. By inclining the track the fish is given a specific speed along it due to the effect of the acceleration of gravity and so that it slides through the measuring apparatus without having to be pushed at all.

A further feature is that the track has at least, at a specific intercept, a continously increasing slope.

This has the effect that, when the fish enters the intercept or the place in the track where the slope starts to increase continuously its speed along the track increases with the effect of separating the fishes sufficently to discern each individual fish without any effect from the next fish following in the track. The apparatus is further characterized in that water flows along the bottom of the track and the flow of the fish is thereby greatly facilitated. The water functions like lubricant between the fish and the track. The method and apparatus which has been described herein may thus have a considerable effect on the practicality of the fish farming.

BRIEF DESCRIPTION OF THE INVENTION The inventia will be described rrore detailed below, by way of ex1e with reference to the accompanying drawings where: Fig. 1 - shows cross-section from fig. 2 normal to the track.

Fig. 2 - shows an illustration of the side of the inclined track along with a filling tank.

Fig. 3 - shows isometric illustration of the track with a filling tank.

Fig. 4 - shows arrangement of the measuring apparatus seen from above.

Fig. 5 - shows arrangement of the measuring apparatus seen in the direction of the movement of the fish.

Fig. 6 - shpws arrangement of the measuring apparatus in the classification system.

Fig. 7 - shows schematic signal/time graph for the measuring apparatus.

Fig. 1 - shows cross-section I-I from fig. 2 norm to the longitudinal direction of the track. The track consists of two wall-units (4,5) forming the track. A fish, the cross-section (3) of which is practicaly oval, as shown in the illustration will lie to the inner walls (6) and the bottom (2) of the track Fig. 2 - shows a side illustration of the track (1) where at its upper end a filling tank (8) has been arranged. At the filling point (7) the slope of the track is practically even, but further down along the track it develops an even and thereafter an increasing slope over a fixed section (19), but at its end (18) the slope has again become even.

In this region a measuring apparatus (11) is arranged. It consists e.g. of two pairs of transmitting and receiving apparatus connected to a micro-computer connection (14). From the track the fish will fall e.g. into a rearing tank, or te directed into rearing tank due to its size.

Fig. 3 - shows a track and a filling tank (8) where fish is shovelled into, through an opening (15) at the top. By hosing water onto the fish, e.g.

through an opening (16) on the wall (17) of the filling tank, facing the upper end (7) of the track, the fish seeks a way out there, or is rinsed down into the track. Thence the fish flows down along the track wedged by the inner walls of the track (6) through the accelerating portion (19) and through the measuring apparatus (11,12,13) and out from the lower end of the track (18), into a rearing tank.

Fig. 4 - shows two transmitters of signals (22,23) which are positioned at a fixed interval (27) in the track through which the fishes (21) are conducted. These transmit light signals (rays) normal on the direction of movement of the fish (21). Opposite to the transmitters of signals (22,23) there are positioned receivers. (25,24) which receive the transmitted signals and in case of a change in the intensity of light these transmit a message accordingly to a micro-computer or recording apparatus (26).

Fig. 5 - shows fish (21) positioned in the track, between a light signal transmitter (22) and receiver (25) so that the ray of light (36) is interrupted and the light signals are blocked from reaching fully the receiver (25).

Fig. 6 - shows the arrangement of the measuring apparatus (37) between a rearing tank (34) and three classification tanks (31,32 and 33). The fish is moved from the rearing tank past the apparatus (37) and into the appropriate tark depending on which classification gate (35) is opened.

Fig. 7 - shows schematically the signal/time graph for the apparatus for counting and measuring length. Al shows deflection when the fish interrupts the ray and crosses the first transmitting and receiving equipment (22,25) and until it has passed the ray. In the same manner A2 shows deflection when the fish interrupts the second ray by means of the nose and the deflection remains until the fish has passed its tail by the sensor. a tl is the period which passes from the time the fish interrupts the first ray and until it interrupts the second ray. tt2 is the time interval in which the first or second ray is interrupted.

The invention which has been described hereinbefore is not limited to the aforementioned version, but may be modelled in many different ways without differing in principle from the main idea described above. For instance the method and apparatus can be used to count, measure size and classify dead fish such as cod as well as other particles.

Claims

1. A method for counting, measuring sizes and classifying moving objects, specifically live fishes, such as salmon smolts, wherein the fish is moved pass measuring apparatus, where one, two or more rays of light are directed between a transmission and receiving apparatus practically normal to a specific direction of movement of the fish and the apparatus is connected to a micro-computer where all measurements are feeded into, the rays being thus positioned at fixed intercepts so that when the fish passes the apparatus and interrupts the rays, the time it takes the fish travelling a fixed intercept between the rays, is measured so that it is possible to calculate its speed and at the same time there is measured the time it takes the fish to pass one of the rays at a speed previously calculated, thus making it possible to calculate its lenght and direct it on a fixed coursse according to its length.

2. A method according to Claim 1. wherein the measurement of the tie interval which passes from the time the fish interrupts the first ray, by means of its nose, and until it interrupts the second ray, by means of its nose, and at the same time measurment of the time interval which passes from the time the fis interrupts either the first or the second ray i= its nose and until the entire fish has passed tre ray, is feeded into micro-computer for calculate of the length of the fish.

3. A method according to Claim 1 or 2, wherein the microcomputer counts and records the number of fishes passing through the equipment from the number of times the rays are interrupted.

4. A method according to Claim 1, 2 or 3, wherein when the computer counts and records the number of fishes passing through the equipment, it records their calculated length and directs them to a specific course due to their length and records, in what course each fish has been directed, and how many fishes have been directed on a specific course.

!. A method according to any of the Claims 1 - 4, wherein from tne calculated length of the fish, the fish is directed by signals from the computer by opening and closing of gates made for the purpose and into specific compartments 6. Apparatus for counting, measuring size and classifying moving objects, specifically live fish such as salmon smolts, comprising a track in which the fish flows or is taken along e.g. through or past measuring apparatus which counts the number of fishes, measures their sizes and classifies the fish wherein the track is in cross-section normal to its longitudional direction, generally V-shaped so the fish will be maintained wedged in the track while it slides pass the measuring apparatus so that one fish may ~e counted simultaneously with size measurement.

7. Apparatus according to Claim 6, wherein, .the angle between the walls of the track, which is V-shaped, is approximately 35-55', particularly 40 , so the fish lies, wedged in the track due to its shape.

8. Apparatus according to Claim 6 or. 7, where' in, the track is installed with a fixed slope its longitudional direction so that the fish slides in the track past the measuring apparatus.

9. Apparatus according to Claim 6, 7 or wherein, water flows along the bottom of the track and facilitates the flow of fish along the track.

10. Apparatus according to Claim 6 or 8, wherein, the slope of the track increases from the original position in its longitudinal direction, at least partially, and thus the fish gains everincreasing acceleration along the track, and an intercept is formed between two or more fishes which slide along the track one after another.

11. Apparatus according to any ome ' of Claim 7-10 wnerein, the track's coefficient of incline in its longitudinal direction at least higher than of the first degree.

12. A method. of measuring the length of a fish comprising the steps of causing a said fish to move past first and second spaced detectors which detect the presence or absence of a said fish adjacent to their respective positions and deriving said length from the instant and duration at which the detectors detect the fish.

13. Apparatus for measuring the length of a fish comprising first and second detectors which detect the presence or absence of a said fish adjacent to their respective positions and means for deriving said length from the instant and duration at which the detectors detect the fish.

14. Apparatus for measuring the length of a fish comprising a channel of substantially W-shaped cross section and arranged to be disposed at an incline and detection means for detecting a said e rsh passing along said channel and means responsive to the detection means for deriving said length.

15. Method and apparatus principally as described hereinbefore and as shown in the enclosed drawing--.