NL1007940C1 - Method for locally stirring the seabed with the aid of a fish trawl for fishing using a knife. - Google Patents

Description

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Method for locally stirring the seabed with the aid of a fish trawl for fishing using a knife.

The invention relates to a method in which a fish trawl is used to stir the seabed over a small depth for fishing. Although suitable for fishing coastal waters, for example fishing razors and cockles, the invention also applies to some types of common fish living in or near the bottom of our coastal waters.

It has been found that catching razors requires special knowledge. Razors usually stand upright in the sandy bottom and stick there at a total length of e.g. 10 to 18 cm, not above so that fishing 15 on the bottom gives no result. The upright razors are lifted out of the bottom sand only by loosening the seabed by a depth that corresponds at least to the standing height and thus the length of the razors and can then be brought on deck via a suction pipe which opens out into the fish basket. For this purpose, a suction line is connected to a centrifugal pump with a relatively large pump impeller and the razors or other product animals are thus transported via the pump impeller to a deck mill where the razors of sand and other fished up unusable material are selected.

Although this method of fishing gives a good yield, however, inevitably more than 20% of the catch of product animals is damaged by the pump impeller in such a way that they can no longer be considered for consumption. It is therefore very important to reduce this high percentage to an acceptable percentage of 1 to 30, at most 5%. This applies on the one hand to the catch, but on the other to the seabed environment. It has been found that this drawback can be remedied by using a greatly improved method for capturing such product animals.

According to the invention this can now be achieved by a method of using a knife depth that can be accurately adjusted in advance by means of a fish trawl that is dragged over the seabed, the latter only over a small depth over a width of e.g. 80 cm 1 n 0 7Q / 1 o - 2 - to 100 cm to chop to a depth the length of an average long razor and using compressed air and / or pressurized water connections which are primarily intended to ensure that the razors are without noteworthy damage to be "harvested". In particular, a pressurized water mouth could be directed against the direction of movement of the fish trawl on the top of the knife-blade surface in order to simultaneously discharge product animals, such as clams, thus loosened at the top out of the fish trawl and via a water suction line to a collecting reservoir on the deck. suction, in which case a fish trawl is preferably equipped with a plunging knife set in the direction of movement of the fish trawl at an oblique angle, which extends over the width direction of the fish trawl, in particular over a length of, for example, at most 100 cm, and wherein in the In particular, the desired insertion depth 15 of the plunging knife is adjustable relative to the bottom of a fish trawl by using an optionally exchangeable plunging knife.

Because an adjustable stitch depth can now be provided, it is already achieved that in that first fishing phase the number of damage during the razor catches is considerably reduced and in any case remains below the aforementioned 20%. In order to achieve an even greater reduction in damage to the product animals, it is important if the stirring zone remains dimensioned such that outflowing press water is directed directly at the knife, so that, on the one hand, the fish trawl can be drawn with a lower power than hitherto and on the other hand, it is precisely because of this and because of the targeted bottom sand turning that the catch is now considerably less damaged.

In principle, two options are feasible without the centrifugal pump. The first has already been described above, the second consists in that with the help of compressed air the suction tube for bringing the catch onto deck is provided with compressed air blowing openings at least near the bottom. These then ensure that the shellfish to be caught, such as the razor blades, easily end up on deck without suffering from mechanical damage from a pump impeller.

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Furthermore, the knife should extend substantially over the full width of the fish basket and it is also conceivable that this knife is divided into a few separate knife blades which together overlap the width of the fish basket. In this respect, the sea bed churning can be compared somewhat with a light form of local seabed loosening plows and a position and shape to be given to normal plow knives may be applied in a comparable manner to the shape and position of one or more blade cutters according to the invention.

10

Due to the speed of movement of the fish trawl over the seabed and the action of the compressed air and / or jet of water on or near the top surface of the knife, the latter can also have a curved shape such that the water flow with, among other things, the loosened product animals within it. the fish trawl is fed in the most favorable way to the suction pipe.

According to the invention, the fish basket is provided with mounting members for the knife or for the knives and means are also provided to adjust the insertion depth between e.g. 20 and 30 cm.

Depending on the nature of the seabed, it is moreover desirable if the angular position under which the knife stirs up the seabed can be adjusted by means of suitable tilting means.

In order to ensure that the loosening takes place as efficiently as possible and to minimize the temporary disturbance on the seabed, it is also proposed to make the cutting knife hollow and to have this hollow cutting knife also function as a pressurized water mouth.

It is clear that the invention aims at promoting, by means of a water or air jet or both, the bringing to deck of as much undamaged shellfish as possible, such as the razors which are easy to damage.

If compressed air is used to raise the razors, a so-called Roots blower, a displacement pump or compressor of a known type, placed on deck for that purpose, will suffice. The maximum catch depth is approx. 12-16 m and by injecting air into the delivery pipe, the effect of a so-called mammoth pump is obtained. While a flow rate of approximately 400 m3 / h was acceptable in the centrifugal pump used hitherto, a larger flow rate was also found to lead to more sand yield, whereby the wear of the pump housing and pump impeller is greatly increased and, moreover, the sand discharge from the deck is of great concern. On the other hand, the displacement pump with air cannot cause any problem, since wear does not occur by compressing air and the pressure height is easily overcome in any range from the seabed.

10

The invention will be explained in more detail below with the aid of the drawing.

Fig. 1 is a schematic side view of a fishing boat provided with the means by which the method can be carried out; FIG. 2 is a schematic side view of a fish trawl equipped with a sticking knife;

Fig. 3 is a front view of the fish basket in FIG. 2;

Fig. 4 is a schematic side view of a mammoth pump for use in the method of the invention, and FIG. 5 is an embodiment of a hollow knife according to the invention.

In Figs. 1 -5 a set of tubes is attached to the front of the fishing boat 1 by means of a rotatable tube coupling. The pipe coupling makes it possible for the movement relative to the ship 25 to continue during swell and wave action. Compressed air is supplied through the upper compressed air pipe 2, and water with a catch is brought to the ship's deck by means of a pump through the second lifting pipe or suction pipe 3. The arrow directions A and B indicate the direction within tubes 2 and 3. Both tubes result in tubes that have been lowered to the sea bottom, into a kind of fish trawl, ie an elongated cage 5 provided with lattice 4, which is mounted on a slide frame 6. The slide frame 6 comprises two parallel carriers 7 which on the front as the points of a ski should be bent slightly upwards so that the fish trawl 5 does not pull itself into the seabed when it is pulled over it by the boat 35 1 in the direction of arrow C.

A plate-shaped knife 8 is mounted on the frame 9 across the width of the fish trawl 5 and transverse to the direction of movement in accordance with arrow C, the fish trawl 5. When fishing for razors, this knife 8 is set at 1007940 - 5 - depth so that only the local loosening of the seabed takes place to a small extent, as a result of which the vertical razors are, as it were, undermined. This undercutting now involves directing such an air and / or water jet on the front side of the plunging knife 8, that this promotes the loosening of the seabed on site. If razors are located on the spot, they detach themselves from the sand on the seabed in which they stand and these razors are then raised and raised by means of suction in lift tube 3. If use is made of a breast pump via the lift tube 3, a compressed air connection is also made at one or more places in that lift tube 3. This injection of compressed air then produces an upward jet effect, which also causes the catch and thus the whole razors to come on deck.

1 5 Due to the lack of transport of the razors via a pump impeller of a centrifugal pump, now considerably less damage in the form of shell breakage occurs.

In FIG. 2 is the fish basket 5 of FIG. 1 shown in more detail. The direction of the loosening compressed air and / or compressed water flow is drawn schematically and runs from the spray nozzle 9 in the direction of the knife 8, so that the knife 8 set at the desired stitch depth ensures that the loosened sand bottom loosens the razors on site. the razors are then brought on board via suction or pressing. The setting of the discharge nozzle direction on the front and top of the cutting knife 8 and the degree of speed of the pressing and / or suction action should preferably be regulated from the deck in such a way that the amount of sand transported upwards remains as small as possible. . Since the water in the immediate vicinity of the dragged fish trawl 5 is virtually opaque as a result of the loosening by the knife 8 and the whirls generated, it is important to pay close attention to the composition of the water that comes up with the catch, which incidentally quickly back into the sea, on the basis of which the pressure, resp. The flow rate must be adjusted.

35 There are actually two options with regard to the use of the vortices that help to loosen the seabed. For example, the nozzle for the compressed air or water jet can be arranged opposite to the movement of the fish trawl 5, but a strong flow can also be produced, which also follows the direction of movement of the fish trawl 5. The choice of this may partly depend on the sailing direction and the flow direction of the water over the seabed. In case a hollow knife 10 is used, as shown in FIG. 5, 5 outflow openings 11 may be provided which open out on top of the knife blade surface and are oriented such that their action on the front underside of the knife 10 becomes noticeable. If the full-width cutting knife 10 is given a hollow opening, reinforced by transverse partitions, the cutting knife 10 can have a completely double function. 10 On the one hand it functions as a blade for loosening the seabed on the spot, on the other hand it also forms the mouthpiece through which the loosening water comes out.

In the embodiment in FIG. 4, the breast pumping action for raising and uncovering the razors has been employed. By the injected air in the catch tube 11, the water contained therein is simply brought to deck with the catch, since much air is always much lighter than water. Because the loosened sand is left as close to the seabed as possible - this can be made empirical by the correct choice of knife stitch depth (eg 25 cm) and sailing speed (eg 250 20 m / h) as well as by the nature and shape of the knife and the applied compressor pressures. determined - this new method of fishing and raising on deck will also provide the aforementioned benefits.

In order to achieve an optimum catch in the case of fishing by means of the method according to the invention, in which the seabed is only slightly turned around, in a preferred embodiment the fish trawl 5 can still be provided with a number of electrodes at the front knife 8. in the form of pins or plates between which a slight tension is maintained. The salty seawater is already a good conductor for electric current and by maintaining a certain electric voltage, the catch objects can even be attracted or reacted. are slightly anesthetized before being "pumped" onto deck via lift tube.

The knife 8, which will be subject to a high degree of wear during fishing, will at least on the parts thereof which are most suitable, e.g. manganese steel with a high wear resistance.

It is also practical to wrap the back of the knife around an I! \ I ·· 7 '! d 0 -7 - to rotate the pivot shaft which is incorporated in the frame of the fish trawl. By changing the angle of the knife with respect to the axis of rotation and thus with respect to the bottom of the fish basket, it is possible with a chosen knife size to adjust the insertion depth for the catch by turning the knife and subsequently securing it. set.

If one estimates the razor catch based on current catch results, e.g. catches 10 tons of whole razors in a 1-week period. In the usual fishing method, 2 tons of damaged razors that are unusable for consumption would then be put on board and of course serve for feeding other creatures living in or on the seawater. The fishing will now have to be less intensive, because with this catch the seabed surface to be loosened can remain smaller due to the catch increase of whole razors. The number of fishable days is set at e.g. 150 days a year, in many ways the proposed new working method achieves meaningful savings, both with regard to the seabed environment and with regard to the limits that may have to be imposed on overfishing on razors. With the aid of the invention it is now possible to determine in a simple manner and without plowing the seabed whether certain razors are in front of the towed fish trawl or not. After all, these can be detected quickly and whether or not they can be seen when the deck is undamaged and the quantity thereof can then be determined whether one should continue on the spot or stop the catch.

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Claims (15)

1. Method by means of a pre-set depth of knife depth pre-set by means of a fish trawl that is dragged over the seabed, the latter to be locally stirred using 10 pressurized water connections which are mainly directed at the top and / or front of the knife located on the bottom side of the fish trawl, and at the same time to discharge product-loosened product animals, such as clams, from the fish trawl at the top and via a water riser to a collecting reservoir on deck, whereby a fish trawl is preferably equipped with a Slitting knife mounted on the fish basket at an oblique angle, which extends over the width direction of the fish basket, preferably over a length of, for example, 100 cm, and in particular the desired insertion depth of the knife and its angular position relative to the bottom of a fish basket 20 can be preset. 2. Method according to claim 1, characterized in that the cutting knife is arranged substantially across the width of the fish trawl and this arrangement is chosen such that the cutting knife is located approximately halfway along the fish trawl length in a direction towards the open front of the fish trawl to. 3. Method as claimed in claim 1 and / or 2, characterized in that the position of the knife in relation to the fish basket is preset to a knife depth of 10 cm to 30 cm, depending on the product animal to be caught, and that the direction of a compressed water supply mouth is thereby oriented such that the loosened sand on or near the knife blade surface is always struck directly on the stirring zone in preparation by the outflowing compressed water or compressed water-air mixture. Fish basket equipped with a knife for applying the method according to any one of the preceding claims, characterized in that the steel frame of the fish beam 1007940-9 is provided with mounting members on which the knife can be mounted. 5. Fish trawl according to claim 4, characterized in that the fastening members are provided with adjusting means for being able to adjust the insertion depth of the plunging knife into the seabed. 6. Fish trawl according to claim 5, characterized in that the fastening members are provided with tilting means to change the insertion angle position of the insertion knife relative to the seabed as desired. Fish trawl according to any one of the preceding claims 4-6, characterized in that the cutting knife is located on the front end of a flat element 15 which serves as "knife handle" for the cutting knife. Fish trawl according to claim 7, characterized in that the end of the "knife handle" facing away from the knife knife is provided with means for presetting the desired insertion angle position of the knife knife. 20 Fish trawl according to claim 9, characterized in that the flat element is provided on its top side with a number of outlets for compressed water and / or compressed air injected therein and fed through the hollow "knife handle" via a compressed water supply mouth and provided for this purpose. is 25 of a compressed water connection and / or a compressed air injection connection. Fish trawl according to claim 8, characterized in that the connection of the "knife handle" and the fish trawl consists of a hinge, in particular a hollow hinge, in which the compressed water supply connection is received. 11. "Knife handle" and knife knife for use with a fish trawl and using the method according to preceding claims 1-10, characterized in that "knife handle" and knife knife are both substantially hollow over their full width, apart from necessary stiffening plates , for the passage of the compressed water. 12. Knife for use with a fish trawl and using the method according to preceding claims 1-11, characterized in that the 1007040 - 10 - substantially flat front of the knife is corrugated and / or (saw) teeth is provided in order to reduce the soil resistance. Fish trawl according to any one of the preceding claims 4-10, characterized in that the fish trawl is provided at the front in the vicinity of the knife with a number of electrodes, e.g. pin or plate electrodes between which, during fishing with the fish trawl, such a tension is maintained that, when fishing for product animals, as a result of the generated tension, the product animals near the fish trawl are temporarily anesthetized before they are covered in the water riser transported. 14. Method and fish trawl according to any one of the preceding claims 1-13, characterized in that a suction line in connection with a so-called Roots pump (compressor) with a high lifting capacity is used for sucking up the product animals without being present in the suction line a pump. Method according to claim 14, characterized in that an amount of air is injected into the riser from below that the effect of a so-called mammoth pumping action is created in the riser. 16. Vessel provided with means for using the method according to any one of the preceding claims 1-3 and 14-15 and provided with a fish trawl according to any one of the preceding claims 4-13. I 007940