GB2335935A

GB2335935A - Harvesting animals living in or on the seabed

Info

Publication number: GB2335935A
Application number: GB9906580A
Authority: GB
Inventors: Stee Marinus Jan Van
Original assignee: GOUDSCHELP CONSERVENFAB BV
Current assignee: GOUDSCHELP CONSERVENFAB BV
Priority date: 1998-04-02
Filing date: 1999-03-22
Publication date: 1999-10-06
Anticipated expiration: 2019-03-22
Also published as: GB9906580D0; BE1011978A3; DE19914703A1; NL1008794C2; GB2335935B

Abstract

Animals living in or on the seabed, in particular shellfish of the "Ensis" species, are harvested by cutting a seabed layer 29 containing the shellfish by means of a cutting mouth 7, provided with a cutting edge 8 and spray means 9 for water and/or air. The water and/or air spray means 9 aid in the cutting action by partially liquidizing the seabed 32 along a peripheral part. Take-up means 5 behind the cutting edge 8 have nozzles 11 for further liquidizing the seabed layer in a cage 3. The shellfish 2 are discharged via a suction conduit 24 while a major part of the seabed layer 29 is discharged from cage 3 via it's perforated housing.

Description

1 2335935 METHOD FOR HARVESTING ANIMALS LIVING IN OR ON THE SEABED AND

APPARATUS THEREFOR The invention relates to a method for harvesting animals living in or on the seabed such as crustaceans and shellfish, in particular shellfish of the 11Ensis,' species, comprising the following steps of:

- cutting into the seabed a seabed layer containing the shellfish, taking up the seabed layer from the seabed, at least partially liquidizing and sieving the removed seabed layer, and - discharging and collecting the harvested shellfish.

Such a method and an apparatus therefor are known from GB-A-1.207.906.

This publication describes a mussel harvesting method and apparatus, wherein cutting into the seabed is obtained solely by a mechanical transmission of forces by means of cutting means.

Such a known method has the drawback that in seabeds with a solid texture and/or a hard structure this cutting proceeds with difficulty or even becomes impossible. The damage caused in harvesting shellfish in this manner is moreover considerable since great forces have to be transmitted in order to be able to break the seabed during the cutting.

The invention has for its object to at least partially obviate this drawback and provides for this purpose a method as according to claim 1.

By combining the mechanical cutting of the seabed layer with spraying of water under pressure, optionally in combination with air, the structure of the seabed will become softer due to liquidizing of the sprayed seabed. This spraying of water or air takes place substantially 2 transverse-v of the seabed layer for taking up, both in radial and in axial direction.

It is noted that US-A-3.862.502 describes a harvesting method for shellfish, wherein the seabed is licuidized by axial spraying of water, whereby only the shellfish are taken up in a collecting net provided behind the spraying means. A complete liquidizing of the bottom herein takes place and no seabed layer is therefore taken up from the seabed.

The method according to the invention has however for its object in a first step to partially liquidize the seabed, whereby a seabed layer adjacent to a liquidized part of the seabed can be taken up more easily. After this seabed layer with the shellfish has been taken up, the liquidizing is continued.

This is particularly suitable for shellfish of the type known as "razorfish" or "Ensis", since they are very fragile. Liquidizing of the removed seabed layer by means of water under pressure or with interposing of air is a more controllable method step, whereby less damage s caused to the shellfish for har-vesting.

During the cutting water or air will preferably be sprayed onto the seabed alcng at least a part of the periphery of the seabed layer for taking up. only a local liquidizing on the periphery of the seabed layer for taking up will hereby take place.

Such peripheral liquidizing can be better controlled. Water can for instance be sprayed into the seabed along the periphery of the seabed layer for taking up at a pressure lying between 0.5 and 50 atm, preferably between 5 and 10 atm, and at a flow rate lying between 100 and 5000 m3/h.

During the cutting water and/or air is preferably also sprayed into the seabed along the full periphery of the seabed layer for taking up. The seabed layer will thus be liquidized in particular along the whole periphery of the seabed layer, whereby this seabed layer 3 is cut and taken up in continuous manner as an elongate beam-shape.

The invention also relates to an apparatus as according to the preamble of claim 7.

Such an apparatus is known from GB-A-1.207-906.

As already explained above, such an apparatus is unsuitable for cutting into seabeds with a hard structure. The invention has for its object to at least partially obviate this drawback and provides for this purpose an apparatus as according to claim 7. Because the cutting means are not only formed by a cutting edge which cuts into the seabed but is also provided with spraying means for water or air for liquidizing the bottom, cutting will be realized more easily and with less mechanical force.

The spraying means are preferably formed by a spraying slot which bounds the cutting edge of the cutting means. By positioning the spraying means as a spraying slot the seabed will only be liquidized along the peripheral part of the seabed layer for taking up.

The invention will be better understood on the basis of the description following hereinbelow of the drawing, in which:

figure 1 shows a partly broken-away perspective view of a preferred embodiment of the apparatus according to the invention; and figure 2 shows a schematic view in longitudinal section of the harvesting apparatus coupled to a fishing vessel. 30 Both the shown embodiments of the apparatus are shown in operational situation. A harvesting apparatus 28 consists of a cage 3 of a stiff and perforated material which can be towed along the seabed surface 32 and is provided at the front with a runner 31 and cutting means 4 situated thereunder. Takeup means 5 are provided behind cutting means 4.

Cutting means 4 are formed by a cutting mouth 7, which is bounded by a cutting edge 8. Arranged on cutting 4 edge 8 are spraying means for water and/or air 9 in the form of a spraying slot provided with a number of nozzles which spray water under pressure or air substantially parallel to the seabed surface 32 and transversely of seabed 1. Spray means 9 are provided along the periphery of cutting mouth 7, whereby the seabed is liquidized only along a peripheral part. A beam-shaped seabed layer 29 will hereby be cut and taken up. Spray means 9 extend axially relative to take-up means 5. It is likewise possible to position a number of these spray means 9 radially.

Take-up means 5 are likewise provided with nozzles for water or air for further liquidizing of the takeup seabed layer. Take-up means 5 enclose an acute angle a is with seabed surface 32.

The cage 3 is provided with a slightly perforated housing through which transport of water, seabed material and air is possible. An underpressure can be created in cage 3 by the suction action of a suction pump 25 and this enhances discharge of the harvested shellfish through the suction conduit. Partly for this purpose a cover member 10 with corresponding apertures can be provided on the housing of cage 3 in order to control the number of perforations or apertures in the housing of cage 3. The operation of suction pump 25, optionally supplemented with additional pressure or suction means, will carry water through the housing into the cage, whereby a further liquidlizing of the seabed layer is caused via additional turbulence.

The air optionally supplied via spray means 9 and will effect a partial air transport of the shellfish.

The towable cage 3 is coupled to discharge means from a preferably flexible suction conduit 24 and the suction pump 25 for extracting and collecting the harvested shellfish 2. For supply of water or air a preferably flexible pressure ccnduit system 26 is coupled to a pressure pump 30 for water and/or air. Both pumps can for instance be arranged on a fishing vessel 14 which further tows harvesting apparatus 28 along the seabed by means of towing cables 22. This towing can likewise take place via a flexible suction line 24.

This harvesting apparatus 28 is provided on its rear side with a collecting tank 19 for heavy bed material which is neither extracted nor emptied, which collecting tank 19 is closed off by a hinged cover 20. A hydraulically operating pivot arm 21 is provided for this purpose.

In addition to being provided with pumps, fishing vessel 14 can also be provided with a winch 23 coupled to hoisting cables 27 for raising and lowering harvesting apparatus 28. in its active situation water or air will be sprayed along the spraying slot transversely into seabed 1 and substantially parallel to the seabed surface. A seabed layer 29 will liquidize along its periphery, whereby the mechanical cutting by thia cutting means is facilitated and a seabed layer 29 is taken up in simple manner by take-up means 5. These take-up means 5 follow on from cutting means 4 and are provided with nozzles 11 for water or air for further liquidizing of the taken-up seabed layer 29 in the cage, whereby shellfish 2 are released from the seabed layer.

Such a separating action will then allow shellfish 2 to be discharged via suction conduit 24 and the major part of the seabed layer 29 will be discharged from cage 3 via its perforated housing. This perforation is preferably smaller than the dimensions of the shellfish 2 30 for harvesting.

41 6

Claims

7. Method for harvestina animals living in or on the seabed, in particular shellfish of the 11Ensis11 species, comprising the following steps of:

- cutting into the seabed a seabed layer containing 5 the shellfish, taking up the seabed layer from the seabed, - at least partially liquidizing and sieving the removed seabed layer, and - discharging and collecting the harvested shellfish, characterized in that cutting of the seabed layer is performed by means of water under pressure and/or by interposing air.
2. Method as claimed in claim 1, characterized in that during the cutting water and/or air is sprayed onto the seabed along at least a part of a periphery of the seabed layer for taking up.
3. Method as claimed in claim 2, characterized in that during the cutting water is sprayed into the seabed along the full periphery of the seabed layer for taking up.
4. Method as claimed in any of the foregoing claims, characterized in that the removed seabed layer is liquidized by means of water under pressure. 25
5. Method as claimed in any of the foregoing claims, characterized in that the removed seabed layer is liquidized by means of air.
6. Method as claimed in any of the foregoing claims, characterized in that during the cutting of the seabed layer water is sprayed onto the seabed along the periphery of the seabed layer for taking up at a pressure lying between 0.5 and 50 atm, preferably between 5 and 10 atm, and at a flow rate lying between 100 and 5000 m3/h.
7. Apparatus for harvesting animals living in or on the seabed, -in particular shellfish of the 11Ensis11 species, comprising a cage towable over the seabed and 7 provided with cutting means for cutting a seabed layer, take-up means for taking up the cut seabed layer and discharge means for discharging the shellfish, characterized in that the cutting means are formed by a cutting mouth provided with a cutting edge and spray means for water and/or air.
8. Apparatus as claimed in claim 7, characterized in that the water spraying means are formed by a spraying slot bounding the cutting edge.
9. Apparatus as claimed in claim 7 or 8, characterized in that the take-up means are provided with nozzles for water or air.
10. Apparatus as claimed in any of the claims 7-9, characterized in that the cage housing is provided with apertures, wh.Lch apertures are variable in size and/or number.
11. Apparatus as claimed in any of the claims 7-10, characterized in that during normal use the take-up means extend at an acute angle relative to the seabed.