WO2005067706A2

WO2005067706A2 - Method and device for cultivating bi-valve molluscs and vessel in particular intended for use with said method and device

Info

Publication number: WO2005067706A2
Application number: PCT/NL2005/000030
Authority: WO
Inventors: Gerke Houwer
Original assignee: Van Ysseldijk, Pieter
Priority date: 2004-01-15
Filing date: 2005-01-14
Publication date: 2005-07-28
Also published as: WO2005067706A3; NL1025255C1

Abstract

The invention relates to a method and a device for cultivating bi-valve molluscs, such as mussels and scallops, wherein use is made of line(s) and/or net(s) suspended in the water, which are supported by at least one floating body (5,6), and to a vessel (43) in particular for use with the present method and device. The floating body (5,6) is disposed some distance below the water surface. The device comprises means which make it possible to dispose the floating body a desired distance below the water surface or on the water surface. The vessel (43) is provided with lifting means for moving a carrier(38) with the line(s) and/or net(s) attached thereto in upward or downward direction, as well as with means for moving the carrier with the line(s) and/or net(s) attached thereto in a direction transversely to its longitudinal direction over the vessel.

Description

Method and device for cultivating bi -valve molluscs and vessel in particular intended for use with sai method, and device

DESCRIPTION The invention relates to a method for cultivating bi -valve molluscs, such as mussels and scallops, wherein use is made of line(s) and/or net(s) suspended in the water, which are supported by at least one floating body. With the known method of the above kind, the floating bodies float on the water surface. Such a method has several drawbacks. Thus, when there is a powerful wind, the resulting waves will lead to substantial movement of the floating bodies and the ines or nets suspended therefrom, which may lead to a significant loss of adhering seed and/or bi-valve molluscs, because said seed or said bi- valve molluscs are shaken off the lines and/or nets. Another drawback is the fact that the floating bodies floati ng on the water are considered to pollute the "seascape", so that the use thereof is bound by strict regulations, if not prohibited altogether, in particular near coastal areas designated as recreation areas or natural parks, which strongly reduces the number of suitable locations available for cultivating bivalve molluscs. According to another known method, nets and/or lines are attached to cables provided between bodies that float on the water surface and anchors placed in the seabed. The harvesting of bi-valve molluscs by means of this method is labourious and costly. With this method, too, there is much loss of seed and/or bi-valve molluscs. According to the invention, the floating body is disposed some distance below the water surface. The main advantage of disposing a floating body some distance^' below the water surface is in the fi st place the fact that the raising and harvesting of bi-valve molluscs, in particular mussels and the like, can be carried out at least substantially independently of the weather conditions, since the floating body disposed below the water surface and the line(s) and/or net(s) supported thereby are hardly affected by the wave motion that occurs. Furthermore, because the floating bodies are not exposed to view, the "seascape" is not adversely affected. Preferably, the buoyancy of the floating body will be set in dependence on the weight of the line(s) and/or net(s) with the bivalve molluscs supported by said line(s) and/or net(s), so that it is possible to maintain an optimum adjustment of the line(s) and/or net(s). According to another aspect of the invention, an efficient device for cultivating bi-valve molluscs, such as mussels and scallops, comprising .at least one floating body for supporting line(s) and/or net(s) suspended in the water, is according to the invention obtained in that the device comprises means which make it possible to dispose the floating body a desired distance below the water surface or on the water surface. In this way a simple device can be obtained, in which the floating body or bodies of the device will not be exposed to view during the cultivation of the bi-valve molluscs, whilst furthermore no undesirable motion will be imparted to the floating body or bodies and the line(s) and/or net(s) supported thereby. The invention further relates to a vessel for handling line(s) and/or net(s) suspended from a floating body by means of a carrier, which line(s) and/or net(s) is (are) suspended in the water for cultivating bi-valve molluscs such as mussels and scallops. The object of the invention is to obtain such a vessel by means of which carriers with lines and/or nets attached thereto can be removed from the water or be placed into the water in a simple manner and by means of which furthermore said lines or nets can be disposed in a suitable position above the vessel for further handling. According to the invention, this object can be accomplished in that the vessel is provided with lifting means for moving the carrier with the line(s) and/or net(s) attached thereto in upward or downward direction, as well as with means for moving the carrier with the line(s) and/or net(s) attached thereto in a direction transversely to its longitudinal direction over the vessel. When using the vessel according to the invention, line(s) and/or net(s) may be suitably positioned above a hold of the vessel, so that bi-valve molluscs and the like hanging from the lines and/or nets can be removed from the lines or nets and be collected in the hold. In comparison with methods that have been used so far, a strong reduction of the loss of bi-valve molluscs and/or seed during harvesting is achieved in this way. The invention, will be explained in more detail hereinafter with reference to the accompanying figures, which show possible embodiments of devices and a vessel according to the invention. Fig. 1 is a schematic, perspective view of a few coupled- together floating bodies, which are anchored in the bottom of a water body. Fig. 2 shows a few coupled-together floating bodies, which are anchored in the bottom of a water body in a manner different from Fig. 1. Fig. 3 is a schematic, perspective view of an embodiment of a floating body according to the invention. Fig. 4 is a larger-scale view of one end of a floating body according to the invention. Fig. 5 is a perspective view of coupled-together ends of two floating bodies according to the invention. Fig. 6 is a perspective view of a few coupled-together floating bodies. Fig. 7 shows a part of a floating body comprising means for controlling the buoyancy of the floating body. Fig. 8 is a perspective, bottom plan view of a part of Fig.

7. Fig. 9 is a schematic, perspective view of a vessel for handling a carrier with line(s) and/or net(s) attached thereto. Fig. 10 is a perspective view of the vessel that is shown in Fig. 9, seen from a different direction. Fig. 11 schematically shows lifting means used with the vessel that is shown in Figs. 9 and 10. Fig. 12 is a larger-scale view of a part of the lifting means that are shown in Fig. 11. Fig. 13 shows a part of a transport chain used with the vessel of Figs. 9 and 10. ^" Fig. 14 is a view corresponding to Figs. 13, whilst in addition a screening plate is shown. Fig. 15 is a schematic, perspective view of a second embodiment of floating bodies with nets connected to the floating bodies. Fig. 16 is a larger-scale view of the ends positioned near each other of two floating bodies that are shown in Fig. 15. Fig. 17 is a schematic, perspective view of a net to be used with the embodiment of Fig. 15. Fig. 18 is a larger-scale, perspective view of one end of a floating body shown in Fig. 15. Fig. 1 shows several coupled-together floating bodies 2 being in line, which are connected by means of anchoring cables 3 to anchors resting on the bottom of a water body, for example in the form of concrete blocks 4. As is shown in more detail in Figs. 3-5, a floating body may be built up of two tubes 5 and 6 extending parallel to each other, which are interconnected by cross tubes 7 and a girder 8. Mounted between the tubes 5 and 6, which may be made of a plastic material, is a shaft 9 that extends parallel to the tubes 5 and 6, which shaft is supported by a bearing 10 mounted on .the girder 8 and which is guided in rings 11 fixed to the cross tubes 7. At one end, the shaft 9 is provided with a pin 12 that extends transversely to the longitudinal direction of the shaft 9, which pin projects from the shaft with both its ends. At its other end, the shaft 9 is provided with a sleeve 13, in which two diametrically opposed slots 14 are provided, which are open at the end of the sleeve. It will be apparent in particular from Fig. 5 that two floating bodies 2 being in line can be coupled together by attaching the flanges 15 present on the ends of the tubes 5 and 6 together by bolts or the like. Also other means of coupling the tubes 5 and 6 are possible, of course, such as welds, glue, sleeve couplings, clamps interconnecting the flanges, etc. The aligned shafts 9 of the coupled-together floating bodies 2 are coupled in that the ends of the pin 12 passed through one end of one shaft 9 are accommodated in recesses 14 of the sleeve 13 that is attached to the other shaft 9. At least one of the coupled-together floating bodies 2 is provided with a transmission box 16, through which the shaft 9 of the floating body in question is passed (Fig. 4), One end of a flexible driving cable 17, such as a Bowden cable, is connected to an ingoing shaft of the transmission box. The other end of the driving cable 17 is connected to a buoy 18 or the like. Furthermore, a connecting cable 19 is provided between the buoy 18 and the transmission box 16, which cable prevents undesirable pulling forces being exerted on the driving cable 17. The driving cable 17 is connected to the shaft 9 in question via a gear mechanism or the like in the transmission box 16. A drive source (not shown), which may be mounted on a vessel, for example, can be coupled to the end of the driving cable 17 that is connected to the buoy 18, if desired, for selectively rotating the shaft 9 and any further shafts 9 coupieα > saiα snar » in one direction or the other via the driving cable 17 and the _..transmission box 16. Cable drums 20 are mounted to the shaft 9 on either side of the bearing 10, on which anchor lines and/or chains 3 or the like extending in opposite directions from the two cable drums are wound. The ends of the anchor lines 3 or the like can be fixed to the shaft 9, for example by means of clamps 21 mounted to the ends of the cable drums. The lines 3 are passed through eyes 22 fixed to the tubes 5 and 6. The two lines 3 are wound on the drums 20 in question in such a manner that upon rotation of the shaft 9 in one direction the lines 3 will be wound onto the drums 20 in question and that upon rotation of the shaft 1 in the opposite direction the lines 3 will be unwound from the drums in question. ^" As is shown in Fig. 1, the arrangement may be such that each of the cables 3 coupled to the respective shafts 9 of each of the coupled-together floating bodies is connected to an anchor 4. As is furthermore shown in Fig. 1, the distance between two anchors 4 located in a plane that extends perpendicularly to the longitudinal direction of the floating bodies 2 is preferably greater than the distance between the respective tubes 5 and 6 of the floating bodies 2, as a result of which an improved stability against forces acting on the floating bodies 2 in a direction transversely to the longitudinal direction of the floating bodies is obtained. As is furthermore apparent from Fig. 1, the anchor means 4 are interconnected by cables 23 extending parallel to the floating bodies 2 and cables 24 extending transversely to the longitudinal direction of the floating bodies, which makes it easier to correctly position the anchors on the bottom of a water body. The lengths of the cables 23 and 24 may be adapted to any unevennesses that may be present in the bottom. Fig. 2 shows an arrangement that is slightly different from the arrangement that is shown in Fig. 1, in which the anchor cables 3 of only a few floating bodies 2, which are connected to the. shafts 9 mounted to said floating bodies, are secured to anchors 4, whereas the anchor cables 3 connected to floating bodies 2 positioned therebetween are attached with their ends facing away from the drums 20 in question to cables 25 extending between the anchors 4 in question that are disposed on either side of the floating bodies. It will be apparent that the cable drums 20 may be mounted to the shaft 9 at locations other than those that are shown in Fig. 4, and/or that more than two cables drums 10 as shown may be mounted on a shaft 9. Furthermore, each floating body is provided with a number of suspension elements 26, which are located mainly on the sides facing away from ^"each other of the tubes 5 and 6, seen i the longitudinal direction of a floating body. In the illustrated embodiment, two suspension elements 26 are provided on either side of the floating body, near the end of a floating body at which also the drums 20 are disposed. Near the other end of the floating body 2 in question, a single suspension element 26 is furthermore disposed on either side of the floating body, whilst a further single suspension element 26 is disposed on either side near the centre of the floating body 2 in question. If desired, more or fewer a suspension elements than indicated above may be provided, of course. Each suspension element 26 comprises a portion 27 that has been bent to a U-shape (Fig. 7), whose upper end located near a respective tube 5 or 6 blends into a horizontal portion 28 by which the suspension element 26 in question is attached to the floating body 2. The other end of the U-shaped bracket 27 blends into a leg 29 that slopes upward in a direction away from the floating body 2, said leg at the end remote from the U-shaped portion 27 blending into a leg 30, which slopes upwards in a direction away from the floating body 2 at a smaller angle than the portion 29 with respect to the horizontal and vjhich is curled over at its end 31. Near the location where the two portions 27 and 28 of the suspension element 26 join, the suspension element 26 is provided with an upwardly extending leg 32, which is connected to the floating body 2 with its bottom end. A leg 34 that slopes downwards in the direction of the leg 29 joins the leg 32 via a bent portion 33, which leg 34 blends into a substantially vertically extending leg 35 at its bottom end, said leg 35 being spaced from the leg 29 by some distance in the position that is shown in the figures. At its bottom end, the leg 35 blends into a horizontally extending leg 36, which is provided with a projecting ear 37 at its end remote from the leg 35, which ear engages the side of the bottom end of the leg 32 that faces away from the leg 29. The parts 32-37 of the suspension elements 26, which form one whole, are preferably made of spring steel, in such a manner that the projecting ear 37 abuts against the lower end of the leg 32 with a certain bias. Alternatively it will also be possible, for example, to pivotally interconnect the upper ends of the legs 32 and 34 by means of a hinge or the like and to provide a spring member or the like between the legs 32 and 34, in such a manner that the ear 37 will abut against the lower end of the leg 32 with a certain bias in the unloaded position of said parts that is shown in the figures. The suspension elements 26 attached to one side of the floating body 2 are intended for receiving an elongated carrier 38 (Fig. 6) made up of a tube or the like, for example, from which a net 39 is suspended via spaced-apart connecting elements (not shown for the sake of clarity), in such a manner that, as will be apparent from Fig. 6, the upper edge of 40 of the net will be spaced from the carrier 38 that extends parallel to said upper edge 40 of the net by some distance. Preferably, a bar 41 or the like is attached to the bottom edge of the net for weighting the net, in such a manner that it will normally take up a substantially vertical position in the water. The carrier 38 can be suspended in the suspension elements 26 by guiding the carrier 38 along the sides of the legs 30 and 29 of the suspension element that face towards the floating body 2, whereby the legs 30 and 29 can be passed through the space between the carrier 38 and the upper edge 40 of the net 39. At some point, the carrier 38 will push back the legs 35 of the suspension elements 26 that receive the carrier 38 in the direction of the floating body against the bias, so that the carrier 38 can move through the space present between the legs 35 and the legs 29 of the suspension elements 26 in question. Once the carrier 38 has passed the lower ends of the legs 35 of the suspension elements 26, the parts 34-37 of the suspension elements will return to the position that is shown in the figures, in which the parts 36 of the suspension elements 26, which form the locking elements, will prevent upward movement of the carrier 38 in question. Upon suspension of carriers 38 supporting lines or nets in the floating bodies 2, the floating bodies will preferably be disposed slightly below the water surface. After the desired number of carriers 38 with lines and/or nets connected thereto has been provided, the assembly of floating bodies 2 and lines and/or nets suspended therefrom can be moved downwards by winding up the cables 3 onto the drums 20 in question by rotating the shafts 9 by means of the above-described driving mechanism 16, 17 for the purpose of winding the cables 3 onto the drums 20. Thus, the floating bodies can be disposed a desired distance below the water surface, so that the floating bodies and the elements associated therewith will be hidden from view and only the small buoy 18 will float on the water surface. The lines and/or nets supported by the floating bodies will then be present in an environment in which they are hardly affected by the motion of the waves, so that they are in an advantageous position for depositing seed and the like thereon, which can subsequently develop into bi-valve molluscs. The weight suspended from the floating, bodies 2 will gradually increase as a result of seed being deposited on and/or bi-valve molluscs being cultivated on the lines and/or nets supported by the floating bodies. In that connection it is furthermore desirable to provide a possibility of influencing the buoyancy of the floating bodies

2. To influence the buoyancy, the tubes 5 and 6 may be configured as closed compartments, for example, into/from which water can be selectively introduced/discharged. Another possibility is to form closed compartments within the tubes 5 and 6. Thus Fig. 7 schematically shows that a further tube 38 is supported in the interior of a tube 5 and/or 6. The ends 39 and 40 of pipes 41 arid 42 extending along the bottom side of a tube 5 or 6 in question open into said tube, which pipes 41 and 42 are connected to the buoy 18, for example by means of hoses 41', 42'. Via said pipe 42, water may be selectively introduced into the compartment formed by the tube 38, for example, for the purpose of reducing the buoyancy of the floating body 2. If desired, water can be driven out of the compartment 38 by forcing pressurised air into the compartment 38 via the pipe 41 and the end 39 connected thereto, as a result of which the water present in the compartment 38 will be discharged via the pipe 42. Another possibility is to utilise the space present between the outer circumference of the tube 38 and the inner circumference of the tubes 5 or 6 for supplying and/or discharging water to influence the buoyancy. By generating an overpressure in the space between the two tubes 38 and 5 or 6, the water pressure being exerted on the outer side of the tube 5 or 6 will be transferred to the tube 38, which has a smaller radius and which is thus more resistant to pressure, so that undesirable deformation of the wall of the tube 5 or 6 can be prevented and the floating bodies can be disposed at a greater depth without any risk of the floating bodies sinking due to undesirable deformations and the like. A vessel 43 (schematically shown in Figs. 9 and 10) may be used for handling the carrier 38 with the lines or nets 40 suspended therefrom. Said vessel 43 comprises a hull 44, in which a hold 45 is present. The vessel 43 is provided with guide rails 46 near opposing ends of the hold 45, which guide rails extend transversely to the longitudinal direction of the vessel 43 in the illustrated embodiment of the invention. The rails 46 support trolleys or slides 47, which support the ends of guide rails 48, which extend in the longitudinal direction of the vessel in the illustrated embodiment of the invention. A known brushing machine 49^"or the like (only indicated schematically) is present on the guide rails 48. The trolleys or slides 47 and the rails 48 supported by said trolleys or slides 47 can be moved forward and backward over the rails 46 in directions transversely to the longitudinal direction of the vessel by driving means (not shown), whilst the brushing machine 49 or the like can be moved forward and backward over the rails 48 by driving means (not shown) and be activated in a desired manner. Vertical standards 50 are provided near the corner points of the hold 45, the upper ends of which standards are interconnected by beams 51 extending in the longitudinal direction of the vessel and beams 52 extending transversely to the longitudinal direction of the vessel. Horizontally extending shafts 53 are provided along the ends facing away from each other of the beams 51 that extend horizontally in the longitudinal direction of the vessel, which shafts are supported in such a manner that they can rotate about their central axes. A number of chain wheels 54 are mounted on each of the shafts 53, with an endless conveying element in the form of a chain 55 being passed over each pair of opposed chain wheels 54. The endless chain comprises pins 56, which are interconnected by links 57 on one side of the chain wheels 54 and which are alternately interconnected by links 58 and by the basic portions of hook-shaped members 59 on the other side. The lower parts and the upper parts of the chains 55 are guided by C-shaped sections 60 and 61, respectively, which extend between the beams 51. To that end, rollers 62 are mounted on the pins 56, which roll in the sections 60 and 61 when the chains 55 are driven. The hooks 59 move through the slots 63 in the sections 60 and 61. The chain wheels 54 are slidably mounted on the shafts 53, in such a manner that the chains 55 can be arranged in abutting relationship near one end of the hold 45, as is shown in Fig. 9, so that the hold 45 is readily accessible from above, on the one hand, and in a position in which the chains 55 are arranged in regularly spaced-apart relationship above the hold, as is shown in Fig. 10, on the other hand. As appears in particular from Fig. 13, one of the shafts 53 is provided with a groove 64 extending in the longitudinal direction of the shaft in question, in which groove cams connected to the chain wheels 54 are slidably accommodated. Thus, the chains 55 can be set in motion in that the shaft 53 provided with a groove 64 is rotated by driving means (not shown). Guide plates 60' joining the ends of the C-shaped beams 60 and 61 guide the chains in their movement over the chain wheels 54. The vessel 43 is furthermore provided with lifting means comprising two upwardly extending standards 65 disposed near the ends of the hold on the side of the ship. Connected to the upper ends of said standard 65, by shafts 66 extending horizontally in the longitudinal direction of the vessel, are the ends of arms 67, which can be pivoted about the shafts 66 with respect to the standards 65 by driving means (not shown). The arms 67 are built up of two parts 68 and 69 that can be telescoped relative to each other by driving means (not shown). The ends of an elongated beam or carrier 70 that extend between the parts 69 are rotatably supported in the free ends of the parts 69 that are capable of sliding movement in the parts 68 of the arms

67. The beam 70 can be rotated about its longitudinal axis by adjusting means (not shown) . An elongated beam or carrier 71 extending parallel to the carrier 70 is coupled to the carrier 70 by a number of spaced-apart pins 72, which are each connected to the carrier 71 with one end and which are slidably (in their longitudinal direction) accommodated in bores formed in the carrier 70. At their ends remote from the carrier 71, the pins 72 are provided with projecting heads 73, which prevent the pins 72 from moving out of the bores formed in the carrier 70. The pins 72 are surrounded by compression springs 74, which are positioned between the two or carriers 70 and 71. A few gripping devices 75 are mounted to the carrier 71 in regularly spaced-apart relationship. Each gripping device 75 comprises a fixed jaw 76 attached to the carrier 71, which jaw is made up of a plate- shaped member that extends some distance below the carrier 71. Furthermore, each gripping element 75 comprises a movable jaw 77, which can be pivoted with respect to the carrier 71 , by adjusting means (not shown), about a pivot pin 78 that extends parallel to the longitudinal direction of the carrier. The jaw 77 is of substantially L-shaped section and is constructed in such a manner that the free ends of the jaws 77 extend some distance below the carrier 71, at least substantially perpendicularly to the fixed jaw 76, in the closed position of the gripping devices 75 that is shown in Fig. 11. The vessel 43 as described above is in particular suitable for use in combination with the device for cultivating bi-valve molluscs as described above with reference to Figs. 1-8. To remove a carrier 38 supporting line(s) or net(s) from said device, the carrier 71, with the gripping devices 75 in the open position (Fig. 12), is manipulated by pivoting and possibly telescoping the arms 67 of the lifting means mounted on the vessel 43, in such a manner that the carrier 71 is introduced into hook-shaped elements 26 supporting the carrier 38 in question, which is facilitated by the fact that the opening of said hook- shaped elements 26 diverges widely in upward direction. When the carrier 71 is moved down into the hook-shaped elements 26 in question, the springing arms 34, 35 will be pushed back so as to release a passage for the carrier 38. Once the carriers 71 and 38 are positioned near each other, the jaws 77 of the gripping devices will be moved to the closed position for retaining the carrier 38 between the carrier 71 and the jaws 76 and 77 of the gripping devices 75. Following that, the carrier 71 and the carrier 38 supporting line(s) and/or net(s) that is coupled thereto are lifted from the water by pivoting and/or telescoping of the arms 67, and be moved to a position in which the carrier 38 in question can be placed into hook-shaped elements 59 of the chains 55 disposed near the relevant side of the vessel. Guide plates 79 are mounted to the standards 50 for guiding the carrier a 38 to a correct position with respect to the chains, which guide plates can mate with the ends of a carrier 38. When the carrier 38 is picked up from the device as described above with reference to Figs. 1-8, paying out the anchor lines 3 will preferably, but not necessarily, cause the device to be positioned in such a manner that the hooks 26 supporting the carrier are still present a short distance below the water surface, with a comparatively stable position of the device still being ensured and any wave motion having comparatively little effect on the device. Movements of the vessel can be effectively offset by the springing connection between the carriers 70 and 71 that is effected by means of the springs 74 and the pins 72. Once a carrier 38 is suspended in the hook-shaped elements 59 of the spaced-apart chains 55 (Fig. 10), the carrier 38 and the line(s) or net(s) suspended therefrom can be positioned above the hold 45 of the vessel 43 by driving the chains via a shaft 53, after which the bi-valve molluscs or the larvae of bi-valve molluscs adhering to the line(s) and/or net(s) can be removed by means of the brushing device 49, falling into the hold 45 of the vessel 43. To keep a net 39 that is suspended from the carrier 38 taut, the vessel may be provided with means by which a pulling force can be exerted on the rod 41 that is fitted under the net 39. The brushing machine 49 may be constructed in such a manner that only part of the bi-valve molluscs and the like, for example in a few vertically spaced-apart areas, will be removed from the line(s) or net(s) to provide space for the further growth of bi-valve molluscs or larvae of bi-valve molluscs that remain behind on the net 39 or the like. After being worked by the brushing machine 49, the carrier

38 and the line(s) and/or net(s) suspended therefrom can be placed back into the water by carrying out the above-described manipulations for removing the carrier from the water in reverse order. To prevent damage being caused to bi-valve molluscs or larvae of bi-valve molluscs detached by the brushing machine 49 upon falling into the hold 45, the hold 45 may be suitably filled with water. Detached material that is not fully grown yet may be collected in a long, open-meshed sock of a biodegradable material, in which one or more lines are present to which the larvae of bi-valve molluscs and the like can adhere. Such a sock can also be suspended from a carrier 38 and subsequently be suspended in the water in the above- described manner. Consequently, the term line and/or net as used above is understood to include such a sock as well. Additions and variations to the embodiments as described above are possible within the scope of the invention, of course. Thus it is possible, for example, to provide the vessel with lifting means on both sides, in which case transport chains will be arranged in mirror symmetry. Furthermore it is possible to use endless conveying elements other than the chai s 55. Yet another possible embodiment of floating bodies with nets, lines or the like attached thereto is shown in Figs. 15-18. In Figs. 15-18, parts that correspond to parts that have been described above are indicated by the same numerals as in Figs. 1-8, and the construction and/or operation of said parts will not be explained again. In this second embodiment, each of the shafts 9 to be driven via the transmission box 16 is surrounded by a floating body 80, with respect to which the relevant shaft 9 extending through the floating body 80 may or may not be freely rotatable. The transmission box 16 is constructed in such a manner that the shafts 9 positioned on either side of the gearbox rotate in opposite directions when driven, since otherwise there is a danger of the transmission box 16 rotating relative to the shafts 9. Each floating body 80 is surrounded by a number of rings

81. Attached to each ring 81 is a downwardly extending armed 82, which connects the ring 81 to C-shaped suspension brackets 83. Legs 84 that slope downwards in a direction away from each other join the free ends of a suspension bracket 83. If the floating body 80 rotates along with the shaft 9, the rings 81 must in any case be freely rotatable relative to the floating body 80. As is furthermore apparent from the figures, the net(s) 41 or lines or the like is (are) attached to an elongated carrier or beam 85 in this embodiment. The carrier 85 is disposed between two elongated auxiliary carriers 86 and 87 extending parallel to the carrier 85. The auxiliary carriers 86 and 87 disposed on either side of the carrier 85 are connected to the carrier 85 by pins 88 extending perpendicularly to the carriers 85-87, which pins are passed through holes formed in the carriers 85-87. At their ends projecting outside the auxiliary carriers 86 and 87, the pins 88 are provided with heads that prevent the auxiliary carriers 86 and 87 from sliding off the pins 88. As is furthermore apparent from the figures, the pins 88 are surrounded by compression springs 89 and 90, which are positioned between the carrier 85 and the auxiliary carrier 86 and between the carrier 85 and the auxiliary carrier 87, respectively. A carrier 85 and a net(s) 41 or the like supported by the carrier can be suspended from a floating body 80 by gripping the carrier 85 and the auxiliary carriers 86 and 87 with one or more grippers, which urge the auxiliary carriers 86-87 together in the direction of the carrier 85 against the action of the springs 89 and 90, whereupon the carrier 85 and the auxiliary carriers 86 and 87 can be moved upwards between the guide legs 84 into the suspension brackets 83 connected to a floating body 80 by suitably manipulating the carrier with the grippers. By subsequently opening the grippers so as to release the auxiliary carriers 86 and 87, said auxiliary carriers 86 and 87 will move in a direction away from the carrier 85 to a position in which they are suitably supported in the supporting brackets 83 in the manner that is shown in particular in Fig. 18. To remove the carrier 85 and the net(s) 41 or the like supported by the carrier, the reverse procedure may be followed. The grippers for connecti g/disconnecting a carrier 85 to/from a floating body 80 may be coupled to lifting means as described above of a vessel 43, so that the net(s) 41 or the like connected to a carrier 85 can be handled in a similar manner as described above in the description of the vessel 43. Furthermore it will be apparent that the floating bodies 80 can be moved in vertical direction in the water in a similar manner as described above by rotating the shafts 9 so as to position the floating bodies near the water surface or on the water surface or some distance below the water surface. If desired, the floating bodies 80 may be coupled to further floating bodies, such as the floating bodies 5 and 6 as indicated above.

Claims

1. A method for cultivating bi-valve molluscs, such as mussels and scallops, wherein use is made of line(s) and/or net(s) suspended in the water, which are supported by at least one floating body, characterized in that the floating body is disposed some distance below the water surface.

2. A method according to claim 1, characterized in that the buoyancy of the floating body is set in dependence on the weight of the line(s) or net(s) with the bi-valve molluscs supported by said line(s) or net(s).

3. A method according to claim 1 or 2, characterized in that the floating body is anchored to the bottom by anchor means disposed on either side of the floating body, seen in vertical direction, spaced therefrom by some distance.

4. A method according to any one of the claims 1-3, characterized in that the line(s) or net(s) are suspended from an elongated, removable carrier supported by the floating body or bodies.

5. A method according to any one of the claims 1-4, characterized in that a carrier supporting the line(s) or net(s) is lifted from the water and positioned above a hold of the vessel by lifting means mounted on board a vessel for the purpose of removing the bi-valve molluscs or the like from the line(s) or net(s).

6. A method according to claim 6, characterized in that the carrier is connected to the lifting means, whilst the carrier is disposed a small distance below the water surface.

7. A method according to any one of the preceding claims, characterized in that the position of the floating body with respect to the water surface is controlled by paying out/drawing in anchor lines connecting the floating body to anchors.

8. A device for cultivating bi-valve molluscs, such as mussels or scallops, comprising at least one floating body for supporting

and/or net(s) suspended in the water, characterized in that the device is provided with means which make it possible to dispose the floating body a desired distance below the water surface.

9. A device according to claim 8, characterized in that the device comprises at least one anchor line to be connected to an anchor and means for controlling the length of the part of the anchor line that extends between the anchor and the device.

10. A device according to claim 9, characterized in that the device comprises a shaft that can be rotated in two directions, said shaft being provided with a drum onto which the anchor line can be wound or from which the anchor line can be unwound, depending on the direction of rotation of the shaft.

11. A device according to claim 10, characterized in that said shaft can be driven via a flexible driving cable, which is connected to a buoy with one end.

12. A device according to any one of the preceding claims 8-11, characterized in that a floating body comprises at least two tubes extending at least substantially parallel to each other, and which are interconnected by cross members.

13. A device according to any one of the preceding claims 10- 12, characterized in that the shaft, which is provided with a drum, is surrounded by a floating body.

14. A device according to any one of the claims 8-13, characterized in that the floating body is so constructed that it can be coupled to a further floating body.

15. A device according to any one of the claims 8-14, characterized in that the floating body is provided with a shaft that extends at least substantially in the longitudinal direction of the floating body, on which shaft drums for anchor lines are mounted, whilst the shaft is provided at the ends thereof with coupling means for being coupled to a further shaft of a further floating body.

16. A device according to any one of the preceding claims, characterized in that a floating body is provided with suspension means for supporting a carrier carrying line(s) or net(s).

17. A device according to claim 16, characterized in that the hook-shaped suspension means are provided with springing locking members, which are so constructed that they can be pushed back by the carrier upon introduction of the carrier into the hook-shaped suspension means and will return to a carrier-locking position after the carrier has passed the springing locking members.

18. A device according to claim 17, characterized in that the carrier is coupled to two auxiliary carriers positioned on either side of the carrier, which can move out resiliently with respect to the carrier in a direction transversely to the longitudinal direction of the carrier, and in that C-shaped suspension means are fixed to a floating body for receiving the carrier and the auxiliary carriers coupled to said carrier.

19. A device according to any one of the preceding claims 8-18, characterized in that the floating body comprises at least one compartment into which/from which a liquid and/or a pressurised gas, in particular air, can be selectively introduced/removed.

20. A device according to claim 19, characterized in that ends of lines that are in communication with the compartment are connected to a buoy for supplying and discharging gas and liquid.

21. A device according to any one of the preceding claims, characterized in that the device comprises two shafts fitted with drums for winding and unwinding anchor cables, said shafts joining opposite sides of a transmission box, via which the shafts can be driven in opposite directions of rotation.

22. A vessel for handling line(s) and/or net(s) suspended from a floating body by means of a carrier, which line(s) and/or net(s) is

(are) suspended in the water for cultivating bi-valve molluscs such as mussels and scallops, characterized in that the vessel is provided with lifting means for moving the carrier with the line(s) and/or net(s) attached thereto in upward or downward direction, as well as with means for moving the carrier with the line(s) and/or net(s) attached thereto in a direction transversely to its longitudinal direction over the vessel.

23. A vessel according to claim 22, characterized in that the vessel is provided with a number of endless conveying elements, which are provided with hooks for supporting carriers supporting lines and/or nets.

24. A vessel according to claim 23, characterized in that said endless conveying elements are movable in a direction transversely to their longitudinal direction, being adjustable in desired positions.

25. A vessel according to any one of the claims 22-24, characterized in that the lifting means comprise telescoping arms that are pivotable about horizontal axes. 26. A vessel according to claim 25, characterized in that said arms, at the ends thereof, support a carrier which is rotatable about its longitudinal axis, to which carrier a further carrier is coupled by spring means, said further carrier being fitted with gripping means for gripping a carrier that supports line(s) and/or net(s). 27. A vessel according to any one of the preceding claims 22-

26. characterized in that the vessel is provided with a device for the detaching bi-valve molluscs and the like from line(s) or net(s), which device is movable with respect to the vessel in the longitudinal direction and in the transverse direction of said vessel.