Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SHELLFISH CULTURE CAGE AND METHOD OF USE THEREOF
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to shellfish
culture in the mariculture industry and, more
particularly, to a cage for shellfish, such as scallops.
2. Description of the Prior Art
The use of various cages has been known in the
prior art to increase the growth and the survival rates
in the mariculture industry. For instance, shellfish
have been produced in aquaculture cages that are
submerged in water. These aquaculture cages are formed
by a series of plates equidistantly stitched one atop
another and surrounded by netting. These plates are
flat and perforated, whereby water can circulate through
the netting and through the perforations for providing
renewed water to the cultured fish. This flow of
renewed water is an essential element for the rapid
growth of the cultured shellfish. Furthermore, the
cultured shellfish is protected from the predators of
the marine environment by the netting.
The above described aquaculture plate is
suitable for shellfish that have developed byssus,
whereby they can attach themselves to the plate and
therefore stay stable thereon. For shellfish species
that have not developed byssus, the above described
aquaculture cage does not provide a stable growing
environment as the shellfish are free to move on the
plates thereof. If this aquaculture cage is subject to
strong currents or wave action, the shellfish on the
plates can collide and possibly be damaged by the edges
of the surrounding shells. Therefore, the growth and
survival rates of the shellfish can be greatly impacted.
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Accordingly, the surviving rate of the scallop is only
about 30~ during its cage culture period.
A further culture plate was developed (under
Chinese Patent No. 98222788.4, naming Yuanling Wang as
inventor), wherein each plate comprises a plurality of
pits for isolating shellfish one from another on the
plate. The pits also comprise holes, whereby renewed
water circulates in the pits. The plates are
equidistantly stacked by ropes. Each stacked plate is
covered by a netting, thereby forming a cage.
One of the main costs in the mariculture
industry consists in the manual labor required for the
various operations during grow-out. For instance, the
process of changing shellfish seeds from one cage to
another to reduce density and/or to change a fouled cage
for a clean one proves to be lengthy and thus costly.
Furthermore, the insertion operation is achieved out of
the water, and must therefore be made quickly in order
to avoid exposing the shellfish seed to the ambient air
for an extended period of time.
SUMMARY OF THE INVENTION
It is therefore an aim of the present
invention to provide a shellfish cage for the culture of
individually isolated shellfish, wherein the insertion
of shellfish seeds is easily and rapidly performed.
Therefore, in accordance with the present
invention, there is provided a shellfish cage for the
culture of individually isolated shellfish, comprising
at least one plate having a top surface and a bottom
surface, a protective member disposed around said top
surface of said plate and allowing a flow of water
therethrough, at least a recess being provided in said
top surface of said plate for receiving a cultured
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shellfish therein, said recess having at least a first
hole extending from said top surface to said bottom
surface for water circulation therethrough, said plate
comprising a second hole extending from said top surface
to said bottom surface thereof for insertion of cultured
shellfish therethrough by said bottom surface, and for
the positioning of the cultured shellfish in said
recess, whereby the cultured shellfish is protected.
Also in accordance with the present invention,
there is provided a shellfish cage for the culture of
individually isolated shellfish, comprising at least one
plate having a top surface and a bottom surface, at
least a recess being provided in said top surface of
said first plate for receiving a cultured shellfish
therein, said recess having at least a first hole
extending from said top surface to said bottom surface
for water circulation therethrough, at least a cover
having at least an opening, said cover being disposed on
said plate such that said opening of said cover is in
registry with said recess of said plate, a protective
member for limiting access through said opening and to
said recess while allowing a flow of water through said
protective member, whereby cultured shellfish disposed
in said plate is protected while being exposed to water
exchange.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of
the invention, reference will now be made to the
accompanying drawings, showing by way of illustration a
preferred embodiment thereof, and in which:
Fig. 1 is a schematic top plan view of a plate
for a shellfish cage in accordance with the present
invention;
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Fig. 2 is a schematic top plan view of the top
plate of Fig. 1 for illustrating the shellfish cage
covered with a netting installed thereon;
Fig. 3 is a schematic top plan view, with
parts removed, of a cap for a plate of the shellfish
cage in accordance with a second embodiment of the
present invention;
Fig. 4 is a schematic bottom plan view, with
parts removed, of the cap of Fig. 3;
Fig. 5 is a schematic perspective view of the
shellfish cage with the netting or cap of each plate
removed;
Fig. 6 is a schematic perspective view of a
pair of shellfish cages mounted on a frame; and
Fig. 7 is a schematic perspective view of a
number of shellfish cages and seed baskets mounted on a
frame .
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, and more
particularly to Fig. 1, a nesting plate in accordance
with the present invention is generally shown at P. The
nesting plate P, for use in the culture of shellfish
(e. g. scallops), is defined by a circular disk 10 having
a top surface 12 , a bottom surface 14 and a peripheral
edge 16 (e.g. diameter of 38 cm and thickness of 3 mm).
The nesting plate P comprises a central nest pit 18,
which consists in a rounded concavity defined in the top
surface 12 (e.g. diameter of 10 cm and depth of 25 mm at
the center thereof). The central nest pit 18 is
concentric with the circular disk 10.
The nesting plate P further comprises a
plurality of peripheral nest pits 20. The peripheral
nest pits 20 are generally equidistantly spaced and are
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circumferentially distributed adjacent the peripheral
edge 16 of the circular disk 10, and, similarly to the
central nest pit 18, they consist in rounded concavities
formed in the top surface 12 (e. g, of the same
dimensions as the central nest pit 18). As shown in
Fig. 1, the nesting plate P comprises eight such
peripheral nest pits 20.
The central nest pit 18 and the peripheral
nest pits 20 each comprise a plurality of water holes 22
therein. The water holes 22 extend from the top surface
12 to the bottom surface 14. For instance, as shown in
Fig. 1, each pit comprises seven water holes 22 (e. g.
diameter of 20 mm). The water holes 22 may have
different sizes according to the shellfish species and
age. Also, depending on their size, the number of water
holes 22 may vary.
Pairs of connection holes 24 (e.g. diameter of
20 mm) are circumferentially distributed adjacent the
peripheral edge 16, between each pair of adjacent
peripheral nest pits 20. The connection holes 24 extend
from the top surface 12 of the circular disk 10 to the
bottom surface 14 thereof.
The nesting plate P also comprises a plurality
of seeding holes 26. The seeding holes 26 are generally
rectangular-shaped (e.g. 45 x 20 mm), and are
equidistantly spaced and circumferentially distributed
between the central nest pit 18 and the peripheral nest
pits 20. The seeding holes 26 also extend from the top
surface 12 to the bottom surface 14.
The nesting plate P consists in a material
adapted for a salty water environment, such as various
plastic materials. For instance, the plate P can be
processed by hot-pressing polymerization with specific
molds.
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Referring now to Fig. 2, the top surface 12 of
the nesting plate P is shown covered with soft mesh
netting N (e. g. mesh of 15 mm). A twine T (e. g.
diameter of 1 to 1.5 mm) fastens the netting N to the
nesting plate P. The shellfish of a given size are
inserted upwardly from below the bottom surface 14 of
the plate P, through the seeding holes 26 when the plate
P is covered with the netting N, which thus does not
have to be removed.
In another embodiment, illustrated in Figs. 3
and 4, a netting N' is imprisoned between the top
surface 12 of the nesting plate P and a cap A. The cap
A includes a circular disk 110 having substantially the
same diameter as the circular disk 10 of the nesting
plate P. The cap A further comprises a central
throughbore 118 and peripheral throughbores 120. The
throughbores 118 and 120 are positioned on the cap A
such that, when the cap A is concentrically disposed on
the nesting plate P, they are in registry with the
nesting pits 18 and 20, respectively. Typically, the
netting N' is mounted to the cap A. Although not shown
in Figs. 3 and 4, the cap A may comprise connection
holes, which will be in registry with the connection
holes 24 of the nesting plate P. The cap A can be
easily detached from the plate P for the seeding
thereof. It is noted that, with the presence of the
removable cap A, the seeding holes 26 shown in Figs. 1
and 2 are not required as seeding is done from the top
of the plate after having removed the cap A.
Referring now to Fig. 5, a shellfish cage in
accordance with the present invention is generally shown
at C. The shellfish cage C comprises a plurality of the
nesting plates P (e.g. 10 nesting plates) described in
Fig. 1, equidistantly spaced (e. g. 15 cm) and parallel
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one to another. The nesting plates P are interconnected
by side ropes S (e. g. 6-8 mm in diameter) that extend
through the connection holes 24 thereof. The side ropes
S are tied up at a top of the cage C and attached to a
hanging rope H (e. g. 8-10 mm in diameter). Similarly,
the side ropes S are tied up at a bottom of the cage C
and connected to a weight W. For clarity purposes, the
protective member, whether it be netting N or cap A with
its netting N', has been removed from each plate P shown
in Fig. 5. The various ropes (e.g. ropes S, H and T) of
the present invention consist of materials also adapted
for a salty water environment, such as polyethylene,
nylon or the like.
Referring to Fig. 6, a pair of cages C are
shown suspended on a frame F. The frame F may vary in
size in order to hold a plurality of cages C (e. g.
length of 5 meters, height of 2 meters) as shown for
instance in Fig. 7. The frame F may then also hold
known-in-the-art baskets B, wherein early stage
shellfish are encaged.
The shellfish are thus isolated from one
another as they are each nested in a different pit.
When a cage C is filled with shellfish, it is removed
from the frame and put in a transportation bin for field
deployment.
As shown in Fig. 5, the weight W keeps the
cage C in balance and steady in the water, and may
consist in some kind of stone, ceramic plummet or the
like, according to the environmental conditions.
The hanging rope H is also chosen in
accordance with the environment of the culture, whereby
all factors are taken into account, such as the water
flow, the wind power, the marine bio fouling and the
like (e. g. 8 mm in diameter).
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The cage C of the present invention provides a
safe, stable and high-water exchange environment. The
growth rate of the shellfish is increased by the
combination of this stable and safe environment,
individual isolation and exposure to renewed water flow.
Accordingly, the growth rate may be increased by 30 to
40~. Furthermore, as the shellfish are divided from
swarm status into an individual condition, they are
prevented from colliding with and occluding one another.
This results in an increased survival rate and shorted
growth period. The survival rate is also increased by
reducing the risk of collision and occlusion between the
shellfish. Furthermore, the shellfish are protected
from the predators by the soft mesh netting N or by the
cap A with its netting N' of the cage C. The survival
rate with the use of a cage C in accordance with the
present invention has been up to 98~. The C cage is
specifically intended for the culture of scallops, but
it is also suitable for the culture of most kinds of
shellfish, including the species without byssus, living
buried or semi-buried.
Therefore, in the present invention, the shellfish
are kept in separate chambers on each plate, in a stable
environment with high water exchange during the entire
grow-out period, while providing an efficient method for
being seeded. The new structures provide little space
or surfaces for fouling organisms and thus, competition
for food between shellfish and these organisms is
decreased. This increases the food availability for the
shellfish and promotes growth. Also, the cage of the
present invention has also opened the way to the
automation of the production of the shellfish grow-out
by the simple and repetitive steps required for the
seeding thereof. Because of the design, the cage is
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easy to handle, to stack, to ship or to store. Workers
with little training are able to handle these cages
efficiently.
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