Note: Descriptions are shown in the official language in which they were submitted.
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A DEVICE FOR DETECTION OF A SEINE WALL
The invention relates to a seine or line device arranged for
submersion into a mass of water, at least parts of the seine
or line being formed of a material exhibiting improved sig-
nal-reflecting properties or being provided with elements ex-
hibiting improved signal-reflecting properties.
By "seine" is meant, in what follows, a material which is
formed of seine twine, the seine twines being knotted to-
gether to form meshes of a mesh width suitable for the pur-
1o pose. Different types of seine twine can be used in the pro-
duction of one and the same seine.
In connection with the fish farming in oceans and lakes,
cages are used, in which the walls and bottom are constituted
substantially by a bag formed of seine hanging from a float-
ing device at the surface. This floating device itself is an-
chored to the floor by solid chains and anchors. In addition
the seine bag can be connected by lines and/or chains to, for
example, a bottom hoop which is also suspended from the sur-
face, but which is positioned below the lower edge of the
seine bag. The bottom hoop is attached at points to the seine
bag with the purpose of bracing the seine bag to limit defor-
mation upon external influence on the bag.
Rearing facilities are often placed in areas with a great
regular exchange of water, so that the fish is constantly
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supplied with oxygen. This may be currents brought about by
the tide or by more continuous sea currents. The great chal-
lenge relative to the seine bag is that it represents a great
flow hindrance, and the flow forces subject the seine wall to
great forces, in particular if the seine wall is foul. These
forces can lead to great deformations of the seines, that is,
the shape of the seine is changed, resulting in problems in
relation to:
= wear, by the seine wall rubbing against moorings and ad-
jacent equipment;
= reduction of the cage volume, the fish stock is driven
together within the cage and subjected to stress;
= extra load on the suspension, anchoring systems and
seine.
In modern rearing the cages have become increasingly deeper.
Seine bags reaching a depth of 50 m are not uncommon. This
makes it very difficult for the farmer to observe the condi-
tion of the seine bag in the daily operation. Even for an
equipment supplier and those projecting and installing the
cage it is difficult to foresee how the structures will be-
have under the prevailing conditions. Mathematical models and
trials in small and large model tanks provide some answers,
but this takes place under simplified conditions which do not
necessarily fully represent reality. To a certain degree, it
is also possible to use cameras for visual information, but
this is complicated by conditions such as visibility in deep
water, limited measuring range and undesired proximity to the
seine wall to be monitored.
Therefore, equipment which can monitor the shape of the seine
bag in its entire extent will be of great interest. The
equipment could be used for several things:
0 Helping the producer to develop the equipment which is
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to be placed at the rearing facility, by enabling meas-
urements at the actual facility instead of taking only
models as a basis.
= Monitoring the facility in the first phase after instal-
s lation to verify that the equipment is functioning under
the prevailing conditions.
= Monitoring the facility continuously in the daily opera-
tion with fixedly installed equipment. This is particu-
larly relevant as the flow forces, to which the seine
bag is subjected, may vary greatly over time. There may
be seasonal variations resulting in different currents,
varying weather conditions, and fouling of the seine
over time results in the flow-obstructing effect of the
seine bag increasing with time from deployment/last
is cleaning.
A common way of detecting objects under water is to use dif-
ferent forms of sonar/echo sounders. In principle, known
equipment will, to a certain degree, detect signal reflection
(echo) from the seine wall and moorings, but owing to the
fact that material used in prior art seine walls does not
provide sufficient reflections, it will not be possible to
provide satisfactory and reliable observations of the shape
of the seine bag.
The invention has for its object to remedy or to reduce at
least one of the drawbacks of the prior art.
The object is achieved through features which are specified
in the description below and in the claims that follow.
The object of the invention is to provide an artificial con-
trast in the seine so as to enable a reliable detection of
the shape of the seine bag by the use of sonar/echo sounding
techniques known per se. This may be done by the use of:
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= spots of high-contrast material which is integrated into
or attached to the seine, for example in different pat-
terns in different portions of the seine bag, for exam-
ple varying across the depth of the seine bag, so that
s the different portions of the seine bag are identifi-
able;
= high-contrast material which is spun with twines which
are used to produce the seine;
= contrast substance, with which the entire seine bag or
parts of it is/are treated.
When the seine exhibits sufficient contrast, a detecting unit
could be used, for example an echo sounder, which is posi-
tioned near the seine bag, for continuously measuring the de-
formation. The detecting unit must receive a sufficient
is amount of information to be able to form a 3D i.mage of a se-
lected portion of the cage. Therefore, it is not enough to
have a single sensor, and the detecting unit must, therefore,
include several sensors. These may be mounted in the same
unit or function in a network of sensors in which the gather-
ing of information is coordinated.
The information may be presented, for example, on a computer
screen in a 3D presentation, so that it is easy to see an un-
desired deformation. It is also conceivable to carry out cur-
rent video image analysis with a computer, so that an alarm
can be given if the actual shape of the seine bag differs
substantially from the desired shape.
The invention is not limited to a seine bag for a cage for
the fish farming, but also includes a seine for other appli-
cations in which net-like or seine-like devices are placed
submerged in a mass of water for catching fish etc., holding
caught live fish etc., closing off an area, and similar
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things, in which there is a need to detect the position of
the device in the mass of water. The invention also relates
to a line to be used submerged in a mass of water, the line
having properties as described above.
5 In a first aspect the invention relates more specifically to
a seine device to be used submerged in a mass of water, a
plurality of seine meshes being formed by one or more thread-
shaped materials being joined together, characterized by the
seine including one or more signal reflection means which are
localized to at least one seine portion and are arranged for
the reflection of an acoustic signal emitted from a sound
source.
The signal-reflecting properties of a first seine portion are
preferably different from the signal-reflecting properties of
a second seine portion.
The signal reflection means are preferably taken from the
group consisting of reflector elements attached to one or
more seine meshes, a wire spun into the mesh-forming seine
twine, twine coating on mesh-forming seine twine and impreg-
nating fluid for mesh-forming seine twine.
The reflector element is preferably formed of a solid, par-
ticularly a metal, or a combination of several solids, with a
resulting specific weight of at least 1.1 g/cm3.
The signal reflection means of the first seine portion are
advantageously arranged in a pattern which is different from
the pattern of the second seine portion.
In a second aspect the invention relates more specifically to
a line to be used submerged in a mass of water, characterized
by at least part of the line exhibiting signal-reflecting
properties which are different from the signal-reflecting
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properties of other parts of the line.
The signal-reflecting properties are preferably provided by
wire which is twisted into the line, or a coating and/or im-
pregnating fluid applied to at least some of the strands of
the line. '
In a third aspect the invention relates to a system for de-
tecting a seine or a line as described above, submerged in a
mass of water, characterized by the system comprising
an acoustic transmitter which is arranged to provide, in
a controlled manner, acoustic signals in the mass of water;
at least one signal receiver which arranged to receive
acoustic signals reflected from the seine or line, is lo-
cated in the mass of water near the seine or line;
a signal-processing unit which is connected, in a sig-
is nal-communicating manner, with the at least one signal re-
ceiver and is arranged to process the signals reflected from
the seine or line; and
a display screen which is arranged for the visualization
of the reflected, processed acoustic signals.
The signal-processing unit is preferably arranged to compare
the actual position of the seine or line, generated from the
reflected, processed acoustic signals, to the normal position
of the seine or line and, when a predetermined deviation from
the normal position is exceeded, to be able to generate an
alarm. I
In what follows, is described an example of a preferred em-
bodiment which is visualized in the accompanying drawings, in
which:
Figure 1 shows schematically a side view of a rearing cage,
in which the seine bag is deformed because of cur-
rents in the mass of water;
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Figure 2 shows schematically a side view of a rearing cage
with a detecting apparatus, the seine bag being
constructed from materials exhibiting different
signal-reflecting properties;
Figure 3a shows a schematic section of a seine in which seine
twines with different signal-reflecting properties
form a recognizable pattern;
Figure 3b shows a schematic section of a seine in which re-
flector elements are arranged in different recog-
nizable patterns;
Figure 3c shows a schematic section of a seine impregnated
with a signal-reflecting impregnating fluid;
Figure 4a shows a line in which some strands exhibit an en-
hanced signal-reflecting property; and
Figure 4b shows a line impregnated with a signal-reflecting
impregnating fluid.
Figure 1 shows a typical situation, in which a seine bag 11
of a cage 1 exhibits, under the influence of currents in a
mass of water 2 in which the cage 1 is placed, a shape which
differs from the regular one, as appears from figure 2. The
seine bag 11 is suspended, in a manner known per se, from a
floating hoop 12 floating at a water surface 21, and the cage
1 is secured by lines 13 to several mountings 14 arranged on
a seabed 15. Further, the cage 1 is provided with theneces-
sary walkways with railings 16. A bottom hoop 17 keeps the
bottom portion of the seine bag 11 expanded.
Figure 2 shows the seine bag 11 in an ideal shape unaffected
by currents in the mass of water 2. The seine bag 11 com-
prises several seine portions lla, llb, llc arranged at dif-
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ferent depths, each seine portion being formed of materials
providing different signal-reflecting properties. A control
unit 3 for detecting the shape and position of the seine bag
relative to surrounding elements, for example, the lines 13
by which the cage i is secured, is arranged in the immediate
vicinity of the cage 1. The control unit 3 is arranged for
emitting acoustic signals through a transmitter 31 arranged
on the control unit 3 and submerged in the mass of water 2.
Several receivers 32 (two shown here) are connected to the
control unit 3 in a pattern providing a satisfactory quality
of the signals reflected from the seine material of the seine
portions lla, llb, llc and other signal-reflecting objects
disposed in the mass of water 2, for example the lines 13.
Finally, the control unit 3 comprises a signal-processing
1s unit 33, for example a computer which is in signal communica-
tion with the transmitter 31 and receivers 32 and possibly
other control and monitoring devices (not shown) at the rear-
ing facility. A display screen 34 is arranged for visualiza-
tion of the reflected, processed acoustic signals.
Figure 3a shows schematically a section of a seine llla which
is arranged for the formation of a seine portion lla, llb,
llc, possibly a seine bag 11. The seine lila is formed by the
use of at least seine twine 112, 113 exhibiting different
signal-reflecting properties, for simplicity illustrated here
with a vertically oriented type of twine 112 which is differ-
ent from a horizontally oriented type of twine 113. By pro-
ducing a seine with different combinations of different seine
twines 112, 113, seine portions with different signal-
reflecting properties may be provided.
Figure 3b shows schematically a section of a seine lllb which
is arranged to form, in the same way as the seine llla, a
seine portion lla, llb, lic, possibly a seine bag 11. The
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seine illb is formed, in a manner known per se, by the use of
normal seine twine 114. Several reflector elements 115 are
secured to the seine lllb, illustrated here with two differ-
ent patterns to provide seine portions with different signal-
reflecting properties.
Figure 3c shows schematically a section of a seine lllc which
is arranged, in the same way as the seine llla, lllb for the
formation of a seine portion lla, llb, llc, possibly a seine
bag 11. The seine lllc is formed in a manner known per se by
the use of standard seine twine 114. To one or more seine
portions lla, llb, llc, possibly the seine bag 11, an impreg-
nation means is applied, having satisfactory signal-
reflecting properties so as to provide seine portions having
better signal-reflecting properties than a seine formed in a
manner known per se.
Figure 4a shows a line 4a formed by being twisted from
strands 41, 42 with different signal-reflecting properties,
indicated here by several strands 42 with good signal reflec-
tion twisted together with several standard strands 41 and
disposed in an appropriate place in the cord. The strand 42
with good signal reflection can be formed of, for example, a
metal, preferably a metal with good corrosion properties, for
example copper or lead.
Figure 4b shows a line 4b which is formed of standard strands
41. At a suitable stage in the production process the line
4b, possibly the individual strands 41, is/are treated with a
material having satisfactory signal-reflecting properties, in
the form of a coating or a permeating impregnation.
The lines described above with reference to the figures 4a
and 4b can be provided in a dimension which is arranged for
individual use, for example for securing a seine bag or a
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cage, or they may have a dimension which is arranged for the
production of a seine material as it is described above with
reference to figure 3a.
When there is a need to detect an element of great vertical
5 extent in the mass of water 2, for example a seine bag 11 of
a cage 1, and the receivers 32 of the control unit 3 are not
arranged across the entire depth of the seine bag 3, it will
be an advantage that different seine portions lla, llb, llc
have different signal-reflecting properties. This improves
10 the quality of the images that the signal-processing unit 33
creates, as several seine portions lla, llb, llc that are
projected on top of each other in a horizontal plane, are
distinguished better from each other in the signal process-
ing.
Even if, in the foregoing, exemplary embodiments are de-
scribed, which are directed towards the field of application
of rearing cages 1, it is obvious to a person skilled in the
art that it is within the scope of the invention also to form
other thread-based elements which are arranged to be disposed
in a mass of water 2, in which there is a need to detect the
orientation or location of the element.
