Note: Descriptions are shown in the official language in which they were submitted.
CA 02063976 1999-06-07
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METHOD AND APPARATUS FOR SEPARATING
TARGETED SPECIES OF AQUATIC LIFE
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for
selectively separating targeted species of aquatic life from
non-targeted species during underwater harvesting operations.
Specifically, the invention separates targeted mature shrimp
from other non-targeted aquatic organisms in shrimp trawls
allowing the non-targeted organism to pass out the open back end
of the trawl while capturing the targeted mature shrimp in a
separated closed portion of the trawl.
The present invention utilizes a method and apparatus which
selectively directs mature shrimp into a collection net portion
of the trawl while allowing the non-targeted species and debris
to pass out the back end of the trawl.
The present invention not only allows non-targeted species
to pass through the trawl, but also allows immature shrimp to
avoid capture and harvesting. Such a selection process ultimately
results in an increase in available mature shrimp for subsequent
harvesting. Thus the numerous problems associated with the
current trawls are eliminated while increasing the productivity
of the harvesting operations.
SUMMARY OF THE INVENTION
The invention in one broad aspect provides an apparatus for
separating targeted species of aquatic life comprising a first
net having a body portion having two opposing side walls, a top
side and a floor, a first open end, and a second open end the
body portion having an opening in the top side with a second net
attached to the opening at a first open end of the second net,
the second net having a second releasably closable end. Means
is positioned at and attached to the side walls below the opening
in the top side and above the floor of the body portion of the
first net for stimulating the targeted species of aquatic life
to enter the second net through the opening in the body portion
of the first net.
CA 02063976 1999-06-07
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Another broad aspect of the invention provides an apparatus
for separating targeted species of aquatic life comprising a
first net having a body portion with a first open end and a
second end, the body portion having an opening in a top side with
a second net attached to the opening at a first open end of the
second net, the second net having a second releasably closable
end. A means is attached to the first net for stimulating the
targeted species of aquatic life to enter the second net through
the opening in the body portion of the first net, the means for
stimulating further comprising a pulser generating pulses in
frequency ranges of 225-350 Hz at 3-5 pulses per second.
Still further the invention provides a method for separating
targeted and non-targeted species of aquatic life comprising the
steps of providing a trawl comprising a first net having a body
portion having two opposing side walls, a top side, a floor, a
first open end, and a second open end, the body portion having
an opening in the top side with a second net attached to the
opening at a first open end of the second net, the second net
having a second releasably closable end. Means is positioned at
and attached to the side walls below the opening in the top side
and above the floor of the body portion of the first net for
stimulating the targeted species of aquatic life to enter the
second net through the opening in the body portion of the first
net, towing a shrimp trawl in a body of water containing the
targeted and non-targeted species, activating the means for
stimulating the targeted species and withdrawing the trawl from
the body of water.
More particularly, the present invention is a specially
designed shrimp trawl or net which has a separate collection
section formed in the trawl either as a second, piggyback net
or as an upper deck in the cod end of the main net. The back end
of the non-collection section is open to allow non-targeted
species and debris to pass out of the trawl during towing of the
net . At the throat of the trawl, a pulsing apparatus is attached
to the net to stimulate mature shrimp to ~~jump~~ or
move upwardly into the opening of the piggyback net or the
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upper deck of the trawl. The back end of the piggyback net
or upper deck is releasably closable to enable the shrimp
operator to close the net or deck during the towing and
collection process, and to open the net or deck once the net
is aboard the shrimp boat so as to release the harvested
shrimp for icing and storage.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a perspective view of the apparatus
of the present invention.
FIG. 2 shows a partial cross sectional view of the
apparatus of the present invention.
FIG. 3 illustrates a perspective view of an alternative
embodiment of the apparatus of the present invention.
FIG. 4 shows a cross sectfional view of the alternative
embodiment of the apparatus of the present invention taken
along lines 4-4 of FIG. 3.
FIG. 5 shows a cross sectional view of the alternative
embodiment of the apparatus of the present invention taken
along lines 5-5 of FIG. 3.
FIG. 6 is a block diagram of the pulser of the present
invention.
FIG. 7 is a schematic diagram of a typical pulser of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 illustrates a perspective view of the
present invention as it is being towed underwater. For
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simplicity, tow lines, doors, tickler chains, bibs, and
floats are not shown. The front opening 12 of trawl or net
is shown in the open position. The height and width of
opening 12 may be varied by many factors known to shrimp
harvesting operators. Such openings may range from small
(25 foot), designed for bays and more shallow bodies of
water, to large (65 foot) for gulf or ocean operations.
The body portion 14 of the net 10 extends from the
front opening 12 to the closable back end 16 of the net.
10 The back end of the net is also called the cod end and this
is the area where the catch is collected in the standard
shrimp trawl or net. Normally, the cod end is closed by a
draw rope during towing of the net under water, and is then
opened, by the release of the draw rope when the net is
withdrawn from the water and placed on the deck of the
towing boat. Many features of the net may be discussed such
as mesh opening size, twine thickness, material composition,
and the like, but these matters are all well known in the
art by one of ordinary skill.
FIGS. 1 and 2 illustrate the unique "piggyback" second
net 20 of the present invention which extends from an
opening 22 in the top side 24 of the body portion 14 of the
basic trawl 10. The second net has a first open end 26 and
a second closable end 28. A draw rope 30 similar to that
normally used on the back end of the basic trawl is shown
such that the second end of the piggyback net is closed
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during towing operations_ Also seen in FIGS. 1 and 2 is a pulsing
apparatus 32, including lead lines 34, and electrodes or
transducers 36. Pulser 32 is attached to the body portion 14 of
the net with lead lines 34 running to electrodes 32 immediately
below opening 22. Transducers or electrodes 36. are positioned
parallel to each other on opposite side walls 40 and 42 above the
floor 37 of the body portion 14 and parallel to the longitudinal
axis of the trawl l0.
FIG. 6 is a general block diagram of the pulser
mechanism. Pulsers of this type are generally well known,
but not utilized in the present type of situation. The
power source is a d.c. battery which operates in the range
of 5 to 24 volts. The power source may be switched on or
off remotely to activate the timer, frequency generator and
transducer. The frequency generator generates a square wave
in the range of 225-350 Hz and the timer pulses the wave in
the range of 3-5 pulses per second. The pulse is
transmitted to the water medium through the transducers.
FIG. 7 is a typical schematic diagram of a pulser circuit of
the present invention.
In operation, trawl 10 is towed in the conventional
method known to shrimp boat operators, with pulser 32
activated and transmitting pulses in the frequency range of
225-350 Hz pulsed at 3-5 pulses per second. As aquatic life
(including mature,shrimp) and debris enter the throat of the
trawl it is exposed to the pulses created by pulser 32.
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Mature shrimp (shown as solid arrows in the flow) are
sensitive to the pulses and tend to "jump" as they sense the
pulse. Thus the targeted species move from the main stream
of the flow and move upwardly toward the opening 22 in the.
top side of the net. Other aquatic life (including immature
shrimp) and debris (shown as dotted arrows in the flow) are
not sensitive to the pulses and remain unaffected. These
non-targeted species and the debris continue to flow through
the main portion of the trawl and out the open back end 16.
The targeted species are collected in the second
piggyback net 20 because the second, back end 28 is drawn
closed by rope 30. When the operator determines that the
second net 20 contains sufficient quantities of the targeted
shrimp species, the pulser may be shut off (remotely) and
the entire trawl 10 withdrawn from the water. Once the
trawl 10 is aboard the boat, rope 30 is loosened and the
captured shrimp released for conventional icing and storage.
The piggyback net system discussed above has proven
effective in bay areas with depths of 7'-30'.
Alternatively, another embodiment of the present
invention is illustrated in FIGS. 3-5. FIG. 3 is a
perspective view which shows the back portion 50 of trawl 11
with an upper deck 52 and a lower deck 54 formed by the
addition of net partition 56. The net partition extends
from one side wall 61 to the other side wall 63 of the net
from the throat 55 to the back end 57 of the net. Upper
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deck 52 has an open end 58 and a releasably closable end 60
(with draw rope 62). Lower deck 54 has a ffirst open end 64
and a second open end 66. A piggyback net 21 may
additionally be attached to trawl 11 as discussed above, and
may be seen in FIGS. 3 and 5. Piggyback net 21 has a front
open end 23 attached at opening 35 in the top side of trawl
11 and a closable back end 27 (by rope 29).
The trawl 11 of FIGS. 3-5 is used in gulf areas with
depths in the 30' to 600' range. As with the embodiment of
FIGS. 1 and 2, activation of pulser 32 results in the
targeted species (mature shrimp) being captured in the upper
deck portion 52 while non-targeted species and debris pass
through deck 54 and out opening 66. Few mature shrimp are
captured in piggyback net 21.
It should be understood that the piggyback net 21 may
be eliminated in situations where the operator simply
desires to have a two deck type net for exclusive use in the
deeper bodies of Water such as the gulf or ocean.
With the alternate embodiment 11, electrodes 36 are again
positioned parallel to each other on opposite side walls of the
trawl below and forward of net partition 56 and above the floor 70
of the trawl, as seen in FIG. 5. The electrodes are extended
generally parallel to the longitudinal axis of the trawl 11. The
operation of the pulser 32 of the alternate embodiment is identical
to that of the preferred embodiment as relates to its operating
frequency and pulse timing.
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While the invention has been described in connection
with a preferred embodiment, it is not intended to limit the
invention to the particular form set forth, but, on the
contrary, it is intended to cover alternatives,
modifications, and equivalents, as may be included within
the spirit and scope of the invention as defined by the
appended claims.
