Abstrict A process and apparatus for harvesting soft shell crayfish wherein
a predetermined pulsating electrical field is established in front
of a moving conveyor assembly having a pulse rate which allows the
tail of the crayfish to contract in synchronization with the pulse
rate causing the crayfish, in most cases, to move toward and be
captured by a moving trawl assembly having a conveyor assembly which
transports the crayfish to an area to be sorted and stored for shipping.
Claims What I claim is:
1. A process for harvesting from a water body crayfish which comprises:
(a) applying in a portion of the water body a pulsating electric
current of sufficient current density to cause the crayfish to move
toward a moving trawl assembly and having a pulse rate that allows
the tail of the crayfish to contract in synchronization with the
pulse rate;
(b) moving the location of the current at a speed greater than
the speed of the crayfish;
(c) catching the moving crayfish by said moving trawl assembly;
(d) conveying the caught crayfish to a sorting area; and
(e) sorting the crayfish as desired; said electric current being
pulsed 2-10 times/sec., having a pulse duration of 10-200 msec.
and creating a pulsed electric field with a current density of 0.05-0.30
ma/cm.sup.2.
2. A process according to claim 1 wherein the trawl assembly is
moved at a speed of 2-5 ft/sec.
3. A process according to claim 1 wherein the soft shell crayfish
are sorted from the hard shell crayfish.
4. An apparatus for harvesting crayfish from a pond comprising;
(a) a trawl assembly having means for catching moving crayfish
and having a conveyor assembly to receive the crayfish from the
means and to convey them to a sorting table;
(b) a variable electric current supply electrically connected to
electrodes attached to the trawl assembly, the electrodes having
their ends positioned in front of the trawl assembly to establish
the desired pulsating electric current and current density to attract
the crayfish toward the trawl; and
(c) vehicular means to move the trawl assembly; said electric current
supply having means to provide the electrodes with an electric current
pulsed 2-10 times/sec., having a 10-200 m sec, pulse duration, and
of being of sufficient magnitude to create a pulsed electric field
having a current density of 0.05-0.30 ma/cm.sup.2.
5. An apparatus according to claim 4 wherein the trawl assembly
comprises:
(a) a flat surface member constructed from parallel tubing and
having spaced apart tubular side walls, and having an upward extending
conveyor bottom pivotly attached to the vehicular means;
(b) scooping means attached to the conveyor bottom end having conveyor
means for carrying the crayfish up the conveyor bottom to the vehicular
means; and
(c) electrode boom assembly attached to the vehicular means having
an arm extending in front of the flat surface member to which is
attached the electrodes.
6. An apparatus according to claim 5 wherein the scooping means
comprises a row of finger members attached to a rod extending across
the conveyor bottom, the rod being attached to a chain and sprocket
assembly that travels up conveyor bottom, the fingers extending
out from the rod to a position adjacent the conveyor bottom during
the rods travel up the conveyor bottom.
7. An apparatus according to claim 5 wherein the lower portion
of the conveyor bottom is provided with vertically extending sidewalls.
8. An apparatus according to claim 5 wherein a pond bottom skid
member is attached at one end to the front end of the flat surface
member and has its opposite end protruding downward to contact the
bottom of the pond.
9. An apparatus according to claim 4 wherein the vehicular means
comprises:
(a) an enclosed body structure;
(b) a wheel and axle assembly attached to the body structure; and
(c) a motor attached to the wheel and axle assembly to cause same
to turn the wheels.
10. An apparatus according to claim 9 wherein the enclosed body
structure has a crayfish holding chamber positioned to receive crayfish
from the conveyor assembly.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to processes and apparati for harvesting
crustaceans and, particularly, soft shell crustaceans such as crayfish.
2. Prior Art
In the the past, crayfish have been harvested principally in the
swamps and marshes of coastal regions by the use of baited traps.
However, as demand has grown, commercial "farms" for the
growing of crayfish have developed. Until recently, the harvesting
of these farms was done by the conventional baited traps. However,
the baited traps have several disadvantages which have slowed the
successful commercial development of these "farms".
Because of the size of the commercial farm ponds, many traps are
required to harvest the crayfish; thus, the yield per acre have
made many "farms" unprofitable. This has led to extensive
research for better baits and other means of harvesting. One such
means has been experimental mechanical devices which, much like
grain combines, attempt to scoop up the crayfish as the devices
move across the field. These devices have also been plagued by problems
inherent in the nature of what crayfish ponds must be like, i.e.,
vegetation, such as rice and algae growing throughout, as well as
the shallow depth of the pond.
Another problem is the fact that crayfish tunnel underground to
build their homes, and if there are logs or stones in the pond,
the crayfish have a tendency to build next to such obstacles or
in the vegetation in the pond. This, in turn, has created problems
for mechanical harvesters.
Soft shell crayfish pose an even greater problem since they rarely
stray far or for long from their home or they stay in the pond vegetation
as they are very vulnerable to predators until their shells harden.
However, it has long been recognized that if they could be harvested,
they would be an immediate commercial success since the entire crayfish
could be eaten rather than just the tail meat which comprises only
ten to fifteen percent of the body weight.
For all of the above reasons, harvesting of soft shell crayfish
in sufficient numbers has been impossible until this invention.
SUMMARY OF THE INVENTION
Therefore, it is an object of this invention to provide a process
and apparatus for improved harvesting of crayfish, particularly,
soft shell crayfish.
Another object of this invention is to provide an apparatus that
can successfully operate to harvest crayfish, particularly soft
shell crayfish, in commercial ponds.
Still another object of this invention is to provide an apparatus
which allows for rapid, manual separation of soft shell crayfish
from hard shell crayfish after their capture.
Other objects and advantages of this invention shall become apparent
from the ensuing descriptions of this invention.
Accordingly, a process for harvesting crayfish is disclosed comprising,
applying in a local area, a pulsating electric current of sufficient
strength to cause crayfish to move but of insufficient strength
to kill the crayfish and having a pulse rate which allows the tail
of the crayfish to contract in synchronization with the pulse rate,
catching the moving crayfish, conveying rapidly the crayfish to
a sorting area, and sorting the crayfish as desired. In another
embodiment of this invention, means are provided for harvesting
crayfish comprising a trawl assembly having conveyor assembly and
being pivotly mounted to a vehicle for moving the trawl assembly,
and a variable electrical current supply electrically connected
to electrodes the ends of which are positioned in front of the trawl
assembly to establish the desired pulsating electric current.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a three dimensional view of a preferred embodiment of
a crayfish harvester of this invention.
FIG. 2 is a side view of the crayfish harvester.
FIG. 3 is a top view of the crayfish harvester.
PREFERRED EMBODIMENTS OF THE INVENTION
Referring now to the Figures, there is shown a preferred crayfish
harvester of this invention comprising a trawl assembly 1 pivotly
mounted to the front end of a marsh buggy 2 or similar water vehicle
and a variable electric current supply, such as a variable voltage
pulsator 3 electrically connected to spaced apart electrodes 4
(positive anodes) attached to trawl assembly 1 (negative anode)
and positioned in front thereof as shown.
The trawl assembly 1 is constructed having a frame assembly comprising
side square stock members 5 and 6 that are fixed in position relative
to one another by front and rear channel iron members 7 and 8 respectively.
In a preferred embodiment, members 5 and 6 are bent upward as shown
in FIG. 2 to better position trawl assembly 1 to the water bottom
9.
The frame assembly is also provided with vertical posts 10 and
11 rigidly supported in position at the front end of members 5 and
6 by cross bar 12 and side braces 13 and 14. Eyelets 15 and 16 are
provided at the top of each post 10 and 11 respectively, to which
the opposite ends of cable 17 attach as shown. Cable 17 in turn
passes through roller 18 of pulley 19 through which a second cable
20 passes and is operatively attached to a second pulley 21 and
winch 22 fixedly positioned to ginny pole 23 vertically mounted
on marsh buggy 2.
To attach the frame assembly to marsh buggy 2 channel iron members
24 and 25 are bolted to the sides 26 and 27 respectively, of the
buggy 2 so that one of their ends protrudes in front of the buggy
whereby side square stock members 5 and 6 can be pivotly attached
by pins 28 and 29 as shown. Thus, when cable 20 in winched, frame
posts 15 and 16 can be pulled up or let down as desired.
The bed or floor of the frame assembly comprises, in a preferred
embodiment, a front section 30 constructed from aluminum or alloy
tubing 37 and a rear section 32 also constructed from aluminum or
alloy tubing material having separated tubes 33 which form vertical
channels 34 to help direct movement of crayfish up section 32. Both
sections 30 and 32 extend between side members 5 and 6. In a preferred
embodiment, side tubing panels 35 and 36 are attached to side members
5 and 6 and posts 10 and 11 to prevent crayfish that are caught
from escaping from the sides of the frame structure. In another
preferred embodiment, small gaps 31 are formed between tubing 37
to allow young crayfish to escape so they can grow to maturity.
In another preferred embodiment, a rigid skid member 38 is attached
to front channel iron member 7 and extends downward to curl under
member 7 to act as a cushion and guide over obstacles that may be
on the water bottom.
A conveyor assembly 39 is provided to move the crayfish up trawl
rear section 32 and onto a sorting table 40 located in buggy 2.
Assembly 39 comprises parallel axles 41 and 42 operatively connected
together by sprocket 43 mounted to the frame assembly at the lower
and upper ends of rear section 32 and chains 44 attached to the
sprockets 43 as shown. Attached to and between chains 44 is a rake
device 45 having tines 46 that can extend downward and into channels
34 as device 45 is carried in the loop formed by chains 44. Although
only one rake device is illustrated, more than one can be attached
to chains 44 if desired. To drive axle 42 and rotate sprockets 43
is electric motor 47.
An electrode boom assembly 48 is provided with a series of hollow
bent tubing 49 attached to cross bar 12 and from which electrodes
4 extend to be positioned in front of front channel iron member
7. A power supply, such as an electrical generator 50 is used to
generate the electrical current that passes through a variable voltage
pulsator 3 then through wires located in conduit pipe 51 and through
pipes 49 to electrodes 4.
In operation, the marsh buggy 2 with trawl assembly 1 in a raised
position is driven into water 52. Trawl assembly 1 is then lowered
by winch 22 until skid member 38 is resting just above the water
bottom 9. Electric current from generator 50 is provided to electrodes
4 in a controlled pulsing manner and of sufficient strength to cause
the tails of the crayfish to contract in synchronization with the
electric pulse rate. The buggy 2 is then moved systematically across
the crayfish pond.
The required pulse rate and electric field established around the
electrode can vary depending on the water temperature, water mineral
and salinity content. However, it is has been found that a field
strength between 0.05-0.30 ma/cm.sup.2 and a pulse rate between
2-10 times/sec wherein each pulse is 10-200 msec is preferred in
providing the desired movement of the crayfish. With this field
and pulse rate, it is preferred that buggy 2 travel at a speed of
2-5 ft/sec. Within these preferred perimeters, the crayfish will
involuntarily move as a result of the pulsed contraction of its
tail. This will cause many crayfish in front of the buggy 2 to move
directly onto parallel tubing 31 of the moving trawl. Water force
then causes the crayfish to continue to move toward trawl rear section
32 until rake tines 46 push the crayfish up tubing 33 to sorting
table 40 where the soft shell crayfish are immediately separated
from the hard shell crayfish.
There are, of course, many alternate embodiments of this invention
not specifically illustrated but which are intended to be included
within the scope of this invention as defined by the following claims.
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