Traps for crustaceans

A trap for crustaceans and fish comprising a plastic mesh forming walls in the shape of a hollow hexagonal prism, made up of two trough shaped parts and end walls. End walls contain frusto conical inlets and interchangeable end walls are closed. Ballast in the shape of elongate extruded hollow square section plastic tubes filled with concrete is fixed to one trough shaped part, an opening in the other trough shaped part can have a frusto conical pipe extending into the trap or a lid, for removing the catch. Tongue and socket connectors for the trough shaped parts have a cross sectional shape for the tongue like a capital letter E with the middle web longer than the outer webs. A bait basket is in two halves which are threaded onto a pin which has a handle at one end and a detent at the other end to clip into a socket in the inner surface of the trough shaped part which carries the ballast.

BACKGROUND OF THE INVENTION 
This invention concerns improvements in and relating to traps for all 
species of fish and in particular crustaceans such as lobsters and 
crayfish. 
FIELD OF THE INVENTION 
Description of the Prior Art 
The catching of lobsters and crayfish by means of traps is a very old art 
which has been practised by fishermen for these crustaceans using hand 
made traps of wood or wicker and metal traps, set in relatively shallow 
waters for example up to five or six fathoms at the most and generally 
shallower than this. 
Very recently fishing for lobsters and crayfish has been extended to much 
greater depths thereby entering heretofore unexploited fishing fields and 
employing traps and techniques which have very substantially increased the 
yields. Despite these increased yields however this fishing is still an 
art deriving many of its techniques and many aspects of construction of 
the traps from the practice of the past rather than from a clear 
understanding of the behavior of the crustaceans in relation to the trap. 
Accordingly the yields provided by traps and techniques of different kinds 
have differed from each other for reasons which have not always been 
clear. Continuing experience in this art however in particular in relation 
to deep sea trapping of crustaceans has now yielded to the inventor an 
understanding of certain of these aspects which has led to a development 
of traps for crustaceans having novel features which provide improved 
yields. 
SUMMARY OF THE INVENTION 
There are many features which are important for the effective trapping of 
crustaceans. A first feature is the employment of a non-galvanic material 
in sea water such for example as a suitable plastic or synthetic polymer. 
Apart from its asset of not rusting in sea water it is believed that for 
example a lobster is able to sense metal under water and tends to be 
repelled by it accordingly, presumably due to electrical polarising or 
galvanic effects. 
A further important feature is collapsibility so as to permit reasonably 
compact stacking of collapsed components of the traps. Combined with this 
it is desirable that the assembled trap nevertheless be sufficiently 
strong to permit walking on top of a trap by adults without damage to it. 
The reason for this is that traps tend to be stacked in very large numbers 
(and sometimes in more than one layer) in the assembled condition all over 
the entire deck of a fishing vessel so that the fishermen are forced to 
walk over the tops of the traps. Also when the traps are raised from a 
depth in the case of deep sea fishing with lobsters inside them they are 
subjected to very large forces as the cable is hauled up dragging the 
traps through the water. Under these conditions it is furthermore 
important that the entrance to the trap be such that they tend to prevent 
or minimise escape from the trap of the crustaceans trapped inside it. 
Thus preferably the entrance to the trap is adapted to permit easy passage 
to the crustacean from outside to the inside of the trap but to tend to 
hinder the crustacean from passing from inside to outside. The features of 
construction of the entrance to achieve this may for example comprise a 
plurality of fingers arranged around the entrance and directed inwardly 
towards the inside of the trap. Preferably the entrance is of converging 
cross section from outside towards the inside, terminating in the fingers 
which are directed inwardly. On the other hand certain authorities insist 
on traps which provide for the eventual escape of crustaceans from those 
traps which have been lost on the bottom for example due to parting of 
haulage cables and cords. 
The positioning of the entrance to the trap also plays an important part 
since if the traps happens to fall on the sea bottom with the entrance 
lying on the bottom the entrance may be partially or completely occluded 
and prevent crustaceans from entering the trap. Thus preferably more than 
one entrance is provided, in diametrically opposed surfaces of the trap. 
Thus if one surface rests on the bottom then the probability is that the 
other surface will be exposed for access of crustaceans. Preferably 
further the overall proportions of the trap are such that the length 
dimension substantially exceeds the height and width dimensions of the 
trap so that the trap is of generally elongated form and in these 
proportions the trap is preferably provided with two entrances located in 
the walls which are defined by the width and height of the trap that is 
the end walls or the walls which are generally orthogonal to the longest 
dimension of the trap. This feature is preferably combined with the 
provision of weights in the trap located against one of the side walls of 
the trap. The effect of these weights is to tend to make the trap unstable 
if it happens to initially fall on one of its end walls, that is with its 
longest dimension upright and the trap will tend to then tip over and fall 
down with its longest dimension substantially horizontal thus leaving the 
end wall substantially upright and their openings generally unobscured for 
access of crustaceans. This arrangement also has the advantage that the 
entrances will be at a readily accessible level for the crustaceans such 
as lobsters which generally tend to crawl over the bottom rather than 
providing the entrance on a surface which would tend to be at the top of 
the trap when its rests on the sea bottom thus requiring that the lobsters 
for example will have to crawl up the side of the trap onto the top and 
only then go into the entrance. Furthermore an important feature is 
preferably that the wall which contains the entrance is given a mesh 
construction which is well adapted to serve as a ladder for the crustacean 
to climp up to the entrance to the trap. Thus the spacing between the 
members of the mesh is preferably quite small for example of the order of 
14 mm or less so that the crutacean is easily able to step from one 
transverse element of the mesh to the one above and thus easily reach the 
entrance to the trap. 
All of these features, any one of which may provide only a marginal 
advantage together are important because for a given time period of the 
trap on the bottom of the sea it will accumulate a larger number of 
crustaceans and when it is hauled up it will tend to lose fewer from the 
trap. Alternatively the trap can be left on the bottom for a shorter 
period of hours than is the practice at present and still have the same 
yield. This is important not merely from the point of view of obtaining a 
given catch in a shorter number of hours but also because the fishing is 
subject to storms and other crises, occurrences such as the unexpected 
appearance of a very deep draught ocean going ship such as an oil tanker. 
The longer the period at which the traps are left on the sea bottom the 
longer they are exposed to a risk of this kind and therefore the larger 
the probability over a season that calamities will occur. Generally when a 
storm arises the traps have to be hauled up quickly so as to save them and 
ensure that an entire cable or hawser carrying many traps is not lost. The 
same applies if a deep draught ocean going vessel approaches. 
The containing of the bait in the trap is always an important feature and 
the container for the bait is preferably an open mesh basket. The reason 
for this is to permit sea lice or mites to reach the bait and the breaking 
up of the bait which results, to freely allow tiny particles of bait to 
float into the surrounding water which may be an important mechanism for 
the attraction of crustaceans to the trap. Preferably the bait basket is 
adapted to be let into one wall of the trap, preferably a wall which will 
lie on the sea bottom. Thus the bait basket is preferably aligned on the 
same wall as the wall on which the weights for the trap are provided. The 
bait basket may furthermore double as a hatch so that when the bait basket 
is removed an opening is left in the wall through which the trapped 
crustaceans may be removed from the trap. 
A preferred overall form for the trap is a hollow prismatic hexagonal form, 
the walls all being formed of a suitable mesh. The cage is preferably 
collapsible by means of the end walls being separate pieces and the side 
walls being divided into two halves each generally channel shaped which 
may be nested for compact packing of the cage. The two halves will be 
connected by suitable arrangement of tongues and grooves, the end walls 
being keyed in position when the halves of the side walls are joined. 
The weights for the trap can simply comprise a brick tied onto the side 
walls of the trap one at each end thereof. Alternatively special provision 
can be made for other types of weights. 
A further factor which has been inferred from experience is that the more 
bait which is used the greater the attraction and accordingly preferably 
provision is made for the location of more than one piece of bait suitable 
inside the trap. Naturally the bait must be so located that it cannot be 
reached from outside the trap by crustaceans and is preferably located so 
that it tends to lead the crustaceans to the entrance of the trap. A 
practical arrangement in one embodiment is to provide two bait baskets in 
the trap. 
It is convenient for the openings in the mesh of the cage or a special 
opening to be of such a size that they allow crustaceans to escape which 
are smaller than the legal limit which may be caught. This is preferable 
because if the undersized crustaceans are first raised to the surface and 
only then discarded they do tend to deteriorate from being raised to the 
surface and it is believed very often die after they have been returned to 
the sea. It will be appreciated this type of deep sea fishing is commonly 
carried out at sixty to eighty fathoms by the long line method in 
accordance with which a large number of traps are attached to a long 
hawser which is lowered from the fishing vessel. It is convenient to 
provide a hatch in an upper surface of the trap for removal of the catch. 
This hatch can be given a lid which can be fixed in the hatch (e.g. by a 
bayonet type connection) and easily removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIGS. 1 to 3 the traps comprises four separate parts from which 
it is assembled and into which it can be disassembled at any stage. The 
overall shape of the trap as can be seen approximates to a hollow 
hexagonal prism with all of the walls being an open mesh. The side walls 
are divided into two trough shaped parts 1 and 2 respectively and the two 
end walls 3 and 4 are flat and contain the entrances 5 and 6 respectively. 
The two side walls parts 1 and 2 are of trough like shape and can be 
nested together for compact packing. They are moreover identical with each 
other save that the bottom part 2 is adapted to receive a bait basket 9 
for carrying bait. The two halves 1 and 2 can be joined together by means 
of tabs 7 locking into sockets 8 in a manner which permits releasing them 
again with the use of for example a screwdriver. Before the two parts 1 
and 2 are joined together however the end walls 3 and 4 are notched into 
channels 60 which face inwardly at the opposite ends of the parts 1 and 2. 
When the parts 1 and 2 are thus joined together the end walls 3 and 4 are 
locked into position in the channels 60. Part 2 as stated is adapted to 
receive a bait basket 9 (visible in FIG. 2) the lower surface 10 of which 
serves also as a closure hatch for a circular opening provided in the part 
2. If the bait basket 9 is removed this thus leaves an opening in the part 
2 through which the catch can be removed. Weights 11 and 12 are also fixed 
onto the bottom of the part 2. As can be seen the end walls 3 and 4 
comprise a mesh in which the cross bars are carefully spaced at desirable 
distances apart indicated in FIG. 1 by the distance indication 13. This 
amount is chosen so as to make it easy for lobsters for example to climb 
up the end wall and enter the entrance 5 or 6. The shape of the entrances 
5 and 6 is conical as can be seen and fingers 14 and 15 project inwardly 
at the entrances 5 and 6 respectively. These fingers are designed to tend 
to collapse together but because of their direction are easily pushed open 
if necessary by a crustacean entering the trap. The contrary applies if it 
tries to leave the trap when the fingers will tend to get hooked in the 
creature and deter it from such attempts. As can be seen apart from being 
frusto-conical the entrances also tend to raise the internal entrance some 
distance from the bait basket 9 so that the animal is obliged to enter the 
trap fully in order to get at the bait. Also the closure member 10 
constituting a lower wall of the bait basket can be made solid if desired 
so as to prevent access to the bait for a crustacean from the outside of 
the trap. This external wall can also be of larger diameter than the 
diameter of the bait basket itself for the same reason. Preferably the 
bait basket 9 is some distance (one to two inches) above the base for the 
same reason. 
As shown in FIG. 4 for example two bait boxes 9a and 9b can be provided, 
other features being the same and being indicated accordingly with the 
same numerals. This will permit more bait to be placed in the trap which 
is believed to provide a stronger attraction and may be preferred for this 
reason. 
The construction of the framework is such to give it strength and 
accordingly the use of ribs and structural cross sections for the mesh is 
resorted to. 
The embodiment of FIG. 4 can also be used by removing the bait basket 9(b) 
and replacing it with a removable lid (not shown). This lid can be useful 
for removing the catch from the trap--alternatively the bait box serves as 
a lid and when removed allows removal of the bait. 
In FIG. 5 an embodiment is shown in "exploded" view showing several 
alternative components of the trap. The trap comprises two trough shaped 
parts 1 and 2 again, and two end walls having entrances 5 and 6 
respectively. The upper trough shaped part 1 has a hole 16 in which a lid 
17 can be fixed by means of a bayonet type connection. A bait basket 18 
comprises two halves joined together on a pin 19; the lower end of the pin 
19 is pressed into a socket in the inner surface of the floor of the lower 
trough shaped parts 2 when the trap is assembled. Two bars 20 and 21 are 
fixed (removably) in the lower trough shaped part 2, projecting 
transversely from the sides of the part and located near opposite ends of 
it. They are extruded plastic rectangular-section tubes which are filled 
with set concrete. 
This FIG. 5 shows an alternative end wall 22 which may replace one of the 
end walls 2 or 3. It also shows a frusto conical cylinder 23 which may 
replace the lid 17. This opening may be insisted on by some authorities so 
as to ensure an escape from the trap after a time if the trap is lost on 
the bottom of the sea. 
FIGS. 6 to 13 inclusive show the trap of FIG. 5 in greater detail. In FIG. 
6 a lower trough 2 is shown in end elevation. It is moulded with five 
tongues 7 along one side and five grooves 8 along the other. The upper 
trough which will fit it is identical except for the hole 16 which is 
moulded by substituting a special insert in the mould. The tongue 7 will 
fit into grooves 8 of an upper trough. A key 24 can lock in a hole 25. The 
tongue 7 has an important feature shown in FIG. 8 in particular, which is 
a central prong 26 opposite the key 24. This prong 26 ensures a snug fit 
of the tongue 7 in the socket 8 while the outer prongs 27 and 28, being 
shorter, do not exert a force on the corners 8a of the socket 8 which 
might weaken the socket. 
FIG. 6 shows the bait basket in more detail. The rod 19 has a handle 19(a) 
for grasping and pulling the bait basket out of the trap and re-inserting 
it. The rod 19 has a circumferential groove 19(b) which is engaged by 
teeth 29 of a bush 30 which is moulded integrally with the lower part 2 of 
the trap. The two halves forming the oblate spheriodal shaped bait basket 
18 are held together by clipping into similar circumferential grooves 30 
and 31 in the rod 19. The height 32 of the bait basket 18 above the bottom 
of the trap 2 is functionally important and may be varied by providing 
alternative circumferential grooves to the groove 19(b). 
The ballast bars 20 may for example weigh 10 kg each and they are attached 
by two bolts each 33 and 34. A possible alternative way of attaching the 
ballast is indicated in FIG. 3. Here the ballast 35 and 36 is again two 
elongated formations, arranged, however, longitudinally with respect to 
the trap instead of transversely. The ballast 35 and 36 is clipped into 
place with suitable formations, but if greater strength is needed bolts or 
binding wires can be used. (The bricks 11 shown in FIGS. 1, 2 and 4 are a 
further alternative). The bars 20 are extruded plastic square tubes in 
which concrete is cast--they are easily replaceable if damaged, and are 
economical to produce. 
FIG. 7 is for purposes of illustration divided into a view on the left of 
the center line of the upper part 1 of the trap and on the right of the 
lower part 2 of the trap. This shows how the upper part 2 has the opening 
16 moulded in it, while the lower part 1 has a continuous bottom mesh. The 
opening 16 is bordered by a circular flange 37 which has rebates 38 in it 
for entry of bayonet type connection formations 39 in the frusto conical 
funnel 40 or lid 41 (see FIGS. 12 and 13, respectively). Underneath the 
flange 37 retaining grooves 42 are moulded. 
In FIGS. 9, 10 and 11 the side entrance 5 is shown in more detail; it has 
several important features for its function. The entrance 5 is formed by a 
moulded mesh 43 of converging funnel shape, larger size at the end wall 3 
and smaller size inwardly of the end wall. The mesh 43 terminates in 
fingers 44 which are convergent in conformity with the funnel shape. The 
mesh 43 comprises throughout transverse (i.e. cirumferentially oriented) 
connecting parts 45 which are spaced apart from each other by a distance 
46 which is carefully determined to suit the crawling characteristics of a 
crayfish, and longitudinal (i.e. axially oriented) connecting parts 47 
which terminate in the fingers 44. The transverse connecting parts 45 are 
staggered with respect to each other between different longitudinal 
connecting parts, giving a resilient mesh. The angle of taper of the upper 
and side portions of the funnel is 15.degree. but the angle of taper of 
the lower portion is 40.degree., having the result that the inner entrance 
48 is raised up sufficiently to locate it above the level of the bait 
basket 18. This is indicated in FIG. 6 and in FIG. 11. This factor and the 
horizontal distance of the bait basket from the inner entrance are pitched 
at enticing the crustacean sufficiently far into the trap that it tends to 
pass right through the entrance or sufficient of its body to protrude into 
the trap from the inner entrance 48 of the funnel 5 for the fingers 44 to 
prevent it retracing its steps out of the trap. The funnel shaped entrance 
5 is moreover not of circular conical shape but is flattened at top and 
bottom. This gives a bottom portion 49 which is wide and flat, providing 
an accommodating surface for the crustacean to walk up. 
The distance 46 is not less than 10 mm and not more than 50 mm, preferably 
about 30 mm, at least on the lower portion. 
FIG. 12 shows a frusto conical cylinder 50 which can be inserted in the 
opening 16 in the upper part of the trap. It can serve several useful 
functions including providing a ready opening for removing the catch, for 
removing and replacing the bait basket, and as a means of escape from the 
trap if it is lost on the sea bottom due for example to a hawser parting. 
This escape is important because if trapped crustaceans eventually die in 
a lost trap they rot and contaminate the surrounding water, driving away 
living crustaceans. 
FIG. 13 shows a lid which can be fixed (removably) in the opening 16, 
having the same bayonet connection lugs 39. 
FIG. 14 is a schematic illustration of one way of using the traps. The 
traps 51 all rest on the sea bottom 52. A main hawser 53 is located by two 
buoys 54 and each trap 51 is tied to the main hawser by ropes 55. 
The hexagonal prismatic shape is considered to be important as it allows 
the trap to right itself under the weight of the ballast. It is felt that 
the shape allows the trap to wedge in coral and rock with a reduced danger 
of getting caught up. 
The frusto conical cylinder 50, shown in FIG. 12, may have one or two slits 
56 in its wall as shown. The slit 56 can be used to tie bait to the outer 
surface of the cylinder inside the trap; the bait is tied to the end of a 
length of string, the string is hooked into the slit with the bait outside 
the cylinder (inside the trap) and the free end of the string is pulled 
tight and secured. 
The cylinder 50 can of course serve as an entrance for crustaceans. The 
relative effectiveness of this entrance compared to the side entrances has 
been tested using six test traps, three having side entrances 5 only (with 
lid 17 in the opening 16) and three having both closed end walls 22 and 
cylinder 23 in the hole 16. Initially tests were done in tanks and later 
at sea. Each trap, fully baited, was placed into a separate tank for 30 
minutes simultaneously. Then the traps were rebaited and interchanged 
between tanks for a further 30 minute period, as far as possible 
subjecting all traps to identical conditions. The catches were: 
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Top (cylinder) 
Side 
Date Entrance Trap Entrance Trap 
______________________________________ 
4.12.76 1 lobster 12 lobsters 
14.12.76: 
Tank 1 12 lobsters 18 lobsters 
Tank 2 12 lobsters 6 lobsters 
Tank 3 4 lobsters 16 lobsters 
Tank 4 3 lobsters 18 lobsters 
Totals: 32 lobsters 70 lobsters 
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Sea tests of two traps: 
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Top (cylinder) Side 
Date Entrance Trap Entrance Trap 
______________________________________ 
8.12.76 2 20 
16/17.12.76 
1 4 
0 1 
Totals: 3 25 
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These results suggest that the side entrance is much more effective.