GB2281181A - Marine trap - Google Patents

Abstract

A marine trap includes: a frame having a base 11, an inlet 9 of smaller dimension to the base, and a bait holder 4 supported within the inlet; and at least a side wall 6 formed between the base and inlet to form a basket type trap having a substantially open inlet; wherein the side wall is inclined leading from the base to the inlet. <IMAGE>

Description

A MARINE TRAP This invention relates generally to the field of traps for vermin marine life, and in particular it relates to a trap specific for star fish.

The ecology of marine life is a fine balance that is readily disturbed by the presence of introduced material, whether that material be pollutants or an introduced species of marine life. Star fish, for example the Northern Pacific sea star are an example of such an introduced specie, that in plague proportions, can reap untold damage upon the marine environment.

The Northern Pacific sea star for example, consumes protein containing tissue, such as animal and plant tissue. In particular, it is destructive toward molluscs such as oysters, muscles, clams, and possibly upon juvenile crustaceans such as crabs or lobsters. The star fish in plague proportion may be responsible for the destnuction of commercial marine farming operations such as commercial oyster beds.

The star fish is able to multiply rapidly and when introduced into certain areas, it has no known natural predators. Accordingly, it is able to rapidly reach plague proportions as has been known to be the case in certain areas around Australia.

In order to control the spread of such star fish, simply catching the star fish by manual means using divers, is relatively ineffective due to the vast area which star fish may spread. Substantially enclosed traps, for example traps that include a narrow entrance where the star fish, may enter readily, and find difficult to leave, are effective for trapping the star fish, but also trap other marine life that are able to enter into the trap. Such substantially enclosed traps are therefore considered unsuitable for large scale trapping of star fish, as they are considered destructive to the marine environment.

It is an object of the present invention to overcome or at least alleviate one or more of the difficulties associated with the prior art.

The present invention resides in a marine trap including: a frame having a base, an inlet of smaller dimension to the base, and a bait holder supported within the inlet; and at least a side wall formed between the base and inlet to form a basket type trap having a substantially open inlet; wherein the side wall is inclined leading from the base to the inlet.

It is a feature of the invention that the inlet to the trap is substantially open. In this sense, it is only the marine life that is unable to swim out of the trap that will remain in the trap. Essentially, star fish are confined to crawling along the ocean bed, and apart from simply drifting with the current, do not generally swim.

The trap of the invention is designed to sit on the marine bed. The base is defined by a base ring, while the inlet is defined by an inlet ring. Generally, these rings are circular and are placed in a concentric relationship to each other. Other configurations, for example square or multisided traps are however, also contemplated.

The inlet ring and the base ring may be connected by supporting rods to provide strength to the trap. In the preferred form, where the base and inlet are formed from circular rings, the side wall will also be of a continuous circumferential wall.

The side wall may be formed of a small mesh plastic netting which stretches from the inlet ring to the base ring and across the base to form a floor in the trap.

The bait holder may be any suitable holder that is able to support bait which is attractive to the vermin marine life. It has been found that for the Northern Pacific sea star, that fish carcass, such as salmon heads are appropriate.

The bait holder may be formed by supporting rods extending from the inlet ring to hold the bait at approximately the same level as the inlet. The supporting rods should include a holder such as a ring, that is able to support a canister, and should be of a narrow diameter so as not to provide an opportunity for star fish to crawl along the supporting rods. The bait may be held within the canister, which may be readily removed in order to replace the bait when desired.

The inlet of the trap is of such a size, that the bait may be held at a sufficient distance from the inlet ring, such that the star fish cannot reach the bait from the inlet ring.

As the star fish, and in particular the Northern Pacific sea star, are essentially crawling creatures, the star fish are able to crawl up the side wall of the trap from the base to the inlet. In their endeavours to reach the bait, they will generally fall through the inlet and into the trap. In this sense, the bait should be held at a sufficient distance from the inlet ring to deny the star fish the opportunity to reach the bait. Generally this distance should at least be 10 cm, preferable 20 cm. The canister is most preferably held at an equidistance from the inlet ring, at the same level as the inlet ring.

As the intemal surface of the wall slopes inward, the star fish are unable to crawl up the interior surface and is trapped within the trap. Other marine life that may have swam into the trap are able to escape as the inlet is of such a diameter that allows such creatures to readily swim out of the trap.

The inlet may have a diameter of from 20 cm to 120 cm but is generally in the order of from 50 cm to 80 cm. This generally provides sufficient room for other marine life to escape from the trap, should they have entered the trap. The base may generally be of a diameter of from 50 cm to 2 m, but is generally in the order of from 25 cm to 1.25 m. The height of this trap is preferred to be in the range of from 5 cm to 70 cm, most preferably, about 15 cm.

The dimensions of the base should always be larger than the inlet. This creates an incline in the side wall leading from the base to the inlet. The incline should be of such a gradient so as to allow a star fish, such as the Northern Pacific Sea Star to crawl up the external wall of the trap. Preferably the incline of the side wall is from 15 to 500, most preferably about 30".

The present invention also resides in a method of trapping star fish said method including the steps of: i) providing a marine trap including: a frame having a base1 an inlet of smaller dimension to the base, and a bait holder supported within the inlet; and at least a side wall formed between the base and inlet to form a basket type trap having a substantially open inlet; wherein the side wall is inclined leading from the base to the inlet, ii) placing bait within the bait holder; and iii) submerging the trap into the marine environment, such that the base frame rests on the marine bed.

The trap itself may also include ropes attached to the frame, preferably at the level of the inlet. The ropes are used to raise and lower the traps from the marine bed.

It will be convenient to describe the invention with reference to the accompanying drawings. It should be understood however that the drawings are merely illustrative of the present invention and the scope thereof should not be considered to be limited thereto.

Figure 1 is illustrative of a plan view of a star fish trap in accordance with the invention.

Figure 2 is illustrative of a side view of the same trap.

Figure 3 is illustrative of a perspective view, of a trap inclusive of a canister within the bait holder.

Figure 1 illustrates a trap (1) in accordance with the invention with the relative diameters of the base (11) and the inlet (9) clearly shown. The base (11) and inlet (9) 2re defined by concentric base ring (2) and inlet ring (3). The bait holder is formed by supporting rods (5), having bait holder ring (4) centrally located within the inlet and concentric with the base and inlet rings. The bait holder is located at approximately the same level as the inlet ring.

The side wall (6) is of a continuous circumferential wall and is formed of mesh material extending between the base ring (2) and the inlet ring (3). The base ring and inlet ring are held in position by rods (7) between the base and the inlet.

As is illustrated in figure 2, the side walls (6) are inclined at a gradient of about 30". In use, the base sits on the floor of the ocean bed and a star fish is able to crawl up the inclined plane of the extemal side wall. In their endeavour to reach the bait, the star fish will fall through inlet (9). The trap itself may be raised from the ocean bed, by raising a rope, (not illustrated) attached to either the inlet ring (3) or supporting rods (5).

Figure 3 illustrates a canister (8), placed within the bait holder ring (4) which is not illustrated in figures 1 and 2. The canister holds the bait. The bait canister is readily removed and replaced for ease in changing the bait.

The internal slope of the side walls does not allow the star fish to crawl up the wall and as such are unable to escape from the trap. The size of the inlet does however enable other creatures to readily swim from the trap, and accordingly the trap does not have a significant impact to the marine life of the area.

It should be understood, that the above description is merely illustrative of the present invention. Any modification or alteration thereto that does not depart from the spirit or ambit of the invention should also be considered as part of the invention.

Claims (12)

The claims defining the invention are as follows:

1. A marine trap including: a frame having a base, an inlet of smaller dimension to the base, and a bait holder supported within the inlet; and at least a side wall formed between the base and inlet to form a basket type trap having a substantially open inlet; wherein the side wall is inclined leading from the base to the inlet.

2, A trap according to claim 1 wherein the inlet has a diameter of between 20 cm to 120 cm.

3. A trap according to claim 1 wherein the base and inlet are defined by a base ring and an inlet ring, positioned in a concentric relationship to each other, and the side wall is a continuous circumferential wall.

4. A trap according to claim 1 or 2 wherein the side wall is formed from a small mesh plastic netting, which extends across the base to form a floor for the trap.

5. A trap according to claim 3 wherein the bait holder consists of supporting rods, extending from the inlet ring, said supporting rods defining a retaining means, the retaining means being adapted to support a canister centrally within the inlet.

6. A trap according to any one of the preceding claims, wherein the trap is specifically constructed to trap star fish.

7. A trap according to claim 1 wherein the incline of the side wall is of such an angle so as to allow a star fish to climb the extemal surface of the wall, but unable to climb the intemal surface of the side wall.

8. A trap according to claim 1 wherein the incline of the side wall is between 150 and 50O.

9. A trap according to claim 8 wherein the incline of the side wall is about 30 .

10. A trap according to claim 1, wherein the frame includes a plurality of supporting struts between the base and the inlet to support the side wall or walls.

11. A method of trapping star fish in a marine environment, said method including the steps of: (i) providing a marine trap including: a frame having a base, an inlet of smaller dimension to the base, and a bait holder supported within the inlet; and at least a side wall formed between the base and inlet to form a basket type trap having a substantially open inlet; wherein the side wall is inclined leading from the base to the inlet, (ii) placing bait within the bait holder; and (iii) submerging the trap into the marine environment, such that the base rests on the marine bed.

12. A trap according to any one of the preceding claims, substantially as hereinbefore described with reference to any one of the drawings.