GB2480437A

GB2480437A - Method and apparatus for exterminating crustaceans

Info

Publication number: GB2480437A
Application number: GB1008175A
Authority: GB
Inventors: Robin Mckimm
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-05-17
Filing date: 2010-05-17
Publication date: 2011-11-23
Anticipated expiration: 2030-05-17
Also published as: GB201008175D0; GB2480437B

Abstract

A method of exterminating crustaceans in particular invasive crayfish species, in a freshwater watercourse, such as a shallow stream, said method comprising placing electrodes into said watercourse and applying a plurality of short pulses of high energy electricity to said electrodes. Said pulses may have a duration of around 5ms. In a preferred embodiment said plurality of pulses are applied to said electrodes over periods of time separated by dormant periods whereby crustaceans that may be in burrows or otherwise out of the water during a first period of pulses are exterminated during a subsequent period of pulses when they have re-entered the water, typically to feed on crustaceans killed during a preceding period of pulses. Also disclosed is apparatus for use in the afore described method.

Description

Method and apparatus for exterminating crustaceans This invention relates to a method and apparatus for exterminating crustaceans, in particular invasive crayfish species, although the present invention may be applicable to many other species of invasive crustaceans, such as mitten crab.

Crayfish are small crustaceans that resemble small lobsters. They are found in freshwater aquatic systems and some species are known to be able to travel over land to new areas. Crayfish are typically found in upper land streams, in shallow water.

Some species of crayfish have become invasive in many parts of the world. In the UK new species of crayfish have become established, in particular the American Signal crayfish, and these species have caused widespread ecological damage. Invasive crayfish species prey on small fish and fish eggs and, at sufficient density, can effectively exterminate all other life in a fresh water stream. In particular, invasive species of crayfish endanger the already threatened white clawed crayfish, native to the UK and Europe. American crayfish species can be carriers of the so-called crayfish plague' -a disease caused by a fungus. The plague' does the American crayfish little apparent harm but is lethal to European species such as the white-clawed crayfish. Crayfish plague carried by signal crayfish is one of the main reasons for the collapse and extinction of native white-clawed crayfish across Europe, including in Britain.

Many species of invasive crayfish also cause damage to river systems by constructing burrows in the banks leaving them prone to collapse.

Invasive species of crayfish are extremely difficult to eradicate once they have established viable populations in a waterway, such as a stream or river. Existing attempts to deal with invasive crayfish in freshwater streams and rivers have typically involved the use of chemical agents intended to effectively sterilise a body of freshwater. However, such methods carry a risk of environmental damage beyond the intended target species and are particularly difficult to utilise effectively in shallow often fast flowing freshwater streams.

While electric fishing techniques, involving the application of electricity to the water to stun fish, have been used to repel and/or kill fish, such techniques have not been considered suitable for killing hard shell crustaceans due to the much higher current/voltage required to affect hard shelled crustaceans.

In flowing water, the size of the power supply required to affect crustaceans using traditional electric fishing techniques makes the application of known electric fishing techniques impractical as a solution to the problem of invasive crustacean species in fast flowing freshwater streams.

According to a present invention there is provided a method of exterminating crustaceans, in particular invasive crayfish species, in a freshwater watercourse, such as a shallow stream, said method comprising placing electrodes into said watercourse and applying a plurality of short pulses of high energy electricity to said electrodes. Said pulses may have a duration of around 5ms.

In a preferred embodiment said plurality of pulses are applied to said electrodes over periods of time separated by dormant periods whereby crustaceans that may be in burrows or otherwise out of the water during a first period of pulses are exterminated during a subsequent period of pulses when they have re-entered the water, typically to feed on crustaceans killed during a preceding period of pulses.

Preferably a plurality of arrays of electrodes are placed into said watercourse at spaced locations therealong, each array comprising at least one cathode and at least one anode. Preferably a plurality of pulses are applied to each array of electrodes in turn during subsequent time intervals.

According to a further aspect of the present invention there is provided an apparatus for exterminating crustaceans, in particular invasive crayfish species, said apparatus comprises a plurality of electrodes to be placed along a freshwater watercourse, at least one power supply and at least one controller connected to said at least one power supply for applying short pulses of high energy electricity to said plurality of pairs of electrodes to kill crustaceans located in said watercourse.

Preferably a plurality of arrays of electrodes are provided to be placed into said watercourse at spaced locations therealong, each array of electrodes comprising at least one cathode and at least one anode. Preferably said at least one controller is programmed to apply a plurality of pulses to each array of electrodes in turn during subsequent time intervals. Preferably each array of electrodes comprises a single cathode located inbetween a pair of spaced apart anodes. The cathode may be arranged in the centre of a watercourse and the anodes may be located on either side of the watercourse.

A method and apparatus for exterminating crustaceans, in particular invasive crayfish species, in accordance with an embodiment of the present invention will now be described, by way of example only.

When American Signal Crayfish have become established in a freshwater stream all other marine life are likely to have been wiped out. Initially a geographical survey is carried out to establish the dimensions of the pools and riffles of the stream. The proposed length of the stream to be cleared of crayfish is first netted upstream and fished to chase out any remaining fish before being netted ay a lower end to enclose the stream and trap the crayfish therein. Any remaining fish may be initially cleared by the use of lower energy electric fishing techniques, which stun and/or repel fish whilst having no effect on the hard shelled crustaceans in the water.

A series of electrode arrays are placed in the stream at spaced locations along the length to be cleared and are multiplexed to a power supply controller, typically in groups of ten electrode arrays to a respective controller. Each electrode array comprises at least one anode and at least one cathode. In a preferred emodiment a central cathode is provided to be located in a central region of the stream, on either side of which are provided respective anodes located adjacent each bank of the stream. It has been found that crayfish tend to move towards the cathode when electricity is supplied to the electrodes. Therefore such arrangement of anodes and a single cathode tends to keep the crayfish in the water.

Each controller is connected to a power supply in the form of a generator, typically a lightweight unit that can support around 120 metres of stream length.

Four or five such series of electrode arrays, each with its own controller and power supply, may be used in a chain along the length of stream to be cleared, although the number used will depend upon the length of the watercourse to be cleared.

The electrode arrays can be placed and adjusted for maximum performance in around one day.

From such time no persons need to be in or near the water, which allows the stream to recover from any silt disturbance.

A safety zone is set up around the banks of the stream with emergency stop buttons every 30 metres to enable the process to be stopped if there is any unauthorised entry into the safety zone.

Once the cabling is completed and checked, the generators are started and the controllers are switched on. The controllers are programmed to apply short bursts of pulsed high energy electricity, each pulse having a duration of around 5ms, to each array of electrodes in turn. Around 100 to 150 pulses may be applied to each electrode array in turn along the length of the stream.

The controllers use capacitors and voltage multiplication circuitry to apply very high energy, very short pulses to the electrode arrays, supplying sufficient energy to kill any crustaceans in the water while requiring a relatively small power supply.

The process may be run continuously over a four day period, by which time no fully mobile crayfish should be observed. By repeating the period of short pulses of electricity to the water over time, any crustacean that may be out of the water or in burrows during one period will be killed once they re-enter the water during a subsequent period.

Whilst the present invention has been described with particular reference to the extermination of invasive crayfish species, the method and apparatus in accordance with the present invention may be used to eradicate invasive crustacean species from any fresh water waterways.

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.

Claims

Claims 1. A method of exterminating crustaceans, in particular invasive crayfish species, in a freshwater watercourse, such as a shallow stream, said method comprising placing electrodes into said watercourse and applying a plurality of short pulses of high energy electricity to said electrodes.
2. A method as claimed in claim 1, wherein said pulses have a duration of around 5ms.
3. A method as claimed in claim 1 or claim 2, wherein said plurality of pulses are applied to said electrodes over periods of time separated by dormant periods whereby crustaceans that may be in burrows or otherwise out of the water during a first period of pulses are exterminated during a subsequent period of pulses when they have re-entered the water, typically to feed on crustaceans killed during a preceding period of pulses.
4. A method as claimed in any preceding claims, wherein a plurality of arrays of electrodes are placed into said watercourse at spaced locations therealong, each array comprising at least one cathode and at least one anode.
5. A method as claimed in claim 4, wherein a plurality of pulses are applied to each array of electrodes in turn during subsequent time intervals.
6. An apparatus for exterminating crustaceans, in particular invasive crayfish species, said CO apparatus comprises a plurality of electrodes to be placed along a freshwater watercourse, at least C\J one power supply and at least one controller connected to said at least one power supply for applying short pulses of high energy electricity to said plurality of pairs of electrodes to kill crustaceans located in said watercourse.
7. An apparatus as claimed in claim 6, wherein a plurality of arrays of electrodes are provided to be placed into said watercourse at spaced locations therealong, each array of electrodes comprising at least one cathode and at least one anode.
8. An apparatus as claimed in claim 7, wherein said at least one controller is programmed to apply a plurality of pulses to each array of electrodes in turn during subsequent time intervals.
9. An apparatus as claimed in claim 7 or claim 8, wherein each array of electrodes comprises a single cathode located inbetween a pair of spaced apart anodes.
10. An apparatus as claimed in claim 9, wherein the cathode may be arranged in the centre of a watercourse and the anodes may be located on either side of the watercourse.