As many of you know I have a background in fish that stretches further than mongery. One of the most enjoyable parts of an old job was to get wet and dirty with the fish. I wrote the account below for my old fisheries management website that details how we removed the fish out of those canals you all drive over – enjoy.
These three images show why water is removed from canal sections. The picture at the top was taken at
There are various ways to de-water a section of canal. Two solid barriers are required; therefore, short pounds with adjoining locks are ideal. Unfortunately this scenario is rare so other water retaining methods need to be employed. Stop planks can be placed in the purpose cut grooves located underneath bridges.
When the use of stop planks and lock gates as dams is not possible temporary structures are required to hold vast quantities of water back. The common choice is the use of an impervious fabric membrane attached to a free standing steel support system. These Portadams are fixed across the canal, shown in the above pictures (
These two images show the completed dams in place. At the top is the dam at Horton on the
The concept is simple. A small boat is pulled along the canal section behind 3 - 4 electrofishermen. The boat contains a generator linked to a control box. From this box run two hand held anodes and one cathode; this is connected to the rear of the boat. 240 volts and 6 amperes are generated and a direct current is implemented. The current is applied via the use of two "dead man's switches", one on each anode. Also within the boat there can be up to four large bins of water which hold the captured fish.; each bin has an aerator pipe that is connected to a battery powered air pump. Up to three stop nets of various sizes can also be carried. Each bin can hold up to 100lbs of large fish or 50lbs of small before they need to be emptied.
With a three man team the outside men will control the anodes, sweeping left to right, whilst the centre man controls the boat. Each team member will also use a small net to collect stunned fish. Large nets are held in the boat if substantial amounts of fish are encountered. If a forth team member is utilized the man can be placed in one of two positions. If the presented canal still has a wide area of water the forth man would be suited at the front alongside his team members. However, if conditions are either 1) good (narrow); he can follow behind netting the smaller fish that rise late (usually perch & ruffe), or 2) Very silty; he will probably have to push the boat if the substrate offers difficult walking conditions.
The length of the canal section is the usual determining factor that dictates where the job will commence. It is beneficial to work into clear water, therefore, if groundwater is entering on the length then the electrofishing should always take place towards the source. However, if the section is being pumped or drained whilst the rescue is in progress then working away from the running pumps or open paddles is again preferable. Incidentally, it is not always possible to fish into clear water as accesses are not always available to launch the boat from.
Once a suitable area has been found for launching, and the water flows and colour has been assessed, the work can commence. The process is fairly simple, however, there is one hard and fast rule. No matter what conditions are presented the job is not complete until all of the fish have been removed. This could mean up to four runs of the whole length; usually two complete runs are sufficient to remove the fish.
These three pictures show a successful fish rescue in progress at Yelvertoft on the Leicester Line of the
The picture on the top gives a clear view of the contents inside the electrofishing boat. The electric box can be seen on the front of the boat (grey) with the yellow cables of each anode attached via specialised waterproof four pin plugs; the UK standard colour for these plugs is blue/grey. The box is connected to the generator (red) which is situated in the rear of the boat. The generator can usually be found in the rear as it counteracts the water bins (yellow) in the front. To the left of the generator the air pump can been seen; the pipes and diffusers from this pump run to the water bins. There can be up to five bins in the boat at any given time. The picture on the bottom shows an electrofisherman (that's me) working an anode whilst netting small roach. He can be seen in a full dry suit and gloves, the only realistic clothing to carry out fish rescues in.
These two pictures show the working conditions in and around solid structures. The image above shows a simple lock system that requires navigating before the next section can be fished. Note the large amount of ice in the lock; never assume all jobs are warm and fun!! The second image gives an excellent view when approaching a portadam.
On occasions it is possible to carry out a drag down with a net before a dam is put in place. These pictures, taken at
A canal drag-down is usually undertaken with a small seine net rarely exceeding 25 metres in length. Again the concept is simple. The net needs to be a sufficient depth to cope with the drag-down; therefore, a net exceeding 1 metre at the deepest point of the canal is required. A man works each bank from the water by pulling the net towards the dam frame; it is imperative that the net stays of equal distance between workmen. The middle of the net needs to be in the centre of the canal. The images above show the net being pulled towards the dam frame (top) and of the excess net bulging behind as the net is pulled (centre). Incidentally, this method is not always feasible as dragging nets is both time consuming and energy sapping. In reality very long stretches cannot be netted as the efficiency decreases over long lengths due to snags.
As a net is pulled through a section numerous obstacles will be encountered. Many areas of canal are used as dumping grounds for all types of rubbish; this will affect the efficiency of any drag-down. As these snags are uncovered the leads attached to the base of the net need careful manoeuvring over the obstacle. The worst type of snags include bicycles, tree branches and brambles and the mandatory car engine. However, if the canal is not to deep most problems can be solved. This image (bottom) shows a large branch being removed from the net.
These two images taken at
Occasionally some very difficult conditions are put in front of a rescue procedure. As many rescues are linked with hugely expensive civil engineering projects the time scale available is always short. Therefore, problems other than deep water, which cannot be solved, require tackling and over coming. These two images were taken in January 2002 at Yelvertoft on the Grand Union canal Leicester Line. This stretch was approximately 2200 metres in length and when presented had 2 inches of ice across the surface. For obvious reasons a rescue could not be undertaken, the only solution was to launch the boat, find some heavy poles, and then tow the boat whilst breaking the ice.