Q: What is Electrofishing ?
A: Electrofishing is a recognised sampling method for freshwater fishes.
Electrofishing is the process of passing an electric current through water to cause involuntary muscular spasms (galvanotaxis) rendering the fish to be unable to regulate it’s motor control and so inhibiting it’s movements. This enables the fish to be removed from the water by hand netting and processed for biometric data collection or removed, in the case of fish removals or fish rescues.
Typically either DC or Pulse DC current is used to immobilize fish. A long specialist braided cable with a high surface area creates the cathode of the system and a non conducting pole mounted electrode often, but not limited to, a ring is used as an anode.
Q: What electrofishing System is right for me ?
A: This depends on the type of fishing/surveying intended and the type of river systems being sampled. Briefly there are 4 main categories:
- Fishing Clubs, NGO’s and rivers Trusts-These usually require equipment which is subjected to occasional to moderate usage during the peak fisheries season for investigative work or sampling fish population status in lakes. The requirements of effective equipment with a variety of options are balanced with affordability and suitability. WMD Club based systems provide a wide range of affordable options under this general category. There are 5 options within the Club systems to choose from within 3 types, IEF PP Club, IEF HP Club and IEF 4000P Club
- Professional use: Consultancies, Government Agencies, Fisheries Boards, Research Organisations, Fish dealers, Aquaculture. Professional use is usually moderate to heavy and can be as often as 5 days/week. They usually require more features since they will be used in a wider range of environments and on a wider range of species. The professional series includes WMD GYH Blue, Wanderer, IEF4000P series or our Ti range
- Upland and wading/backpack surveys: Upland river systems are often low conductivity and small in size. These require less power than lowland, high conductivity systems, but greater flexibility of equipment since site access can often be challenging. The Wanderer series is suitable for this type of electrofishing. Wanderer IEF systems are lightweight and flexible with range of outputs and are feature rich to provide the professional with many options. They also provide a genuine alternative to backpacks. There are 6 versions to choose from within 3 main types, Wanderer, Wanderer Plus and Wanderer Pro
- Boat and lowland surveys: Usually sampling in higher conductivity waters requires higher powered systems. Typical work includes coarse fish surveys, fish removals and rescues. Electrofishing equipment suitable for this type of work range from the higher powered Consultant systems (IEF 4000P) to the Ti series, either Ti Plus or Ti Pro. Each Ti series has successively more features and options and all feature Titanium technology
- Flexible consultancy National fish survey work: Typical consultancy work means surveys carried out Nationally in a variety of waters and on a variety of different fish species. The WMD IEF Wanderer Pro and the Ti series are most suitable for this type of work. Typical electrofishing setup for larger consultancies comprises of a Wanderer Pro system for headwaters and upland systems and a Ti Pro for all other situations
Q: What do I need for electrofishing?
A: Traditionally an electrofishing setup would comprise of: Large electrofishing control box (500x350x400) and separate generator plus anodes and cathodes usually with large caravan type connectors. WMD innovative systems are much more compact and comprise of 3 main items: Integrated electrofishing control box/generator, anode and cathode. Simple! Lightweight, less bulk and more efficient. We also supply accessories for electrofishing surveys including tweezer sets, scale packets, waterproof paper, hand nets, fish bins, oxygen regulators and hose sets, diffusers etc
Q: What Cathode length Should I choose ?
A: Cathode length can be split into cathode cable length and cathode tail length, with the later being the conductive braid that is immersed in the water. Cathode cable length is usually specified according to electrofishing activity. Boat work may specify a shorter cathode cable in order to provide minimal cable coil and reduce trip hazards. Cathode braid is also kept relatively short, circa 2-3m, in order to reduce entanglement on underwater obstacles. Conversely, wading sites tend to require longer cathode cable, in order for the cathode to reach the river from the bankside generator and also longer cathode tails, since this reduces voltage gradients and is less harmful to fish whilst improving electrofishing efficiency. Typically, a good wading cathode setup would comprise of 5-8m of cathode cable and 6-8m of cathode braid. The best approach to wading surveys would be deployment of our electrified end stop system. This provides optimum cathode braid and an end stop to prevent fish leaving the survey area, which in turn reduces the need for carrying and deploying bulky stop nets
Q: What cathode length is best for fish welfare ?
A: Independent research has found that a minimum of 6m, and preferably 8m+, provides the best electrical contact that allows full current to be transferred to the water with the softest field, minimizing damage to the fish and reducing chances of burning or causing muscle, nerve and blood vessel damage to the fish. Therefore, always specify the longest cathode that can be practically used in order to maximise electrofishing efficiency and fish welfare
Q: What Anode ring size is best for fish welfare ?
A: The larger the ring size the softer the electrical gradient and the least harm is done to the fish whist allowing lower voltages to be used to induce galvanotaxsis. However, practical considerations usually mean a compromise between large size and portability/fishability are made. Typical anode ring size is 38-40cm with variations available (30-45cm). The material that anode rings are made from also influences their performance characteristics as well as operator handling experience. WMD manufacture out of stainless steel, aerospace alloys, and Titanium. Each has unique properties and specific uses:
–Stainless steel is the industry standard anode material since it is hard wearing and corrosion resistant. They provide a reliable, cost efficient conductor, though a little larger in CSA and heavier than some of our new alternatives
–Aerospace alloys are very effective in low conductivity waters. These alloys are the most conductive of all anode rings currently in production Worldwide!
–Titanium is more conductive than stainless steel, harder, lighter and stronger. This means smaller CSA of anode ring tubing, reducing drag and weight as well as increasing electrofishing efficiency. We are the only electrofishing manufacturer of Titanium anode rings in the World!
Q: What anode cable length is right for me ?
A: Anode cable length depends upon activity. Typically for boat work shorter cable lengths are preferred (3-5m) in order to reduce trip hazards and to maintain safety (like all electrical equipment it should not be operated with supply cables coiled up). Most of our anodes can be specified with set cable lengths. Custom lengths are also available for some models
Small survey work with a mixture of potential boat and wading work 10-20m is about right. Longer cable lengths such as 25, 50 or 100m, often termed Wander anodes, can be used, frequently in conjunction with a long cabled cathode or electrified end stop. This is because wading surveys are often 50m-100m long and frequently stipulated for sectional analysis by Government Agencies and regulatory authorities
Q: What anode pole length is right for me ?
A: This is a subjective question. When conducting wading surveys the more experienced electrofisher will often opt for a 1.2m anode as this allows ease of wading in rocky shallow rivers and easy manipulation into crevices and pools. However, this anode length is not good for boat surveys or deeper water. where only a single length anode is desired then often a 1.5m anode is chosen, since this provides the optimal compromise as it is usually suitable for wading surveys and enables good reach and fishability for the deeper pools between riffles and glides. The 1.5m anode allows boat surveys and point abundance sampling surveys to be undertaken, but is less suitable for deeper lakes or very high sided boat work. A 1.8m or longer anode is suitable for boat work and deeper open water surveys and fish removals allowing a larger reach and depth. If the operator is tall (>6’2″) then a longer anode will usually be more suitable
Q: What do I need to do undertake an Electrofishing Survey?
A: External electrofishing control box, Generator, Anode, Cathode or….IEF electrofishing system, anode and cathode. Other typical ancillaries are:
Hand nets, fish bins, measuring board, tweezers, scale packets, waterproof paper, pencils, water pump, trugs, aeration, oxygenation (inc bottles, diffusers, regulators and hoses), thermometer, fishing consents, landowner approval, possibly boat, outboard, electric outboard, oars, first aid kit, mobile, life jackets, throw line, spare rope, waterproofs, waders, drysuit, hand towel, change of cloths (in case of falling in), Duck tape and bungee cords, knife and hand saw (improvisations and emergency fixings). You will also need landowner permission and EA FR2 or NRW/SEPA consent
Q: What safety considerations to observe when Electrofishing ?
A: Ensure those undertaking electrofishing have received adequate training and are deemed competent. Ensure first aid kit is always on hand and personnel know how to use it. Only in test electrofishing equipment should be used. All equipment should be free of faults and cable breaks etc and deemed fit for purpose. Generator should be securely located to prevent falling over or falling into the water. Ensure all personnel are wearing appropriate and adequate PPE. Bankside, generator-based fishing should always have assigned personnel as the banksperson to provide switching off of electrical systems in case of emergency. No one should place hands into the water whilst electrofishing is being undertaken. Only those carrying out the activity should be in the water and all should know their assigned roles. Only non-conductive poles and hand nets should be used. Operators preferably to wear gloves. Avoid electrofishing in rain and strong winds. Boat based electrofishing should be crewed by qualified crew and captained by experienced skipper (RYA).
Q: How many people are needed for Electrofishing ?
A: A minimum of 2-3 personnel, depending upon type of electrofishing activity. Bankside, generator-based, electrofishing usually requires 4-5 personnel: 2 electrofishers, 1-2 fish catchers and 1 banks person with variations upon this depending upon river flow, width and species targeted. Wander surveys usually require 3-4 personnel and backpacks 2-3.
Safety and Electrofishing
Q: When can I electrofish ?
A: Electrofishing is typically carried out from autumn through to spring, avoiding spawning and elevated temperatures of high summer where possible. Electrofishing for assessing fish kills, fish rescues etc (pollution’s etc) as well as fish removals where emergency work is being carried out are sometimes undertaken.
Q: Can I electrofish alone ?
A: No, electrofishing is potentially hazardous and requires at least 2 personnel, though typically 3-4, depending upon the size of the water, nature of electrofishing and number of staff fishing. If two personnel are electrofishing and catching fish, then a third member must be assigned banksman duties where generator fishing from river or lake bank is being undertaken. Electrofishing alone would expose the operator to risks of electrocution, falls and trips and drowning without the aid of a colleague. IF in doubt, don’t!
Q: Do I need permission to electrofish ?
A: Yes, statutory authorities require a legal consent to electrofish, whether fish are being removed or merely surveyed. In England it is the remit of the Environment Agency (EA), Scotland, Scottish Environment Protection Agency (SEPA) and Wales, Natural Resource Wales (NRW). Landowner permission is also required
Q: How many people are needed for Electrofishing ?
A: Typically 3-4 personnel are used for carry out electrofishing activities. more may be used where larger teams of electrofishers are deployed or where large numbers of fish are known to be present
Q: Can I fish in the rain ?
A: It is not advisable to electrofish in rain. From a health and safety perspective, fishing in rain exposes the operators to more risk, reduced visibility, less grip on equipment, high chance of rain ingress into generators which are not IP67 rated. Visibility is reduced and the rain on water impedes detection of fish by the operator. This in turn may cause some fish to be held within the field too long and others too little. The effectiveness of the survey would be compromised and the data less robust. There are often situations where a survey has been compromised by rainfall. If rain is light and the survey nearly complete, some operators will elect to finish the survey, others not so. The decision is a risk based one and made using experience
Q: Can I fish in the sea ?
A: No, the conductivity is far too great and the resultant excessive flow of current will cause the electrofishing equipment to draw too much power and blow the box, or generator or both
Q: Is electrofishing harmful to fish ?
A: Yes it can be. Electrofishing at high power and/or in close proximity to a fish or holding power on for too long can cause various injuries from burst blood vessels to broken backs or immediate mortality. Only the former will fish survive. Experience and training greatly reduce incidents with fish health during electrofishing operations. Knowledge of different species and their vulnerability to the electrical field whilst electrofishing also helps reduce incidents. Using experienced operators and correct electrofishing settings usually results in no to minimal harm to fishes
Q: Can I get an electric shock ?
A: Yes, without adopting correct settings, operating protocol and ensuring all equipment is regularly serviced there are risks of electrocution. All electrofishing operators should undergo formal training in the deployment of electrofishing equipment. All electrofishing equipment should be regularly serviced
Q: What anode ring size/material is best at catching fish?
A: Anode ring size varies with water type, species and fishing effort. Generally, smaller anode rings appear to fish better than larger ones but the effects upon the fish are greater due to the higher voltage gradient. This high voltage gradient is more harmful to the fish and using too small anode rings at higher power outputs can cause health issues to the fish. The most widely used material for anode rings is stainless steel. stainless steel is not however the most conductive. Copper is probably the best conductor but is very soft and prone to damage too easily. If we regard copper conductiveness as 100, then stainless is 1 and titanium is 3. Aerospace alloys are around 30. Thus, the choice of anode material is dependent upon type of fishing and personal choice. Generally, the best options are titanium for light weight, narrow tube diameter and low CSA for reduced drag or aerospace alloys for increased efficiency in low conductivity waters and stainless for affordability.
Q: How do I get started?
A: The best and most cost effective way of starting out with electrofishing equipment is to purchase an electrofishing kit. Kits provide all that is needed to get started (excluding hand nets & fish bins) and provide significant savings over individual purchases
Q: How do I use/set up my electrofishing gear ?
A: connecting the equipment is usually carried out in the following order:
1. Set the generator or IEF in a secure and stable location away from water’s edge.
2. Connect the cathode to the control box or IEF cathode port, ensuring the cathode tail is completely submerged in the water and across the survey section, perpendicular to the bank.
3. Place stop nets where used at each end of the survey section avoiding walking through the section if at all possible.
4. Ditto if using electrified end stops.
5. ensure anode cables are free of tangles and are ready for deployment.
6. connect anode cables to control box or anode port on the IEF generator system.
7. Ensure both operators are standing in the water apart from each other and away from close proximity of the cathode. Operators to have switches OFF on the anodes at this stage.
8. Check control box/IEF generator is ready to start and double check that fishing activation is set to off with potentiometer/power switch turned to lowest setting. Start generator/IEF generator and switch on power to electrofishing system. Check both anode staff simultaneously operate their anode switches.
9. Power should flow into the water, indicated by control box/IEF control display.
10. Adjust power setting to desired power output (informed by the target species, water temperature and conductivity, ensuring power increments are gradual .
11. Check fishing effectiveness and adjust again until fish response is predictable and only just inhibiting fish movement.
12. Fishing can commence
Q: What setups are used to carry out a fisheries survey ?
A: Broadly, there are 3 ways of carrying out fisheries surveys. 1. Bankside generator/IEF generator and wading. This approach is usually used in moderately sized to smaller rivers and streams with suitable water depth for wading
2. Boat based generator/IEF generator survey. This setup is used in larger and deeper rivers that preclude wading
3. Backpack or Wanderer based surveys using backpack or a WMD Wanderer System. This approach is used in smaller first order streams and shallow rivers
Q: How often does my gear need servicing?
A: Servicing of electrofishing equipment is partially dependent upon usage and always by manufactures requirements. Typically, a de minimus for servicing is 12 months, but many users service between 3-6 months. Equipment not in use may be laid up but will require servicing prior to being placed back into use
Q: How do I conduct a fisheries survey?
A: Typical 1 and 2 man electrofishing surveys are illustrated below:
Illustrations courtesy of Environment Agency
Q: What do I look for in a electrofishing control box ?
A: Choice of electrofishing control box equipment varies with the purpose it is intended. However, key features of any system are flexibility, convenience, weight, portability, size, transportability, effectiveness, efficiency, design, features. For example; WMD IEF systems are light weight, highly portable and full featured electrofishing systems. The integration of the control box within the electrofishing generator itself saves bulk and weight, increases portability and flexibility since they can be carried virtually anywhere and have innovative features that make day to day use easier on the operator. WMD IEF systems can support 2 anodes and have integrated digital displays. Some models feature full colour HMI touch screen controls for even more features and greater control. Whichever system is chosen all have easy control of power and frequency and ergonomic IP67 rated connectors, some have quick connect features and even higher water resistance (IP69K). Integrated systems save having to lug another large bulky separate electrofishing control box and the smaller form factor connectors are easy to use, positive in connection and save weight and bulk.
Q: Is more power better ?
A: Not necessarily. In waters with high conductivity, higher power is an advantage, but in lower conductivity waters this extra power will not be transmitted to the water due to the impedance of the water itself. In low conductivity systems, consider using better conducting anodes such as WMD Titanium or Aerospace alloy to increase fishing efficiency and/or using a higher voltage electrofishing control box such as the WMD IEF 4000HVP
Q: Is higher voltage better?
A: Higher voltage is an advantage in low conductivity water but less so in moderate or high conductivity water
Q: How heavy is the equipment ?
A: WMD electrofishing equipment is some of the lightest equipment available. Our Ti anode rings are the lightest in the World, weighing in at only 92gms! Our IEF systems are much lighter than conventional electrofishing control box and generator setups since the control box uses latest technology to achieve an integrated build inside the generator itself. This saves >25Kg over competitors systems! Our approach to anode design also provides weight savings as well as reduced operator fatigue and enhanced ergonomics
Q: What health and safety considerations should be observed?
A: 1. A standard first aid kit and throw line should form part of the safety equipment
2. Fire extinguishers suitable for electrical and petrol fires must be part of the standard equipment and near the fishing equipment. Personnel should be familiar with their use
3. Equipment such as buckets, landing net handles and fish containers, must be made of non-conducting material
4. Clothing should not have buttons or buckles that could snag on cables and landing nets or unprotected conductive or fasteners or zips that could be a current path if they enter the water during fishing operations
5. Lifejackets must be worn at all times
6. All staff should be aware of who is the lead person and clear understanding of agreed signals should always be disseminated at the start of each electrofishing session
Q: What actions should I take in an emergency ?
A: ● Switch off the electrodes/anodes
● Switch off the emergency stop button
● Stop the generator
● Attend victim and apply First Aid
● Call ambulance if necessary giving grid ref and location
● Report accident in accident book and ensure management are notified
Q: What data should I collect ?
A: ● Survey method
● Equipment used
● Field settings, anode number and type
● Number of runs
● Survey strategy
● Fishing direction
● Use of stop-nets
● Site name and river name
● Survey purpose
● Date
● NGR
● Team
● Weather conditions
● Water level / flow
● Visibility (colour and/or turbidity of the water)
● Conductivity of water (μS)
● Temperature of water (oC)
● Length of river section surveyed (m)
● Average width of wetted area (m)
● Average depth (m) and maximum depth (m)
● Flow type
● Substrate
● Habitat type and sources of cover
● ID Species
● Individual length (Fork length mm)
● Gender
● Biometric data
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