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Fish farms in otter habitats are popular sources of food.

The number of otters in Germany has increased significantly. Subsequently, major economic problems are arising in traditional pond farming. Once the rivers are bare of fish in the winter, these predators increasingly turn to the pond facilities of fish farms for prey. In summer, the female otters teach their young to fish, killing more fish than they eat. Otter consultants and the fishery associations can provide information on any support available for defence measures.

One of these is the use of electric fences. The wires are electrified either using a powerful 12 V AKO fence device or a 230 V AKO power pack where there is a nearby power supply. The advantages of power packs (we recommend installing a ground fault circuit breaker): unrestricted tending periods, more secure in the case of heavy vegetation and long fences and also saves more energy than battery units. AKO Duo electric fence devices are an interesting alternative – 230 V mains supply and 12 V battery as two energy sources in one device. In general, this requires a powerful 12 V AKO fence device with a fence voltage of around 4000 to 5000 volts and an impulse energy of 1 to 5 Joules. Optimum earthing must be ensured.

AKO plastic posts with a total height of 70 cm (18 cm ground nails) are set up in intervals of 5 to 6 m around the fish ponds. A wooden post is driven in at the corners of the pond for stability and insulators screwed in.

Ein Zaun um einen Fischteich vor Fischotter zu schützen

Pond protection with electric fence.

Otter defence fence

White-blue TopLine Plus fence wire
Blue TopLine Plus fence tape
Fence connection cable with alligator clips
Warning sign
Signal light
Insulators

Our product tips for otter defence

Two white-blue AKO TopLine Plus polywires are attached at 10 and 30 cm from the ground. In between them, a blue AKO TopLine Plus fence tape is tensioned at 20 cm and, above that, at 40 cm.

Please note:
uneven terrain must be taken into account.

The key to success:
in regions with deep snow and risk of flooding, AKO posts of at least 160 to 180 cm length must be used, on which the wire heights are also freely adjustable. AKO T-post metal posts or AKO fibreglass posts are suitable, for example. Although it is labour-intensive, the ground clearance of the wires must increase along with the height of the snow. Keeping the vegetation short around the electric fence is also important in the growing season.

Tip:
where permanent fencing systems around fish ponds are permitted, there is a risk that otters will climb over the fence. This can be prevented by attaching insulators to the outer side of the fence at 20 and 40 cm above the ground and tensioning and electrifying an AKO TopLine Plus polywire on each one. A current-carrying wire tensioned 10 to 15 cm above the fence is also effective.

Problems:
AKO Agrartechnik feels obliged to point out that

Fish farms or their pond facilities are often easily accessible. Children in particular could grab the electric fence. Therefore, you must attach clearly visible warning signs at these points.
Wandering amphibians such as toads and frogs are drawn to the pools during the spawning season. Often, two or even three males sit on a female frog. If the topmost one touches the wire, all the frogs can be killed by electric shock.

“Otters have become very widespread in Lower Bavaria since around 2003. They have cause major damage to fish farms and will continue to do so. This is why many fish farmers have already abandoned their facilities. As a mobile device, electric fences are a suitable defensive measure against otters if they are correctly installed and maintained.”

MARTIN MASCHKE –Fishery master, Fischerzeugerring Niederbayern