Once constructed, our ponds become part of the local food chain and as a consequence our koi are on the menu
Expectations of eternal harmony are unrealistic - both within and around the pond |
We are naturally upset when wild animals attack our fish but it's important to understand that they are just trying to survive. It's not surprising to see so many wild animals dwelling within the cities, their habitat is being consumed by urban sprawl and they lose their natural hunting grounds
With some moditications and design considerations fish loses can be minimized in most circumstances. Remember fish, being low in the food chain, are a potential meal for many predators. Among them are cats, raccoons, weasels and birds such as herons and hawks [osprey]
Ultimately its important to realize that once a predator has targeted your pond, you have a real problem that needs to be dealt with |
- Sun Tzu, The Art of War
The Cat
Damage Rating - low
Cats are not a going concern but can scratch or take the odd fish, more likely goldfish than koi. If your fish are tame that will odd to the potential loss |
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The Turtle
Damage Rating - High [but rarely occur]
As slow and stupid as they appear, turtles have been around a long long time. They are ambush predators and big fish eaters. Luckily they are not common in urban centres.
Anecdotal Notes:
Strangely enough, a client in Scarborough told me he discovered a large snapping turtle in his pond. Of course this discover happened after he had gone wading barefoot in the pond. Ouch. |
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The BullFrog
Damage Rating - Serious
Frogs will eat anything they can fit into their mouths - rodents, birds, snakes and even their bretheren. Females are larger measuring up to a whopping 18" in total length, this size and power enables them to take larger fish, This is one serious amphibian weighing in at close to 2 lb.
Anecdotal Notes:
One client told me frogs took over his pond one Summer. They ate a lot of his fish. They also started eating each other. The one remaining frog was massive and he saw it eat a poor bird that had come to drink. And this occured within the city of Toronto, not some rural area |
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The Raccoon
Damage Rating - deadly in shallow ponds, minimal impact in deep ponds
Raccons are intelligent, nocturanal and omniverous. These qualifications mean danger for our fish. A large male raccon can weigh over 50 lb. after a Summer of feeding so they are formidable and capable of taking larger koi
For the most part, water depth and the lack of a wade in entry point is enough to send raccoons to easier hunting grounds. I have spoken to clients who had shallow ponds for years only to wake and find all their fish gone. Ponds with deep sections of 4+ feet pretty much guarantee security from raccoons although I have heard of one case in a 5 foot deep pond where raccoons damaged several fish
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Anecdotal Notes
If raccoons can't get to you fish, they will often damage plants and I have even seen a submersible pump chewed up to render it inoperable. Additionally, if you pond is shallow and your fish have miraculously survived, don't expect that to continue inevitably. I had one client who had her pond for about 2 years without incident and then it was cleaned out |
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The Heron
Damage Rating - Deadly
Herons have been genetically engineered to catch fish and other aquatic fauna such as frogs and insects. They also take snakes, mice etc. The Great Blue Heron is the largest heron in North America with a 7 foot wingspan and 4 foot height. This immense size is beneficial in smaller treed backyards where the bird is unable to land. Once a Heron has your pond on its rounds you need to take quick action or your fish will all be gone in no time . Herons take a 30 mile junket in search of food and are sure to be back |
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Anecdotal Notes:
Herons like to wade into the water after landing on solid ground. Once they are familiar with a pond, I have heard they will land right into the pond, even if there is netting on it. They are patient and determined
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The Mink
Damage Rating - Deadly
Weasesl are deadly to fish and voracious eaters. They are considered semi-aquatic predators, very versatile and opportunistic. I have spoken to clients who have had the ponds fished out in a single night. They are intelligent and very bold - don't expectd them to flee in terror if they see you. Unlike Herons who can have large overlapping territories, they are territorial and solitary. Attempts to trap this animal fail from what I have seen. I have also had clients mistake mink for squirrels. Although they are small [males being up to 2.5 ft. in length with tail] they are larger than squirrels |
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Anecdotal Notes:
In larger ponds, fish can ususally evade mink in the warmer Summer months. However when koi slow down in the Fall, they become easy prey. I have seen a mink fish out a swimming pool conversion of approx. 400 fish over a Winter. They can swim under the ice for about 20 seconds. They may visit 3 times per day to eat your fish
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Pond Design
First, your pond should be deep - at least 5 feet but preferably there should be a section 7 feet in depth. This provides a relatively safe sanctuary for your fish. Additionally the ponds side walls should be relatively step and there should be no shallow sections less than 2.5 feet deep. With these features alone, you are eliminating most of the predators chances for a meal . A snapper will have a shot and of course a mink in colder weather. Large perimeter boulders are good at detering herons, making it hard for them to spear from a higher than water vantage point
Electric Fence
Aside from design modifications, you may also have to utilize some other strategies - your success rate will vary. These include motion detector water jets, having a dog, covering the pond with netting or wiring, artificial owls or herons etc. As far as I'm concerned, an electric fence is your best option. While the other strategies are deterrents and can have varying degrees of success, , an electric fence creates a physiological barrier for the predator. After 1-2 jolts, the predator will want no part of your property, let alone your pond. We do carry and install electric fences and have had very good success with them. Remember, you are setting a trap with the fence, not trying to run wires everywhere
We have very good success with electric fences. The picture right is a pond that was fished out 2 years in a row during the Fall. The installation of the fence took place 3 years ago and not a fish has been lost since that time
Some predators like Ospreys and other fish eating raptors are not a problem in the city, at least I have not heard of this in Toronto. If you are in the country with a large pond you will ultimately have to accept loses as snapping turtles and other hungry predators join the fray |
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Winter Strategies
The only real predatory threat in the Winter comes from mink. When your pond is frozen over you can freeze galavanized metal into the ice at the deicer / bubbler location so that the weasel can't gain entry. An in pond metal cage can also work, with the deicer and bubbler in the centre. If the weasel dives in, it can't get far |
An electric fence surrounds this pond and unlike other deterrents, shocks the animal creating a psychological barrier
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