koi predators

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

"Know thy lot, Know thine enemies, Know thyself."
- Sun Tzu, The Art of War
We naturally get 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 modifications 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

Bullfrogs will eat anything that they can fit in there mouths. This one is eating a bat
Great Blue Herons are intelligent determined birds that are designed to catch fish
Well fed turtles are not really a problem when cohabitating with koi
Mink have become the most deadly predator for koi over the last 5 years in the Toronto area

Minor Predatory Threats to your Pond

Felines
Cats are not a going concern but can scratch or take the odd fish, more likely goldfish than koi. If your fish are tame there is of course an increased risk of attack

Terrapins
As slow 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.

Ranidae
Frogs will eat anything they can fit into their mouths - rodents, birds, snakes and even their brethren. Females are larger weighing 2 lbs. and measuring up to a whopping 18" in total length. This size enables them to take larger game

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 occurred within the city of Toronto, not some rural area bullfrog

Serious Threats to your Pond

Raccoons
Deadly in shallow ponds, minimal impact in deep ponds. Raccoons are intelligent, nocturnal and omnivorous. These qualifications mean danger for our fish. A large male raccoon 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 raccoon

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 raccoon tracks

Herons

Herons have been genetically engineered to catch fish and other aquatic fauna such as frogs and insects. They also take snakes, mice and even rabbits. 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 to us 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

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

The Mink

Weasels 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 expected them to flee in terror if they see you

A net won't stop mink, you need something more substantial

Unlike Herons who can have large overlapping territories, they are territorial and solitary - however some clients claim to have up to 5 different individuals visiting their pond. Attempts to successfully trap this animal are not guaranteed. Although they are small [males being up to 2.5 ft. in length with tail] they are larger than squirrels

Anecdotal Notes:
In larger ponds, fish can usually evade mink in the warmer Summer months. However when koi slow down in the Fall, they become easy prey. In Winters stationary topor, they are sitting ducks. I have seen a mink fish out a swimming pool conversion of approx. 400 fish over a single Winter. They can swim under the ice for about 20 seconds to deeper water. Voracious, they may visit 3 times per day to eat your fish

electric fences for Koi Ponds

For these more dangerous attackers, we have had about a 90% success rate with electric fences. We sell and install them and the feedback is mostly positive. About 50% of our clients install the setup themselves and it's pretty easy for the average DIYer. The line needs to be set up like a trip line, not a matrix of line in which the animal will just jump over