What is Eating your Pond Fish and More Importantly How to Stop Them
Finding some or all your pond fish missing, or worse half eaten is an upsetting sight for most pond-keepers. It is however virtually impossible to completely prevent from happening.
Garden ponds, unlike aquariums, are outside in the open and will naturally attract an array of wildlife. Not all wildlife attracted to your pond is bad. In fact, certain wildlife such as frogs or toads may well be encouraged.
However, other more predatory animals will also be attracted to your pond as an easy source of food. After all it is not every day a predator finds such a convenient well-kept source of food.
So, who are these predators eating your fish and more importantly how can you stop them?
Below is a list of potential predators for your pond fish in the UK listed in order of risk as well as some animal specific deterrents you can use.
High risk pond fish predators in the UK
The high-risk category represents the most likely predators to your pond fish in the UK. The below list of high-risk predators are the most likely culprits for what is eating your pond fish.
Fortunately, most predators can be deterred eventually depending on the animal in question. Below we discuss deterrents for each potential predator you may be up against.
Herons
Herons are probably one of the more common culprits when it comes to missing pond fish. For a heron garden ponds are an easy source of food as well as a great educational space to hone their fishing skills.
The heron diet is effectively just lots of fish and they will quite literally “harvest” a whole pond if they come across one which is easy to access.
There are around 10,000 to 13,000 herons who live permanently in the UK. However, in the winter months the heron population can swell to 60,000 plus. As herons are a protected species in the UK (you are not allowed to lawful kill a heron) their populations have also been growing quite nicely in recent years.
Signs herons are eating your fish
Herons are a freshwater bird who usually live in and around coastal areas. Therefore, the further away your pond is from the coast or a large source of freshwater the less likely it is a heron is eating your pond fish.
That is not to say herons do not stray from the coast or freshwater sources such as rivers but the risk to your pond fish certainly will diminish the further away you are.
Other signs a heron might eb eating your pond fish would be if all your fish are missing. As previously mentioned, herons eat a lot of fish and are unlikely just to eat one or two, they will probably gobble up any and all fish they can get at.
Deterrents for herons
Herons are such a notorious culprit we have dedicated a whole article on how to heron proof your pond. So, if you think herons are behind your missing fish it is certainly worth a read.
Mink
You would be mistaken for confusing a mink with a otter if you ever saw one. Mink look incredibly similar to otters. In fact, there are only a handful of differences between the two such as mink are generally smaller and have more pointed snouts.
Perhaps more importantly mink are indiscriminate killers of fish and other species such as birds and smaller mammals.
Mink are an invasive species in the UK who were brought over in the early 20th century for fur-farming. By the mid to late 20th century wild mink populations began to appear as a side effect to the fur-farming industry.
Mink have no natural predators in the UK and as a result the wild population of mink has been allowed to grow relatively unchecked.
Signs mink are eating your fish
Mink are nocturnal creatures who are very quick and effective killers. Mink won’t generally just kill for food there is some anecdotal evidence that mink kill for fun as well.
If a mink or group of minks have found your garden pond, chances are they will have wiped out all your fish. However, unlike a heron you may find half eaten or dead fish in and around your pond, this would be a sign your missing fish was caused by mink.
Mink usually live in or around waterways or rivers, particularly in the countryside. Therefore, if your pond is located close to a river and all your fish go missing this could be a sign of mink as well.
Deterrents for mink
Most predator deterrents such as pond nets do not work with mink. Mink are rather clever creatures who are small enough to fit under or through netting thus rendering a pond net and similar deterrents useless.
In fact, in many ways there are no mink deterrents only preventative options. Preventative options include things like building a raised bricked pond as this will make access harder with a thick tight mesh which is well fitted. In other words, you must make your pond a bit of a fortress to stop mink.
Domestic cats
It is thought 24% of UK adults own a domestic cat, this equates to almost 11 million cats. There are also countless feral cats which live in the UK. Therefore, there are a lot of potential feline predators for your koi and goldfish.
Countless centuries of evolution have enabled cats to be quite good at catching fish. Cats are quick, agile and despite common stereotypes not overly afraid of water. Cats also have sharp claws which make killing fish straightforward.
Fortunately, cats, unlike other predators, are not greedy animals therefore are likely to only take one or two fish at a time for a snack rather than massacre your pond fish like a mink potentially would.
Signs cats are eating your fish
You are unlikely to catch a cat swimming in your pond, most cats would wait by the edge of your pond until they saw an opportunity to swipe a fish or two.
As a result, if the water levels of your pond are high and the water relatively clear and you only notice one or two fish missing this could mean an opportunistic cat could be the culprit.
Cats are also far more common in urban areas and will likely stumble across your pond and see an opportunity for an easy snack rather than continually return to your pond as their main source of food.
So, if you live in an urban area and are noticing one or two fish go missing sporadically it could well be a cat.
Deterrents for cats
Cats are usually well fed by their owners and therefore will only take a fish if they deem it an easy meal. Simple design elements such as having sloped rather flat edges can be enough to deter a cat.
In addition, ensuring water levels are a good 6 inches below the land surface can also put your fish out of a cat’s reach.
Another deterrent could be keeping your pond well oxygenated thus reducing the likeliness of your pond fish venturing too close to the water’s surface. Pond pumps or filters are a good way to keep stable oxygen levels in your pond.
Medium risk pond fish predators in the UK
The medium-risk category represents the somewhat likely predators to your pond fish in the UK. The below list is potential predators who are fairly or somewhat likely to be the culprit of your missing pond fish.
Fortunately, these predators are more opportunistic animals who may eat your fish as an easy meal and therefore can be deterred more easily.
Otters
Otters have similar physical characteristics to a mink. However, unlike mink otters have lived in the UK for centuries. The UK’s wild otter population has recently recovered thanks to a respite from years of persecution and can now be found in virtually every county, particularly in parts of Scotland, South Wales, and the South West of England.
Otters have adapted well and are able to live both in water and on land. As a result, otters are usually found close to the UK’s rivers, waterways, and coastal areas.
The otters diet primarily consists of fish and whilst otters usually feast on eels, salmon, and trout it would not be unusual for otters to go after koi or goldfish as well.
Signs otters are eating your fish
Otters are incredibly elusive and generally only come out during the night. Therefore, spotting an otter eating your pond fish would be highly unlikely.
Depending on where you live will determine the risk otters pose to your fish. For example, if your pond is located close to a river in a rural part of the South West of England the risk is far greater then if your pond was in a small garden in the middle of Birmingham.
If you are noticing your fish are going missing and you live close to a river or waterway or know of recent otter sighting, then it could well be that otters are eating your fish.
Deterrents for otters
Unfortunately, otters, much like mink, are not easily deterred. Common deterrents like pond nets would not work with otters as they will be able either slip under the net or find a way through a large enough hole.
Having a raised pond will help. Combined with a tightly fitted metal mesh over the top should do the trick in preventing otters physically accessing your pond. This will however also prevent other wildlife such a frog from entering as well.
Crows
Crows are a common sight in both urban and rural areas of the UK. With their distinctive black feathers and beaks, they are hard to miss.
Crows have a long and rich history in the UK and in many ways should be encouraged as part of the wildlife eco system of your garden.
However, like any animal a crow will not pass up an opportunity of an easy meal and therefore pose a real danger to your fish.
Signs crows are eating your fish
If crows are eating your fish chances, are they are spotting a large, slow moving koi which is floating close to the water’s surface. A crow would then swoop in and pluck the koi from your pond.
Therefore, if you are seeing one or two of your larger koi missing from your pond it could well be the result of a crow.
Deterrents for crows
As crows will swoop in and take fish from the air a simple pond net should be enough to deter a crow. Also by having plenty of pond plants your fish will have cover from any aerial predators fancying an easy meal.
Rats
Rats will probably not be the first predator you think of when considering what might be eating your garden pond fish however rats are extremely good swimmers and will bring back virtually anything to their nests to eat.
Rats are also extraordinarily strong and resourceful creatures who have more than enough ability to take a small to medium sized fish from your pond if it was determined or hungry.
Signs rats are eating your fish
If you have rats, you are probably already aware of them. If this also coincides with a few small to medium sized fish disappearing from your pond it would not be out of the question to consider the rats as the culprits.
Rats will usually live-in urban areas so even if you are not aware of any rats if you live in a big town or city, you can be quite sure a rat is never too far away.
Deterrents for rats
Fish are not part of a rat’s normal diet so if a rat is eating your fish, it is probably doing so out of ease or hunger. As previously mentioned, you could well be already aware of rats living nearby. If this is the case, then pest control should be able to help.
If you are not aware of any rats but are still suspicious having a raised pond or a net should be enough to stop them gaining access to your pond.
Low risk pond fish predators in the UK
The low-risk category represents the less likely predators to your pond fish. The below list are predators that have been known to eat pond fish but who are rarely found doing so.
As these animals pose a low risk to your fish a few simple yet effective deterrents should be enough to prevent them.
Foxes
Foxes are excellent urban scavengers and are a common sight across many UK towns and cities. A recent survey put the UK fox population at around 357,000.
With so many foxes the chances are a fox will stumble upon your garden pond at some point. Whilst foxes are not natural predators to fish if they consider your koi an easy meal they will not hesitate, especially if the fox is hungry.
Signs foxes are eating your fish
Unlike many of the predators mentioned foxes have not evolved and adapted to catch fish. Therefore, a fox is only likely to be able to catch a slow-moving larger koi.
In addition, a fox will stand at the edge of your pond and dip its head in to catch the fish. Therefore, if you find fish dead in your pond with their face or nose missing it could well be the result of a hungry fox.
Deterrents for foxes
Having your pond water level at least 6 inches from the edge of the pond should make it so that a fox would not be able to reach your fish. Keeping your pond well oxygenated through a pond pump will also reduce the need for your fish to come to the surface to breathe.
Another deterrent could be to use lights or motion sensors around your pond. Most animals are easily scared so this could be one option.
Grass snakes
Grass snakes are natural predators of amphibians and therefore may well be attracted to your garden pond, especially if you have frogs or toads.
It is not uncommon for grass snakes to hunt in water and would consider your fish a potential meal as well as any amphibians your pond attracts.
Grass snakes do not eat frequently so the impact on your fish population would be minimal if noticeable at all.
Signs grass snakes are eating your fish
Frogs are much more likely to make up a grass snakes’ diet then fish. Therefore, if you have a healthy frog or toad population in your garden it is possible a curious snake is taking the odd fish too.
However, it would be the amphibians attracting the snakes not your fish. In other words, your gold or koi fish would be like a Brussel sprout (sorry Brussel sprout lovers!) to a snake, simply not the main meal but a necessary side dish on occasion.
Deterrents for grass snakes
Grass snakes are protected by UK law so you cannot lawfully kill or harm a grass snake. In fact, there is argument to support grass snakes as their populations are in decline in the UK.
If you have a compost heap close to your pond, I would perhaps consider moving it. Grass snakes like to lay their eggs in compost heaps due to its warmth.
Supporting a healthy population of amphibians could well attract grass snakes so you could potentially try to move them away from your pond.
Cormorants
Cormorants are not common in the UK except for rocky coastal areas. This means that the risk of a cormorant finding your pond is exceptionally low.
However, it has been noted that cormorants are increasingly being found further inland on estuaries and rivers. In fact, due to successful conservation work, inland populations of cormorants are now flourishing.
Cormorants are very much like herons and will gobble as much of your fish population as they can. You might even think of a cormorant as a more industrial heron.
Signs cormorants are eating your fish
Cormorants catch fish by diving into water and chasing their prey until they catch something. Cormorants are also known to hunt in groups.
As a result, if you have a deep or relatively large pond and you find all your pond fish missing it could well be a group of cormorants.
Deterrents for cormorants
As cormorants dive into water to catch their prey having a physical barrier such as a pond net should prevent any cormorants preying on your fish.
Having significant cover of pond plants will also help to deter a cormorant as well as provide a level of protection for your fish.
Conclusion
To conclude, the main reason for this article was to give answers to a common pond keeper question, what is eating my pond fish?
The short answer is it could be several potential predators.
The most likely answer however is a heron. Herons are common in the UK and love to gorge on fish as the main part of their diet.
Whilst there are many different types of deterrents you could use against the wide variety of predators the most effective would be a pond net.