One of the most common questions I see all the time is “How did a fish get into this pond or lake?” Well today we will discuss all possibilities.
There are multiple ways that fish can be brought into any body of water and they don’t just magically end up there. They can get there naturally, via a carrier animal, or through human placement. Below we will go through each one and maybe you’ll know how the fish got into any of your local lakes and ponds.
How fish got into rivers, ponds, and lakes historically
First we need to look at this from a historic perspective. There are literally thousands of lakes and probably millions of ponds in the world that have fish in them. Many of them contain the same species of fish. But if they aren’t connected, how are the same species of fish in each?
The answer lies with the long history of Earth as a planet long before humans were its inhabitants.
The world has not looked the way it does currently for most of its existence. There has been the Ice Age where quite literally the Earth froze over. Interestingly enough, some lakes were created during this time as glaciers worked their way into the land, creating holes. Then, when they eventually melted, a lake was left behind. This is how the Great Lakes were formed.
There have also been great floods throughout history. Just take a look at this top 10 list of known floods in human history. Now consider that humans have only been around for about 200,000 years. The earth is estimated to be about 4.5 billion years old. This means humans have only inhabited earth for .004% percent of it’s lifetime. Basically no time at all. So we don’t even know the amount of flooding that has happened over Earth’s history.
There have also been millions of tectonic shifts, eruptions, and many other changes that we likely aren’t fully aware of. There was even a time where all of the continents on ear formed together called Pangaea, which existed 335 million years ago. Take a look at the image below which shows it with modern day countries revealed.
But what does that have to do with how fish get in new water systems?
I only bring this up to show how throughout points in history the Earth has had water connected and then disconnected many times over. This is the main reason that fish of various species exist in many different bodies of water that may never be connected today. But historically, it is quite possible that large scale flooding, glacier development and melting, or other connecting forces brought these together along with the animals that lived within them.
So if a river had a largemouth bass in it and it flooded, the largemouth bass may have washed out with the flood and into the new pool. They then would have reproduced naturally in the new lake or pond that formed and voila, fish begin to grow. Because the earth has underwent so many changes in its lifetime – there are endless possibilities into how fish ended up in the well-known ponds and lakes that have been around for centuries.
But, that doesn’t explain how a fish could end up in a pond or lake created only decades ago? How could that have occurred? Let’s discuss several theories of that below
Fish in new ponds and lakes due to connected waterways
Generally lakes or ponds aren’t developed in places that have no natural water features to them. Beavers or even humans will dam up rivers or creeks to create natural pools of water that become ponds and lakes, or springs feed into the pools which creates them.
So this creates a very natural way for fish to get into new lakes or ponds. If there is any body of water connecting the new lake or pond to old waterways – fish will end up getting in it somehow. Fish naturally travel and end up finding their way into the new area. If there are no natural predators in the area, they will quickly reproduce over the years and their population will grow.
So the first sure sign to know if a pond or lake has had fish naturally introduced is to look at the other creeks, rivers, or waterways that they are connected to and what may already exist in those.
Flooding brings in new fish
As mentioned above, flooding is also a major contributing factor in fish ending up in lakes and ponds. Historically this is true but it can even happen currently.
The means is quite simple – a river or creek that is close to a pond or lake rises due to flood conditions. Maybe a heavy rainfall or other natural occurrence. As the water rises it becomes connected for a very short period of time to another body of water. The fish, not knowing any better, travel during the flood into the new water. Then as the water levels decrease again, they are stuck in the new water without a way to return home.
Will many fish make this trip? No. But it only takes one male and one female to create an entire population of fish in a pond or lake. With no natural predators in the water, they can grow exponentially for a few years.
Mudfish and old waterway connections
An interesting opposing natural occurrence that can cause fish to randomly appear is a long period of drought. Perhaps a body of water or river existed but a drought made it dry up for many years. Then as rains come back, the water re-appears and there is fish in it! How could that possibly be?
Take a look at this example of a fish that can live underground in completely dry dirt for years.
While these are certainly far from the norm, there are several species of fish which have become accustomed to essentially hibernating in mud or dirt for years until water returns and they can return to their normal existence. So this is another possibility if a pond has been drained and brought back months or even years later. Certain species of fish may have burrowed into the mud and dirt and survived to come back when the water re-pooled.
Fish get to new lakes and pond via carriers
Lets move on to other techniques which do not require the areas of water themselves to be connected. While this explains the transfer of most fish throughout history – it doesn’t explain many of the farm ponds we see today. You can create a small pond in the middle of a field with no water in sight and after years fish may just naturally show up in it. How?
The most common way for this to happen is transfer via birds. There are an abundance of birds which will use lakes, streams, or any freshwater for drinking, hunting, or even bathing. When these animals land in the water they aren’t particularly careful on what attaches to their feathers or feet. So as they travel from lake to stream to pond, they carry a lot of what was in the old one with them.
What they carry with them could include fish eggs. So as they land in one pond with fish in it, they swim around and a few fish eggs attach themselves. Then, as they drop off in the next fish-less pond they fall off. The fish hatch in the new pond and begin their life cycle eventually reproducing and creating more fish.
This has been a commonly held belief for years, but interesting there is no scientific evidence to support it.
This however is more likely due to a lack of real research than the complete inability for it to actually transpire. There are some bodies of water where this seems to be one of the only possible solutions as to how fish got there. But, it is also said among some fisherman to be a common occurrence. In reality, it probably isn’t as common as some people believe but I also believe it is a real possibility.
But I do want to mention that birds are not the only animals that could possibly carry fish eggs from pond to pond. Beavers, muskrats, otters, snakes, large insects, and a variety of other animals also have the possibility of accidentally taking fish eggs from one body of water to another.
Boats and other watercrafts
And it’s not just animals that have the ability to move fish from one place to another. Boats and watercrafts are notorious for getting materials in the water stuck to their hulls that aren’t seen by the human eye. Then, as the boater travels from place to place, they unwillingly mix the ecology of one pond with another and introduce a variety of unwanted organisms into new waters.
I remember when I first fished in California with my father-in-law on his boat I was amazed that all boats were required by law to be deep-cleaned before being put in another body of water. They have had so many issues with cross-contamination from one body of water to another they actually have had to regulate it. So why can fish eggs not be moved this same way?
So do be careful with any watercraft you take from one body of water and put into another. In all likelihood, you are not going to harming anything. But it’s good practice to wash it thoroughly so you don’t accidentally introduce anything invasive into a body of water that you know and love. Whether it be vegetation or otherwise – it can cause real harm to a fishery.
Fish end up in new lakes and ponds by stocked purposefully
Finally we get into the reason that most ponds or lakes have fish in it – people purposefully put them there.
Fisherman love nothing more than a honey hole that no one knows about. So if you see a nice, secluded body of water that no one is fishing – you may be tempted to catch a few fish from a nearby lake or river and then put them in your unknown pond to let them grow. And they will grow and reproduce very quickly from it.
This is done extremely often. And in most cases, professionals should be called who are experts at knowing how to properly stock fish in ponds and what numbers and types of fish should be stocked. But regardless of how it is done, humans putting fish into new waters is usually the number one way fish are quickly introduced into new waters.
Fish stocking is often done by large lake managers or governmental entities as well to keep populations up for fisherman. In Virginia, for example, over 80% of all trout caught were purposefully stocked by the Virginia Department of Wildlife Resources. Trout do not naturally reproduce quickly or effectively enough for long-term success, so hatcheries grow new trout each year for Virginians to catch and hopefully eat at their dinner table.
When done correctly, fish stocking is a harmless and often beneficial practice for ponds and lakes. For example, some species such as grass carp are often introduced to keep algae bloom in check so that the current fish can have clean waters to swim through and don’t become overrun by aquatic vegetation. These grass carp pose no threat to the fish that live there and are not invasive or will quickly overrun the ecosystem.
Others though, like the snakehead, differ. Somehow (though it’s widely believed to have been human introduction) snakeheads have entered many waterways across the United States and are quickly overtaking populations of more desirable, native species. Read this article for more information and to understand why fish stocking should always be done with care.
There are hundreds of ways that fish can end up in new waters from flooding, water changes, animal carriers, and stocking programs. Ultimately a combination or variety of any of these could explain why your local pond or lake has many species of fish in it. If you have another theory or know more information, please leave a comment below!