Category: Carp Science

Carp Genetics and Catchability

Have you ever noticed that some carp are nearly impossible to catch? What makes one carp easier to catch than another? Searching to answer this question, I came upon a handful of scientific studies that discussed some of the issues involved. Of course, there are many factors such as the amount of fishing pressure, what the fish are naturally feeding on, location in the water body, and many, many other things that can impact fishing. However, I became interested in one that is less talked about: genetics. Carp have been domesticated for a long time and the result is many different “strains”, much like breeds of dogs or any other domesticated animal. And just like dog breeds these strains have different characteristics that impact everything from appearance to growth rate. While this selective breeding was not with angling in mind, the outcome of it is of major interest to anglers—and not just if the fish is a common or mirror, or how big it can ultimately get. It turns out that this selective breeding also has an impact on how easy the fish are to catch. This is isn’t just a minor difference either, as studies have shown that some strains of carp are much harder to catch than others. Most of these comparisons were between wild type carp (common) and more domesticated mirror carp. Mirror carp have been bred for two things: few scales (obviously) and a high growth rate. These traits were useful in the production of carp for food and set these fish apart from their wild brethren. In order to achieve a higher growth rate these fish have to eat more, which in turn naturally makes them easier to catch as a fish that eats more has more chance of getting a hook in the process.

There is also a difference in what the strains prefer to eat. Both have been shown to prefer to eat sweet corn over pellets (even when raised on pellets) which is likely a combination of the bright color but even more importantly the sugar content of sweet corn (the fish prefer to eat candy). But in another study the wild type carp preferred worms over other food types which can go a long way to explaining why there are many waters in the USA (and possibly other places) where often the biggest carp out of a lake was caught by someone who was not fishing for carp at all but rather by someone fishing for sunfish or catfish – using worms. Iain Sorrel has an article on “Alternative Approaches” that discusses this very topic.

But back to the impact of genetics. Studies have also found that even with the easier to catch domesticated strains there is a relatively high percentage of fish that were never caught at all in experimental ponds. For mirror carp this was about 45% of fish never being caught, and for the wild type this number was 68%! That means that 68% of the fish in a small pond could not be caught in 20 days of fishing. Keep in mind these were fish that had been raised in a hatchery and were used to eating pellets and had never been fished for before. Now think about the fish that you are fishing for and it makes you wonder how you ever catch anything!

The impact of angling pressure was similar for both strains as they become harder to catch the more they are fished for. This means that the carp get better at not getting hooked – which is no surprise to anglers on heavily fished waters. Even if you can see the fish feeding over your baited area it doesn’t mean that you will catch any: a study using tagged fish showed that even when fish are feeding directly where angler’s baits were located, it made little difference on whether certain fish were caught. The interesting thing is that it has been found that the carp kept feeding similarly but more slowly and with more inspection of the food. Not only did they use sight, though, the carp were likely able to detect the rig by feel as well.

Added to all of the above are individual differences between carp in the same lake, from food preference to handling of that food. This also makes some easier to catch than others. Feeling overwhelmed? Some take home messages for carp anglers include this advice: keep your rigs concealed. The fish can and will learn to avoid the rigs. This is not “smart” so much as the same conditioning they use to avoid other predators. Try alternative baits. There are potentially a lot of “wild” fish out there that are never caught because they prefer to eat wild food. Make sure your hooks are sharp. When the carp can feel the rig, you’ve got a much better chance of hooking them before they reject it if you aren’t making it easy for them with a dull hook!

Carp Food

Unlike in trout fish, carp fishing rarely relies on matching the hatch yet it’s not often that a carp finds a boilie or pile of sweet corn if someone has not put it there, so the majority of food a carp eats are actually things that are living there already. With this in mind, it is worth considering a few things. Carp are omnivorous, meaning that they eat both plants and animals, and which also means that what they feed on in one water will not necessarily be what they will be feeding on some place else. While what they are feeding on does vary by location, not all food items are created equal in a carp eyes. Bloodworms (the larvae of midges) are at the top of the list on a carps menu, and while carp have been shown to have a strong preference for them, there are a host of other items that they will eat. This is also size dependent; there is little overlap between the diets of small and large carp – something that may help you to select the better fish. Here is a pictorial list (in no particular order) of some of the things that carp like to eat:



Zebra Mussels


Midge Larva

UIRW-003 Chaoborus_sp._pupa,_Netherlands 220px-Chironomus_plumosus01


Aquatic plants (Macrophytes) and Detritus (dead particulate organic material)

Fresh water clams (Corbicula)

2015_0823_12194900 2015_0823_12164500


FloridaFlusskrebs Orconectes_limosus_-_Kamberkrebs



So, how to use this to your advantage? Often times what the carp are feeding on is really not that important as they will happily eat your bait regardless. However, there are certain places and times when “matching the hatch” is important if you want to catch the biggest fish or at times, any fish. A option to consider is alternative techniques (See Iain Sorrell’s post) that incorporate the natural food item or some artificial look-a-like.

Some baits designed for Black Bass may be just the thing for stalking large carp.

Another is to use a bait that is designed to smell like, and even better be made out of, the real thing. There are are number of baits available that are designed with this in mind. Bloodworm, crayfish, mussel, and worm flavors and extracts are all available.

Blood worms are a natural food, and some bait companies have made baits to take advantage of this, incorporating real blood worms into the bait.

When you are on the bank keep in mind what the carp might be feeding on (in between your bait) and it might help you to put an extra fish on the mat.


How the Thermocline Impacts Your Fishing in the Summer

The thermocline is an layer in the water column where the temperature rapidly changes. This occurs during the warmer months when the surface of the water heats the the area below does not. These drastically different temperatures cause the water to no longer mix with the result that the colder, deeper, water can become oxygen depleted. While carp are highly tolerant of  low oxygen, they are not happy in these conditions, and what is more their food is not happy and tends to smother. The result is that while the temperature might seem ideal everything else is not – no food means no carp.

Whats under the water often depends on the season
Whats under the water often depends on the season


The area right above this is where there is oxygen and the water temps are the lowest. This is where the carp will often be the most comfortable and importantly have plenty to eat. Where this zone is is highly variable from lake to lake. (Rivers are not affected as the moving water keeps things mixed.) In general the clearer the water the deeper the fishable zone as photosynthetic organisms (plants and algae) can produce oxygen deeper in clearer water.

Finding how deep you should fish is the kicker. If you pull a lead along the bottom and find some vegetation you are not too deep as these plants will produce oxygen. In many lakes a good way to find out how deep you can fish is by looking at the fishing report. No, you will not see a section titled “carp” but you may see how deep the bass or the trout are being caught at. If trout can survive carp will be doing great and you can feel confident in fishing at that depth. You can also talk to the local fisheries biologist who should be able to give you idea of the “temp/DO” profile of the lake. After that get out the marker float and find where this depth is.

So what is you see fish crashing in open water? Maybe try a zig rig. If you see carp crashing in water that is deeper than the thermocline, and you know roughly where the thermocline is (from fishing report, etc) why not try a zig set to just above it? I have seen first hand while diving massive amounts of zooplankton that can be found in this part of the water column in really deep water and if I have seen them the carp know they are there and will focus in on them. Knowing this might make the difference between blanking and banking.


Carp in Space and Time

As carp anglers, we are always looking for that little bit of extra knowledge that will get us more fish on the bank. Tons of effort has been spent on making a better bait or rig, and lots of excellent information is available on choosing the best spot to cast your baited hook. This is all, of course useful…but only to the point of getting the most out of the swim. The key thing is location, because if no carp are in the area to find your bait all the rest is really pointless.


Just because the swim is nice to fish from does not mean it’s the best place!


While relatively little is known about the movements of carp, a few researchers have studied carp with radio tracking implants and have been able to shed some light on where exactly the carp are at a given time of year and how they move around.

At first glance carp might seem to be a rather sedentary fish, but this is not always the case – especially in rivers. For example, some tagged carp in the Murray River in Australia were found to move up to 890km (553mi), with a number of fish moving at least 100km. While the majority of carp did not move this distance (most moved no more than 5km), a movement a fraction of this can easily put fish in an area that is well away from your swim.

One of the more interesting bits of information gleaned from carp radio tagging is the amount of variability found between individuals. As anglers we may have noticed that all carp don’t behave the same way, with some fish having a preference for a certain bait, or maybe that you never catch this one carp in the same place twice? This same phenomenon was found in the fish that were tracked, with some fish doing things very different than others for no known reason. While this may seem like a case of why bother, there is some good news for carp anglers: females and larger males move less than smaller males. In other words, the fish we want to catch move less, so once you find them they will likely stay in the general area.


Carp_Spawning_areas (2)
Shallow flats at the upper ends of reservoirs are good locations for carp to spawn.


Naturally, over the course of the year how much carp move differs, with less movement during the winter. Movements start to get into full swing when water temps get around 13°C in the spring as fish start to get ready for spawning  (with spawning happening in water temps between ~18 and ~23°C) by moving into areas near shallow flats with submerged vegetation and woody debris . Right after spawning, carp spread out and can be found in more locations. Once temperatures fall to near freezing there is a rapid movement to the over-wintering location. Once in this location there is very little movement until the following spring. This schooling is most pronounced in areas that get really cold with temperatures of only a few degrees above freezing tending to produce the largest schools. Where these schools form can be very predictable from year to year, so if you find fish one year they will likely be there the next.


If they are to be found in the water you are fishing, a key factor to locating carp are weeds beds. During all seasons it has been noted that carp strongly prefer to be near some sort of vegetation. This is not really surprising as most of the carps’ natural food is found in these areas. After vegetation, the next most utilized habitat type is silt, again where a number of different food items are to be found. Sandy areas are not used as much by carp in a natural setting. Even during the winter the carp don’t prefer the deepest areas. There is a general trend of increasing distance to shore and water depth during the winter but vegetated areas are still preferred if available.

Okay, so how does this help? Well that is up to individual interpretation. What I see is this: carp like vegetation and shallower water. There are a few obvious reasons for why this is the case and they include food and cover. But what about in locations where there is little vegetation to be found such as large reservoirs? In these lakes most of a carps food will be from soft silt where there will be blood worms and clams. I would also conjecture that carp can also be found over rock areas as they forage for crayfish, but at this time I have not found any research looking at this.

One thing thats keeps coming up is “shallow water”. How shallow is shallow? While not mentioned in any of the works I have read I think that the fact that carp tend not to use the deepest water available is likely linked to  where their food is likely to be found. Since carp primarily eat aquatic invertebrates which are largely unable to move with changing condition these organisms need to be in areas that have enough oxygen to support them, in deeper lakes this is above the thermocline. The thermocline is a rapid change in water temp that keeps the surface water (with lots of oxygen) from mixing with the colder deeper water (oxygen poor). How deep the thermocline is will vary with the a number of factors, but in general the clearer the water the deeper the thermocline will be. A simple way to learn how deep the thermocline is is just call your local fisheries management agency that works on the lake you are interested in – they should be able to tell you. I will post more about the thermocline in another article.


Using a bathymetric map can help you to choose a swim that meets the criteria you are looking for.


I hope this will help when you are trying to decide where to fish and give you a better understanding of where the fish will be.

Betaine: how much is too much?

Betaine (BEET-uh-een) is a feeding stimulant for a number of fish species, including common carp, and less fortunately, channel catfish. Studies have shown that Betaine hydrochloride (HCL) is better at stimulating a feeding response than pure Betaine and has been tested to determine the optimum concentration in a paste type food.

ChemSpider 2D Image | Betaine Hydrochloride | C5H12ClNO2
Betaine Hydrochloride is better than pure Betanine at stimulating feeding in fishes

The results of some of these tests are interesting. As would be expected, very low levels did not preform as well as higher levels – however, this trend did not keep going. A concentration of 15.66ppm was found to be more attractive than a concentration of 1566ppm. Concentration of Betaine HCL above 1566ppm were not tested, but if this trend is supposed to continue it could be assumed that very high concentrations of Betanine HCL might at some point put fish off.

The response of the carp to different concentrations of Betaine HCL. I had to transform the concentrations as they could not really be seen in their original form.

According to this graph (by solving for y=2.94), once the concentration of Betaine HCL reaches 25 ppt it is only as effective as the food that has a very low concentration in it, indicating that you could add to much Betaine and decrease the attractiveness of the bait.

So, how much Betaine should you use? It seems that a concentration of 0.01566 ppt is a good starting point. This means that you would add ~0.01566 grams to 1 kg of bait.  A 1/4 teaspoon is ~1.19 grams.

Before you take these results as the last word on Betaine concentrations there are a few things to remember. First is that this test was done on small farmed raised carp in a relatively small tank with recirculated water. This is about as unlike any of the waters we fish as you can get. Second, these fish were not actually eating the food containing the Betaine, they were just assumed to have been attracted to it. And third, the results could look a lot different if more concentration levels were tested, and could show that higher levels keep working better…you just can’t tell from the results as these levels were not tested.

I have added parts per thousand (ppt) to the results table below.  Ppt is equal to grams per kilogram for making bait, so if you want to add a concentration of 20ppt, you would add 20 grams of Betaine per kilogram of bait.

I know that I have rethought my Betaine use,  and I hope this helps you when trying to decide what levels of Betaine to add to your next bait.

Results of the Betaine HCL exsperiment.

Number of fish Treatment (ppm) Log(ppm) ppt (grams per kg)
8.29 1566 3.194791758 1.566
9.69 15.66 1.194791758 0.01566
7.68 0.1566 -0.805208242 0.000157
2.94 0.001566 -2.805208242 1.57E-06
3.25 0.00001566 -4.805208242 1.57E-08

What Makes a Big Carp Water?

In the parts of the world where carp are less than popular with the general public, it can be very hard to tell if a body of water will hold large carp before actually fishing in it and finding out (and possibly wasting your time). The factors that allow a lake or river to contain large carp are many and difficult to pin down. However, there are some things that do seem to contribute to how big the carp can get. These factors are similar to those of any other “sport” fish species, and while not often applied to carp in the USA I think they will at least help to narrow down the choices of what waters are worth a try.

The theory behind this is pretty clear when you think about the life history of carp. The more carp there are, the more competition there is for food. This leads to there being less food for each individual carp, which leads to slower growth and smaller average size.

So we will focus on factors that contribute to too many carp in the water:



Spawning areas

While at first it might seem that an ample spawning area would be good for a carp fishery this is not always the case. Obviously the general trend is the more suitable spawning habitat (shallow weedy areas) the more carp there will be. So, look for waters that have a limited amount of shallow, weedy areas.

If there are lots of shallow weedy areas then there is a good chance that there will be lots of carp…and they may be small.
Spring fed lakes
I was discussing with David Moore of Big Carp Tackle what he thought were factors that contribute to a water having big carp, and he mentioned spring fed lakes as often having better fish in them. This makes perfect sense. Spring fed lakes are often oligotrophic–meaning they have clear water, little vegetation, and a firm substrate – all things that often add up to some good size fish.

Bottom and water clarity

When the bottom is soft (think muddy), large numbers of feeding carp can stir up the bottom, uproot vegetation, and cause the water to become muddier.  This muddy water is good for protection from predators, which most often feed by sight (like bass or pike). However, this also causes a loss of aquatic vegetation as the sunlight they need to grow can no longer reach the bottom. This vegetation dies and makes the bottom easier to stir up, making the water even muddier. This is bad because many of the carps’ food items are found in vegetated areas. The net effect is smaller, stunted carp. Carp causing muddy water only really occurs when there is a lot of carp in the water – if you think the whole body of water is muddy due to carp feeding, you might want to look elsewhere.

Believe it or not there is a carp <5in in in front of the camera. Water that looks like this much of the time will have smaller carp. I took this picture in a lake that has very small carp in it.
Believe it or not there is a carp less than 5 inches in front of the camera. Water that looks like this much of the time will have smaller carp. I took this picture in a lake that has only very small carp in it.


Big carp require lots of food. In European waters this is often not a problem as many of the carp are feeding on food items introduced by anglers. In waters where the carp are not fed by humans, the food they select can vary greatly with the location. The bulk of a carp’s diet is made up of bloodworms, which there are often a lot of and are available pretty much all year. They would prefer larger food items, such as snails, mussels, and crayfish, but these items have to be easy enough to crack open. Studies have shown that when carp are given a choice between hard and soft-shelled snails, they will go for the soft ones first. So when you get to a new lake, take a small net and scoop along the bottom. If you find small invertebrates you can crush with your fingers, you’ve found some good carp food!

Bloodworms are often a large part of a carp’s diet.
Bloodworms are often a large part of a carp’s diet.


Carp are a very prolific and hardy species that can quickly populate a body of water. If left unchecked carp will consume all the resources available and will become stunted and in poor condition. A necessary component of good carp waters is a decent predator population that will keep the carp from becoming too numerous. Any species that eats fish will eat a small carp. However, it takes a larger predator to eat a carp that has gotten bigger than about 4-6 inches. A good population of large predators such as flathead or blue catfish is often a good sign that there will be some good carp as well.

Carp removal projects
In fisheries terms, a good sport fishery is one that has a high biomass and low density (that is, fewer, but larger fish). Carp removal projects only work if every carp is killed, which means you have to remove all the fish either by rotenone (poison) or draining. Efforts that remove the better fish (think bowfishing) or most but not all the carp (think netting) just make things worse as it triggers a spawn of the smaller carp that remain. This results in – guess what carp haters – a lot more really small carp! This makes no one happy. It is much better to remove the smaller individuals and leave the larger ones in the lake.

In summary

The bottom line is very simple. The more carp that survive from each spawning lowers the amount of food per carp, thus making the carp attain a smaller size. Lakes with the biggest carp will have fewer spawning areas, hard bottoms, clear water, and lots of food and predators. Of course things are not always this simple, but this general scheme should help to narrow down your search as you look to fish new waters.

Clear, hard bottom reservoirs with plenty of predatory fish have the best potential for big carp in many parts of the country.
Clear, hard bottom reservoirs with plenty of predatory fish have the best potential for big carp in many parts of the country.


Carp feeding in the spring—the ecology of zig rigs

Zig rigs are a popular type of rig, especially in the spring. Most articles and anglers generally attribute their success to carp sunning themselves near the surface in the newly warmed water. While carp may indeed be higher in the water column to raise their body temperatures, another reason is every bit as likely to account for their departure from bottom-feeding.

To better understand this phenomenon, we will first look at some basic aquatic ecology. There are two types of plankton found floating within the water of a lake: phytoplankton—microscopic plant like organisms, and zooplankton—tiny animals.  These little organisms are what often give the water a greenish cast. Food availability within a lake is dependent on the nutrients found in the water. These nutrients are used by the phytoplankton which are then eaten by zooplankton. Zooplankton are eaten by all sorts of things, but most importantly for us they eventually end up feeding the carp.

Daphnia is a common zooplankton eaten by carp. This species can grow up to about 6mm. During the spring the number of daphnia in a lake increase, providing a ready food source for carp.
Daphnia is a common zooplankton eaten by carp. This species can grow up to about 6mm. During the spring the number of daphnia in a lake increase, providing a ready food source for carp.

Because phytoplankton need the sun to grow, during the winter when the light levels are low there aren’t too many of them around. This, in turn, means there are fewer zooplankton. Spring rolls around, and with it, more sunlight. Nutrients have accumulated all winter, and with this combination the plankton levels near the sunny surface skyrocket! These effects are particularly large in northern lakes, where ice and snows have made the water darker. Now there is an abundant food source in the lake that is off the bottom. The carp follow the food, and rise higher in the water column.

If there is enough phytoplankton you get what is commonly called an algae bloom.
If there is enough phytoplankton you get what is commonly called an algae bloom.

Now we know why the carp are there, but how can we use this knowledge to catch more fish? First, let’s talk bait size and flavor. It is well known that smaller zig rig baits are more effective than larger ones, and this makes sense considering the tiny size of the zooplankton. Because plankton don’t smell very strongly, the carp are locating them mainly by sight. If you are trying to closely “match the hatch”, it might be a good idea to stay away from flavored bait. Zooplankton are mostly clear or light colored, so for really picky fish and in clear water you might try to mimic them realistically using a light gray or off white bait. However, most of the time a high visibility zig rig is still the best, so pick bright yellow or white for daytime trips and black for evening/night for the highest contrast.

A selection of small experimental zig flies. Smaller baits better represent the natural food item – zooplankton – that are normally not more than a few millimeters in length.
A selection of small experimental zig flies. Smaller baits better represent the natural food item – zooplankton – that are normally not more than a few millimeters in length.

To locate the carp, remember our food web. Phytoplankton need high light levels, and so will be found no deeper than twice the depth that you can see a white object (this is approximately how deep light can penetrate). Zooplankton (and carp) will be nearby, so this is a good depth to start your search. In the evening the many plankton species will rise up higher in the water, so try fishing higher up during lower light conditions. Wind will also have some effect on the concentration of plankton. You should look for areas on the windward side of the lake where the current generated will concentrate the plankton.

Because a smaller bait is more realistic, you won’t be able to support a 6 foot leader off the bottom on the buoyancy of the bait alone, so a sliding type zig rig will be the best bet. I have seen a number of rigs that will do the job, but I have found that the ones with only the swivel of the lead to allow the rig to slide tend to jam with mud and weeds in most of the venues that I fish. A run ring rig similar to a marker float setup reduces this problem. Clear floats are popular for these rigs, and are supposed to give the rig a lower visibility. However, I am not sure that this will make a huge difference in waters where the carp are used to seeing all sorts of trash in the water, and/or when visibility is low.

Plankton are often overlooked as a food source by anglers, but carp will eat them when they are available. In fact, studies have shown that in the spring zooplankton make up the bulk of the carp’s diet! The plankton phenomenon, while most pronounced in the spring is by no means restricted to this season. There are reports of zigs working during all seasons, and this is at least partially due to the fact that zooplankton are available all year. While SCUBA diving during warmer months I have seen clouds of daphnia (a zooplankton that is often eaten by carp) in mid-water well off the bottom. A zig rig would be the only way of fishing in this zone, and would no doubt be effective. Taking the carps’ natural feeding habits into consideration when using a zig rig could mean the difference between a fish on the bank and blanking when faced with plankton feeding fish.

Nash tackle zig bugs have accounted for many large carp over 50lb in Europe.
Nash tackle zig bugs have accounted for many large carp over 50lb in Europe.

Nash zig bugs are available in the USA from big carp tackle: