New project enlists Czech public to help save one of the country’s most common but increasingly endangered fish

The crucian carp (karas obecný) was once among the most common fish found in Czech waters. Now, however, biologists have registered its rapid disappearance from the country’s ponds and lakes. To save the fish, a new project has been set up with the support of Prague Zoo and the University of Life Sciences.

The initiator of the Zachraň karase (Save the Crucian Carp) project is Dr Marek Šmejkal from the Biology Centre at the Czech Academy of Sciences. I interviewed him about the initiative and began by asking why the carp is disappearing.

“There are several reasons. One of them is the destruction of their natural habitats. The rivers are not working properly anymore due to dams and the construction of transverse structures.

“However, the most important factor is definitely the Gibel carp (Prussian carp) invasion.”

You started the Save the Crucian Carp project to combat this. This initiative seeks to map out where there are crucian carp populations currently in the Czech Republic and where more of these fish could be planted. I understand that there are four stages in the project. Could you explain how it works exactly?

“The first stage of this project involves tracing both Crucian and Gibel carp populations in our waters by asking the public to report to us if they have found locations that house fish from either one of these species.

“Then we would like to map out the genetic diversity of the remaining crucian carp population in the Czech Republic and potentially find some locations where we can re-plant the crucian carp.”

You said that members of the public can help in the project. How would one go about this, practically speaking?

“The first thing to do is to register with our project (zachrankarase.cz). You fill in some basic information and, if you know, you can then add in some locations where you have spotted the fish.

“In the subsequent stages, which will be introduced in the future, you can find a suitable pond which can be completely fished out and then we will provide you with some crucian carp that you can start breeding.

“There are many ways to do this. For example, garden ponds, where people tend to have those colourful carp and goldfish, can easily be used to house crucian carp.

“I do this myself. My crucian carp populations in these relatively small five-by-five metre ponds breed easily. I have hundreds of these carp in each one.”

The crucian carp is not the only previously common fish in Czech waters at risk of disappearing. I understand that the Atlantic salmon and the Allis shad have already disappeared in the Czech Republic. Is that true? And, if so, is it for the same reasons?

“No. Those were migratory fish coming from the sea to the Czech Republic. They were the most prone to disappear due to the construction of transverse structures in streams. This was quite a fast process which happened during the eighteenth and nineteenth centuries.

“The crucian carp was originally a really common fish. You could basically find it in almost any village pond. It is less vulnerable to human destruction of its natural habitat than those migratory species you mentioned, so its disappearance is more serious.”

Do you have any data on the current numbers of crucian carp in the Czech Republic, or is that something that your project is also seeking to document?

“Yes, that’s the case. We want to find out. No one was actually mapping waters such as village ponds, small lakes left after mining craters, or those in forests. Focus was placed on rivers and dam reservoirs, so these smaller waters were not really mapped out in the past, and we do not know how fast the crucian carp is disappearing, nor when it happened.

“Based on my own experience, I believe it happened sometime around the beginning of this century, but we don’t know for sure.”

I am guessing that the crucian carp is also going to be a common fish in neighbouring states. Do we know if they are also disappearing there?

“I think that is the case. It is even happening in Sweden, which is one of the last countries where the crucian carp is still a quite common fish. Event there the Gibel carp is taking over through their distribution in the Baltic Sea and entering into Swedish rivers. It was a cryptic invasion. They were not aware of it at first, only finding out recently.”

How long are you planning that your project will run?

“I am not the only one responsible for the project. There are important partners, such as the Prague Zoo and the Czech University of Life Sciences in Prague.

“I think that they are planning on this project running for at least several years or even a decade before the crucian carp becomes a slightly more common fish again in Czech waters.”