The ziege is the only species in Poland that, similarly to tropical flying fish, in the moment of danger is able to leap out of water and glide even a few meters in the air. What enables the fish to fly above water’s surface, is its exceptional body plan. The ziege is about 35cm long, up to 7cm high, and only 2cm thick. Contrary to the majority of fish, its pectoral fins are located horizontally, not vertically. When the fish leaps out of water, it spreads its wing-like fins, which may reach even 24cm of length.
The ziege is a predator that feeds on alevin and larvae. However, very often the fish itself becomes a victim of other predators, and it is also commonly caught by people. Fishermen say that the ziege does not have bones only in its eyes, but as a matter of fact, when three times minced, it is perfect for fish cutlets. Unfortunately, because the influence that a man exerts on the environment is constantly increasing, the population of the ziege has dramatically decreased in the last few years. The last location where it can be found is the Vistula Lagoon. Moreover, the ziege has been put on the IUCN Red List of Threatened Species, which is why Prof. Roman Kujawa, who works in the Department of Lake and River Fisheries at the Faculty of Environmental Sciences, decided to take further interest in this species. A project titled Biotechnology of breeding and rearing the ziege (Pelecus Cultratus) under controlled conditions, enabled Prof. Kujawa to proceed with his research, for which he obtained a grant of 230.000 zlotys from the National Science Centre. The project started in 2011, lasted for three years and has recently ended with a full success.
– The ziege is an endangered species, thus I decided to deal with its protection, and develop biotechnology of restocking material production, which solves the question of repopulation. What additionally surprised me, was the fact that none of the scientists has succeeded in multiplying the population under controlled conditions. I found it puzzling, because according to literature, the ziege is not biologically complex – Prof. Kujawa says. It took the Professor little time to discover why it happened.
In order to carry out the research, he needed some spawners. Therefore, he established cooperation with fishermen of the Vistula Lagoon. Fyke netting turned out to be the most effective fishing gear, as it enabled obtaining the right amount of fish. However, their quality was most problematic. Once the fish entered a creel, they were exposed to strong waves. Consequently, when bouncing around the trap, they significantly bruised their bodies, causing scale loss. The fish were also at risk when fishermen emptied out the net contents, since spawners could be injured by rays of the zander, perch or ruffe. If so, their wounds got infected, so the fish were soon dead, and it was impossible to obtain eggs and semen. In order to minimize fish injuries, fishermen took out every single fish individually.
– Developing a method for catching spawners without injuring their bodies was the most difficult part. Afterwards, it was much easier– recollects Prof. Kujawa.
Apart from that, are there any other difficulties in breeding the ziege?
– This species can be easily frightened. For instance, knocking at the tank makes them startled. Thus, one needs to be very careful so as not to scare the fish, because in a moment of danger, they reach really high speed. Even seven or eight-centimetre fish is able to jump out of a tank, so it always needs to be covered, as it is impossible to avoid making some noises. Unfortunately, when the fish cannot jump out of the tank, it bangs against its sides and eventually dies – Prof. Kujawa continues.
Once the method for obtaining spawners was already elaborated, the Professor was able to acquire eggs and semen. Then, he obtained larvae, and in the end – alevin. He finished the project when the fish were mature enough to live freely in natural environment. The results of his research were published in a scientific paper, which may as well serve as a textbook about breeding the ziege under artificial conditions, which can be highly useful for regional water management authorities, or tenants of water bodies. It constitutes the first and the most important step concerning the ziege protection.
Professor Roman Kujawa is currently working on developing the technology of breeding and rearing river lamprey (Lampetra fluviatilis), which is another endangered species. The population of river lamprey in Poland and other European countries is constantly decreasing, for nearly the same reasons, as with the ziege.
Transl. by AP