Danube Virtual Museum

Fish

Fish world on the Danube through Serbia

The Danube is 2,783 km long taking 33rd place in the world. Its surface area is 817,000 km2, which puts it at 32nd place here.

It originates in the southeastern slopes of the Black Forest in the town of Donaueschingen at the confluence of two small rivers, the Breg (47.6 km) and the Brigach (42.7 km).

The Danube Basin is divided into three physical/geographic parts: the upper Danube or the Alps, the middle or the Pannonian Basin and the Lower Basin or Vlach-Pontic Danube. Tributaries that have a greater impact on the average discharge are: The Drava, Tisa, Sava, Velika Morava, Olt and Siret, while many other tributaries have much less impact on flow.

Today, the river passes through or forms the borders of ten countries, from the source to mouth they are: Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine.

The Danube is entering in Serbia on its 1,433rd km (Serbian-Hungarian border) and on its 588 km flow through Vojvodina and Serbia it diverges into backwater creating a unique oasis of life. Fishing areas of the Danube occupy over 150,000 hectares.

The maximum depth of the Danube in Europe is in the Iron Gate/Đerdap Gorge (Kazan) where it is 87 m. This is followed by Dalj and Bogojevo where it is 27 m.
The Danube's fish fauna is rich offering about 75 species. This accounts for a large percentage of the total fish fauna for all of Serbia. Many species are protected due to the reduced number, such as the Black Sea and Danube herring, weather loach, sturgeon, beluga, small and large zingel.

The northwestern part of the Danube lies in Vojvodina, which borders the waters of the low-warm type (cyprinid), waters characteristic of the entire Pannonian Plain. This is exactly why this part of the Danube is much richer in fish than in other countries which it flows through. In addition, this section of the Danube in Serbia is the richest in fish.

Sturgeon (Acipenser ruthenus)

Sturgeon reaches up to 125 cm in length and weighs up to 16 kg. The Danube contains the smallest species of sturgeon. The fact that they do not migrate to the sea differs them from their relatives. Sturgeon spend their whole life in rivers, usually in the parent zone, or in the deep depressions of the river bottom during winter stagnation.

They feed on bottom invertebrates, primarily insect larvae. They spawn from April to June in the fast water flows over a gravel bottom. Sexually maturity is at 4-5 years, while their life expectancy is about 25 years. Sturgeon is considered to be very commercial fish, and the fishing season (with fishing nets) starts in early spring.

Beluga (Huso huso)

Beluga fish belongs to the family Acipenseridae. This is the biggest fish in the Danube - it grows up to 9 m and weighs up to 2000 kg.

They spend larger part of their lives in the deep sea at depths of 70-180 m and up to 12 km from the coast. They feed on fish, anchovies, rub, minor flatfish, goby, but also on crustaceans and molluscs.

At the time of spawning in March and autumn, they migrate from the Black and Caspian seas into large rivers. In search of suitable spawning habitats, those containing a gravelly or rocky bottom with a strong flow of water. Because of this, they usually reach the Danube waters. Before construction of the second Iron Gate/Đеrdаp Dam, beluga would even reach Bratislava in their upstream migration. However, their route was ended by construction the dam. Due to excessive fishing, as well as disruption of spawning by ending the migration route, the number of beluga has been reduced to a minimum. Beluga is a protected species everywhere in the world. In Serbia, according to the IUCN list, it has a status EN - endangered species. The status is given to a species which is likely to disappear in the future.

Carp (Cyprinus carpio)

Originally from Kazakhstan, the area between the Black and the Caspian seas, it has been taken to fresh waters of Europe, North America, and Asia.

Due to its adaptability, it is widely distributed today, which allows it to mix with other fish.

In Serbia, the carp live in slow low water, in the calmer parts with vegetation. It feeds on bottom fauna and plants, while the adults eat small fish. They spawn in groups, one female with three males in the period from late April to August. It grows over 1 m and weighs 27 kg. They reach sexual maturity in the period 2-4 years. It has a large commercial and sport fishing importance.

Black-striped Pipefish (Syngnathus abaster)

In winter when the waters of the Danube are colder, Black-striped pipefish retreat to the depths, while with increasing water temperature they move closer to the surface. Apart from sea waters, syngnthatus abaster also inhabit fresh water. In Serbia, in the Danube they can grow up to 15 cm.

They are recognizable by their long pipe-shaped mouth that easily sucks water, and with it the prey. They have an external skeleton, “armor” made of bony plates, and, depending on the type can exhibit up to 50 of these.

In the period from May to October they can be found in the coastal zone among the dense underwater vegetation. It is difficult to spot them, because of a well-developed mimicry - their appearance completely mimics the surrounding vegetation. During the period spent in the shallow waters, they reproduce even several times. Before each mating, there is a ritual performed when females choose males for mating. Males have an incubation chamber where females lay their eggs. The incubation of eggs in the male’s chamber lasts at least ten days, while a maximum is 25 days. Males are one of the few animals in the world that 'bear offspring into the world'.

Pike (Esox lucius)

Pike are fish predators and are considered the best ambush hunters.

They have a cylindrical body with a dorsal fin set far back near the tail root. The head has strong jaws with sharp teeth that vary in appearance depending on the position.

They inhabit stagnant and slow freshwater of Eurasia and North America.

Their elongated body covered with small scales is a real muscular spring, which enables initial acceleration up to 11 m/s2 when attacked, a record among fish. However, the maximum swimming speed is not as fascinating and does not exceed 60 km / h. This suggests that pike is not a persistent predator and in the case of an unsuccessful attack, they quickly give up chasing their prey. Pike is the first fish to spawn - at the end of winter, which (in our climate) is from February to April. They start spawning at 3-4 years of age. Female pike, depending on the size, lay 16-75 thousand eggs, with an incubation period of 10-15 days after mating.

Paddlefish (Polyodon spathulaL)

Paddlefish, with a scientific name Polyodon spathula, can be found naturally in the U.S. Mississippi River drainage system - including Missouri and Ohio rivers and their tributaries.

It inhabits slow-flowing rivers and is usually found at waters deeper than 1.5 meters. It may grow up to a length of 220 cm and weigh up to 90 kg. Their life expectancy is around 55 years. Females reach sexual maturity at 9, while males do at 6.

What characterizes the paddlefish is a snout on the upper jaw, which is greatly elongated and flattened into a paddle shape so it resembles a trowel. It feeds on plankton. Adult specimens have no teeth. It is popular for its delicious meat and eggs, which are used to make caviar. Paddlefish is related to our sturgeon species (Acipenseriformes). Like sturgeon, polyodon has a cartilaginous skeleton, a smooth and scale-free body, with four mustaches above the mouth.
(Text: Natural History Museum in Belgrade)