09 November 2013

From zingel to pipefish - Tack diary of the 3rd Joint Danube Survey

We got to the end of September and the Joint Danube Survey 3 was also finished. The researchers have already gone home, the samples have been taken into laboratories and the ships have been navigated into their harbours. Then the work will continue within the four walls and the results are expected by the next year. On the one and a half month voyage new friendships, contributions of knowledge were born and there was a great pleasure for the Donau Inseln was shared in the researchwork. I have been thinking a lot what I should finish this expedition with, and at last I was led to the conclusion that I will end with the results of the concretest and the most spectacular project: the fish. Anyway they are hardly represented on this page, but in the gallery of JDS3 webpage many different types of fish can be seen which got in the boat and I have heard of them mostly from books.

The biggest catch of the expedition was this 2 metres long wels catfish (Silurus glanis) covered in wedding gown. It was caught in the Hungarian section, near Szob.

The expedition was life threatening only for one species and it was no other, than the common bream (Abramis brama). This is the most common Danubian fish, that is why it was presumable that it occured at every sampling point, so their blood and liver is good to benchmark for the whole Danube.

It is a young sterlet (Acipenser ruthenus), which is the relative of the sturgeon (Huso huso). But alas it had died out from the Hungarian part of the Danube. The sterlet is not protected in Hungary.

The white-eye bream (Abramis sapa) is a pretty much common fish. It occurs in every bigger stagnant and fluviatile water. Is is benthic fish, usually it is hooked with common breams.

The Austrian fish team captured this brilliant common barbel (Barbus barbus). It exceeds by far the smallest catchable measure (40 centimetres) on the face of it. It likes clear and rapid-flowing section, where it gets nutrition from the hard bottom. Naturally after taking this picture it was set free!

Common nase (Chondrostoma nasus) is also a benthic fish, gravel bars is its main habitat.

An adult cobitis (Cobitis elongatoides) is 12 centimetres long maximum. In Hungary it is protected, its goodwill value is 9 $! At twilight it starts to searh feed on the muddy and sandy bottom of the rivers.

As a young bobbler I would have liked very much to catch a real ukrainian brook lamprey (Eudontomyzon mariae), which I guesstimated approximately for eel-measured at that time. Since then I have never seen it yet, neither in an aquarium, but at any rate now I know it grows only 21 centimetres at longest. They are so similar as an Ephoron virgo that after the spawning the lampreys died, too. In Hungary it is highly protected, its goodwill value is 447 $!

Balon's ruffe (Gymnocephalus baloni) is a young species, because it is noted as separate species only since 1974. It is separated from its relative, eurasian ruffe (Gymnocephalus cernua) by ecological isolation. It likes clear and rapid-flowing section of rivers, but sometimes it could tramp into the tributaries, too. At this time they are teeming at occlusion or sluice, it is signed the liking into the fresh water. It is also a protected species, its goodwill value is 9 $!

Huchen or Danube salmon (Hucho hucho) suggests to trout as its body type, to asp (Aspius aspius) as its lifestyle and nutrition, and its latin name to the sturgeon's latin name (Huso huso). Long ago it lived only in the upper and middle section of the Danube, but nowdays it occurs also in the river basins of Rhine and Rhone. It is a cylindrical fish. It is highly protected, its goodwill value is 447 $!

In 2013 burbot (Lota lota) was the fish of the year, which is seen in the photo. Although it is not protected, but the members under 20 centimetres are not allowed to catch. It likes a lot to dwell near hanging roots of eroded banks, which alas is less and less since the regulation of Danube.

Originally monkey goby (Neogobius fluviatilis) lived in the shoal, offshore zone of Black Sea and Sea of Azov and from here it has expanded to Europe. It was discovered in Lake Balaton in 1970 since then it occurs in the Vistula basin, too. Just because it reckons an invasive species.

Ottó Herman's fish, the sichel (Pelecus cultratus) mainly got its repute from the fishermen of Tihany Peninsula. They directed the fishing boats from the top of the peninsula it depends on where the sichel shoal swam. It is very flat fish, easy to recognize about its upward mouth. It likes slow waters and eats fallen insects on to the watersurface.

Until now I have never known such fish living in the Danube. It is the black-striped pipefish (Syngnathus nigrolineatus). It is not very flashy although it can be 22 centimetres long. This marine fish lives in shallow waters with thick sea grass, it could be occur in estuaries.

Vimba bream (Vimba vimba) is often in the whole Europe, but its the nicest name subspecies (Vimba vimba vimba) lives in the rivers, which run into the North Sea. Congregating in schools and it lives in slaw waters. In Hungary it is abundant.

Streber (Zingel streber) is a Percidae which is resident of the shallow waters shoals. Its habitats along the Danube are in danger, because of the regulation and riverbed dredging. It is rare and protected species, its goodwill value is 447 $!

It is easily confused the streber with the common zingel (Zingel zingel), expert fishbiologists determine them about their scales and fins. It is not so sensible, but it disappeared from the damed sections of the river. Good news it was succeeded to meet these two species on the expedition. Both of them are represented great natural values.

Joint Danube Survey 3 says fairwell in Vylkove (Ukraine). The fourth will be 6 years later in 2019.

Source of photos: http://www.danubesurvey.org/photos/fish-photos

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Translated by: Kovács Sztríkó Zsuzsanna

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