Photo credit: (c) BOGDAN BARBULESCU/ AGERPRES ARCHIVE

As regards some species, a non-capturing ban is in force, yet one third of the total of the fish species with the Danube Delta according to the Tulcea authorities has been and still is economically capitalized through commercial fishing.

Even those we believe we know everything about and cannot offer big surprises do have specific particularities, according to the Teodor Buliga’s “Danube Delta” book.

The carp or Cyprinus carpio, the standard fish of the most spread vertebrate family in the world, is one of the fish species with a very sensitive hearing, therefore no fisherman should wonder when he doesn’t catch any carp if plodding on the banks or making strong noises in the boat. In addition, they are a weather changes’ proper flag, the Danube Delta’s experienced fishermen knowing that when the specimens of this species emerge a storm is about to come. In reality, the carp needs air to even pressure of its own body with the outside.

The crucian or Carassius vulgaris is one of the world’s two species of fish whose females need not spermatozoon exclusively from the crucian in order to reproduce themselves. It looks like the sperm of other species could start the division of the ovule resulting in a totally female’s population. The phenomenon is called gynogenesis and it generates specimens which borrow characteristics from other species, the hybrids between crucians and carp never being a rare thing. Moreover, the crucian specimens captured last 24 hours outside water considering the water temperature is low.

The perch or Perca fluviatilis, the most numerous species of the Danube Delta, seems to be the most greedy fish as well. Its favourite prey consists of small fish, and in the above-mentioned work the author mentions he found often perches swimming with fish as large as them hanging over their mouths!

Photo credit: (c) LUISIANA BIGEA/ AGERPRES ARCHIVE

The European catfish or Silurus glanis or the pond’s pig is the largest freshwater fish in Europe and among the largest 20 fish in the world. The catfish skin lacks scales, yet it’s very thick, as it is so resistant it could be used in leatherworking. Complex nerve endings are on its entire skin capable to identify any being close to it, the tiniest abnormalities of the water flow, and the alteration of the water’s chemical composition. The performing receptors are on its tail as well, and one moustache senses fine differences in the chemistry of the water against the other moustache. Of all the fish in Romania, except for the sturgeons, the catfish reaches the longest dimensions, yet the species is harder to find in the natural waters.

The pikeperch or Lucioperca, one of the most wanted fish in the Danube Delta, is big, round-eyed, glowing in the light due to a layer of cells which reflect the light, by amplifying it. This characteristic is also seen at mammals and about that there is a legend saying that the pikeperch has nocturnal vision. Unfortunately for the fishermen, several studies say the pikeperch is more active during daytime.

The pike or Esox lucius or Northern pike is one of the species until now never domesticated. Researchers have agreed that the sense of touch given by the numerous cutaneous nerve endings perceiving the aquatic environment vibrations is guilty for the attacks on prey. The maximum density of the sensors is recorded on its head, while preys are captured only if moving. This situation makes the pike one of the few species not yet domesticated. To note is that in the world of the pikes the cannibalism phenomenon is a fact that helps the species to balance its population hence there will never be an over-population of the specimens of this kind.

Photo credit: (c) SIMION MECHNO/ AGERPRES ARCHIVE

The small roach or Rutilus rutilus lives in large schools of fish, yet as it gets larger it becomes more lonely, gathering only when it reproduces or to winter. In the rivers, it is silver-coloured, rusty in the ponds and red-brown in the lakes. Its fins are bluish, and its life span is up to 100 years.

Six of the species reported in the Danube Delta come from other continents, as specialists call them allochthonous. So, the silver carp was brought from China at the beginning of the 18th century, and in Romania was for the first time reported in 1920, according to researcher Vasile Otel.

Photo credit: (c) BOGDAN BARBULESCU/ AGERPRES ARCHIVE

After 1970 in the Danube Delta the silver carp has emerged massively, as it currently holds 1st place in industrial fishing. Along with this species the sun perch or Lepomis appeared as it comes from North America and was brought to Europe at mid-20th century. The species related of Singer, Novac and Cosas were imported from China in 1960 and 1961 in order to populate some ponds, yet they’ve reached the natural environment next to a smaller species, the Pseudorasbora parva, imported accidentally. In 1984, a small species of the perch living in the Eastern area of the Black Sea has penetrated the Danube Delta, a numerous population existing in the Razim-Sinoie lakes’ complex.

Besides the economic interest of the professional fishermen and sportsmen, the fish resource is also the object of the researchers, the sturgeons being labeled since 1909 by Romanian scientist Grigore Antipa as the most interesting fish scientifically.

The fossil species of this family are known for over 200 million years, so that present day sturgeons are known as ”living fossils”. Currently all over the world some 26 species of sturgeons are known, six of which being reported in Romania as well at the beginning of the past century.

It seems that initially these species were of freshwater or estuary, but the long of the way as they were looking for food they have adapted the sea life where they spend most of their time. According to researchers, the fact that during the reproduction period the specimens of this family ascend some streams or rivers is the proof that sturgeons were freshwater species.

Since the beginning of the ?60s, the Acipenser sturio (sip) and Acipenser nudriventis (viza) used to be species very rare or even extinct, so that currently in Romania only four species of sturgeon could be seen: Huso huso (morun), Acipenser gueldenstaedti (nisetru), Acipenser stellatus (pastruga) and Acipenser ruthenus (cega).

Ever since 2006, the sturgeons’ capturing in Romania is banned for 10 years, the specialists being to decide if prohibition will last.

A special place in the sturgeons’ family is occupied by the albino sturgeons. Unlike their peers, the sturgeons of this kind are white, their eggs extremely valuable, as they are sold in golden small boxes. The price of a white caviar kilo surnamed ‘diamond’ reaches up to EUR 25,000, specimens of such species being seen by the Romanian researchers in the Danube. The albino sturgeons are very sensitive and never grow old, yet in captivity if all conditions created they have big chances to survive.

The species of the Danube Delta are a visitors’ attraction.AGERPRES