The Danube Delta is a genuine fauna paradise. It shelters over 3,400 species of vertebrates and invertebrates, many of them unique in the country, in Europe or even in the world. About 90% of the aquatic European fauna live here; the entire Odonate, aquatic Lepidoptera, gastropods shellfish fauna live here, as well as rare mammals, who take refuge here; these are the European mink (Mustela lutreola), the Eurasian otter (Lutra lutra) and the European Wild Cat (Felis silvestris).
The animals in the Danube Delta are mainly mammals, which live in the higher areas that cannot be reached by waters. Otters, minks, muskrats, foxes, wild bears, wolves, polecats, hares are to be found along with tortoises, adders and colonies of snakes, especially on the islands of Lake Razim. Amphibians are represented by two species of caudates and six species of salientia. Hunting is not allowed in the Danube Delta Biosphere Reserve in order to protect wildlife.
Birds are the ones who have made the name of the Danube Delta, known from the beginning of the century as an avian paradise. The fame of the Delta is due to the over 300 species which can be found here. Most of them lay eggs here, while the other species fly to the delta and stay here for different periods of time in autumn, winter and spring. Birds fall into 5 categories, namely: Mediterranean, i.e. herons, eastern flossy ibises, small cormorants, golden eagles, black-winged eagles, “Ciocintorses” avocets, shelldrakes, pelicans; European i.e. songsters – reed nightingales, buntings, “boicusi”, sea swallows, seagulls, fishing eagles, and sea eagles; Siberian i.e. singing swans, plovers, polar grebes, half snipes, and cranes; Mongolian i.e. golden eagles and saker falcons; Chinese i.e. egrets, mute swans, large cormorants, Mandarin ducks.
From another point of view, the birds of the Delta can also be grouped in 5 main ecological types: species which are highly linked to water, exclusively stenotope species (grebes, diverse, puffins, pelicans, cormorans, somm anatides), reed plot species (all aquatic Paseriformes species), coast species (herons, rowers, eastern flossy ibis, some anatides), species of hydrophilic meadows with luxuriant vegetation and reed plots (Rallydae), marine shores species (some Laridae). Many species especially some ducks, geese, common terns, frequently appear in different biotopes. Riverside coppices are inhabited by Sylvas, fly catchers, nightingales, tits, chaffinches, including ducks, cormorants and herons during egg laying. In the forests in the marine fields Letea and Caraorman 64 species typical of the forests avifauna (Sylvas, blackbirds, peckers, robins, tits, starlings and a with-tailed (Haliaetus albicilla), brown jackdaws, the pygmy eagle, vultures, etc.) the pheasant (phasianus colchicus) has been introduced by colonization, the population growing rapidly. Partridges, quails, larks, field birds (Burchinus oedicnemus) are characteristic of sandy steppe meadows. Ring doves sparrows, swallows, storks martins are present in the villages of the Danube Delta, nearby households.
A series of aquatic species gather during egg laying, forming colonies, which are, and nest agglomerations covering small areas. Bird’s colonies have always been a great attraction of the Delta. The thousands of nests made up of branches of the willows in riverside coppices or in reed plots, the infernal noise, the atmosphere specific to other geological periods, the shooting flight of birds feeding their nestling, turn the bird colonies into a paradise for both ornithologists and for many nature fans. There are several types of colonies in the Danube Delta: herons, rowers, pelicans, cormorans,common terns, crested larks, and terns. The pelican colony from the entirely preserved area Rosca-Buhaiova is the greatest in Europe, and is an instance of mixed colony. It is the place where thousands of common pelican pairs associates with tens and even hundreds of curly pelicans pairs and of big cormorants.
The Danube Delta is home to the largest colony of pelicans outside Africa. Two-and-a-half thousand breeding pairs of pelicans arrive every spring in the Danube delta. They’re attracted to the 5,000 square kilometer region because it is such an isolated wildlife haven and the largest reed bed in the world. Half a million wild geese winter here, including all the world’s red-breasted geese. Another 300 species of birds – including spoonbills and glossy ibis – spend half their lives here, too.
Some species of birds have been acknowledged as “monuments of nature”, and they fall into two groups: “white monuments” – those having shining white feathers (the roseate pelican, the Dalmatian pelican, the spoonbill, the great white egret, the small egret, the mute swan), and “polychrome monuments” whose feathering combines white and black with green, yellow, rust colored, brown, blue (the black winged marsh bird similar to a stork, the avocet, the shelldrake, the ruby shelldrake and the sea-eagle).
The Danube Delta is formed of hundreds of lakes, streams, channels, branches, sheltering some 110 species of fish. The delta accounts for 50 percent of the fresh-water fish production of Romania.
In the branches through which the Danube flows into the sea, where the flow is faster, there are usually sterlets, large beaks, great sturgeons, common sturgeons, sevrugas, mackerels, carps, sheat fish, perches, pikes, barbles, rapacious carps, and aspruses. In the still waters of the many lakes between the branches of the river are to be found crucians, perches, breams, pikes, and carps, while in the saltwater-fish environment of the Razim-Sinoe lagoonlike system one may find fish ranging from perches and pikes to grey mullets and flounders, their distribution depending on water salinity. The marine area in front of the delta shelters mostly sturgeons (to be found only in the Black and the Caspian Seas), common sturgeons and Danube mackerels.
Some of the above-mentioned species of fish can be found in other waters in Romania, but specific to the delta are sturgeons (the great sturgeon, the common sturgeon, the sevruga, and the red sterlet) which yield fine black roe (caviar); the great mullet, of which there are four species of the Mugil type; the Danube mackerel.
In the Danube Delta fishing is allowed all the year round except for a period of sixty days, starting from April 1, when fish spawn their roe.