Due to very favorable conditions created by the big variety of terrestrial and aquatic habitats, as well as the proximity of some palearctic fauna regions (mediterranean, eurasian, Black Sea), the fauna from the DDBR is represented by 4.029 species, from which 3 477 invertebrates and 522 vertebrates.
The invertebrates represent from far the most important part of the DDBR fauna, with more than 3 477 species. There are 73 species of worms, 91 species of mollusks, 115 crustaceans, 168 spiders and 2 244 other species of insects. 37 new species were described, including 1 worm Proleptobchusdeltaicus, 5 species of spiders, 1 fish Knipowitschiacameliae and 30 species of insects (Isophyadobrogensis, Diaulinopsisdeltaicus, Homoporusdeltaicusetc).
The fish fauna from the DDBR is remarkably rich, with 135 species. The majority is fresh water fishes, but there are also marine species that come into the Danube Delta and on the Danube course during the reproduction season.
Approximately a third of these species were and still are subject to commercial fishing, including the sturgeons (since 2006 there is a 10 year prohibition) and the Danube mackerel (Alosapontica).
The amphibians and the reptiles are also well represented in the DDBR, most of the species being under legal protection. There are 10 species of amphibians: marsh frog (Rana ridibunda), fire-bellied toad (Bombinabombina), European tree frog (Hylaarborea), common spadefoot (Pelobatesfuscus), common toad (Bufobufo), European green toad (Bufoviridis), Syrian spadefoot (Pelobatessyriacusbalcanicus), Rana lessone and two species of water lizard, Danube crested newt (Triturusdobrogicus, Triturus vulgaris). The reptiles are represented by 12 species including testaceous, lezards (Sauria) and snakes (Serpentes).