The aim of this study is the qualitative analysis of ichthyofauna of the river Prut in 2006 - 2007 Harvesting biological material was done on the whole course of the river, the river channel, on the following sections: The section I Rădăuţi (km 652) – Stânca - Costeşti (km 544); The section II Stânca - Costeşti (km 544) – Drânceni (km 284); The section III Dranceni (km 284) - Danube confluence.After the scientific fishing conducted in the two years, has been identified a number that ranged from 23-32 species (depending on the sector of the river).we mention that in the literature appear a greater number of species, but it should be specified that this number includes both species collected from the bed river and the artificial lakes, natural tributaries and farms. Thus, Al. Moshu, Gr. Davideanu, A. Ciobanu (2007) mention that the taxonomic structure of the Prut River consists of 53 species.The high number of species demonstrates that the ichytiodiversity of the Prut River is good. This high diversity of fish communities is due to very different morpho – topo - hydrographic conditions. To make a qualitative analysis of the river, we divided the species caught during the two years of study in functional groups (guilds), after their affinities for breeding habitat, food and current preference.Thus, depending to the strategies they realize the main physiological processes (feeding, breeding, habitat preference which perform certain stages of life) has been achieved a classification of fish species (Table 1).The concept of ecological guilds or functional groups is already recognized in the scientific study of populationa. Their analysis can be applied to a much larger scale of natural resource management, because, pursuing their dynamics in an ecosystem, can be gained important conclusions about the quality of the habitat. The study of guilds distribution in space and time can give clear information on the structure and functioning of an ecosystem.The functional groups (ecological guilds) are represented by communities of species, which present the same ecological characteristics that play an equivalent role in the community (Cummins, 1974; Smith et al., 1997; Steneck, 2001; Blondel, 2003).The functional groups present similar responses to the environmental factors or major processes that take place in an ecosystem.The functional group structure is more stable over time than the species composition, because a species can take over the functional role of others in the same group when there are changes in environmental conditions.  In terms of preferred breeding habitat, the functional groups of the ichthyofauna in the Prut River are represented by: phytophils species group (41%), species to which spawning takes place on aquatic plants, 28% of species are lithophils, spawning taking place on hard bottom (pebbles, gravel), in current, and 19% species are pelagophils, spawning taking place in the water column Reproductive guild: li- lithophils; Fi – phytophils; pe – pelagophils; Fi-Li – fhyto - lithophils; po – polyphils;Trophic guild: ben –benthivores; pla – planktivores; phy – fhytivores; par – parasitivores; om – omnivores; det – detritivores;Habitat guild: r – rheophilic ; Sm – semi-migratory; l – limnophilic; e – eurytopic; am – anadromy; Depending on the dominant nutritional spectrum, in order of abundance, the Prut River ichthyofauna is represented by groups of piscivores fish and benthivores - piscivores (25%) followed by group benthivores (19%) and planktivores (13%) species. Depending on the preference for water flow dominates the rheophilic species group (41%), followed by eurytopic species group (31%) and the semi-migratory species (16%).