The fish conservation was quantified by means of the index SUMIN, composed by the summation of 12 outstanding variables for the species survival and/or conservation. An arranged list of 53 species was obtained according to a gradient of conservation necessity. The species determined as vulnerable of maximum priority: Salminus brasiliensis, Pygocentrus nattereri, Serrasalmus marginatus and S. rhombeus; species vulnerable of special attention: Brycon orbygnianus, Triportheus paranensis, Serrasalmus serrulatus, S. spilopleura, Piaractus mesopotamicus, Hemigrammus mattei, Cynopotamus argenteus, Astyanax correntinus, Gymnocorymbus ternetzi, Hyphessobrycon anisitsi and Mylossoma orbignyanus. The remaining species, were qualified as not threatened: Poptella paraguayensis, Astyanax abramis, A. bimaculatus, A. fasciatus, A. taeniatus, A. erythropterus, A. lineatus, A. paranahybae, Charax stenopterus, Roeboides bonariensis, R. paranensis, Pseudocorynopoma doriai, Moenkhausia dichroura, M. sanctaefilomenae, Mylossoma paraguayensis, Odontostilbe microcephala, Galeocharax humeralis, Aphyocharax anisitsi, A. rathbuni, A. nasutus, A. paraguayensis, Bryconamericus stramineus, Oligosarcus oligolepis, O. jenynsi, Odontostilbe pequira, Metynnis mola, M. otuquensis, Prionobrama paraguayensis, Bryconamericus iheringi, Hyphessobrycon igneus, H. meridionalis, H. eques, H. reticulatus, Tetragonopterus argenteus, Clupeacharax anchoveoides, Markiana nigripinnis, Cheirodon interruptus and Cynopotamus kincaidi. This index allows estimating quantitatively the conservation state of the ichthyic species.