STRUCTURE AND ECOLOGICAL ASSESSMENT OF FISH COMMUNITIES FROM PREDELTAIC DANUBE SECTOR, BETWEEN SIRET RIVER AND PRUT RIVER MOUTH

Petronela Georgiana Calin Sandu, L. Oprea, Daniela Gheorghe, N. Patriche

Abstract
The paper is presenting some aspects regarding the structure of fish communities from 22 Km of predeltaic sector of Danube River, between the mouth of Siret River (km 155) and Prut River (Mm 72.5). The aim of the study is to assess the ecological status of the area, using the main ecological indices as abundance, dominance, constancy and ecological significance. From April to December 2011, in four fishing areas (km 150-151, Mm 77-78, Mm 76-77, Mm 74-74.5), 4805 fish of twenty three species, from six famillies, were collected. The best represented family is Cyprinidae with 14 breeds. The numerical abundance ranged between 2 fish/breed (zingel, common nase) and 2035 fish/breed (pontic shad). The pontic shad (42.35%), common bream (11.63%) and common carp (10.9%) are eudominant breeds, having the biggest potential in fish productivity. Pike-perch (75%), common bream (75%), common barbel (75%), vimbe (75%), white-eye bream (75%), asp (66.66%), prussian carp (66.66%), white bream (58.33%), common carp (58.33%), silver carp (58.33%) and sterlet (58.33%) are constant species with high adaptability. In term of ecological significance, Danube shad (14.11%), common bream (8.72%), common carp (6.36%) and common barbel (5.32%) are characteristic species.

Key words: Danube, fish communities, abundance, dominance, constancy, ecological significance