Between May of 2003 and April of 2004 the temporal changes were monitored in the structure of the demersal ichthyofauna of the Bay of Pinheiros (Paraná), through three bottom trawls accomplished monthly in each one of the four areas between the access bar and the most internal areas. In the 144 accomplished trawls 58 species belonging to 25 families were collected, totaling 18154 fishes. The families that presented larger wealth of species were Sciaenidae (15 species), Ariidae (5), Tetraodontidae (4), Engraulidae (4), Carangidae (4), Paralichthyidae (3) and Haemulidae (3). The species Stellifer rastrifer, Cathorops spixii, Chirocentrodon bleekerianus, Cynoscion leiarchus, Stellifer brasiliensis, Achirus lineatus and Micropogonias furnieri dominated in number of individuals, representing 91,4% of the total capture. Significantly, there was larger capture of number of fishes in April. Between the indexes of diversity of Shannon-Wiener and eveness of Pielou differences were not observed. Through the grouping analyses and ordination of the dominant species two groups were formed in the level of 70% of similarity. The first was composed by the dominant species S. rastrifer, C. spixii and C. leiarchus, and the second was formed by C. jamaicensis and P. harroweri, presents almost exclusively in the summer and autumn.