Fish were sampled from the entire 34.4-km Bronx River each year from 2001 to 2005 inclusive, yielding a database of 4000 fish comprising 23 freshwater species and 22 estuarine species. These data were compared to the historic data from 1936–1998 as recorded in the New York State Department of Environmental Conservation's digital database, Albany, NY. Only 6 freshwater species reported in the historic data—Rhodeus sericeus (Bitterling), Salmo trutta (Brown Trout), Semotilus corporalis (Fallfish), Esox americanus vermiculatus (Grass Pickerel), Etheostoma nigrum (Johnny Darter), and Esox lucius (Northern Pike)—are no longer in the river. However, the original report of the presence of the Johnny Darter probably resulted from taxonomic confusion since this species has never been in the Hudson Valley, and we strongly believe that the report of the presence of grass pickerel is also the result of misidentification of the specimen for the same reason as given for the johnny darter. The report of the Brown Trout should be discounted since this species has been only taken in the Bronx River following a stocking event. We have found a breeding population of Brown Trout in the southern end of Davis Brook, but these have not yet traversed the multi-channel marsh area to enter the Bronx River proper. Therefore, only three previously reported species—Bitterling, Fallfish, and Northern Pike—are no longer in the river. Four spe cies—Fundulus diaphanus (Banded Killifish), Ameiurus nebulosus (Brown Bullhead), Apeltes quadracus (Fourspine Stick leback), and Micropterus dolomieu (Smallmouth Bass)—not reported in the historic database were part of our 2001–2005 freshwater collection. These discrepancies are explained, and on balance, it was determined that for the past 70 years, the Bronx River has been remarkably stable in terms of fish species and diversity. Examination of the estuarine portion of the river shows that it functions as an important nursery ground for many commercial and recreational fish harvested from New York waters.