LAUSR

How fish assemblages change over time in highly-modified urban rivers, where physical and chemical properties rarely mimic non-urban systems, has sparsely been documented. Data have been collected on fishes within the boundaries of the Chicago Metropolitan area routinely since the mid-1980’s. Representing fish assemblages in one of the largest cities of America, this dataset offers the ability to investigate and track changes in assemblage composition in an urbanized river. To this end, multivariate modelling, as well as various visualization techniques, were used to assess and describe compositional changes in the fish assemblage of Chicago’s waterways. In general, there were gradual enhancements in the fish assemblages of Chicago’s waterways throughout the years studied, which are characterized by more fish, of which more are native species. Small-bodied native fishes (Cyprinidae), game fishes (Centrarchidae), as well as catfish (Ictaluridae) have increased in relative abundance, whereas several invasive fish species exhibited declines. Exponential growth of Banded Killifish ( Fundulus diaphanous ) relative abundance appears to continue from previously noted range expansions. As Chicago and other cities move towards supporting fishable waterways, interest may lay in investigating population vital rates and habitat or water quality factors affecting them in heavily urbanized settings.