Fatty Acids as Indicators of Nutritional History of Channel Catfish and Aquatic Food Webs in the Lower Kaskaskia River, Illinois

The use of fatty acid (FA) analysis has become an important tool in recent years to investigate a broad spectrum of questions in fisheries science. One of those applications has been the use of FA as biomarkers for indicating diet and feeding duration in aquatic food webs, and thereby answering questions of habitat use and origin for fish. It is therefore crucial that we understand the relationship between habitat types and FA profiles, and the time-scale over which FA profiles change. The objectives of this study were to test whether the FA profiles of channel catfish (Ictalurus punctatus) differ among various reaches of the Kaskaskia River and its floodplain lakes, to determine a time-course for FA profile turnover when fish moved into a new habitat type, and to compare FA profiles between muscle, liver, and adipose fin tissue. FA profiles of channel catfish were significantly different among sites, especially between upper and lower river sites, and between river channel and oxbow lake sites. The FA dilution-time portion of the study moved fish from the river channel to small study ponds, and showed a significant linear decrease in N-3 and medium chain polyunsaturates, and a significant linear increase in monounsaturates with longer residence time in a lentic environment. Results suggest that the use of FA profiles may shed new light on aquatic food webs by discerning the use of specific energy sources and habitats, and by providing a time-scale over which these FA profiles vary with changing resource utilization.