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Knowledge of habitats used by riverine fishes throughout their life history is important for management and conservation. Naturally occurring chemical markers in otoliths have recently been used to determine natal origins and environmental history of fishes in a variety of marine and freshwater environments. However, to our knowledge no studies have examined the applicability of this technique in large floodplain rivers in United States. We evaluated otolith microchemistry and stable isotopic composition as tools for determining origins of fishes in the upper and middle Mississippi and lower Illinois Rivers, their tributaries, and associated floodplain lakes. Fishes were collected from 21 sites during summer 2006 and 2 additional sites in spring 2007. Water samples were obtained from the same 23 sites plus three additional sites during summer and fall 2006 and spring 2007. Otoliths and water samples were analyzed for δ18O, and a suite of trace elements; otoliths were also analyzed for δ13C. Tributaries, floodplain lakes, and the Illinois and Mississippi Rivers had distinct isotopic and elemental signatures. Tributaries on the Missouri and Illinois sides of the middle Mississippi River could also be differentiated by their elemental and isotopic fingerprints. Otoliths reflected differences in water chemistry among habitats. Results indicate that otolith microchemistry and stable isotope analyses provide a potentially effective means of determining origins and environmental history of fishes in large river-floodplain systems. |
