Population Characteristics, Connectivity and Recruitment Sources of Spotted Bass in Southern Illinois Streams

Naturally occurring chemical markers within calcified structures of fishes have proven useful for determining environmental history of fishes. Differences in the chemical signatures of tributaries within lotic networks are reflected within structures such as otoliths, fin rays, and spines. In this study, we are using fin ray microchemistry to determine environmental history and age estimates derived from sectioned fin rays to characterize population demographics (age composition, growth, and mortality) of stream-dwelling spotted bass in southern Illinois. Spotted bass were collected from southern Illinois streams using a variety of gear types in 2014.  In 2015, spotted bass were collected from the Ohio River and several tributaries by electrofishing to allow for comparison of population characteristics among these habitats.  Spotted bass sampled from the Ohio River generally reached older age, larger size, and displayed slower growth and lower mortality rates than the tributary populations.  Consistent differences in water chemistry parameters among streams and the Ohio River enable movement among the Ohio River and tributaries to be detected.  Analysis of fin ray chemistry data for fish collected in 2014 indicated that Ba:Ca was needed in addition to Sr:Ca to reconstruct environmental history of fish within the study area.