Otolith δ15N Distinguishes Fish from Forested and Agricultural Streams in Southern Illinois

We investigated the ability of otolith stable nitrogen isotope ratio (δ15N) to discriminate among fishes from southern Illinois streams that differed in proportions of watershed agricultural land. Otolith δ15N was nearly as effective as muscle δ15N in identifying fishes from individual sites with different percentages of agricultural land cover; both had accuracies of \u3e75%. However, because of the relatively low N content of otoliths, substantial amounts (~8 mg) of otolith material are required for δ15N analysis compared to fish muscle tissue (~0.3 mg), which precludes the use of otolith δ15N as an indicator of dietary and environmental history for small fishes