Implications of dissolved organic carbon on fish feeding and predator prey interactions

Background/Question/Methods

Non-resource mediated effects of dissolved organic carbon concentration (DOC) have the potential to influence predator prey interactions by changing light levels and fish feeding efficiency. We manipulated dissolved organic carbon concentration (range = 3 - 25 mg/L) in yellow perch Perca flavescens zooplanktivory trials to understand how light level, as mediated by DOC, influences planktivory in common temperate juvenile fishes. In experimental trials, age 0 yellow perch, total length 45 - 60 mm, fed for 2 hours on diverse zooplankton communities at natural densities. 

Results/Conclusions

The total number of zooplankton consumed by yellow perch was significantly higher in the low DOC, high-light treatments. This change was primarily attributed to an increased number of empty stomachs in the high DOC, low-light treatment. Perch diets were primarily comprised of Daphnia sp., Bosmina sp. and calanoid copepods. We found no taxonomic feeding selectivity differences between the dark and light treatments (ANOSIM p>0.1). Over a DOC range, we estimated a negative relationship between DOC concentration and the rate of yellow perch zooplanktivory. We found DOC concentration can have a strong influence on rates of zooplankton consumption in juvenile yellow perch. The trends of increasing DOC concentrations across north temperate aquatic ecosystems have the potential to negatively influence fish feeding efficiency and potentially reduce abundance or production.