Effect of Elevated Nutrients and Sediments on Growth of Juvenile Black and White Crappies

Anthropogenic influences can cause dramatic increases in turbidity through sediment and nutrient inputs to lakes and reservoirs. Increased nutrients can affect fish growth via increased productivity, whereas increased sediments can decrease reactive distance and reduce feeding rates. Our objective was to evaluate the effect of increased nutrients and sediments on growth of juvenile Black Crappie (Pomoxis nigromaculatus) and White Crappie (Pomoxis annularis). We selected these species as they exhibit similar feeding ontogeny and co-occur in many systems, but are hypothesized to respond to turbidity differently with Black Crappie being more negatively affected. We examined growth in mesocosms with nutrient and sediment additions over a four week period using species as a split-plot within a full factorial model of nutrients and sediments. Environmental variables were collected weekly and averaged over the course of the study and used as covariates. We detected a significant effect of species on change in length with White Crappie expressing greater growth than Black Crappie in all treatments. Change in condition was significantly affected by species and nutrients with Black Crappie condition greater than White Crappie. Our results highlight the importance of parsing out the drivers of increased turbidity to better understand the effects on fish growth.