Predation and Selectivity of Mysid Neomysis americana on Copepods, Rotifers and Phytoplankton
The ingestion rates, clearance rates and selectivity of Neomysis americana on copepods, rotifers and phytoplankton were of key investigation. Since there was no significant difference in mysid length between all experiments mysid predation was not a result of various sizes but rather various prey. Mysids did prey on Thalassiosira weissflogii but it was so insignificant further consideration was extraneous. The functional response of N. americana on copepods was linear suggesting no saturation, whereas the function response of mysids on rotifers became logarithmic at concentrations exceeding 300 rotifers/liter. Ingestion rates significantly increased when copepods were offered in the presence of rotifers when compared to copepods offered alone; the same trend was seen for clearance rates. Rotifers offered in the presence of copepods showed no significant differences between rotifers offered alone. Clearance rates did, however, show a significant decrease suggesting that N. americana does prefer copepods to rotifers when presented with a choice. The presence of rotifers may be interfering with copepod escape and defense tactics resulting in greater mysid predation. Copepods may also be of greater nutritional value than rotifers to mysids. This investigation will act as a precursor for future studies applying these results in a non-turbid environment to the turbid waters of the Chesapeake Bay Estuary.