High-resolution video observations of freely swimming adult female cop
epods were utilized to characterize the flow fields produced by Centro
pages velificatus, an omnivore with strong tendencies toward carnivory
, and Paracalanus aculeatus, a herbivore. Horizontal and vertical comp
onents of the translational velocity of the copepod were subtracted fr
om the corresponding components of flow field velocity, allowing fluid
velocities to be calculated from an external frame of reference and w
ithout the need for mechanical restraints on the copepod. Large differ
ences in the geometry of flow fields were found between species. The f
low field geometry of P. aculeatus is similar between individuals, and
lower in velocity than the flow field of C. velificatus. The now fiel
d geometry of C. velificatus is variable between individuals and seems
to be dependent on copepod body orientation and swimming trajectory.
Evidence is presented that a third factor, fluid distortion around the
moving copepod, also affects the flow field geometry. The ecological
implications regarding behavioral plasticity and the influence of flow
field velocity and geometry on the feeding success of copepods in the
field are discussed.