A fish farmer operating a composite fish culture pond stocks six species of carp together, choosing species that occupy different feeding zones within the pond, such as the surface, water column and bottom, so that the available food resources of the pond are utilised efficiently without excessive competition between species. If one of the species he has stocked is specifically known to feed at the surface on phytoplankton and is an exotic species not native to India, which of the following is most likely that species?