Alosa "oligorakered." The multirakered are primarily plankton feeders, the oligorakered have large rakers and are predators, and the medium-rakered generally consume a mixed diet. Most current species of the genus "Alosa" in North America can be found in Florida, whereas the distribution of most of them is broader. Morphology is notoriously liable to adapt to changing food availability in these fish. Several taxa seem to have evolved quite recently, making molecular analyses difficult. In addition, hybridization may be a factor in shad phylogeny. Nonetheless, some trends are emerging. The North American species except the American shad "A. sapidissima" can probably be
Assabet River followed by deliberate introduction into ponds near the Concord and Sudbury Rivers. This is now an invasive, habitat-destroying plant across many of the eastern states. On the Assabet River, OARS (Organization for the Assabet, Sudbury and Concord Rivers) organizes an annual plant pulling event in early July. Volunteers in canoes hand-pull the surface-floating rosettes of leaves and nuts before the nuts mature and fall to the bottom. Alewife, "Alosa pseudoharengus" is an anadromous species of herring found in North America, anadromous meaning that it mates and is born in fresh water, but live most of its life in saltwater. In