River herring are anadromous species of fish, meaning that they live much of their life in the ocean, but then migrate to freshwater to spawn. These two species, Alewife Alosa pseudoharengus and Blueback Herring Alosa aestivalis are migratory fish used to be among the most abundant fish in the Chesapeake Bay, but in the past few decades their populations have declined over 90% due to habitat loss, overfishing, and other causes. Our lab is studying the spawning migrations of the river herring populations that visit the Chesapeake Bay tributaries every spring. These studies include using PIT tagging to track individual fish movements within a river system. Tracking movements helps us learn how long individual fish spend on the spawning grounds, whether they return to the same sites each year, and what the survival rate is from year to year.