Environmental DNA (eDNA) has become a vital tool for early detection of invasive Asian carp, including bighead carp (BHC) and silver carp (SVC). eDNA is genetic material from cells shed from fish into the water, and can include skin cells, intestinal cells, and sperm and eggs. eDNA can also come from fish carcasses in the water, from boats and fishing gear that have been used in areas with Asian carp, and from waste from animals that have eaten the fish. Our previous work has shown that the amount of eDNA in the water increases with the amount of fish, that feeding the fish increases eDNA, that most eDNA from sperm in the water degrades within a couple days but some stays in the water for at least a few weeks. We have also found other ways that eDNA enters the water including via fish-eating birds (bald eagles, cormorants, pelicans) that shed silver carp eDNA in their waste, , or in fish slime deposited on metal surfaces which was found to persist for at least 28 days. The presence, relative quantity and quality of silver carp eDNA in the Wabash River (Indiana) was also characterized in response to the movement of telemetry tagged fish.
Further, studies were completed to compare the microbes present in the digestive tracts of gizzard shad and silver carp – known as microbial source tracking (MST); it is similar to eDNA but focuses on the detection of a bacteria unique to the target species instead of the eDNA of the target species. Bacteria unique to silver carp were identified which may allow the use of MST to supplement surveillance of Asian carp eDNA.
This year (2014) we will focus on the validation of new genetic markers for use in eDNA monitoring programs, data development to determine the applicability of MST within eDNA surveillance programs, and characterize the eDNA that comes from Asian carp spawning in the Missouri River, where they are already established. Our studies focus on improving the usefulness of eDNA monitoring to managers working to stop the spread of Asian carp.