Abstract
As eel populations decline worldwide, research tools for scientists and managers to better understand eel populations and dynamics will be vitally important. This research focuses on the relatively understudied silver phase eel, the sexually mature adult life stage that will make the single spawning journey to the oceanic spawning grounds. A non-lethal index of eel maturity was designed based on external measurements and was able to correctly classify individuals into one of seven maturity classes 83% of the time overall, yielding similar results to other non-lethal indices. Habitats above and below barriers to migration, at varying levels of watershed urbanization, and different distances from the ocean were compared in terms of eel maturity, size, age, and parasite parameters. Two methods of bioelectrical impedance analysis (BIA) were evaluated in their ability to estimate eel lipid concentration, a key factor in eel maturity and successful spawning.