Ontogenetic, diel, and seasonal variation in habitat use of American eel in a tributary of the Hudson River

We examined the habitat use of American eel (Anguilla rostrata) in Hannacroix Creek, a tributary of the Hudson River.  Habitat use was examined by fish size (≤ 199 mm, 200-399 mm, ≥ 400 mm), time of day (day, night), and season (summer, autumn).  The amount of cover and water depth used by eels increased with fish size.  Pronounced difference in the habitat used by each size of eel occurred between day and night periods, especially during summer.  At night in summer all size groups of eel occupied areas that were deeper, had slower water velocities, smaller sized substrate materials, and less cover than during the day.  In autumn, only eels ≤ 199 mm exhibited these same diel differences for all four habitat variables.  Diel differences in habitat use in autumn were less pronounced for eels 200-399 mm (substrate, cover) and eels ≥ 400 mm (cover).  When comparing eel habitat use to available habitat, habitat selection by eels was greatest in summer during the day, with less habitat selection occurring in autumn.  Eels ≤199 mm exhibited the strongest habitat selection whereas eels 200-399 mm exhibited the least.  These findings have important implications for habitat management in streams occupied by American eel.