Demographic attributes of yellow-phase American eels (Anguilla rostrata) in the Hudson River estuary

Management of American eels (Anguilla rostrata) requires an understanding of how demographic attributes vary within large estuaries. Yellow-phase American eel length and age structure, growth, dispersal, nematode infestation rates, loss rate (natural mortality and emigration), and production were measured at six sites throughout the tidal portion of the Hudson River. Short-term dispersal was low, with >70% of eels at all sites captured <1 km from their original tagging area. Length was similar among sites (total length = 45.7 ± 0.3 cm), whereas age was substantially lower for brackish-water sites (8 ± 4 years) than for freshwater sites (17 ± 4 years). Growth was higher for brackish-water sites than for freshwater sites (8.0 cm·year–1 and 3.4 cm·year–1, respectively). From 1997 to 2000, infestation by the exotic nematode Anguillicola crassus increased dramatically in mean intensity as well as prevalence. Annual loss rates measured for the six sites varied between 9% and 24%, with no statistical difference between freshwater and brackish-water sites. Estimated eel production was higher in a brackish-water habitat (1.10–1.77 kg·ha–1·year–1) than in a freshwater location (0.21–0.58 kg·ha–1·year–1). The results of this study support a recent proposal to establish freshwater areas as exploitation reserves.