Homing Ability and Home Range of Yellow-Phase American Eels in a Tidally Dominated Estuary

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Abstract
Yellow-phase American eels, Anguilla rostrata, were displaced 10–17 km between tidal fresh water and salinity-stratified water and followed to determine the degree of home site fidelity, swiftness of homing and whether environmental factors affect orientation or homing behaviour. Twenty-one eels were tracked continuously (eight eels displaced up the estuary, eight down the estuary and five controls) in the Penobscot Estuary, Maine, USA for 4–80 h each, while recording position every 20 min. Nine of the 16 displaced eels (56%) returned to their capture site either during the track or shortly afterwards. Three of the remaining seven eels made substantial progress towards their capture site within the time observed. Eels homed with equal frequency whether displaced up or down the estuary in an average of 220 h ±87 (SE). After release, no eel moved farther away from its capture site. The eels were active mostly at night but used only the appropriate tidal currents rather than directed swimming to move about their home range and to home. Control tracks provided a home-range estimate in this habitat of 6.7 ±1.6 km of estuary or 325 ±64 ha. Lunar phase or position of the moon did not appear to influence either homing behaviour or activity patterns. This study shows that orientation and homing to a specific site in eels occurs relatively quickly and with no initial errors in orientation.