Swimming ability of eels (<Emphasis Type="Italic">Anguilla rostrata,Conger oceanicus</Emphasis>) at estuarine ingress: contrasting patterns of cross-shelf transport? |
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Authors: | M J Wuenschel K W Able |
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Institution: | (1) Marine Field Station, Institute of Marine and Coastal Sciences, Rutgers University, 800 c/o 132 Great Bay Blvd, Tuckerton, NJ 08087, USA;(2) NOAA NMFS NEFSC, Woods Hole Laboratory, 166 Water Street, Woods Hole, MA 02543, USA |
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Abstract: | The transport of eel early life stages may be critical to their population dynamics. This transport from ocean spawning to
freshwater, estuarine and coastal nursery areas is a combination of physical and biological processes (including swimming
behavior). In New Jersey, USA, the American eel (Anguilla rostrata) enters estuaries as glass eels (48.7–68.1 mm TL) in contrast to the Conger eel (Conger oceanicus) that enters as larger (metamorphosing) leptocephali (68.3–117.8 mm TL). To begin to understand the mechanisms of cross-shelf
transport for these species, we measured the potential swimming capability (critical swimming speed, U
crit) under ambient conditions throughout the ingress season. A. rostrata glass eels were collected over many months (January–June) at a range of temperatures (4–21°C), with relative condition declining
over the course of the ingress period as temperatures warmed. C. oceanicus occurred later in the season (April–June) and at warmer temperatures (14–24.5°C). Mean U
crit values for A. rostrata (11.7–13.3 cm s−1) and C. oceanicus (14.7–18.6 cm s−1) were comparable, but variable, with portions of the variability explained by water temperature, relative condition, ontogenetic
stage, and fish length. Travel times to Little Egg Inlet, New Jersey, estimated using 50% U
crit values, indicate it would take A. rostrata ~30 and ~60 days to swim from the shelf edge and Gulf Stream, respectively. Travel times for C. oceanicus were shorter, ~20 days from the shelf edge, and ~45 days from the Gulf Stream. Despite differences in life stage, our results
indicate both species are competent swimmers, and suggest they are capable of swimming from the Gulf Stream and/or edge of
the continental shelf to estuarine inlets. |
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