Catadromous Fishes

The only catadromous species in the Hudson River is the American eel (Anguilla rostrata). This species has a unique but well known life cycle (Smith, 1985) involving migratory adults spawning in the Sargasso Sea and passive transport of small lep-tocephalus larvae by the Gulf Stream along the Atlantic coast. American eels enter the Hudson River as small unpigmented "glass eels" after transforming from the planktonic leptocephalus stage (Smith, 1989). Glass eels are passively transported up tidal rivers using selective tidal stream transport behavior and a circa-tidal endogenous clock (McCleave and Wippelhauser, 1987). In Hudson River tributaries, we see glass eels essentially at the end of this migratory phase when they are transforming into pigmented benthic elvers (juveniles). In this section, we will only present our observations on these small young-of-year (yoy) eels and we will discuss older elvers as part of the resident fish community.

Most of our observations of yoy eels are based on captures in drift nets and incidental encounters. Drift net captures cannot be considered a proper representative sampling of this species since drift nets are placed to catch fishes moving passively downstream while the yoy eels are actively moving upstream. We have collected yoy eels from mid-March through mid-June, which correlates well with the presence of glass eels at sea (Kleckner and McCleave, 1985), in Great Bay, New Jersey (Able and Fahay, 1998), and with quantitative data recently collected in two Hudson River tributaries (Schmidt and Lake, 2003).

Summary. Tidal creek mouths and streams further upland are critical habitat for American eel. The subadultfreshwater stages havebeenrelatively well studied, but we know very little about the glass eel stage in the Hudson River.

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