American Eel Ingress

Marine Field Station

Patterns of American eel (Anguilla rostrata) ingress in a southern New Jersey watershed

Commercial catch data, trawl/seine surveys, and upstream passage counts indicate numbers of American eels ( Anguilla rostrata) are dropping at an alarming rate in multiple regions throughout North America. In fact, population estimates are so dire that the American eel is currently being petitioned for inclusion on the endangered species list. Middle Atlantic Bight eel “populations,” including those in New Jersey , mirror these trends and concerns. Eels are critical components of local estuarine ecosystems as well as an important source of bait for recreational fisherman, yet their numbers have fallen considerably over the last two decades. Despite these warning signs, the early life history of the American eel remains enigmatic and poorly understood, thus it is difficult to accurately determine their status. Adult eels spawn in the Sargasso Sea , yet are elusive as oceanic larvae. In fact, during the 11-year National Marine Fisheries Service MARMAP study, only 34 young-of-the-year individuals were collected throughout the entire Middle Atlantic Bight. Thus, transformed “glass eels” entering estuaries (left), including those in New Jersey , represent a first glimpse into the black box of American eel early life history. Unfortunately, little is known about long-term trends in glass eel abundance, spatial variability, timing, size, as well as the environmental factors moderating ingress. Because the abundance and size of recruits entering estuaries may function as indicators of population status for these estuarine-dependent fishes, information related to the arrival of early stage eels is critical for validating the reported declines in the stock.

The primary goals of this research on American eel early life history are centered around three themes, based on the premise that it is difficult to make progress on processes without first understanding patterns: (1) Establishing patterns: Quantify variability of glass eels entering the Mullica River–Great Bay estuary using the Rutgers University Marine Field Station long-term ichthyoplankton data set and expanded local sampling. (2) Evaluate consistency of patterns across ecosystems: Evaluate the relative degree of glass eel synchrony exhibited between the Mullica River–Great Bay and Great Egg Harbor estuaries in southern New Jersey using arrays of novel glass eel collectors (right) over multiple spatial/temporal scales. (3) Test process-oriented mechanisms: Conduct analyses into the proximate environmental cues moderating variability in glass eel supply using long-term data sets and expanded collections.  This work examines the linkages between glass eel supply and environmental variability for Middle Atlantic Bight populations of the potentially endangered American eel. Given the paucity of available early life history data for American eels, this information is highly relevant to the biology and management of local eel fisheries along the entire U.S. east coast. In New Jersey alone, this research will help address concerns by recreational fisherman who rely on eels as bait for the economically important striped bass fishery.

The Rutgers University Marine Field Station, where I conducted my post-doc, has already initiated collaborative glass eel research efforts with: (1) Atlantic States Marine Fisheries Commission – ASMFC is funding a preliminary analysis of the long-term, New Jersey glass eel data, (2) New Jersey Department of Environmental Protection – NJ DEP is participating in reciprocal data sharing and site comparisons, and (3) NOAA, Beaufort Laboratory - This laboratory is providing access to North Carolina glass eel data sets for larger-scale comparisons.   The Richard Stockton College of NJ, where I am currently teaching, is providing research space and equipment funding to continue this research.    Funding provided by New Jersey Sea Grant, Atlantic States Marine Fisheries Commission, and the Rutgers Marine Field Station.
Principal investigators:
   Ken Able (
   Mark Sullivan (   

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