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American Eel Status Review Workshop Two:
Great Lakes/Canada Threats and Population Dynamics
Jan. 31 — Feb. 2, 2006

Draft Summaries of Sessions


Three experts discussed the impacts of disease to the American eel. The first of two presentations discussed new information on the extent of the introduced parasite (A. crassus) in the U.S., the parasites prevalence and intensity in the Northeast, and the effects of the parasite on eels. The second presentation focused on recently completed research on the tributaries to the Hudson River, N.Y.; looking at local eel densities and their condition relative to A. crassus infections and barriers. The impact to individual eels from heavy infestations of A. crassus was thought to be failure to reach the spawning area. Although prevalence of A. crassus has been reported for some areas in the U.S., range-wide impacts are still unknown. To date the parasite has not reached Canadian waters, but is likely to do so in the future. Its presence in Central and South America is unknown. Other diseases (viruses and bacteria) were discussed, but none of these are of the same scale of impact.

Panel members for disease: Ken Oliveira (UMass), Len Machut (State Univ. of N.Y.), and Bob Graham (Dominion Power)


See Population Dynamics, below.

Stock Assement

See Population Dynamics, below.

Conceptual Model

See Population Dynamics, below.


Two contaminants experts discussed the impacts of contaminants on American eels. Impacts discussed included early life stage impacts; the inability to successfully raise and test embryos and leptochephali with contaminants; impacts to maturation during the yellow and silver eel life stages; impacts of combined stressors such as disease, parasites, and contaminants on eel health, migration, and reproduction; impacts of other persistent contaminants such as polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) and non persistent contaminants such as pharmaceutical chemicals; impacts of new and emergent contaminants; impacts of vitamin deficiency due to diet changes. The lack of information and data on contaminant impacts to reproduction and maturation made definitive statements about the impacts unfeasible.

Panel Members for Contaminant Impacts: Catherine Couillard (Institut Maurice Lamontagne) and Petter Hodson (School of Environmental Studies, Kingston).

Population Dynamics (including Lakes and Stock Assessment Sessions and Conceptual Model Discussion)

Nine panelists, specializing in lake habitats and the relative contribution of Lake Ontario to eel population dynamics; the ASMFC stock assessment and peer review; conceptual models; and aspects of population dynamics including drivers, uncertainties, species vulnerabilities and resiliencies, were challenged with assisting the FWS/NMFS in understanding the information from the workshops and associated literature (discs with relevant literature had been provided to the panelists in advance of the workshop).

The sessions discussed the appropriateness to the American eel range-wide status review of the recently completed analysis on the relative contribution of the St. Lawrence/Lake Ontario area to the Canadian eel stock. Additionally, the strengths and weaknesses of the analysis were discussed. One of the peer reviewers of the ASMFC stock assessment provided an overview of the stock assessment data most useful to our purposes and there was discussion as to the limitations of extrapolating the information range-wide. The complexity of this species life history, compensatory adaptations, and numerous impacts was highlighted by the very complex conceptual model resulting from last year’s population dynamics workshop undertaken by the USGS and others. By focusing on those threats and/or life stages (known to or plausibly) that are most significant in driving eel population dynamics we identified the factors most likely to be influencing the population dynamics of this unique species along with the uncertainties in the information, and the potential implications of these uncertainties to our decision process. Additionally, we conducted an exercise to get at any deficiencies in our information collection by requesting individual evaluations of the risk of extinction faced by this species. We found this exercise useful in that no new vulnerabilities or resiliencies of the species were presented, and no new uncertainties or threats were revealed. An added benefit was in providing very useful directions for research and monitoring that would focus on range-wide questions/issues.

Panel members for Population Dynamics/Lakes/Stock Assessment: Dawn Dittman (USGS Tunison Lab), Alastair Mathers (Ontario Ministry of Natural Resources), Rob Macgregor (Ontario Ministry of Natural Resources, Guy Verreault (et de la Faune du Québec), John Casselman (Queen’s University), Karin Limburg (State University of New York), Paul Angermeier (USGS V. Tech), Joseph Hightower (USGS NC State Univ.), and Tim Brush (Normandeau Associates). Also invited, but unable to attend at the last minute, was Kevin Reid (Ontario Commercial Fisheries Assoc.).

In seeking to keep our process as transparent as possible, we are posting a draft working copy of the minutes and the associated attachments. Please note: these minutes are in draft form and have not yet been reviewed by all the experts and observers present. Corrections are expected.

02/22/2006 revision, Great Lakes/Canada Threats
And Population Dynamics Workshop,
Jan. 31 — Feb. 2, Buffalo, N.Y.

Attachments (to be posted as they become available)

  1. Opening Remarks and Definitions
  2. K. Oliveira’s Presentation - Distribution of the swimbladder parasite Anguillicola crassus in American eels in the Northeastern Atlantic
  3. L. Machut’s Presentation – American Eel Dynamics (Anguilla rostrata) in Hudson River Tributaries, New York
  4. Questions for Experts: Disease
  5. J. Casselman’s presentations – Changes in Relative Contribution to Overall Fecundity of the Species; American eel update Buffalo; Canadian eels in the North American context
  6. Questions for Experts: Lakes
  7. J. Hightower’s presentation – Overview of ASMFC Stock Assessment
  8. Questions for Experts: Stock Assessment
  9. P. Angermeier’s presentation – A Conceptual Model for Population Dynamics of American Eel
  10. A. Roe’s presentation – Draft American eel Contaminants Review
  11. Questions for Experts: Contaminants
  12. K. Limburg’s presentation – All in the Family? Diversity of habitat use in anguillicolid eels
  13. Questions for Experts: Population Dynamics
  14. Decline of the American Eel
  15. Canadian Eel Subpopulations in the North American Context
  16. Diagram of Most Significant Impacts at Most Critical Life Stages