Official Logo and Link to the Service Home Page United States Fish and Wildlife Service
American Eel Status Review Workshop One:
Atlantic Coast/Islands Threats
Nov. 29 – Dec. 1, 2005


Draft Summaries of Sessions

Habitat

Eight experts discussed the information available on the importance of freshwater, estuarine, and continental shelf habitats to the eel. Both habitat quantity and quality were discussed and there were differing assessments as to the importance of those habitats to the long-term persistence of the species. Lakes and still water were said to be important in the production of females, however a number of uncertainties remained, particularly in the areas of: the relationship between eel density and production of females and the relationship between size and fecundity; size composition, relative importance of upstream habitat with varying annual recruitment, and the proportion of silver eels produced in coastal and estuarine areas. Certain life history characteristics add complexity to the issues, including density-dependant sex ratios, possibly density-dependent upstream migratory cues, and migration behavior between estuary and upstream areas. As to whether we had already gone below the minimum level of habitat necessary to sustain the American eel population, there were responses that we had not gone below a minimum and responses that we couldn’t’ determine; in the end no data for having gone below a minimum appeared to exist.

Panel Members for Habitat: Ken Oliveria (Univ. of Massachusetts), John Casselman (OMNR/Queens University, retired), Kevin McGrath (NY Power Authority), Rob Macgregor (OMNR, Lake Ontario Manager), Brian Knights (Kings College, London, retired), Alastair Mathers (Ontario MNR), Bill Richkus (Versar), Paul Angermeier (US Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Blacksburg, VA)

Barriers to Successful Upstream Migration

Eight experts were assembled to discuss the effect of barriers on successful upstream migration. There was considerable discussion as to what constitutes a barrier and whether using existing databases could provide us with a permeability measure, or if the complicated nature of barriers and flow, and that life stages are affected differently by barriers, precluded generalizations or exptrapolations. Effects discussed included changes in sex ratios; increased predation rate; and/or growth rate, which effects fecundity. Mortality was thought to be only site-specific. Uncertainties such as when or what determines sex, made definitive statements about the effects rare. In the end only a few papers appear to be available that quantify the impact of barriers on upstream migration (or persistence within a watershed).

Panel Members for Barriers to Successful Upstream Migration: Ken Oliveria (Univ. of Massachusetts), John Casselman (OMNR/Queens University, retired), Kevin McGrath (NY Power Authority), Rob Macgregor (OMNR, Lake Ontario Manager), Brian Knights (Kings College, London, retired), Alastair Mathers (Ontario MNR), Bill Richkus (Versar), Paul Angermeier (US Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Blacksburg, VA)

Barriers to Successful Downstream Migration

Eight experts were assembled to discuss the effect of barriers on successful downstream migration. There was considerable discussion about the impact of dams and hydropower generation facilities. In general there appeared to be no disagreement that individual eels can be significantly impacted by hydropower operations. However, given that turbine mortality rates vary depending on numerous factors, and turbines are not present on every stream throughout the species range, making broad generalizations about the impacts range-wide and at a population level was thought to be an appropriate approach with numerous caveats attached. When asked if the effects of downstream barriers have already been realized (given that many of these dams and hydropower operations have been in place for substantial time), the panelists expressed that eel populations may still be responding to man-made barriers (generational impacts, cumulative impacts, continues to effect the reproductive potential) but there was disagreement as to the nature and degree.

Panel Members for Barriers to Successful Downstream Migration: Ken Oliveria (Univ. of Massachusetts), John Casselman (OMNR/Queens University, retired), Kevin McGrath (NY Power Authority), Rob Macgregor (OMNR, Lake Ontario Manager), Brian Knights (Kings College, London, retired), Alastair Mathers (Ontario MNR), Bill Richkus (Versar), Paul Angermeier (US Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Blacksburg, VA)

Changes in Oceanic Conditions

Six experts on oceanic processes and leptochephali were assembled for a four hour session on the second day. Two experts (Knights and Friedland) provided excellent presentations on two hypotheses of eel transport during its oceanic phase and how this may relate to changes in recruitment to freshwater. This prompted lively discussion from the panel experts and the agency observers. All experts thought that oceanic conditions play a significant role in recruitment, although there was disagreement about the actual mechanisms. Because of the unique nature of the leptochaphali, observational data are lacking, however, there is a correlation between recruitment (in both European and American eel in Canadian waters) and the North Atlantic Oscillation Index. The duration of the current North Atlantic Oscillation was stated to be within normal parameters and would currently be negatively affecting recruitment. Additional papers were suggested.

Panel Members for Changes in Oceanic Conditions: Kevin Friedland (NMFS Science Center, Narragansett, RI), Jacob Kritzer (Environmental Defense), Brian Knights ,(Kings College, London, retired) Jeff Govoni (NOAA, NOS, Beaufort, NC), John Casselman (OMNR/Queens University, retired), and Mike Miller (Ocean Research Institute, University of Tokyo, Japan).


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.

DRAFT WORKING COPY OF THE MINUTES,
12/21/2005 revision, Atlantic Coast/Islands Workshop
,
Nov. 30 – Dec. 1, Shepherdstown, W. Va.

Attachments (to be posted as they become available)

  1. Opening Remarks and Definitions
  2. Habitat Questions
  3. Draft Conceptual Model — P. Angermeier et al.
  4. European Schematic of Threats
  5. Handout — NAO and possible effects on eels
  6. Handout — Oceans: What we do/don’t know
  7. B. Knights’ Presentation — NAO and Recruitment
  8. Graph — NAO/glass eel recruitment
  9. Gulf Stream Map — M. Miller
  10. Salmon Presentation Slide #48 — K. Friedland
  11. Gulf of Mexico Map — M. Miller
  12. K. Friedland’s Salmon Presentation
  13. B. Knights Presentation — Adaptive Strategies
  14. Harvest Graph — Corrected Landings Data US/Canada
  15. Harvest Graph — U.S. Commercial Landings by Region
  16. Harvest Graph — Maine Commercial Landings
  17. J. Uphoff’s Presentation — Analysis of Factors Influencing U.S. Atlantic Coast Eel Harvest
  18. FAO Table — International Harvest

 




HOME | TOP