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John Skinner

John Skinner is the author of Fishing the Bucktail and A Season on the Edge. He’s the creator of the fishing log software FishersLog. He’s a consistent producer of trophy striped bass and holds the current New York State false albacore record.

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March 04, 2012

Eels and the Endangered Species List. Here we go again.

by John Skinner

Last fall, the US Fish and Wildlife Service announced that they will begin an extensive review for the American Eel to determine if adding the species to the Federal List of Endangered and Threatened Wildlife is warranted. Normally I would report on something like this pretty fast, but the first time I saw something about it I wrote it off as old news. That's because the Fish and Wildlife Service went down this same road five years ago, and concluded after a two-year study that listing was not warranted. I wrote an in-depth article for Nor'east Saltwater at that time, which I have reproduced below because it is once again very relevant. So why is this happening again?
In 2010, a group of environmentalists based in California petitioned the Fish and Wildlife Service to protect eels under the Endangered Species Act. At the time the petition was submitted they called themselves "The Council for Endangered Species Act Reliability". They have since changed their name to "The Center for Environmental Science, Advocacy and Reliability". I found it entertaining that they managed that substantial name change while preserving its acronym (CESAR). After somehow resisting the multiple donation links on their website,, I learned a little about who these people are. Their Executive Director, Craig Manson, was President George W. Bush's Assistant Interior Secretary. So it would seem they are lead by a heavy hitter who is likely well connected in Washington.
When the new petition was reviewed, the F&WS decided to initiate another full review. Their justification was that "New information indicates that changes in ocean conditions may be negatively impacting the eel's reproduction rates." They said they are particularly interested in the following types of new information not known at the time of the 2007 status review: species' population structure, range-wide analysis of impacts from the parasitic nematode Anguillicola crassus, statistically significant long-term glass eel recruitment declines, and the correlation of climate change and glass eel recruitment.
The potential impact on anglers goes beyond losing the ability to use eels for bass bait. If the eels end up on the Endangered Species List, we could see habitat protection of the type we see associated with protection of the Piping Plover. In the case of this shorebird, it means beach access restrictions. What might it mean to our waterways if eels are given a similar level of protection? It's a scary thought. Considering that I can go to any number of local tackle shops during the season and buy as many eels as I want for about $20/dozen, I have a very difficult time rationalizing the possibility that their species is threatened by extinction. But it's not up to me. We'll have to leave that to the government scientists who will once again launch a full-blown evaluation of the species. We can only hope that it will be unbiased and accurate.

Consideration of the American Eel for Endangered Species Act Protection
(Original publication February 2007)

By John Skinner


On January 30, 2007, the U.S. Fish and Wildlife Service (USFWS) announced the completion of an extensive status review of the American eel, and concluded that protecting the eel as an endangered or threatened species under the Endangered Species Act of 1973 is not warranted. The review examined all available information about the American Eel population from Greenland south along the North American coast to Brazil in South America and as far inland as the Great Lakes and the Mississippi River.
The Service initiated the review in September of 2004 at the request of the Atlantic States Marine Fisheries Commission (ASMFC). In November of 2004, Douglas and Timothy Watts petitioned that Endangered Species Act protection be extended to the eel. In July of 2005 the USFWS issued a 90-day finding that found that the petition presented substantial information indicating that listing the American eel may be warranted. The USFWS hosted two workshops to discuss threats with eel experts from federal and state agencies, nonprofit organizations, private industry, Native American tribes, academia, the ASMFC, Great Lakes Fishery Commission, Canada, England, and Japan. The following is a summary of the USFWS evaluation and finding. A link to the full 31-page report in the Federal Register as well as other relevant information can be found at


American eels have a fascinating life history. All eels are born in the Atlantic Ocean's Sargasso Sea near Bermuda where their eggs hatch into a larval stage known as "leptocephali". These larvae are transported by ocean currents to the Atlantic coasts of North America and the upper portions of South America. Unpigmented juvenile eels arriving along the coast are known as "glass eels", while the newly arrived pigmented eels are referred to as "elvers". Eels that survive this juvenile stage mature into fully pigmented "yellow eels". This is the stage that most anglers are familiar with. Some eels grow to adulthood in the marine environment, some go into freshwater/saltwater estuaries, some migrate up rivers and streams, and others move from one habitat to another as they grow as juveniles and mature. Beginning at 3 years old and up to 24 years, yellow eels change into "silver eels", which is a key physiological event preparing these future spawners for oceanic migration and reproduction. During this metamorphosis the eels take on a silvery color, develop enlarged eyes and nostrils, and a more visible lateral line. Upon nearing sexual maturity, silver eels stop feeding, and begin migration toward the Sargasso Sea. Spawning occurs there, after which the adults die. Each female will produce between a half million and 30 million eggs. The American eel is said to have the broadest diversity of habitats of any fish species, and this enhances the species' ability to survive despite threats in one or more environments.

Population Status

The USFWS looked at the best available scientific and commercial information to assess the population status. They concluded that, despite a population reduction over the past century, eels remain very abundant and occupy diverse habitats over an exceptionally broad geographic range. In the words of Dr. David Perkins, senior fisheries biologist with the USFWS, "Although the current status of American eels cannot be described in absolute terms because rangewide estimates of abundance do not exist, the number of yellow phase and silver phase eels is probably in the many millions, perhaps billions."
The USFWS also noted that trends in abundance over recent decades vary among locations and life stages, showing decreases in some areas, and increases or no trends in others. They took special note of the fact that records of glass eel recruitment do not show declines that would signal recent declines in annual reproductive success or the effect of new or increased threats. Although variable from year to year, glass eel recruitment appears stable over the past 15 years. Taken as a whole, investigators felt that a clear trend could not be detected in species-wide abundance during recent decades, and determined that the species currently appears stable.

Factors Affecting the Species

Five factors are weighed in determining the need for ESA protection of any species.
Factor A: The present or threatened destruction, modification, or curtailment of the species' habitat or range. Factor B: Over-utilization for commercial, recreational, scientific, or educational purposes. Factor C: Disease or predation. Factor D: Inadequacy of existing regulatory mechanisms. Factor E: Other natural or manmade factors affecting the species' continued existence.

Factor A : The Present or Threatened Destruction, Modification, or Curtailment of the Species' Habitat or Range.

Spawning and ocean migration habitats are essential to the persistence of the American eel, and the USFWS concluded that there are no apparent human-caused or significant threats to these habitats, and they remain available and occupied by eels. Estuarine, marine, and freshwater habitats provide maturation habitat, and it was verified that some portion of the eel population completes its lifecycle without ever entering freshwater. Although some dams appear to form a complete barrier to upstream migration and likely caused regional removal of eels from 25 percent of their historic freshwater habitat, American eels are able to negotiate many barriers. This has allowed them to remain well distributed throughout roughly 75 percent of their historic freshwater range.
The USFWS noted that males and highly productive females continue to be present in extensive areas of fresh water, estuarine, and marine environments, and there appeared to be no evidence of reduction in glass eel recruitment. For these reasons, they concluded that available freshwater, estuarine, and marine habitats are sufficient to sustain the American eel population.

Factor B: Over-utilization for Commercial, Recreational, Scientific, or Educational Purposes

Investigators found no evidence that subsistence harvest (people catching their own eels for food), bycatch, or recreational fishing was having an impact on eels regionally or rangewide. They found that commercial harvest, which included the bait eel fishery, had a strong influence on eel densities in some local and regional areas, but there was no evidence that it was a threat at a population level.
A population level threat is one that threatens the species with extinction. Such a threat would be seen in declines in juvenile recruitment rangewide, but this hasn't been found. Researchers think that the random dispersal of the larval stage enables the species to successfully recruit to other areas, including extensively unfished areas, resulting in a buffering effect against harvest. Eels demonstrated another compensatory mechanism related to commercial fishing. One study of the glass eel fishery suggested an exploitation rate of 30 to 50 percent on arriving glass eels and elvers, but that high rate did not translate to a similar level of reproduction loss. The explanation was that the glass eels and elvers that weren't harvested had a greater potential for survival because of the decreased density of the eels. One can probably observe something similar with a home aquarium. Pack the aquarium to its maximum fish density and odds are that some will die due to stress. If there are only a few fish in the tank, they stand a higher chance at long-term survival. The USFWS concluded that density-dependent mechanisms such as these combined with fishing regulations were sufficient to maintain the species as a whole even under foreseeable fishing pressure.

Factor C: Disease or Predation

The main concern in this category was a parasite, Anguillicolla crassus, which matures in the swim bladder of the eel. Studies have suggested that this parasite may impair the capacity of the eels to migrate to the Sargasso Sea for spawning. Researchers acknowledged a high degree of uncertainty with regards to the impact of this parasite on individual silver eels, but they found no evidence of a population-level effect. Given that there are extensive areas of the American eel's range that have not been invaded by A. crassus, the USFWS felt that it does not pose a threat at the population level. They also found no evidence of a significant threat to the eel population from other diseases or predation.

Factor D: Inadequacy of Existing Regulatory Mechanisms

The regulatory mechanisms considered here dealt with seaweed harvest, habitat degradation, harvest and trade, contaminants, and fish passage. Much of this is addressed in the sections A, B, C, and E, and found not to present population threats. Given those findings, the USFWS felt that it was reasonable to conclude that the current regulatory mechanisms that are in place are sufficient to protect the eel from extinction.

Factor E: Other Natural or Manmade Factors Affecting the Species' Continued Existence

The factors considered here included hydropower turbines, contaminants, and oceanic conditions. Turbines were recognized as a source of ongoing mortality that affects regional presence and abundance of eels. However, the current information did not identify turbines as a significant threat to the eels at a population level. There was substantial uncertainty on the effects of contaminants on the American eel, but there was nothing to support a population level impact. Oceanic conditions are highly variable and cyclical. They determine recruitment to the continent, and therefore have a substantial influence on the presence and abundance of eels on the continent, especially in freshwater habitats. Oceanic conditions are a naturally occurring influence on the American eel during its early life history, but are not considered a threat to the eel.


The Endangered Species Act defines the term "threatened species" as any species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. The term "endangered species" is defined as any species that is in danger of extinction throughout all or a significant portion of its range.
The USFWS found that American eels remain widely distributed over their vast range including most of their historic freshwater habitat. They are not solely dependent on freshwater habitat to complete their lifecycle, and utilize estuarine and marine habitats as well. Their number remains in the millions, with recruitment trends variable but stable. Threats acting individually or in combination do not threaten the species at a population level. Taking these factors and the best available scientific and commercial information into consideration, the USFWS determined that listing the American eel as threatened or endangered under the Endangered Species Act is not warranted.

Angler Impact

The USFWS decision is good news for anglers who use eels for bait. Had they decided to list the species, eels would have become protected in the same fashion as the piping plover shorebirds. Eel possession certainly would have become illegal. It's also reasonable to assume that there would have been new restrictions applied to activities in important eel habitats, in the same way that we face beach access restrictions to protect the piping plover.
This marks the passage of one threat to the future availability of eels for bait or food. The ASMFC manages the commercial and recreational fisheries, and it's possible we'll see some tightening of those regulations somewhere in the future if they feel it's necessary to protect the stocks.

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