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American Eel


By Dan Burden, content specialist, AgMRC, Iowa State University, djburden@iastate.edu.

Revised April 2012 by C. Greg Lutz, specialist and professor, LSU Ag Center, glutz@agcenter.lsu.edu.


Although not popular as a food fish in the United States, eels are considered a delicacy in many European and Asian countries. Traditionally, these fish have been harvested from the wild at marketable size, but young eels are now widely captured and cultured to market size. Global production of eels (Anguilla spp.) increased nearly 20-fold from 1950 to 2007 (Crook 2010), and 90-95 percent of current production is attributed to aquaculture of wild-caught young (FAO 2009, Crook 2010). Eel farming, whether in Europe, Asia or North America, relies on wild-caught juveniles because it has been difficult or impossible to produce viable offspring using captive spawning methods.

Eel species have provoked little commercial interest in the United States in recent decades. The 2005 Census of Aquaculture reported that three eel farms, one each in Maryland, New Jersey and Pennsylvania, were in operation. Other facilities have operated in other states over the past several decades, but the unique reliance of eel aquaculture on a supply of wild seed stock has proven to be a serious constraint for commercial operations. Because most of the world considers eel a gourmet item, this species could potentially be a high-value export and niche market product.

Distribution and Life Cycle
The distribution of the American eel (Anguilla rostrata) includes the entire eastern seaboard of the United States, southeastern Canada and the Gulf of Mexico. Eel can be found as far inland as the Great Lakes.

Eels are referred to as a catadromous (the opposite of anadromous) and amphihaline species, meaning that they spend part of their life in the ocean, then part of their life in freshwater and then they migrate from freshwater to the ocean once more to spawn. Adult eels move from rivers into the ocean in the fall, traveling to a region in the southwest part of the North Atlantic called the Sargasso Sea. After spawning, the adults die and the larvae travel on ocean currents back toward the mainland, feeding and growing along the way. Eel larvae undergo three stages during this oceanic period, reaching the coast as glass eels and elvers. Elvers are migratory, reaching estuaries and stream mouths in the spring and then eventually traveling up rivers. Eels may spend anywhere from 8 to 30 years in freshwater as they grow and ultimately mature.

Commercial Catches
Current research suggests that commercial catches of the American eel and related species in Europe and Asia are rapidly declining, indicating that they are in jeopardy. There are several fisheries for eels in the U.S., focusing on glass eels and elvers (for sale as stocking animals for commercial farms primarily in Asia and Europe), juveniles (yellow eels), and adults moving downstream to return to the sea (silver eels). Elver and glass eel fisheries still persist in several locations in North America, with market prices reaching as much as $2200 per pound of live animals (USFWS 2010 "Fish Facts - American Eel", Trotter 2012). International trade in glass eels has exploded over the past two decades as eel farms in Japan and other Asian countries exhausted supplies of their local species, Anguilla japonica.

The bulk of U.S. eel catches in recent years has occurred in central Atlantic coastal states. Official statistics (NMFS 2011) suggest that domestic landings of American eel increased from 330 metric tons in 2009 (slightly below the 5-year average) to 385 metric tons in 2010 (slightly above the 5-year average). The value of these landings also increased, from $1.87 million to $2.45 million, over the same 12-month period. These figures may underestimate the actual landings, based on export data from the U.S. Trade Internet System (see below). In either case, U.S. eel landings are comparatively small when compared to the global production of eels, which was estimated to be over 275,000 metric tons from aquaculture operations and 8,591 metric tons from capture fisheries in 2009 (FAO 2010).

There is considerable concern about heavy fishery exploitation of all American eel life stages, coinciding with a continent-wide decline in commercial catch. The causes of these declines include the cumulative effects of intensive fishing of this slow-growing, late-maturing fish. Fishing for yellow (juvenile and sub-adult) eels results in continuous pressure on each year class until it finally returns to the sea. However, many scientists doubt that fishing pressure alone explains the decline of the eel. Habitat loss through dam construction may be another cause. Water control structures and hydroelectric dams in particular have hindered the migration of eels both upstream and downstream. Other possible causes are pressures from climate change, parasites and diseases and pollution. Because of their long lifespan and high fat content, eels have a high potential to accumulate toxic contaminants, which may compromise their survival before or during their return to the sea.

In response to widespread concerns over declining populations, the U.S. Fish and Wildlife Service (USFWS) and the National Marine Fisheries Service (NMFS) were asked to consider a petition to have the American eel listed as an endangered species (see webpage listed below: American Eel Anguilla rostrata). Following a series of workshops beginning in 2004, these agencies determined in 2007 that such protected status was not warranted. In 2010, a new petition prompted an extensive review of the status of eel populations, and a 90-day finding and 60-day comment period was announced by the USFWS in late 2011. This (and other) information will be utilized by USFWS to ultimately determine whether endangered status is now warranted for the American eel, and a decision may come as early as late 2012 (USFWS 2011 "The American Eel").

The provincial government of Ontario, Canada, has also responded by banning commercial eel fishing in Lake Ontario and the upper St. Lawrence River and ended the sport fishing of eels across Ontario, but other eel fisheries continue in various parts of Canada. In Europe, a European eel (Anguilla anguilla) stock recovery plan was established by the European Commission in 2007. The species was subsequently listed in appendix II of the Convention on International Trade in Endangered Species (CITES) in 2009 (Crook 2010). Currently, eel cannot be exported from the EU unless such export "has been deemed not to harm the stock" and originates in a country with an approved eel management and recovery plan in place.

Eel Farms
Aquaculture production of juvenile eels for re-stocking programs or grow-out to adult fish for meat products is a well-established industry in the United Kingdom, France, the Scandinavian countries, Morocco, Australia, China, Taiwan and Japan. Glass eels are preferred over elvers for stocking, primarily because they are easier to transport and to wean unto artificial diets. Roughly 2.5 kg of glass eels are required to produce one metric ton of marketable live eels, at a preferred market size of seven eels per kg (averaging about 1/3 pound each). Glass eels must be gradually weaned off natural food (minced fish or fish eggs) and trained to artificial diets. Under optimum conditions, when stocked as glass eels, farmed eels can reach market size in 18 months or less. To attain these results, high-protein (42-49 percent) diets are required, but feed conversions are very economical, generally in the range of 1.0 to 1.8.

Eel farming takes one of two general forms - high-intensity recirculating tank systems, which are typically indoor facilities, or intensive pond-based operations, often incorporating greenhouse covers during colder months of the year. Open-pond grow-out of eels can be successful under a variety of conditions. In temperate regions of Japan, eel prices actually justify the cost of covering ponds with greenhouse structures and even heating the water during winter months. Pond production densities may reach as much as 20 kg/cubic meter, and aeration is generally utilized to maximize yields. A good rule of thumb for this type of intensive pond culture is to have a water exchange capacity of 4000 cubic meters per day (an average flow of 730 gallons per minute) for every 100 metric tons (220,000 pounds) of production. Much lower exchange rates can still result in profitable production, however.

Recirculating systems are well-suited for eel production, especially since eels tend to tolerate very high densities and associated high levels of ammonia and comparatively low PH conditions. In Europe, where most production relies on recirculating systems, densities of up to 120 kg of eels per cubic meter are not uncommon. Exchange rates are typically in the range of 5 to 8 percent daily. Investment costs, and risk, are high with this type of enterprise, but technology suitable for recirculating production of eels is available and can be employed virtually anywhere one can find a reliable supply of electricity and suitable make-up water. The economics of this production approach depend, however, on a dependable supply of glass eels or elvers, access to inputs such as high protein diets and approved health management products, and suitable market demand within 1 to 2 days transport time. In most of the U.S., these markets will be comprised of urban populations of Asian and European ancestry with an appreciation for eels as a delicacy.

Exports/Imports
The largest single market for farmed eels continues to be the Japanese 'kabayaki' (marinated, grilled eel) market. The kabayaki markets prefer eels weighing 0.44 pounds. Despite the high price paid for kabayaki eels, marketing of large eels up to 11 pounds each into alternative markets may be equally if not more economical (see: Eel Aquaculture). In Europe and North America, many eel consumers prefer a smoked and stewed product. In Italy, France and Spain, glass eels are still eaten, in spite of increasing scarcity and high prices.

Since 2001, the United States has exported frozen American eels, primarily to South Korea and Belgium. In 2010, South Korea purchased eels valued at $3.0 million, while Belgium purchased eels valued at $1.7 million. Hong Kong, is now the third largest importer of American eels, purchasing $1.2 million worth of eels that same year. Total U.S. exports of American eels in 2010 were 2,202 metric tons valued at $7.4 million. (U.S. Trade Internet System).

In June 2007, the U.S. Food and Drug Administration announced that it was initiating import controls for certain species of farmed seafood from China, including eels. The action was in response to numerous cases of contamination. China is the major supplier of eels to the United States (82 percent of the total). In 2010, the United States imported an estimated 573 metric tons of eels valued at $5.2 million.

Outlook
Eel is probably not in demand as a U.S. seafood product due to its “snake-like” persona and a lack of educated consumers. If markets could be developed, however, eels have the potential to become one of the highest-quality, highest-value aquaculture products because the science for raising the fish is well established. The most promising approach for U.S. producers would probably involve establishment of production facilities near large ethnic Asian or European markets. In certain regions, economical production might be accomplished with outdoor facilities, but in others, the preferred technology would involve indoor closed loop systems, as has been successfully demonstrated with North American live markets for tilapia.


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Links checked July 2013.

 

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