Julie Endrizzi
12/21/08 Bio 394
The American Eel
Anguilla rostrata
Real British race track food is not fish and chips but jellied eels. So far as I know these are an exclusively British delicacy and, because they are regarded as the food of the common hordes, are sold only in working class areas of London and the cheaper enclosures at race tracks.
Served from outdoor stalls with vinegar and crisp new bread, they are exquisite. The eels come in a savory jelly and are chopped into bite-sized pieces. The eating technique is to crunch up the backbone and swallow it along with the flesh. Lovely.[1]
Eel - photo by Heather Perry
Eels are commonly used in a variety of cuisines across the world, though they are generally considered unappealing to the American palette. In Britain jellied, eels are a traditional delicacy, boiling the eels in water releases a gelatinous component from the flesh, which gels upon cooling leaving the chunks of eel embedded in a pale yellow gelatin[2]. In China and Japan eels are often used as an aphrodisiac[3]and have even been found in soft drinks[4]. There is no known method of breeding eels in captivity, so the eel young are captured and transported to East Asian and European markets for aquaculture, as a result, prices for these eel young have at times surpassed the price of caviar[5]. The fisheries around Merrymeeting Bay are in tune to these demands, and the local harvest of this resource varies considerably in conjunction with the fluctuating market prices.
Life History
The American Eel, Anguilla rostrata, is a unique catadromous species of fish, meaning that it lives primarily in rivers and freshwater ecosystems, but breeds and spawns out at sea. Every American eel found in the waterways from South America all the way up to Greenland is part of a single breeding population[6]. The eel breeds in the Sargasso Sea off the Atlantic coast and the larval forms are carried by currents into the land.[7] The eel lifecycle reflects the many changes that the eel faces over its lifetime. The leptocephalus, or larval, stage is a flattened transparent form that can easily be transported by currents, as it is carried by the current it develops into the glass eel stage, which allows it to swim into the coast[8]. The change from the drifting to swimming form is triggered by unknown cues and presumably at random, so that the eel young are deposited indiscriminately to coastal points along the Gulf Stream, Antilles Current, Caribbean Current, Yucatan Current, Florida Current, North Atlantic Current and up to the Greenland Current[9].
Once the eels reach fresh or brackish water they develop into the pigmented elver form, which will then develop into the adult Yellow eel form after about two years. The elver and yellow eels can live and mature in the brackish estuaries, however many of them make their way upstream. It can take anywhere from 4 to 30+ years for an eel to reach sexual maturity. Once sexually mature the eel undergoes yet another metamorphosis to the silver eel form, changing pigmentation, shape and size and even its digestive system. The silver eel will return to the Sargasso Sea to breed and then die. The eels breed only once in their lifetimes, so mortality at any stage of their lifecycle affects the fecundity of the entire breeding population.[10]
Eels are nocturnal carnivores and consume both benthic invertebrates and other fish species[11]. The eels in turn are predated on by other fish, fish-eating birds and mammals such as mink[12]. Eels are harvested by humans at the elver/glass eel stage as well as at the yellow/silver eel stage. The elvers and glass eels are transported to East Asian markets for aquaculture, where adult eels are in high demand. In contemporary North America the adult eels are used mainly as bait fish for anglers.[13]
Decline in the American Eel Populations
There are many sources that hint at former historical abundances of eels[14]. Forest and Stream: a Journal of Outdoor Life, Travel Nature Study, Shooting, Fishing and Yachting in a report on eels in New York said that “the young fish could be seen ascending the river in vast numbers”[15]. There are other reports of elvers being so abundant that one individual caught over 500 with his bare hands[16]. There has been widespread evidence for decline in the eel populations across the Atlantic seaboard based on both survey and commercial harvest data[17]. Declines in American eel populations in other states directly affect the eel recruitment in Merrymeeting Bay because the eels are one single breeding population.
Threats to the American Eel
Modern American eels face a variety of problems including changes in habitat, overharvesting and parasites. Introduction of dams have impeded migration of eels both upstream and downstream, and it has been suggested that pollution has also affected the survival of eels. The local cuisine of both Europe and Asia creates a high demand for eel, and the European eel population has faced serious decline, thus much of the harvesting pressure has moved to the American eel population. The introduction of the eel parasite Anguillicola crassus, a native of Southeast Asia, also poses a potential threat to the American eel populations. This nematode parasite affects the swim bladders of the silver eel, and therefore affects its ability to travel to the Sargasso Sea to reproduce. The catadromous lifecycle of the American eel also creates a regulatory issue for the management of the fishery because the habitat spans a variety of state and national jurisdictions.[18]
Eel Fisheries in Maine
Maine has taken significant steps to address at least the commercial harvest of eels by creating very specific legislation that regulates the tools used to harvest eels and the places and times they can be harvested. Additionally the state charges a relatively expensive license fee, for which the revenue is to be dedicated to further research on eel populations[19]. Harvest of eels is performed at night as eels are nocturnal and display an aversion to light[20]. Tools used include fyke nets, weirs (put a hyperlink here), eel pots and dip nets. There were 15 commercially licensed eel weirs on the Kennebec River in 1999. Many models of eel weirs, which are only permitted to be in place during the fall fishing season, reduce the overall survival of adult eels to between 5-25%[21]. The eel fishery is particularly vulnerable to poaching because it is done at night, and the total number of recorded infractions in the eel fishery increases with demand[22].
Historical monitoring and even mention of eel populations was sporadic at best. Eels were an important traditional resource for many Native American cultures[23]. In the Merrymeeting Bay watershed, a fish weir dating to 4200 BCE was discovered on the Sebasticook, a tributary of the Kennebec, and it appears to have been used to capture American eels and other fish for harvest, pointing to the longevity of this fishery[24].
Commercial landings have been used as a proxy for eel populations but their usefulness is limited because of inconsistent reporting and fluctuating market demand, as well as the fact that measuring the harvest in pounds does not account for differences in elver and adult weight. Reports of commercial landings in Maine date back to 1887, and the highest recorded state harvest was 400,130 pounds in 1912[25]. Maine was also at the forefront of the national eel fishery[26]; “The rivers of Maine, centre of the industry, supply practically the entire country.”[27] The total annual harvest of the eels varies greatly depending on market demands, the adult eel harvest peaked in the late 1970s, but the elver harvest boomed in the 1990s reaching its height in 1995, when their price reached $230 per pound due to the demands of the Asian market[28]. The prices have since fallen, but commercial harvest continues, with 407 fishing permits sold for adult and elvers in the year 2008[29].
Dams and Eel Passage
Dams in the Merrymeeting Bay watershed are seen as a major obstacle to both upstream recruitment of elvers and the downstream migration of silver eels to breed. It has been calculated that the Kennebec and Androscoggin River Basins have a total of 192 dams, 108 of which are hydroelectric, and the presence of these dams has reduced the total navigable length of these waterways from 13,653 km to just 403 km[30]. Some eel passageways have been developed to allow elvers to pass upstream of dams, however these passages are not on all dams and there is a question of their effectiveness[31]. More importantly the hydroelectric dams have been shown to injure and kill adult eels[32]. One model calculated that the length of the eel was directly proportional to its mortality rates in hydroelectric dam turbines, thus the longer eels were more likely to die or suffer injuries from these dams[33]. This is directly relevant to eel reproduction because the fertility of the female eel is also correlated with size and increases exponentially as the length of the female increases[34]. These findings suggest that the presence of hydroelectric dams in eel habitats is selecting for a less fertile population, which has potential implications for the long term survival of the entire species. The Maine DMR has completed a series of experimental eel passages and monitoring for effectiveness, investigation of effective eel passage systems is ongoing.
Bioaccumulation of Toxins
Eels are subject to both problems of bioaccumulation of toxins, as well as residual effects after pollutants have been removed from a system as a result of their long lifespan[35]. The historical use of the Merrymeeting Bay watershed for industrial waste and incidental runoff during the 19th and 20th century has exposed the eel populations to heavy metals and other toxins. Though many of these waste products are now regulated and are not being introduced into the system any longer, eels, as primarily benthic feeders, could potentially be exposed to their effects for many years to come.
Climatic Changes
The eel is expected to be resistant to changes in temperature predicted by climate models as a result of its ability to survive in a broad range of habitats. However there is evidence that eels in the more northern latitudes are more fertile, which could be a function of water temperature[36]. Additionally climatic effects on the oceanic currents that distribute the leptocephalus larval stage are unknown and could have a particularly dramatic effect on eel recruitment in Maine rivers[37].
Local Efforts to Restore Eel Populations in Merrymeeting Bay
There has been considerable progress in increasing local and national monitoring and preservation of the American eel, spurred in part by requirements instituted by the Atlantic States Marine Fisheries Commission. Maine has been at the forefront of eel research and regulation. Members of the Friends of Merrymeeting Bay were indispensable in presenting the National Fish and Wildlife Service with a petition to list eels as endangered, although the proposal was rejected after a 12 month review. The Maine Department of Marine Resources began in 1997 to request that all hydropower dams up for licensing renewal allow for upstream and downstream passage for eels, but dam license renewal occurs every 30-50 years depending on the dam so these changes will not have immediate effects on the eel populations[38]. Fish ladders have been built with a climbing substrate specifically designed to minimize dam effects on the upstream migration of the young. There have been efforts in Canada to develop grate systems that deflect adult eels away from the turbines during their downstream migrations. Those dams up for licensing renewal are also being asked to simply turn off their turbines during peak periods of upstream and downstream eel migrations.[39]
The American eel fishery has proved to be important and fairly resilient to many of the modern challenges it faces, not only in Maine but also within Merrymeeting Bay. Additionally, conservation efforts in favor of the American eel have broader implications not just within the Merrymeeting Bay ecosystem but also in fisheries across the Atlantic coast because of the relatively unique characteristic that all American eels are one single breeding population. The American eel could continue to be a culturally and commercially significant resource in the future and its management within the Merrymeeting Bay ecosystem requires collaborative efforts on the part of the dam owners, fishermen, legislature and the community.
USFWS 12 month finding on American eel
http://www.mnr.gov.on.ca/en/Business/SORR/2ColumnSubPage/EELPAGE.html
USFWS
Maine DMR, Oct 28 2004.
[1] Leapman, 47.
[2] Ibid.
[3] Wyatt, 1.
[4] Green.
[5] Wyatt, 1.
[6] Williams et al., 192-204; Avise et al., 4350-4354.
[7] Bigelow and Schroeder, 578.
[8] Gulf of Maine Council on the Marine Environment, 2-3.
[9] Ibid.
[10] Bigelow and Schroeder, 579-580; Gulf of Maine Council on the Marine Environment, 2-3; ASMFC, 20-25.
[11] ASMFC, 16.
[12] Ibid. 3.
[13] ASMFC, 32-44.
[14] Davis et al., 360.
[15] Goode, G.B., 91.
[16] Bigelow and Schroeder, 579.
[17] ASMFC 27-31; MacGregor et al. 1-26.
[18] ASMFC ; Gulf of Maine Council on the Marine Environment, 4; MacGregor et al. 1-26; Eel and Elver Management Fund Committee, 3, 7-9.
[19] Eel and Elver Management Fund Committee, 12-13.
[20] Hadderingh et al. 365-371.
[21] McCleave, J.D., 599-600.
[22] Eel and Elver Mangement Fund Committee, Tables 11 & 12.
[23] Davis et al., 357-388.
[24] Petersen et al., 197.
[25] Committee on American Eel Management for Maine, 1996, 13.
[26] Bryant, N., S8.
[27] Anonymous, Jan 15, 1928.
[28] ASMFC, 22.
[29] Personal communication with Ann Tarr from the Department of Marine Resources Licensing.
[30] ASMFC, Table 5.
[31] MDMR Kennebec River Anadromous Fish Restoration, 43.
[32] Eel and Elver Mangement Fund Committee, 8-10; Maine DMR, 26.
[33] McCleave, J.D., 592-605.
[34] Barbin, G.P. & McCleave, J.D. 840-847.
[35] ASMFC, 54.
[36] Barbin & McCleave, 840-847.
[37] ASMFC, 7; Fish and Wildlife Service, 4979-4984.
[38] MDMR Kennebec River Anadromous Fish Restoration, 42.
[39] Gulf of Maine Council on the Marine Environment, 8-10; Verreault and Therrien, powerpoint.