MFR PAPER 1303

Eels and Their Utilization

J. PERRY LANE

INTRODUCTION several eastern States, notably, Maine, common or American eel, Anguilla To the average American, the image Massachusetts, New York, New Jer­ rostrata. Other names used in this of the common eel conjures up a picture sey, Maryland, Virginia, North Caro­ country are the yellow eel, silver eel, of a snake-like creature slithering lina, and Florida, with varying amounts and freshwater eel. Young eels are through brooks and rivers. The mental from other States. In 1970 from recrea­ called elvers after they acquire pigment picture is often accompanied by an in­ tional fishing alone, it was estimated and "glass" eels when colorless. The ward shudder of revulsion. This unfor­ (Statistics and Market News Division, American eel is found along the coast tunate association of eels with snakes 1975a) that over 4 million pounds and in freshwater streams and rivers has deprived most Americans from en­ (1,814 metric tons) of eels were taken from Greenland to the Gulf of Mexico joying a fish that has been considered a from the Atlantic coastal States, while and as far south as Panama, the West gourmet delicacy for thousands ofyears another I V2 million pounds (680 metric Indies, and rarely to the northern coast in many parts of the world. Not only tons) were taken commercially in 1972 of South America. that, but the reptilian association ofeels (Statistics and Market News Division, The taxonomic or biological clas­ is completely erroneous. The American 1975b). Eels are usually caught with sification of eels is as follows: eel, Anguilla rostrata, is a true fish with traps, but otter trawls, hand lines, long lines, fyke and hoop nets, floating gills and scales. Kingdom: Animalia traps, spears, haul seines, and pound The eel itself is a fascinating creature Phylum: Chordata nets have also been used. Most of this and was, and still is to some extent, the Class: Osteichthyes gear was used in some form by the early object of one of the greatest biological Order: Anguilliformes settlers along the eastern coast, particu­ detective studies of all times. Since the Family: Anguillidae larly in New England. time of the ancient Greeks, man has Genus: Anguilla wondered where the eels came With the worldwide interest in eels from-where they spawned. For hun­ and the fact that eel fisheries in the dreds of years, no one had seen an eel United States go back to the time of the There have been about 17 species with eggs or milt. Did they really origi­ Pilgrims, why have eels been shunned found of the Anguilla genus. These are nate from horse hairs dropped into by most of the citizens of the United identified in Table 1 along with the streams as was once believed? States? Why are they still largely parts of the world where they normally As a food, the eel is consumed in underutilized here, particularly in light occur. many ways; and in parts of Europe and of the present shortage of so many of Other eels resemble the American eel particularly in Japan, demand has so our more established marine food fish? to varying degrees. The conger or sea outstripped supply that young eels-or Perhaps part of the reason is that the eel has the same serpentine body but elvers-have brought several hundred public is so unfamiliar with eels, except grows to a larger size. The conger eel dollars a pound. The Netherlands has for the vague misconception mentioned has more vertebrae than the American sent a specially designed ship with live earlier. This paper presents some basic eel, and the dorsal fin begins just behind wells to the United States and Canada to information on the eel, its life history, the pectoral or side fins, whereas the collect mature eels and transport them the various methods of catching and dorsal fin ofthe American eel originates alive to Europe. The lucrative foreign preparing them, and some indication of much farther back. The conger eel does market for eels has promoted the estab­ world demand. not enter fresh water. Another fish that lishment or expansion of eel fisheries in DESCRIPTION might be confused with the American eel is the sea lamprey, Petromyzon Eels are found worldwide and there marinus. This species is parasitic and J. Perry Lane is with the Gloucester are a number of different species. In the was responsible for nearly wiping out Laboratory, Northeast Fisheries Center, National Marine Fisheries United States, when the word "eel" is the lake trout population in the Great Service, NOAA, Emerson Avenue, used alone, one can be quite certain that Lakes. It has almost no jaws but rather Gloucester, MA 01930. the fish referred to is the so-called an oval-shaped mouth with many

April 1978 1 Table I.-Distribution 01 species 01 the genus Anguilla in illumination. They can alter their as in the sea where seaweed accumu­ (Eales, 1968). skin color within a matter of hours by lates, in rivers and at the water's edge, Species Distribution redistributing pigments. When these for it was there that the heat of the sun A. anguilla Europe, Iceland, and North Atrica A. australis Australia. Aukland Island. and eels reach maturity, the yellow gradu­ develops and produces putrefaction. By New Zealand A. bengaJensis Indian Ocean ally changes to a silvery white, and they "entrails of the earth," Aristotle may A bicolor Indian Ocean to Malayan Islands. are known as silver eels. have meant that eels were born from Philippines. and New Guinea A. borneensis Borneo Female eels grow to a larger size than worms or larvae. The idea of spontane­ A ce/ebesensis Indo-Malaya, Philippines, and western males. A mature female will vary from ous generation was common in Europe New Guinea A dieffenbachi Australia. Aukland Islands. and 30 to 42 inches (76.2-106.7 cm) in for hundreds of years after Aristotle, of New Zealand 1 A iaponica China and Japan length and weigh from about 2 /2 to 31/2 course, and thought to be the way mag­ A. marmorata Indian Ocean, most oceanic islands north pounds (1.1-1.6 kg). Females up to 4 gots arose from rotting flesh. 10 the Marianas and south 10 New Guinea. New Caledonia and Society feet (1.22 m) and weighing over 16 Pliny, in his "Natural History," had Islands as eastern limit pounds (7.3 kg) have been reported. a unique explanation as to the reproduc­ A. mauritania Central Pacific A. megastomata New Caledonia, Solomon Islands, The male can mature at 12 inches (30.5 tive process of eels. He said, "to repro­ eastern Polynesia, Fiji, Tonga, Samoa, cm) and usually does not go much over duce themselves, eels rub their bodies Marquesas, Tuamotu, and Tahiti A mossBmbica Indian Ocean 18 inches (45.7 cm) in length. Any eel against the rocks; from the shreds of A. nebulara Indian Ocean A obscura Australia, New Guinea. East Indies, over 18 inches (45.7 cm) would proba­ skin thus detached come new ones." eastern Polynesia, Fiji. Tonga. Samoa, bly be a female, and any over 24 inches appian, in the second century in Sicily, Marquesas, Tuamotu, and Tahili A paciHca East Pacific (61 cm) would certainly be a female. had an equally unique explanation. His A. reinhardi Australia and New Caledonia theory was that eels mate with snakes. A. rostrata NMh Arnerica and Greenland LIFE HISTORY The female eel takes the snake's head in Historical Background her mouth. Following this union, the eel went to sea and the snake to land. hooked teeth which it uses to fasten The eel was prized as a delicacy by There was no further scientific en­ onto other fish, rasp a hole in their side, the ancient Romans and was widely ob­ lightenment of the origin of eels and draw out blood which seems to be served throughout the waterways of throughout the Middle Ages. Scholars their main food. Europe. In fact, the origins of the eel of that time mainly reflected the views The American eel has an elongated have fascinated people since the begin­ of earlier philosophers such as Aristo­ serpentine body that tapers to a point at ning of European civilization. They tle. It was not until the 17th century that the tail. It is closely related to the Euro­ noted that the eels never contained roe Francesco Redi of Tuscany observed pean eel but has a lesser number of or milt as did other fish and this gave that eels leave fresh water around Au­ vertebrae-about 107 as compared rise to a variety of strange myths as to gust and go to sea where, he concluded, with 114. There are a pair of pectoral their origin. Some thought they de­ the female dropped her eggs. Later the fins just behind the head with a small veloped from horse hairs falling into young eels, or elvers, returned to fresh gill opening in front of each pectoral streams or rivers or from water beetles. water. This was the first time the small fin. The dorsal fin originates far behind Aristotle, in 350 B.C. in "Historia elvers were observed entering fresh the pectorals, back about a quarter to Animalium," gave his views and ob­ water and correctly identified as young one-third the length of the body. The servations to support his theory of spon­ eels. dorsal fin runs into and is continuous taneous generation. He observed that Redi was the first person to refute the with the caudal and anal fins. The lower eels had no seminal fluid or eggs and theory that eels were born alive. Others jaw at least equals the upper jaw in when dissected showed no seminal had found parasites in mature eels and length and sometimes projects slightly canal or womb; therefore, no eels are assumed they were young eels waiting beyond the upper. Both jaws are lined born from mating or from eggs. to be born. Leeuwenhoek in 1692 had with many needle-like teeth (Bigelow The eel goes from fresh water to salt described the eel's bladder as the womb and Schroeder, 1953). water and not vice versa, as do other and the parasitic worms found there as The color of eels varies widely, de­ fish (apparently the migration from salt young eels. Others, including Linnaeus pending on the stage of maturity and water to fresh water of the young glass in the 1700's, made this same mistake. their habitat. Prior to sexual maturity, eels and elvers was not observed). Aris­ It was not until 1777 that Mondini in they are usually a dark muddy brown or totle further observed that in pools that Italy discovered an ovary in an eel, and olive brown to black above, yellowish had been drained, eels could be found another hundred years, J874, passed along the sides, and light yellow or "reforming" themselves after a rain. before an eel testis was discovered. dirty yellow-white on the belly. It is in (Actually, the eels were simply buried This was done by finally looking at the this stage that they are referred to as in the mud and reemerged when the smaller eels rather than the largest, yellow eels and can be found in fresh pool again had water.) Finally, he which were females. In 1896, two ital­ water, estuaries, or the sea. Their color pointed out that eels come from the ians proved that the small leptocephali can change, depending on the type bot­ "entrails of the earth" where there is the larval stage of the eel by watching tom where they are found and changes were places with rotting material such it change in an aquarium.

2 Marine Fisheries Review With this basis of information con­ American eels. Anguilla ros/rala. Photo­ graphs courtesy of John J. Poluhowich, cerning the European eel at the begin­ Research Director, Institute for Anguil­ ning of the 20th century, it was the liform Research, Department of Biology, remarkable work of a Danish oceanog­ University of Bridgeport, Bridgeport, eN rapher, Johannes Schmidt, that finally 06602. traced the origin of the spawning area of the European eel and also tentatively identified the spawning grounds of the American eel. His work covered a period of nearly 20 years from 1904 to 1922. He observed that eels from all over Europe had, on the average, the same number of vertebrae, around 114 to I J5. This led to the conclusion in 1907 that all eels found in Europe be­ longed to the same species. This launched Schmidt on his search for the common spawning ground of these eels. This search was to take another 15 years and cover a good portion of the North Atlantic from Greenland along the coast of Europe and North America to the Caribbean and Mediterranean Seas. He took samples from various depths over a large part of the North Atlantic Ocean and followed the trail of young eels of decreasing size until he iden­ tified the Sargasso Sea in the southwest part of the North Atlantic, generally between Puerto Rico and Bermuda, as the common spawning ground of all European eels. During his studies, he also took a relatively few specimens of the larvae of American eels and iden­ tified their spawning area as somewhat to the west of the European eel, but still in the general area of the Sargasso Sea. Schmidt defined the European eel's spawning area as being between lar. 22°-30 0 N and between long. 48°_ 65°W. The dividing line between the spawning area of American and Euro­ pean eels is considered to be long. 500 W.

Life Cycle

The description of the life cycle which follows applies to both the Euro­ pean eel, A. anguilla, and the Ameri­ can eel, except where specific differ­ to environment, to temperature, to sa­ Irc (63°F) isotherm. Each species of ences are noted. Leon Bertin (1956), linity, to light, and to current," than eel seems to have a definite temperature from which most of the information on that exhibited by the eel during the preference for spawning, and this life cycle is drawn, said that "there can course of its life. seems to be the best evidence for the hardly in the whole of natural history be The European eel spawns at a depth location of the spawning area of the a more remarkable example of response of about 400 m (437 yards) inside a. European eel in the Sargasso Sea. The

April 1978 3 evidence supporting the actual location the freshwater streams of North Trinidad and the Guianas which are of the spawning grounds of the Ameri­ America by the spring of the year after about 13 0 of latitude south of the re­ can eel is not as clear cut. The spawning they were spawned. The European lep­ ported Sargasso Sea spawning area. time for the European eel is during the tocephali take about 2 1/2 to 3 years as The currents would take the young lar­ spring, with most spawning occurring was noted above. During this time, the vae north, not south, and seem to make in May and June. The American eel transformation or metamorphosis to a southern migration impossible. With spawns over a longer period from Feb­ young eels or elvers is accomplished. these questions still unresolved, the ruary to July (Bertin, 1956). Each fe­ This is probably the most significant best that can be said at this time is that male is capable of producing as many as difference between the European and the true spawning area of the American 15-20 million eggs about 1 mm (0.04 American eels; that is, the time spent in eel has not been definitely established. inch) in diameter. migration from the spawning ground to No spawning eels have been taken their respective continental waters and Metamorphosis of nor have any mature eels been seen the timing of their metamorphosis to Leptocephali to Elvers after they have spawned. It therefore coincide with this journey. Regardless of where they were appears that the adult eels die after Before describing this change in the spawned, by the time they reach the spawning so that the Sargasso Sea be­ young eels, it should be pointed out that continental waters the change to elvers comes at the same time the nursery of there has been some question as to the is accomplished. This change consists young eels and the graveyard of adults. accuracy of Schmidt's assumption that of a change in shape from leaf-like to After the larvae are hatched, they go the westerly part of the Saragasso Sea is the beginning of a cylindrical shape. through an embryonic phase lasting a the spawning ground of the American Both the length and weight of the young few days. During this time, they derive eel as well as the European eel. Vla­ eel decrease as it goes from lepto­ their nourishment from the yolk sac. dykov and March (1975), raise several cephali to glass eel, which is an unpig­ They next enter the larval stage and points concerning the information and mented elver. The loss in weight is due gradually rise to the surface. During the conclusions drawn from Schmidt's mainly to loss of water from the body. larvae stage, the young eels are known work. First, no female American eels The intestines become shorter and the as leptocephali. These are transparent have been taken in as advanced stages long larval teeth fall out and are re­ and ribbon-like and are said to resemble of sexual maturity, as have been re­ placed by definitive teeth. These elvers willow leaves. They have small pointed ported for European eels. No spawning go through a short inactive phase of heads and long teeth. They join drifting eels or eggs have been taken (Schmidt's metamorphosis during which these plankton on which they feed and travel evidence is based on the capture of changes take place, and this is partly under the influence of the ocean cur­ young larvae). Schmidt followed the responsible for the loss in weight as rents towards continental water. These trail of the European eel by capturing well as the decrease in length. The flat and glassy leptocephali are so un­ larvae of decreasing size. Since he was young elvers after the inactive phase are like mature eels that it is not surprising not studying the American eel, it may vigorous and agile as they approach the it took so long to identify them as young be that the collection stations used were coast. eels. In fact, the name leptocephalus not in the proper locations to take About 1 year after hatching, around means flat head. American eels. The same applies to the December and January, the American One of the major differences be­ water depth sampled. Each eel species eels reach the coast and undergo the tween American and European eels is seems to have its own depth and tem­ changes described above. The elvers the length of time they remain in the perature preference, and again it may are about Ilh-2~ inches (6.4-7.0 cm) leptocephali stage and the time it takes be that in sampling depths preferred by long. The European eels reach the them to reach the continent. For the the European larvae, the American Spanish coast in October but do not small leptocephali that are carried north ones were missed. The actual spawning complete their journey to the Baltic Sea or south into cold currents from Lab­ season is still only generally defined, until the following May. rador or into the warm ones from the particularly for the American eel. As the glass eels approach brackish equator, there is death. Only those that There is limited information on the water, metamorphosis is completed and reach the proper currents to carry them exact duration of the larval stage of the pigmentation begins. This requires a toward Europe or North America sur­ American eel (reported as I year as variable amount of time, and in many vive. It takes the European eel from 2V2 opposed to 2lh to 3 years for the Euro­ streams during the spring, migration of to 3 years to make the long migration; pean eel). Ifthe western Sargasso Sea is glass eels can be observed before pig­ whereas, the American eels make their the spawning ground for the American mentation occurs. The upstream run to journey in about I year. During their eel, the question is raised as to the fresh water begins as early as February transatlantic migration, the eel larvae mechanism by which the larvae suc­ in North Carolina and in May and June travel on the surface at night and de­ cessfUlly cross the complex currents of in Canada. After pigmentation is com­ scend into deep water during the day. the Gulf Stream. Finally, there is the plete, the elvers gain weight and in­ The leptocephali of the American eel question as to how the American eels crease in length. The change from elver with a shorter distance to travel reach reach their southernmost limits of to young eel is thus completed.

4 Marine Fisheries Review Only a portion of the young eels or grass if the distance is not too great. sluggish and inactive and will bury el vers enter fresh water. The rest stay in They will also use underground water themselves in the mud. Should a body estuarine areas such as tidal marshes pipes if an access can be found and have of water dry up, eels are capable of and harbors or remain in coastal areas been known to fill the pipes in such staying alive in the moist mud and will of the sea. While the evidence is not numbers that they block them com­ reappear after a rain has replenished the conclusive, it appears that the female pletely. water supply. eels migrate into fresh water while the Eels rely primarily on olfactory At about 6 years of age, they develop males generally stay in the estuarine or stimuli to direct them to fresh water, tiny scales. These are definite and coastal area. and there is no evidence to indicate that well-defined scales but are so small that the young elvers return to the same they may escape detection. Upstream Migration waterways which their parents inhab­ Since eels will eat almost anything, The migration of the young elvers ited. Indeed, since chance in the form they do have some effect on other fish into fresh water lasts anywhere from a of ocean currents and winds plays such populations. Larger eels have been re­ few days to a month or more. The elvers a large part during their migration as ported to eat young salmon eggs. On move upstream at night, and during the larvae in the sea, the odds against any the other hand, trout have been known time of their spring run, may be seen by given elver returning to the exact same to eat young eels. The eel is extremely the thousands by use of a light on the body of water occupied by his parents hardy and can live out of water longer water surface at night. They are very would seem astronomical. than most other fish because of the pro­ strongly oriented toward swimming The young eels populate warm shal­ tection of the gills from drying out and against the current, and this fact has low lakes in large numbers and tend to the fact that it has a lower metabolic rate been utilized in trapping the elvers­ avoid extremely cold streams. After than a species such as the brown trout. opening of trap downstream, blind end reaching their destination, they will Because the eel can thrive in such a upstream. During the daylight hours, remain in fresh water from 5 to 18 variety of freshwater conditions, it is the elvers will seek cover by burrowing years, although this time is quite vari­ often thought to have a superior surviv­ into the mud or hiding under rocks. able and eels as old as 20 years have al potential than most other fresh water As American glass eels enter fresh been taken from fresh water. fish, although in general this does not water, they average about 2Y2 inches seem to be the case. Where there ap­ Yellow Eel Stage (62 rom) in length and number about pears to be a struggle for survival be­ 2,500 per pound (5,500 per kg). It is in the freshwater ponds, lakes, tween eels and trout or salmon, it is During the upstream migration, the and streams that the eels change to the mainly due to the competition for a elvers tend to follow along the banks of yellow state and assume the black­ common food supply rather than preda­ rivers and streams in shallow water. yellowish condition described earlier. tion by one species on another. Their persistence during migration up­ This is the growth stage. The male There is little information available stream is remarkable. They will cling to European eel will stay in this stage for on the habits of those yellow eels that damp rocks and will even climb up con­ 8- 10 years, while the females may re­ remain in marine waters and estuaries. crete dams as long as the surface is main in fresh water for 10-18 years. It is believed that at least some of them moist. Should they reach a portion of The American eel is believed to stay in move into the warmer fresh waters and the waterway where the current is too fresh water a shorter time, generally bury themselves in the mud during strong, they may leave the stream and from 5 to 10 years. winter as do their freshwater relatives. go around it through the damp grass and During their stay in fresh water, eels It is also thought that when yellow eels over wet rocks along the edges until the grow slowly. They are generally have been reported migrating down­ swift water is passed and then return to omnivorous during this period and will stream in the spring that it may simply the stream. When an obstruction is en­ eat a wide variety of organisms such as be some of these marine eels going back countered, such as a waterfall or dam, insects, fish, crustaceans, snails, to saltwater. during the peak of the migration, large worms, and even one another on occa­ In general, the more rapid the sexual numbers of elvers may collect while sion. They rely on an acute sense of development of an eel, the less is the waiting their turn to climb the rocks or smell to locate and catch food. Eels body growth. Males develop faster than dam and thus resume their journey on definitely prefer fresh food and will not females and as a results are consider­ the other side. eat rotten or decaying material. They ably smaller. There is a record (Bertin, The more barriers between an inland are active and feeding on warm dark 1956) of a female eel being kept in an 1 body of water and the sea, the less nights. Feeding activity is largely re­ aquarium for 38 /2 years and reaching a likelihood there is of the elvers reaching lated to light intensity-the less light, length of 55 inches (140 em), and of it. It is possible for them to gain en­ the more active. During daylight hours, another that was kept to an age of 25 trance to bodies of water with no visible eels generally hide in deep holes or bury years and grew to 43 inches (110 em) connection to the sea. They may do this themselves in mud, although occasion­ and a weight of 5 Y2 pounds (2,500 g). by using underground channels or even ally they will be active during daylight The increase in size and weight attained traveling overland through dew-laden hours. In cold weather, they become during the growth phase (yellow eel)

April/978 5 depends more on the availability of the of the other 90 percent is due to various the American eel, although the eyes do food supply than anything else. Tem­ external conditions as yet not clearly not enlarge as much (at least American perature is also a factor since cold understaod, but this is not the case for eels with such extreme enlargement weather inhibits activity and cuts down the 10 percent that are females from the have not been taken, although there is feeding. A colder environment will also beginning. Apparently, the environ­ the possibility that further enlargement slow sexual development so that in the ment plays no part in determining their takes place during the marine migra­ long run cold-water eels may grow to a sex. Final sexual maturity is completed tion). larger size than their warmwater coun­ by the time the spawning grounds are The passage of the silver eels from terparts, although it takes them longer reached or shortly thereafter. fresh water to salt water takes place to do so. Eels of the same species, age, between late August and mid-No­ Silver Eel Stage and sex can vary greatly in size, de­ vember for American eels, while the pending on environmental factors, and Each fall some of the larger and older European eels generally run from Oc­ the weight of one eel may be as much as yellow eels undergo transformation tober to December. The exodus of eels five times that of another of the same into silver eels. This change has not from European waters will run into age. been well documented for the Ameri­ millions and possibly billions of indi­ can eel, and most of the studies have viduals. The silver eels will show as Sexual Development been on European eels. Again, it is as­ much determination in reaching the sea The sexual development of the eel, sumed that the following information as the young elvers did in reaching their like so many other of its traits, is rather applies to both species unless otherwise freshwater home. unique. About 90 percent of the Euro­ noted. The downstream movement is set in pean eels (and it is assumed the Ameri­ Several changes take place during motion by changes in the environment. can eels also) pass successively through this transformation. First, and most An increase in water level and a dark a neutral (no sex differentiation) phase, noticeable, is the change in coloration. night seem to be favorable conditions a period of precocious feminization The color of the European eel goes from for beginning the migration. Large runs (when they will begin to develop fe­ yellowish to silver, while the American of American eels often occur on warm, male traits), and a phase of juvenile eel has been described as being more dark, stormy nights in late summer or hermpahroditism (both female and "bronze." This change in coloration fall. Light intensity is a critical factor, male characteristics) before becoming from yellow to silver has been de­ and this fact has been capitalized in definitely male or female. In the young scribed by Bertin (1956) as "acquiring catching eels during the fall run. Lights eel, the gonads are undifferentiated; the specific nuptial dress or, a more are placed in strategic positions to block this is the neutral phase. During the appropriate term, migration livery" as the passage of the eels and to divert yellow eel phase, usually between 5 it prepares for its long journey to the them into waiting traps or nets. On the and 8 years of age, they will develop spawning grounds. Mediterranean coast, up to 10 tons of both male and female characteristics In addition to changes in coloration, eels have been caught in one night dur­ and yet be incapable of reproduction. this metamorphosis is marked by sev­ ing this fall run. This is the hermaphroditic stage and is eral other changes. The digesti ve tract One of the remarkable adaptions that generally a temporary condition, al­ degenerates and the eel ceases to feed. takes place during this final metamor­ though some eels never leave this stage (For this reason, during the full phosis is the eel's ability to go directly of development. Next, when the eel is downstream migration the silver eels from fresh water to salt water. This nearing maturity and ready to leave the are impervious to the temptation of any property of euryhalinity involves a yellow eel stage for that of the silver (or type of bait.) Other changes include an series of complicated physiological bronze) stage, final differentiation into increase in the production and a thick­ changes that enable eels to resist male or female takes place. This is usu­ ening of the mucus, which is plentiful changes in salinity. Part of this resis­ ally not completed until the eels are and copious during the yellow eel stage tance is due to the thick viscous mucus well into their final marine migration but thinner in nature, a thickening of the or slime that coats the eel and forms a towards the spawning grounds. Those skin, and an accumulation of fat. There barrier to osmotic exchange between that will develop into males are more is an al teration in body flexibility and a the eel's body and its environment. precocious and will become silver eels, change in locomotive behavior and the A factor that helps sustain the eel sexually mature, around 8 years of age, eyes are greatly enlarged. Sexual de­ during its long migration at sea without where the females will not reach matur­ velopment is accompanied by an in­ eating is a toxic property (ichthyotoxin) ity until 10 to 18 years (somewhat crease in endocrine activity. The num­ of the eel's blood. This toxin is potent younger for American eels). ber of chloride cells in gills increases enough to cause infections in humans It is interesting to note that while and there are changes in osmoregula­ who might come in contact with it most eels pass through these various tory capacity to assist in adapting to a through an open cut or break in their phases of sexual development, about 10 saltwater en·,ironment again (D' An­ skin. The blood serum has a neurotoxin percent are females from the very be­ cona, 1960). Similar, although perhaps that can destroy red blood cells. In ginning. The final sexual determination not exactly parallel, changes occur in some way the toxin helps the eels to

6 Marine Fisheries Review resist starvation, asphyxiation, and Table 2.-World catch of eels. Anguilla sp. (Food and Agriculture Organization of the United Nations. 1974). wounds. To quote Bertin (1956) again Calch (1.000 I) in describing the eel, "Its exceptional Species Country 1965 1966 1967 1968 1969 1970 1971 1972 1973 European eel Morocco 0.3 03 03 0.3 0.3 03 03 03 0 endurance, its untiring energy, and its A. angUlI/a Tunisia 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 08 tenacity of life which manifests them­ Turkey 02 02 0.1 03 0.3 0.4 0.5 05 05 Denmark 3.2 3.7 3.5 4.3 3.7 3.4 3.2 33 36 selves particularly on the long migra­ German Oem. Rep. 1.1 1.2 1.3 12 1.0 1.1 08 09 0.9 Ilaly 32 3.1 3.1 32 3.4 32 33 3.2 3.2 tions would be sustained by the Nelherlands 26 28 3.1 2.7 2.8 1.5 1.2 1.1 1.1 ichthyotoxin impregnating its whole Poland 09 1.0 1.1 1.1 1.1 1.0 09 0.9 08 Portugal 0.1 0 organism.' , Spain 1.7 1.7 1.6 1.5 1.5 1.2 1.2 1.5 1.2 Of the long spawning migration of France 1.7 1.3 20 2.7 1.9 4.2 4.9 26 39 German Fed. Rep. 0.4 0.5 0.6 0.6 05 0.5 0.5 0.4 0.4 both the European and American eels, Ireland 02 0.1 0.1 0.1 0.1 02 0.1 0.1 0.1 little is known. Presumably, it takes Norway 0.5 0.5 0.5 0.6 0.5 0.4 0.4 0.4 0.4 Sweden 1.8 2.0 1.6 1.8 1.7 1.2 1.4 1.2 1.1 them 2 or 3 months to reach the spawn­ U.K. N. Ireland 08 1.0 06 0.6 06 08 08 0.7 08 U.SSR. 03 0.4 0.4 0.4 05 0.6 0.6 06 1.1 ing grounds from North America and a - -- - longer period of time from Europe. Total A. anguilla 19.1 19.9 20.0 21.5 20.0 20.1 20.2 17.9 19.9 What depths they swim at or what fac­ American eel Canada 0.8 0.7 0.8 0.9 1.1 1.1 1.2 1.1 0.7 A. raslrata U.SA 0.8 0.6 0.7 0.8 09 1.0 1.1 09 1.1 tors guide them to their final destination - Total A. rostrata 1.6 1.3 1.5 1.7 2.0 2.1 2.3 20 1.8 is unknown, but return they do. Here in Japanese eel Japan 18.8 19.8 22.8 26.7 26.5 19.4 16.8 16.5 17.3 the depths they mate, spawn, and pre­ A. iaponico Korea Rep. 03 0.4 0.1 0.2 0.1 0.1 sumably undergo disintegration of O1her 02 02 03 06 1.6 2.0 3.9 - - - some type and die. Tolal A japonica 19.0 20.0 23.1 27.6 285 21.5 20.9 16.6 17.4

Australian eel Australia 01 0.1 0.1 0.2 0.2 0.1 0.2 02 0 Summary of Life Cycle A. australis New Zealand 0 0.1 0.1 03 0.4 0.9 1.5 2.1 1.3 - - The life cycle of the eel can be sum­ Total A. ausrralis 0.1 0.2 0.2 0.5 0.6 1.0 1.7 2.3 1.3 marized as follows: Eels have several Total. all Anguilla 39.8 41.4 44.8 51.3 51.1 44.7 45.1 38.8 40.4 life phases and two distinct metamor­ 1 Dash indicates no data reported. phoses. First is the embryonic phase, lasting a few days, when they are nourished by the yolk sac. Second, the that constitute the vast majority of the (21,500 t) out of a total reported world marine larval phase (leptocephalus) or commercial catch in the world. The catch of 98 ,340,000 pounds (44,700 t). dispersal phase, lasts 1-3 years, de­ European eel, A. anguilla, is caught by The U.S. catch that year, as reported to pending on the species. During this some 17 European countries plus FAO, was only 1,000 t (2,200,000 phase, they are carried by the ocean Morocco and Tunisia in Africa, Syrian pounds). The Japanese production of currents towards North America­ Arab Republic and Turkey in Asia, and eels is largely from eel culture rather Europe and feed on microplankton. the U.S.S.R. The American eel, A. than harvesting of wild eels; and in Third is the inactive phase or first rostrata, is taken on the east coast of 1970, of 19,400 t reported, 16,700 t metamorphosis from leptocephalus into Canada, the United States, and Mexi­ were from cultured eels and 2,700 t elver. This lasts a few months. Fourth is co. The Japanese eel, A. japonica, is from inland catch. the growth phase or yellow eel phase taken principally by Japan with lesser It can be seen from Table 2 that Japan which lasts several years in fresh water, amounts by Korea and other Asian is far and away the leading eel produc­ estuaries, or coastal salt water. During counties; the Australian eel, A. au­ ing country in the world. European this phase, the eels are omnivorous. stralis, is taken commercially by Aus­ countries with significant production Fifth is the second metamorphosis from tralia and New Zealand. Another spe­ are Denmark, German Democratic Re­ yellow eel to silver eel. This is also an cies, A. dieffenbachii, is also caught in public, Italy, Netherlands, Poland, inactive growth phase and lasts about I the latter two countries but not reported Spain, France, and Sweden. In the past, year. During this time sexual maturity separately in FAO (Food and Agricul­ England had an active eel fishery. The takes place. Sixth is the adult marine ture Organization, United Nations) migration of elvers in the spring phase or phase of reproduction. This is statistics. Table 2 gives information on brought huge numbers ofthe young eels the time of the marine migration to the world catch ofeels in thousands of met­ up the rivers. These swarms were called spawning grounds, mating, reproduc­ ric tons (t) as reported to FAO for the "eel fares" and were actively pursued. tion, and presumably death. years 1965 to 1973. Yet, since 1963 no landings ofeels have The world commercial catch is com­ been reported from any part of the FISHERIES posed primarily of the European and United Kingdom except Northern Ire­ Of the seventeen or so species of eels Japanese eels. In 1970, for example, land. European eel fisheries, in general, of the genus Anguilla found in the European eels accounted for are feeling the impact of increased world, five of them occur in the temper­ 44,220,000 pounds (20,100 t) and population and urbanization. Problems ate zone. It is these temperate zone eels Japanese eels for 47,300,000 pounds with pollution, waterways blocked by

April 1978 7 Table 3.-Eel producllon and value In the Unlied Nova Scotia, Prince Edward Island, pounds (299 t) in J 962 to a high of States by stete, 1972. Melric 1.000 and New Brunswick. Eels have entered about 21h million pounds (1,134 t) in State 1.0001b Ions dollars the SI. Lawrence River and reached 1971 with the catch most years between Maine 70 31.7 25 Lakes Ontario and Erie. In fact, the best I and 2 million pounds (454 and 907 t). New Hampshire 5 23 1 Massachuselts 55 24.9 22 Canadian commercial fisheries are Eel production and value sales for the Rhode Island 22 10.0 8 along the SI. Lawrence estuary. The year 1972 are gi ven in Table 3. Connecticut 48 21.8 14 New York 149 67.1 65 northeast shore of New Brunswick and The data in Table 3 show that in 1972 New Jersey 262 118.8 58 the southwest coast of Nova Scotia also Virginia was the leading state in eel Delaware 45 20.4 11 Maryland 230 104.3 33 support small commercial eel fisheries. production with nearly half a million Virginia 492 223.2 145 NOf1h Carolina 77 34.5 12 Canadian catches have run around 2 pounds (227 t) followed by New South Carolina 42 19.1 4 million pounds (907 t) per year the last Jersey, Maryland, New York, North Georgia 10 4.5 2 Florida 61 27.2 9 10 years and reached a high of 2.7 mil­ Carolina, and Maine, in that order. Total 1.568 7098 409 lion pounds (1,224 t) in 1933. Most of However, this situation may be chang­ the Canadian catch comes from Quebec ing rapidly. In Maryland, one of the where the fishing is primarily for silver primary uses of eels has been as salted dams and other obstructions, all inhibit eels (Eales, 1968). bait for use in catching crabs on trot the traditional freshwater fisheries for In the United States, eel fisheries on a lines. Increased use of crab pots, which eels; and this, in turn, has promoted limited scale have existed since colo­ do not use salt eels for bait, has reduced increased interest in eel culture. In fact, nial times. In 1621, Edward Winslow landings in that state; and in 1973, only the harvest of eels has not increased of Plymouth wrote, "In September we 157,000 pounds (71.2 t) were landed. much in the last 30 years. can take a hogshead of eels in a night, North Carolina, on the other hand, has Japan has had a long-standing eel with small labor, and can dig them out been rapidly expanding her eel fishery fishery. This was the first country to of their beds all winter. " In fact, one of for export as a food product, and it is tum to eel culture to supplement their the rivers near Plymouth was called Eel estimated that in 1973 the catch may harvest of wild eels. In recent years, the River; and in 1833, the eel fishery in have jumped to over half a million proportion of wild eels to cultured eels this same river was described: "It is pounds (227 t) (Angel and Jones, has steadily declined. There is an active appropriately called Eel River from the 1974). Maine has been attempting to fishery for elvers which are used to abundance of eels which it yields to the establish an elver fishery, with mixed stock the ponds for cultured eels. The support of the industrious poor. results to date. Elvers will not increase domestic catch of elvers cannot keep up Perhaps it will not be extravagant to say poundage landed significantly since a with the demand and has prompted the that about 150 barrels are annually pound (0.45 kg) may contain from Japanese to actively seek American and taken there," (Goode, 1887). 1,000 to over 5,000 individuals but can European elvers, although these are not There were eels taken along the appreciably increase the value because considered as desirable as the Japanese coasts of Cape Cod and Maine and of the high price per pound. eels. Massachusetts in the 1600's and Several coastal states are taking an In Australia and New Zealand, near­ 1700's. In 1887, several eel fisheries acti ve interest in exploiting the in­ ly all eels caught belong to the species were reported from Maine, Mas­ creased demand for eels in Europe and A. australis. These eels were a tradi­ sachusetts, Rhode Island, Connecticut, Japan. It may be that the U.S. fisheries tional food for the native New Zealand New York, New Jersey, Delaware, for this species will increase in future Maoris, but it has only been in recent Maryland, and North Carolina. In years as our resource seems to be years, the late 1960's and early 1970's, 1879, small catches from Gloucester, greatly underutilized. However, based that eels were fished commercially to Newburyport, Salem, and Marblehead, on the longer experience of both Europe any extent. They are now becoming an all in Massachusetts, brought 5 cents/ and Japan, it seems unlikely that pro­ important export commodity. It is esti­ pound, while Boston with landings duction of wild eels will ever rise above mated that New Zealand has a potential over a quarter of a million pounds (454 a few million pounds per year. Even an sustainable harvest of 10-20 million t) for that year seemed to be the center increase in landings to say 5 million pounds (4,535 to 9,070 t) of eels per of the New England eel trade. New pounds (2,268 t) annually would more year (Skrzynski, 1974), although the Jersey in the Cape May area also had a than double present U.S. supply and at reported catch in 1972 was only around significant eel fishery in J879. Most of an average price of 30 to 40 cents/ 4.5 million pounds (2,041 t). In Aus­ these eels were speared in the winter or pound (0.45 kg) to the fishermen be tralia, silver eels are preferred. The taken in the sea in summer and con­ worth $1.5 to 2.0 million a year. While fishery is increasing but still limited sumed locally or sent to New York or little information is available as to the with about 0.5 million pounds (227 t) Philadelphia. The price paid to the stocks or the maximum sustainable reported in 1972 and none reported in fishermen was 4 to 5 cents/pound. yield that can be achieved in the United 1973. Over the last 40 years, the U. S. eel States with eels, 5,610,000 pounds In Canada, eels are found in most of catch has remained fairly constant, (2,544 t) a year would appear to be the coastal rivers in Newfoundland, ranging from a low of around 660,000 attainable. Due to the increasing pres-

8 Marine Fisheries Review Dip nening elvers (left), just one of several ways in which elvers are captured, At right is a catch of approximately 2 kg of elvers, Photos courtesy of the North Carolina State University Eel Culture Project, a part of the University of North Carolina Sea Grant Program,

The round or cylindrical eel pot (left) is commonly used by North Carolina eel fishermen, At right is the newer square eel pot which may replace the cylindrical one, Photos courtesy of the North Carolina State University Eel Culture Project, a part of the University of North Carolina Sea Grant Program, sure on our waterways from popula­ dreds of years. The method chosen de­ also be found in limited numbers mak­ tion, power sources, and obstructions, pends on the type of eel, the stage of ing a spring run from fresh water to salt it is likely that increased interest on the development one wishes to capture, water. These are primarily male eels part of the United States in eel produc­ and makes use of the biological habits returning to their estuaries or marine tion will result in more attention being of the eel during these different stages. environment and are therefore gener­ given to eel culture as was the case in Eels tend to congregate at three dif­ ally smaller than female yellow eels Japan and is beginning in Europe, ferent times. The first time is the spring remaining in fresh water. In the late run of elvers going upstream. These summer or fall, there is a second migra­ METHODS OF young eels are strongly oriented toward tion of silver eels from fresh water to CATCHING EELS going upstream, and this fact can be the sea. Since these eels cannot feed, There are a number of means of cap­ capitalized on in capturing them. The the method ofcatch is based on trapping turing eels in use around the world. yellow eels tend to congregate during them in their journey down the water­ Most of these methods are essentialy their winter inactive phase in deep holes ways to the sea. Yellow eels can be the same as have been in use for hun- with muddy bottoms. Yellow eels may taken at other times when they are not

April /978 9 JAPANESE ELVER NET (as from tidal action), the elvers will continue to head upstream and not turn around and escape through the down­ stream opening. The trap is placed in a constricted part of the waterway or has wings or leaders of fine mesh netting of wire set to direct the elvers into the trap. A trap of this type can be made using any fine mesh screen, although nylon is preferred to metal since it is not suscep­ E tible to rusting. A good description of '" an elver trap is given by Sheldon (1974). The Japanese use a mesh net and an upstream light source to catch elvers (Fig. 1). Lights can be used to attract glass eels, but once they become pigmented the elvers will avoid light. Elvers may also be taken from areas below obstructions such as waterfalls or dams with dip nets. In small shallow pockets of water, an aquarium-type dip net is better than the larger variety (be­ cause of the size of the water pocket). It must be stressed that while many mod­ ifications of these nets and traps will work ifpositioned in the right spot, they are useless unless one knows when the elver run will occur in a given area and which streams, rivers, etc., are most frequented. LEAD LINE Yellow Eels Figure I.-Japanese elver net, from Topp and Raulerson, 1973. Since yellow eels are actively feed­ ing except in cold weather, they can be attracted by bait. A large variety of closely congregated but are actively a series of floats on the top and weights baited traps have been used success­ feeding, by using bait. We will con­ on the bottom so that it will float upright fully 10 catch them. Goode (1887) de­ sider ways of catching elvers. in the water. The net is fastened at one scribed a trap used in colonial times: Elvers are caught for food to a very end to a boat or the shore and the other "When ascending the rivers and small limited extent. Young elvers or glass end moved by another boat (or by hand streams in the fall or leaving them in the eels are fleshy, white when cooked, and in very shallow water) to encircle a early spring, large quantities are taken reported to be quite tasty. Once they school of fish. Once the encirclement is by obstructing the flow of water and become pigmented elvers, they lose completed, a line running through a placing in the center of the stream a flesh, become tough, and are dark when series of rings along the bottom of the strong barrel pierced with auger holes cooked. In England, glass eels were net is pulled tight to close or "purse" into which the eels creep, but out of used to make an elver cheese. In Spain, the net. The net is gathered in, forcing which, curiously enough, they seem they were consumed in elver omelettes the elvers into a small pocket from unwilling to stir. The barrels have been and as pates (Bertin, 1956). They may whence they are lifted out with a small so filled at times as to suffocate a large also be canned in oil. Most elvers are dip net. part of the catch before morning." It is caught, however, for use in stocking Another method of catching elvers is interesting to note the reverse run of inland lakes or for use in more control­ used in streams or rivers and involves eels mentioned here-that is, descend­ led eel culture. trapping them as they make their way ing in the fall and ascending in the fine mesh purse seines have been upstream. So strong is the instinct to spring. Either this was a large run of used in France from boats near the travel upstream that a V-shaped trap male eels or Goode has made an error. shore to capture the young elvers as with the small end upstream leading to He later describes a box trap used in they approach the coast. The purse another enclosure will catch elvers. As New Bedford, Mass., in the 1800's as seine is a long net of unifonn width with long as the flow of water is not reversed being 4 feet long and 10 inches wide

10 Marine Fisheries Review with slatted sides and 4-inch square holes in each end with 2 smal I wooden slats that opened when the eel went in but snapped shut behind him. These traps were weighted with stones and used clams for bait. All baited traps or pots, of which there are a wide variety, operate on the same principle. The eels are attracted by the smell of the bait into the large end of a funnel-like opening. The nar­ row end of the funnel leads to a small opening into a container and quite often the process is repeated into a second compartment. Sometimes the bait will be exposed to the eels after they enter the trap and in other cases only the odor will reach them as the bait itself is pro­ tected by a bag or perforated container of some type. Eel pots come in all shapes and sizes. A pot or trap made of willow branches was used by the American Indians and the early colonists and is still in use to some extent in parts of the United Kingdom and Canada. This trap resem­ bled a large basket with the funnel-like opening fonning a double lining into the basket. The smaller end of the bas­ ket was tied off with twine while the trap was fishing and released to remove the captured eels. From willow branches, the construc­ tion of eel pots evolved more to those with wooden frames and netting. Traps were also made of wood slats and were either round or rectangular in shape (Fig. 2). Today, most eel pots closely Figure 2. -Eel pot (a). slat trap (b). and baskel trap (c) (after Dumonl and Sundslrom. 1961). resemble the eel pot in the middle of Figure 2, except that they are made of galvanized wire rather than twine net­ some hay or straw to make it more bait, depending on what is available ting. The cones or funnels may be of difficult for the eel to find his way back locally. Herring is often used, but wire, nylon cloth, nylon twine, or even out of the pipe. Modified lobster and menhaden, alewives, mackerel, squid, light gauge sheet metal. The bait is crab traps have been used. The en­ crabs, clams, mussels, and even fish placed in the last section so the eel must trances are changed to a funnel ar­ waste ("gurry") from a filleting opera­ pass through both funnels before reach­ rangement; and, of course, the space tion could also be used as long as they ing it, thus making it doubly difficult to between the wood slats or the size of the are fresh. Frozen bait can be used either find the two small openings that would mesh in the wire must be small enough slacked out (thawed) or frozen as it will lead to escape. Detailed information on to prevent the eels from escaping. The quickly thaw in the water. The pots the construction of both a round and a traps made from wooden slats are also should be tended daily, and the bait square pot made of galvanized wire or shown in Figure 2. changed. Pots and traps are usually set vinyl coated wire is given by Berg et al. The bait used in these traps must be in rivers or streams with the opening (1975). fresh and can be placed loose or fas­ facing downstream I or in estuarine Other baited traps have been made tened in the inner chamber (usually cal­ areas facing the tide and anchored with from such simple things as a section of led a "parlor") or can be cut or chop­ pipe to which a burlap sack is tied. The ped fine and placed in a bag. Most any 1 Upstream during the downstream migrations in sack will contain the bait and perhaps form of marine life can be used as the spring.

April 1978 II several feet in diameter and tapers down to a small terminal hoop (Fig. 3). A fyke net is a hoop net with one or two leaders or wings extending out from the opening to lead the fish into it. These traps work best where they can be so located in a restricted body of water that the fish cannot get around them. Hooks can also be used to catch eels. These are generally put out in sets and the method of fishing called trawling, longlining, or trotline. The gear con­ sists of a long line to which shorter and a lighter lines with hooks are attached at intervals. At each end of the line will be a weight or an anchor attached to a float or buoy. In rivers and streams, one, or both, ends of the line may be tied to a tree or stake on the bank. Eels can be taken from spring to fall by hooks. However, hooks are more apt to injure or kill the eels than are traps. This is important if the intended market for eels demands live delivery. Another method of catching eels in­ volves a line but no hook. A single line is fished by hand or with a rod and reel. Worms are threaded end to end by means of a dull needle. Several worms are threaded on the line, then the worms and line are formed into loops by wind­ ing around one's fingers. The loops are tied together then fastened to the end of the fishing line. The bait is fished on or near the bottom. When the eel bites, steady but gentle pressure is kept on the line until the eel is lifted out of the water. The eel has many small teeth that become entangled in the baited loops; and if the line is pulled in steadily, they will not falloff. In England, a length of wool may be used to thread the worms and the method of fishing called" bob­ bing." This is primarily a sportfishing Figure 3.-Hoop net (a) and fyke net (b) (after Dumont and Sundstrom. 196). method and is used on warm summer nights. In the winter when the eels bury ballast or rocks, bricks, or cement. The from his course of travel into the trap themselves in mud, they can be taken number of pots set should be limited to rather than entering it actively to seek by spears. The inactive eels will be those that can be tended daily. the bait. The most common examples found concentrated around entrances to In addition to baited traps, a variety of the unbaited trap are the hoop net or lakes or rivers or streams or in deep of unbaited traps and nets are used. the fyke net. A hoop net is made by holes near tidal entrances to fresh water Gear of this type depends on leading the covering hoops or frames with netting or estuaries. The taking of eels by prey into an easily accessible opening or wire mesh. They are usually of de­ spears or forks is called spearing, gig­ from which the return is restricted­ creasing size from front to back and ging, or in England-"pritching." just the same principle as in the baited have one or more funnel-shaped open­ This method was used in colonial times traps except now the eel is diverted ings inside. The mouth of the net can be in the United States and is still the same

/2 Marine Fisheries Review today. Since the eels are often killed by this method, it is used mainly for sports purposes where the eels will be con­ sumed soon after catching. The secret of success to this method is to find where there is a concentration of eels buried in the mud. Once a suitable spot is located, it can usually be used year after year, and the easiest way of finding such a spot is to contact some­ one who has speared eels in the past. In cold weather, a hole can be chopped in the ice. A three (or more) pronged spear is used with a long handle. The prongs of the spear are usually barbed. Some spears will have an unbarbed center prong with the barbs on the two outside prongs facing in. A variation of this type spear is one that has an unbarbed center prong and two outside spiny loaded clamps that prevent the eel from Sorting wild-harvested eels to remove those below market size. Photo courtesy of the North wriggling off the center prong. Other Carolina State University Eel Culture Project, a part of the University of North Carolina Sea methods use a spear with serrated Grant Program. blades. When the spear is pushed down sluiceway or capture box that must be STORAGE AND TRANSPORT on the eel, it is forced up between two so designed as to permit ready passage of the serrated blades. The eel is thus of water while retaining the eels. Eales Elvers imprisoned between the teeth but not (1968) reports that "at St. Jean (lber­ pierced. ville), Quebec, a highly profitable weir The demand for elvers is for use in has been operated at the same site for stocking natural bodies of water or for Silver Eels more than 100 years by fi ve generations culture purposes. This means that the Silver eels are the most desirable for of a family. The catches have averaged elvers must be held and transported smoking as they have a high fat content. about 60,000 pounds (27.2 t) per year alive if they are to have any market They have fattened in preparation for and have recently2 climbed to 100,000 value. At the present time, the demand the long marine migration during which pounds (45.4 t) per year." for elvers is primarily in Japan and to a they cannot feed. During the fall run, The construction of weirs varies de­ lesser extent, Europe, so that transpor­ silver eels can be caught in large num­ pending on the water conditions and the tation for considerable distances is in­ bers by various forms of unbaited traps materials at hand and local regulations. volved. and nets. Some of the traps designed for They all are designed to lead the eels After being caught, the elvers can be fishing silver eels are very elaborate and during their downstream migration into held temporarily in small holding nets require considerable time and expense an area from which they cannot escape. until a sufficient quantity is accumu­ to construct. Obviously, these more Less elaborate means, such as fyke nets lated for transporting them to shore. elaborate traps are only used where the and hoop nets described for catching The most important consideration in commercial harvest is sufficient to jus­ yellow eels, can be used in smaller holding elvers is to ensure a sufficient tify their expense. streams. supply of oxygen-about II ppm. A By and large, eel fishing has not One thing must be kept in mind in holding pen or box about 2 feet x 4 feet reached the stage of commercial de­ catching eels. Since most of the fishery x 2 feet (61 cm x 120 cm x 61 cm) velopment where these elaborate meth­ takes place in fresh water, State and with small mesh screens on the ends can ods of trapping are used. In Canada, local regulations should be carefully be used near the point of catch. This one type of trap or weir is built in the considered before any method is at­ box should be placed in a flow of water summer when the rivers are lowest by tempted. The more elaborate weirs and so the water will pass through the box. making a large V in the river with the traps actually block off a whole section With a good water flow, about 20 small end downstream. The wings or of the river, and generally the place­ pounds (9.1 kg) of elvers can be held in sides of the V may be made of stones, ment of such devices must be cleared a box this size. The screen must be branches, brush, poles, or planks. and approved by the appropriate au­ cleaned daily to ensure a good flow of These wings must be strong enough to thorities. water and any dead elvers removed. resist the flow of water and the impact A collecting station ashore can use a of floating debris. The wings lead to a 21968. natural flow of water to maintain the

April 1978 13 oxygen level. In any event, only should be considered in designing a ice. The bags are packed in wax­ natural, unchlorinated water should be holding container for live eels: I) With impregnated boxes. For air shipment, it used. Since the elvers instinctively a constant supply of aerated water, 100 is very important that the containers are 3 swim upstream, any holding pen using cubic feet (3 m ) of water will hold water-tight to prevent leakage in a natural flow of water should not be 1,500 pounds (682 kg) of eels. If the transit. overstocked, as the elvers will bunch up rate of water supply is limited, the Eels can be held for several months at the upstream end and may suffocate. eel-water ratio should be substantially without feeding. However, in general, Elvers can be transported for short limited. 2) Remove dead eels as soon as it is probably not a good idea to hold distances in aerated tanks. For overseas possible from the container. 3) The in­ them for more than a few weeks. If shipment by air, the Japanese prefer side of the tank should be smooth to longer storage is necessary, the eels shipping them on ice. About 10 pounds prevent abrasion of eels. 4) Handle live should have access to salt water occa­ (4.5 kg) of el vers are placed in a spe­ eels as little as possible to prevent loss sionally; otherwise, they tend to get cially designed Styrofoam3 container. of slime. The slime layer aids the eels in hard and lose their wriggling charac­ The elvers are mixed with crushed ice maintaining their salt balance, and loss teri stics. They should not remain in salt and the containers packed in 50-pound of this protection may cause death. 5) water more than 24-48 hours at a time (22.7-kg) master cartons. A similar unit Be sure the openings around the con­ or they may lose their slime and die is made of expanded polystyrene, mea­ tainer are small as eels can escape from (Eales, 1968). sures 321/2 inches x 31/2 feet x 4 feet very narrow openings. Variations of (0.83 m x 0.89 m x 1.2 m) and weighs these tanks have been used. In England, PROCESSING only 8 ounces (227 g). A slitted sliding one company used a barge with a perfo­ Frozen Live Eels top provides ventilation. Each box rated steel bottom. The barge is kept holds 4 pounds (1.8 kg) of elvers. A afloat by two buoyancy tanks and can As mentioned in the previous sec­ separate section inside the box holds a hold a million pounds (454 t) of eels. tion, the most lucrative market forU.S. 2 1/2-pound (I. I-kg) cake of ice which The Dutch have used ships to pick up eels is in Europe. This market pays provides cool fresh water as it melts. eels from Canada, the United States, highest price for live eels. Shipment of Europe, and Africa. One of the ships, live eels poses several problems con­ Yellow and Silver Eels Mercurius, is a 300-ton (272-t) con­ nected with packing methods, transport Both the small domestic market for verted naval landing craft which uses scheduling, and possible delays en eels and the European market pay a circulating seawater. The other ship has route. Eels that die in transit may not be premium for live eels. It is usually de­ a perforated hold which permits free accepted at all; or ifthey are, the price is sirable to hold eels for a week or two in exchange of water with the surrounding greatly reduced. An alternate way of running water to purge them and to sea. Eels transported this way are sub­ marketing is to ship the eels in frozen eliminate any muddy flavor. Any en­ ject to whatever sources ofpollution are form. This reduces the price received closed pen or box that permits a flow of present in the surrounding water, and but also reduces the risk involved in water through it will do for a holding one shipment of eels was killed in the shipping live eels. station as long as it is tended to ensure a St. Lawrence waterway by a temporary Eels should be held in fresh water for flow of water and to eliminate dead pollution condition. 1-2 weeks after capture to pennit them eels. (Handling of dead eels will be In Great Britain, tray boxes are used to clean, or purge, themselves of feed. discussed in the section on processing.) for transporting live eels from Ireland to This also helps to eliminate any off Eels are normally collected with a London. The unit consists of an outer flavor that might be present with eels truck with one or more tanks. One ar­ case 36 inches x 18 inches x 14 inches taken in muddy water. The eels are then rangement uses a paired series of small (0.91 m x 0.46 m x 0.36 m) made of size graded, with the most common tanks on a flatbed truck. Each tank is 1/2-inch (12.5-mm) pine. Each case has sizes being 1;4-1/2 pound (0.11-0.23 filled with fresh potable water. An aera­ five trays about 2 inches (50.8 mm) kg), 1/2_1 pound (0.23-0.45 kg), and tion unit is mounted on each tank to deep. Each tray is divided into two over I pound (>0.45 kg). The graded provide oxygen. Other arrangements compartments. The four bottom trays eels are packed live in 25-pound utilize small tank trucks or large tanks are packed with about 20 pounds (9 kg) (11.4-kg) lots in plastic bags which are, mounted singly or in pairs. As long as of eels each. The top tray is filled with in tum, inside a wax-impregnated cor­ the eels are not overcrowded and aera­ crushed ice. All the trays have 20 half­ rugated cardboard box. Freezing tion is sufficient, little difficulty is en­ inch (12.5-mm) holes in the bottom so should be done rapidly at -40°F countered in transporting eels several the melt water trickles down over the (-40°C). During the freezing process, hours, even in hot weather. eels in all the lower trays. the eels will intertwine. The European Eales (1968) lists several points that Air shipping live eels from the Unit­ buyers look for this condition, and if it ed States to Europe is done by packing is not present consider this evidence the them in 30-pound () 3.6-kg) lots in eel was dead when it was frozen and 3Menlion of lrade names or commercial tinns does no! imply endorsement by the National polyethylene bags. The bags are vented may reject the entire lot. Usually two of Marine Fisheries Service, NOAA. near the top and contain a small piece of the cardboard cartons are packed in an

14 Marine Fisheries Review . I

insulated master carton for air shipment Next, lay the skin back from the cut and 10 ripe (black) olives, chopped or in uninsulated master cartons for strip it off intact using a pair of pliers. I tablespoon seedless raisins shipment by refrigerated ship. The cost Gutting the skinned or unskinned 'h cup water of the latter method is considerably eels is facilitated by sprinkling salt or Cut the eel into 2- to 3-inch (51- to less, and if a sufficient volume is in­ sawdust on it or dipping one's hands in 76-mm) pieces. Brown garlic in oil. volved would be the preferred shipping salt or using a rough cloth to hold and Remove the garlic from the pan and add method on the basis of economic con­ getting a good grip on the fish. With a tomatoes, salt, pepper, and eel. Cook siderations. sharp knife, make a shallow cut from 10 minutes then add olives, raisins, and the gills to a point about 2 inches past Killing and Cleaning water. Cover pan and cook about 20 the vent (to expose the kidney). In re­ minutes or until the eel is tender (cook­ Most of the eels consumed through­ moving the viscera, a knife with a ing time will vary depending on size of out the world are smoked. Jellied eels rounded, blunt end and a serrated edge eel). Place slices of toast in a dish and are preferred in parts of England. Lim­ is helpful. The rounded part of the knife pour the mixture over them. Serve hot. ited amounts are used as fresh or frozen is used to separate the lower part of the eels. Most of the U.S. eels frozen alive gut from the body cavity near the vent. Smoked Eels and sent to Europe will be used for The serrated edge is used to remove the Smoking has been the traditional smoking. blood vessel along the backbone and way of preparing eels. They are one of Live eels can be killed by placing the kidney. The knife is then slid for­ the most important smoked fish prod­ them in a container and liberally sprink­ ward to complete removal ofthe viscera ucts in Germany and the Netherlands. ling them with salt. They should not be (Lynch, 1964). Scrub out the gut cavity Eels may be smoked from either the buried in the salt; just a good sprinkling to remove all traces of blood and rinse fresh or frozen state, although fresh eels will do. They should be left for about 2 with cold water. are reported to give a better finished hours. This process also aids in remov­ If the eels will not be further proces­ product. Frozen eels thawed and de­ ing the slime. Electro-killing has been sed, it is advisable to remove the head slimed are dressed as described earlier. tried by placing the eels in water and and the last 2-3 inches (50 to 75 mm) Skin and heads remain on. Large eels then passing an electric current through from the tail. The eels can then be may be cut into two sections before the container. This will kill the eels but cooked fresh or frozen. If frozen, they smoking, but most eels are smoked presents possible safety hazards for the should be packaged in a good gas/vapor whole. workers and still leaves the problem of proof material. Eels, especially silver An Australian method of smoking, getting rid of the slime. eels, have a high fat content and unless based on the German method, is as fol­ Once the eels are dead, the slime can adequately protected during frozen lows: Eels weighing 9-14 ounces be seen floating on the surface of the storage may develop rancidity (Berg et (257-400 g) are cleaned and dressed. brine. The slimy water is poured offand aI., 1975). They are placed in a brine. The brine the eels thoroughly washed in fresh wa­ concentration may be as low as 10 per­ ter. This may take up to a half hour in PREPARATION OF EELS cent for 24 hours, but unless cooled cold water, after which they are scraped Fresh or Frozen Eels with ice, the eels may spoil before the or scrubbed to remove any remaining brining process is complete. In hot traces of slime. It is important to re­ Eels can be used fresh or frozen for weather, more often a strong brine ( 100 move all slime since failure to do so frying, baking, smoking, or gelling. ppt salinometer) is used. The time will may affect the flavor of the finished Fresh eels are preferred for gelling, and vary from 2 to 24 hours, depending on product. If the eels are to be smoked eels for smoking should have the head the degree of salt desired. After re­ with skin on, the scrubbing will also and skin left on. moval from the brine, they are washed improve the appearance. Fried eels are prepared by starting with fresh water and air dried. The eels Once the eels are washed, they are with a cleaned and skinned eel cut into are then hung by the head on hooks and gutted. If the eels are to be used in the 3-inch sections. Wipe the sections dry dipped in boiling water until the sides skinned form, it is easier to skin them and dip in an egg batter then in bread open out. The fish are then placed in the before gutting. To skin, fasten the eel crumbs. Deep fat fry at 375°F (190°C) smokehouse and given a two-stage hot with a nail or clamping device on the for 3-5 minutes. A more elaborate Ital­ smoke. head in a vertical position. Make a cir­ ian recipe is Eel Neapolitan: In the first stage, hardwood chips are cular cut about three inches behind the burned to give clean hot flames and head. The cut should not penetrate the l'h pounds (0.7 kg) of dressed eels quickly bring the temperature up to flesh as there is a danger of cutting into 3 tablespoons olive oil 248-257°F (120-129°C). This tempera­ the gall bladder, and this can cause off I clove sliced garlic ture is maintained for 5-10 minutes so flavor. Also, care should be taken to medium can of peeled tomatoes the eels are partially cooked and oil and avoid contact through an open cut with 1/2 teaspoon salt water content is lowered. In the second the blood from the eel because of its 1/2 teaspoon pepper stage, the flames are smothered with toxic properties mentioned earlier. 4 thin slices of Italian bread, toasted damp chips and the draft reduced to

April /978 /5 Jellied Eels fisheries to meet the increasing de­ Oland, and correspondingly higher The method given for preparation of prices, of the export market. jellied eels is used commercially in Great Britain where this product is Elver Market popular. Eels are cleaned, dressed, The market for elvers has been stimu­ skinned, and cut into 2-inch (51-mOl) lated by the failure of commercial har­ pieces. The pieces are parboiled for 10 vest in Europe and Japan to satisfy local minutes in water with 2 percent vin­ demands. This has led to an increased egaI', 3 percent salt, and 2 ounces (57 g) interest in eel culture in Europe and an of mixed pickling spices per gallon. expanded interest in the long­ After cooking, the pieces are drained, established culture operations in Japan. cooled, and packed in glass jars or flat Spain is the only country where there is cans and covered with a 10 percent Smoked eels. Photo counesy of the Nonh a direct market for elvers for food pur­ gelatine solution containing I percent Carolina Stale University Eel Cllhure Project, poses. All other markets seek elvers for a pan of the Univer,ity of Nonh Carolina Sea acetic acid and a few drops of lemon use in stocking natural waterways or for Granl Program. essence. The containers are vacuum eel culture. sealed and heat processed. The process Germany, Netherlands, England, may be varied by using a spiced produce a heavy smoke. fhe tempera­ and France are all exploring eel culture vinegar-salt solution to cover the ture is lowered to 104-122°F (40­ operations. The primary market for el­ cooked meats in the container (Home 50°C). Smoking time is from 90 min­ vers at this time, however, is Japan. and Birnie, 1969). utes to 4 hours, depending on the size of Reports on the prices paid for elvers the eels; although for some markets, Proximate Composition have varied widely. A range of value this time can be extended to as long as from $50 to $900 per pound (the higher 12 hours. The eels are then cooled in the The fat content of eels is highly vari­ price was for small elvers running smokehouse and given a light brushing able. Silver eels will usually have a 7,000 and over count per pound) was of edible oil on the outside to improve higher fat content than yellow eels. The reported in Maine (Ricker and Squires, appearance. Yield is about 60 percent content of the American yellow eels, 1974). The U.S. Regional Fisheries At­ of live weight (5-10 percent loss in gut­ edible portion only, is about 72 percent tache in Tokyo reported that one ting and about 30 percent loss during water, 19 percent protei n, 9 percent fat, Japanese firm quoted a retail price for the hot smoke process) (Anonymous, and I percent mineral or ash. For Japanese elvers of $417 per pound in 1955). smoked eels, edible portion, it is 50 1973 (Folsom, 1973). However, Amer­ Another method used in England in a percent water, 19 percent protein, 28 ican elvers are not considered as desir­ mechanical smokehouse calls for using percent fat, and 2 percent ash (Chatfield able by the Japanese as their local eels 3,4 to l'h pounds (0.34 to 0.68 kg). and Adams, 1940). Typical composi­ species, and these reported high prices The eels are brined (lightly for domestic tion of raw European silver eels is should not be expected by anyone seek­ use and heavier for export) and smoked 58-60 percent water, 14 percent pro­ ing to go into the export elver market in for I hour at 95°F (35°C), 30 minutes at tein, and 26-28 percent fat. Because of this country. 120°F (49°C), and finally at 170°F the high fat content of silver eels, the Maine fishermen have been interest­ (n°C) for I hour. The smoking loss is calorie value can be as high as 1,350 ed in the Japanese elver market. Prices about 15-20 percent by this method. calories/pound (0.45 kg) (Home and received are much lower than the The smoked eels must be refrigerated Birnie, 1969). figures cited above would indicate­ and have a chilled storage life of 3-4 about $20-$99/pound (0.45 kg) for MARKETS days (Horne and Birnie, 1969). It Asian eels and $14/pound (0.45 kg) for should be noted that any smoking of Since the days of the early American European elvers. In 1971 and 1972, the eels for sale in the United States must be colonists, there has been a steady, but Japanese paid an average of approxi­ done according to the guidelines estab­ small, commercial fishery for eels in mately $12 and $4/pound (0.45 kg) for lished for smoked fish by the U.S. Food the United States. For the 40 years pre­ U.S. elvers. and Drug Administration. ceding 1974, the domestic catch of eels There are several reasons why Smoked eels may be sold chilled, had been fairly constant between 1.3 American and European elvers bring a frozen, or canned as a fully preserved and 2.5 million pounds (590 and 1,134 lower price on the Japanese market. product. Chilled smoked eels have a t) annually. Nearly all of these eels The smaller the elver, the higher the relatively short storage life and must be went to satisfy domestic ethnic markets price. That means that the young glass properly refrigerated at all times. Fro­ primarily in the large population cen­ eels are highest in value. There is the zen smoked eels require the same type ters of the nOl theast. It is only in the last problem of shipping them so they arrive of package protection as do unsmoked few years that interest has developed in alive and remain in good condition after eels. the possibility of expanding our eel they are stocked. The price paid reflects

/6 Marine Fisheries Review •

this risk. The American elvers are re­ average price to fishermen in 1972 of23 them in specially constructed ponds and ceived later in the growing season than cents/pound (0.45 kg) and in 1973, 45 this is eel culture. the Japanese elvers, and this has an cents/pound (0.45 kg). Dealers in Culture, as used here, means that adverse effect on their growth and even­ North Carolina and Virginia have ship­ something is done to assist or control tual time of marketing. The American ped frozen eels to Europe, primarily the growth of eels that is different from (and European) eels are adapted to Germany, for further processing as the natural or wild state. Transporting cooler water than their Asian counter­ smoked eels. The price for frozen eels elvers to a natural body of water where parts and grow slower, and the Asian is much less than for live eels. The they live and grow on whatever food is eels are collected at a younger age so relative prices are similar to those available and then are harvested as any there are more per pound. quoted for the Japanese market. wild fish would be is the simplest form Despite these drawbacks, it would The export market would seem to of culture under this definition. This is appear that the Japanese demand for offer the greatest potential for expan­ what the Macedonians did and it is the el vers will continue to grow. This sion. The domestic ethnic market in the method used for centuries in the Valli means that there is a potential for the northeast is quite stable, and the possi­ of Comacchio in Italy. This is a lagoon development of a U.S. export market bility of expanding domestic consump­ of 80,000 acres (32,389 hectares) lo­ for elvers. Astronomical prices should tion in the near future is limited without cated between two branches of the Po not be expected, however, and any a considerable marketing and promo­ Delta and divided by dikes. It provides entry into this field should be done with tion effort. about 2 million pounds of eels per year caution until the holding and shipping (Eales, 1968). EEL CULTURE techniques are well developed and the A more controlled culture method is market established (Folsom, 1973). As the demand for eels throughout one that uses natural or artificially While the price received per pound is the world continues to grow and as constructed bodies of water where con­ relatively high, there are several risks supplies of readily available wild eels trolled feeding, management, and har­ involved in the part of the supplier; the becomes more restricted, the interest in vesting are practiced. greatest being the death of the elver in culture of eels increases. Eel culture is The Japanese have practiced control­ transit. Prices received for elvers must not a new technique and involves catch­ led culture of eels since 1879. Eel cul­ cover the costs of catching, buying the ing elvers and placing them in a suitable ture did not become a significant source elvers locally, construction and opera­ environment for growth to market size. of supply in Japan until the early tion of pickup facilities and holding sta­ Elvers were thus reported to have been 1960's. In 1962 about 7,600 tons tions, packing materials, and air freight transported and raised in ponds in (6,893 t) of cultured eels were har­ and marketing fees. The profit margin Macedonia over 2,000 years ago. The vested in Japan. By 1969, this in­ should be carefully examined before a next step beyond transporting of elvers creased to 23,000 tons (20,861 t). A large scale elver operation is launched. to natural bodies of water is to place year later the production of cultured

Markets for Adult Eels An indoor tank holding 5 kg of elvers for parasite and disease treatment and initial feeding. Food is placed in the wire mesh tray al center. Photograph courtesy of the North Carolina Slate University The market for larger eels is primar­ Eel Culture Project, a part of the University of North Carolina Sea Grant Program. ily in Europe, although there may be some potential in Japan as well. In 1972, Japanese importers were offering $1.23 to $1.36/pound (0.45 kg) of live eels weighing 150-200 g (about 6-8 ounces). For frozen eels of the same size, the price was 22-27 cents/pound (0.45 kg). In contrast, $2.50-$3.00/ pound (0.45 kg) was the price for Asian eels (Folsom, 1973). In 1972 a firm delivered 70 tons (64 t) of live eels by air freight to England. Mortality rates were generally under 2 percent. Live eels are flown to Ger­ many from several east coast States, particularly from Maine, Massachu­ setts, Pennsylvania, Virginia, and North Carolina. Prices paid to New En­ gland fishermen have generally been in the 25-35 cents/pound (0.45 kg) range. One dealer in North Carolina paid an

April /978 /7 A small outdoor pond in which eels are grown to market size (\4-'12 pound). Photograph counesy of the Nonh Carolina State Universily Eel Culture Project, a pan of the University of Nonh Carolina Sea Grant Program. eels was sharply reduced to 16,700 tons Italy, Great Britain, and France (Angel "Elvers are caught in the winter (15,147 t) due to a disease that affects and Jones, 1974). New Zealand has at as they migrate upstream from the the gills and kidneys of the eels. least two eel culture operations also. spawning grounds in the open sea, Thousands of eels died and losses were Taiwan began experimenting with eel and are cultured in relatively small in the millions of dollars. This disease culture in 1967. In 6 years, the industry ponds of 150 to 350 square meters by was thought to come from the first el­ rapidly expanded, and in 1973, an es­ 70 cm deep. This phase of culture vers imported from Europe in 1969 timated 10,000 tons (9,070 t) of eels lasts for about one year, during (Folsom, 1973). were raised (Forrest, 1974). which time the young eels grow to about 20 gm in weight. The original Although Japan has the best estab­ Most of the European culture opera­ stocking density is about 500 to 600 lished eel culture operation, interest is tions rely on natural sources of feed. gm per square meter. increasing in Europe and the United More intensive methods are under in­ "The growth of individual eels is States. In the United States, an experi­ vestigation or are in the experimental tremendously variable and constant mental eel culture operation has been stages, however. The Japanese pond culling is required during all stages started by the University of North culture of eels is described by J. F. of culture to ensure approximately Carolina. In Europe, eel culture ac­ Sanders in the publication Australian uniform sizes in each pond. tivities are being carried out in Spain, Fisheries (Folsom, 1973) as follows: "When elvers begin feeding they

/8 Marine Fisheries Review •

are given small oligochaete worms lated for eels. They are fed twice a culture. In general phytoplankton for about two to three days, then for day and the quantity of feed given is are beneficial to eel culture and zoo­ seven to ten days a paste of mixed about 30 percent of body weight. plankton are not. Well managed eel oligochaete worms and fish flesh. "Young eels prefer to eat in a ponds are a blue-green color, with a Then they are weaned on to fish flesh darkened place and feeding is done plankton composition of 0.3 to 2.9 or synthetic diets especially formu- in a shelter at one side of the pond. percent zooplankton and 97. I to The food is placed in a wire basket 99.7 percent phytoplankton. " suspended just above the water to prevent undue contamination of the Disease control is an important factor water. When young eels reach a in a successful culture operation. There weight of 20 gm they are ready for are some 10 different types of disease the next phase which takes them to that affect Japanese eels, and anyone of adulthood. them is capable of wiping out an eel "The aim of adult culture is to produce 150 gm eels for market and farm overnight (Folsom, 1973). Euro­ this is achieved in about two years pean and American eels also are suscep­ from the elver stage, which is double tible to disease although the types and the growth rate of wild eels. The size extent of the problem are not as yet as of the adult ponds is about 3,000 to well defined. To date, eels have not 10,000 square meters by 50 cm been spawned successfully in captivity deep. The stocking rate is about thus the importance of obtaining elvers 500-700 gm of seed eels per square to start the culture process. meter of pond. Growth is most rapid Despite the problems facing the cul­ during April to October and during turist, the potential for gain is great. If the period the eels must be fed as much as possible. The quantity of one started with a pound of elvers con­ food supplied is about 10 percent of taining 2,000 individuals and had a sur­ body weight and is fresh or frozen vival rate of80 percent by the time they fish flesh or synthetic diets. If fish reached a half pound, there would be an flesh is used the feed coefficient is 6 800-fold increase in weight. If the el­ to 7 while for synthetic diets it is less vers cost $30 and the finished product than two. (Feed coefficient is pounds brought $1.25 per pound, this would be feed required per pound of weight $1,000 or an increase in value of 33­ gain.) fold. Balanced against this potential in­ "During culture care must be crease in value is the risk of loss Placing food in a feeding tray (above) in the taken to maintain a satisfactory outdoor pond. Below, young eels consume water quality. As all phases of cul­ through disease or a depressed market the prepared diet. Photographs courtesy of the ture are in still water and the density that could lower the prices. Also, there North Carolina Slate University Eel Culture of stocking is high, the maintenance is the cost of feed, labor, facilities, Project. a part of the University of North transportation, and marketing to be Carolina Sea Grant Program. of water quality is relatively difficult. pH levels in the water considered. Any would-be culturist should be about 8.0 to 9.2 during the would be well advised to start on a daytime, and about 6.8 to 7.2 at small basis and develop the necessary night. information relative to the conditions "Ponds located on acid soils usu­ where the operation is to take place, be­ ally have a pH around 5.5 to 6.5 fore investing large sums of money in a which is too low for satisfactory eel culture. A high dissolved oxygen large-scale culture operation. level is absolutely necessary and the SUMMARY minimum desirable value for eels is 2.0 to 2.5 cc per litre. Water wheels We have reviewed some of the char­ which oxygenate and mix water acteristics of the genus Anguilla, the layers are a common feature of eel common eel. This fascinating creature ponds. Satisfactory levels of cal­ is a true fish with a unique life cycle that cium nitrate and phosphate should is still not fUlly understood. The Euro­ be maintained and this can often be pean species spawns in the Sargasso done by the addition of fertilizers. Sea, and the American species is "Ponds are usually drained and the bottom mud turned and sprinkled thought to spawn somewhere to the with lime at the end of each year. west of its European relative. After "The species composition and spawning, the young leptocephali abundance of micro-organisms is of travel toward their respective conti­ considerable importance during eel nents. For the European eel, this trip

April 1978 19 lasts 3 years, while the American eel Topp, R., and R. Raulerson. 1973. Elver investi­ Anonymous. 1955. Smoked eels. Food Preserv. gations in the southeast. Mar. Fish. Rev. Q. 15(2):36-37. completes the journey in about I year. 35(5-6):45-47. Berg, D. R.. W. R. Jones, and G. L. Crow. 1975. When they reach the coast, the leaf-like The case of the slippery eel. North Carolina leptocephali undergo metamorphosis to Adult Eels State Univ., Raleigh, Publ. UNC-SG·75-20, glass eels and then to pigmented el vers. Berg, D. R., W. R. Jones, and G. L. Crow. 1975. 20 p. Bertin, L. 1956. Eels. A biological study. Females head upstream into fresh water The case of the slippery eel. North Carolina Slate Univ., Raleigh, Publ. UNC-SG-75-20, Cleaver-Hume Press. Lond., 192 p. while males stay near the coast. They 20 p. Bigelow, H. B., and W. C. Schroeder. 1953. spend several years here as yellow eels. Eales, J. G. 1968. The eel fisheries of eastern Fishes of the Gulf of Maine. U.S. Fish Wildl. Finally, they change to silver eels and Canada. Fish. Res. Board Can., Bull. 166, Serv., Fish. Bull. 53:1-577. 79 p. Chatfield, c., and G. Adams. 1940. Proximate begin the reverse migration to their composition of American food materials. breeding area where they spawn and Storage and Transport USDA (U.S. Dairy Assoc.) Circ. No. 549, die. 92 p. Eales, J. G., 1968. The eel fisheries of eastern D'Ancona, U. 1960. The life cycle ofthe Atlantic Eels have an ancient and well­ Canada. Fish. Res. Board Can., Bull. 166, eel. Symp. Zool. Soc. Lond. 1:61-75. established following of avid consum­ 79 p. Dumont, W. H., and G. T. Sundstrom. 1961. ers in Europe and parts of Asia, partic­ Home, J., and K. Birnie. 1969. Catching, han­ Commercial fishing gear of the United States. dling and processing eels. Torry Res. SIn .. U.S. Fish Wildl. Serv., Circ. 109,61 p. ularly in Japan, but are relatively Aberdeen, Torry Advis. Note 37, 12 p. Eales, J. G. 1968. The eel fisheries of eastern unutilized in the United States. World Processing and Preparation Canada. Fish. Res. Board Can., Bull. 166, catch, fishing methods, processing, 79 p. preparation techniques, and informa­ Anonymous. 1955. Smoked eels. Food Preserv. Food and Agriculture Organization of the United Q. 15(2):36-37. Nations. 1974. Catches and landings. 1973. tion on eel culture throughout the world Jarvis, N. D. 1943. Principles and methods in the FAO (Food Agric. Organ. U.N.) Yearb. Fish. were also covered. canning of fishery products. U.S. Dep. Inter., Stal. 36. 590 p. Fish Wildl. Serv., Res. Rep. No.7, 366 p. Folsom, W. B. 1973. Japan's eel fishery. Mar. SUGGESTED REFERENCES ____ . 1950. Curing of fishery products. Fish. Rev. 35(5-6):41-45. U.S. Dep. Inter., Fish Wildl. Serv., Res. Rep. Forrest, D. M. 1974. The international trade in Biology - Life Cycle No. 18,271 p. eels and elvers. Fish. News Int. 13(6):29-33. Lisae, H. 1970. Some techniques ofsmoking fish Goode, G. 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MFR Paper 1303. From Marine Fisheries Review, Vol. 40. No.4, April 1978. Copies of this paper, in limited numbers, are available from 0822, User Ser­ vices Branch, Environmental Science Information Center, NOAA, Rockville, MO 20852. Copies of Marine Fisheries Review are available from the Superinten­ dent of Documents, U. S. Government Printing Office, Washington, DC 20402 for $1. 10 each.

20 Marine Fisheries Review