Kamis, 05 Mei 2011

SIDHAT AMERIKA - American Eel - Anguilla rostrata - 美洲鳗

SIDHAT AMERIKA - American Eel - Anguilla rostrata - 美洲鳗

American Eel / Anguille d'Amérique
Anguilla rostrata
(Lesueur, 1817)

Other common names include Common Eel, Atlantic Eel, Boston Eel, Snakefish, Silver Eel, Yellow-bellied Eel, Bronze Eel, Black Eel or Green Eel and Anguille argentée.

Key Characters
The American Eel is distinguished by its shape, confluent dorsal, caudal and anal fins, the toothed jaws, and the single gill opening. Lampreys have a similar shape and confluent fins but have no jaws (teeth are in a sucking disc) and there are 7 gill openings.

Scales are small and embedded in the skin and not readily visible without close examination. The dorsal fin has about 240 rays, the anal fin somewhat fewer around 200, and the pectoral fin has 14-20 rays. Branchiostegal rays number 8-14 and vertebrae 103-112. The lower jaw projects and the mouth extends to the rear, or beyond, of the eye. The gill opening is a small slit in front of the pectoral fin. Migrating fish change colour and the eyes of males almost triple in size.

Freshwater adults are overall yellow, greenish, muddy or olive-brown with a dark back, sometimes yellow, green, orange or pink flank tinges and a creamy or yellowish-white belly. Such adults are called Yellow Eels. Adults migrating to the sea have a bronze to black back, a metallic sheen and a light to silvery belly. They are then known as Silver, Bronze or Black Eels. Colour will also change gradually to match the substrate. The larvae are transparent, the transformed elvers or glass eels are also transparent (with black eyes) but soon become grey-green to black, but only adults are found in the NCR.

Reaches 1.52 m and 7.5 kg in females and 50.3 cm in males. Fish larger than 40 cm total length are almost always females. The world, all-tackle angling record weighed 3.88 kg and was caught at Cliff Pond, Massachusetts in 1992. A 5.1 lbs (2.32 kg), 38.5 inch (97.8 cm) long and 9.25 inch (23.5 cm) girth was caught in the Ottawa River on 30 July 2002 by Kyle Richards (www.ofah.org/Registry/fish.cfm?RecID=1, downloaded 14 May 2004).

Found in the western North Atlantic from central Labrador south to Brazil. Also in freshwater drainages of the Mississippi and Great Lakes basins, the Hudson Bay drainage of Alberta and Saskatchewan (by introduction) and throughout Maritime Canada. Eels are reported from the Mississippi Lake and therefore can be expected to occur in the Mississippi River of the NCR as well as the Ottawa River.

Fishes of Canada's National Capital Region  
American Eel / Anguille d'Amérique / Anguilla rostrata

This species entered the NCR from an Atlantic coastal refugium.

Eels are found in mud-bottomed rivers, streams and lakes. They can be seen looped over weeds in rivers but are usually nocturnal and lie buried in mud during the day. Their preferred temperature is 19.0°C. In winter they bury themselves in mud and are torpid. They can travel overland to reach isolated water bodies, using snake-like movements when the ground is wet. Elvers can climb short vertical, wet walls such as those at canal locks. The Moses-Saunders Hydroelectric Power Dam on the St. Lawrence River at Cornwall was a barrier to young eels migrating into Lake Ontario. An eel ladder (a trough and baffle system with rest pools crisscrossing an ice chute through the dam) was built and over 3 million eels used it in 4 years. There is some evidence of a homing ability to their river of origin if they are displaced. In Lake Ainslie, Nova Scotia, eels have been observed in clumps or eel balls of up to 30 fish found on the bottom or even breaking the surface. Eels can be heard making chirping or sucking noises in warm summer weather on Cape Breton Island. Silver Eels in Newfoundland migrate to sea at age 9-18 years. They leave Nova Scotian waters in late August to mid-November. Adults in Passamaquoddy Bay, N.B. are active by day and night in contrast to freshwater eels, and made frequent surface to bottom dives perhaps to sample geoelectric fields as orientation cues for migration. Migration is often nocturnal.

Age and Growth
Life span is at least 43 years, possibly 50 years or more. Males mature at about 28-30 cm and females at 46 cm. Females grow larger than males, as much as twice the length. The leptocephalus larva has a 1 year life span in the sea.

In freshwater food is any bottom invertebrates, frogs and fishes. Smaller eels favour insects but large eels eat fish and crayfish as well as carrion. In New Brunswick eels are important predators of Atlantic Salmon in nets or traps. Elvers are cannibals. A wide variety of fishes and birds eat eels at various life stages. When they migrate back to the sea, they stop feeding.

Spawning in the Sargasso Sea is believed to occur from February to July but has not been observed. Egg numbers have been estimated as up to 20 million per female but the number released is guesswork as none have been found. The adults take 2-3 months to reach the Sargasso and the adults die after spawning. The Sargasso spawning grounds of the American Eel are to the southwest of the European Eel grounds although there is evidence for a more southern spawning ground. Leptocephali take 1 (perhaps more) year to drift to Canadian shores and transformation to a young eel or elver occurs at 60-65 mm during winter while drifting to or in nearshore waters. Glass eels near Saint John's, Newfoundland have been observed about 2 m below the surface drifting heads up and tails down. This may be done as camouflage from predators which swim horizontally, to counteract sinking, to escape vertically from predators and to facilitate vertical migration. The elvers enter estuaries in April and are 65-90 mm long. They are found in coastal rivers from May to July. The run lasts from a few days to several weeks depending on the river. In the northern Gulf of St. Lawrence young eels only move upstream in their second summer of stream residence. Temperature may be a factor in successful elver arrival. Males tend to stay near the coast in estuaries while females move up rivers sometimes as much as thousands of kilometres. All 356 eels sexed in Lake Champlain were female for example. Males also appear to be much rarer than females in northern waters. Males may have this distribution to ensure rapid maturation and return to the spawning ground. They do not need to be large to produce adequate amounts of sperm and estuaries are good feeding areas. Females require a delayed maturation as a larger body size results in more eggs. Cold northern and inland waters favour this. There are different stocks of eels in Canadian waters. Lake Ontario eels can be distinguished from those in St. Lawrence River tributaries and the Maritimes by the presence of mirex, a chemical used in insecticides. Pollutants are now a convenient method for stock identification but a sad reflection on the state of the environment.

Eels can be a nuisance to fishermen as they eat other fish caught in nets. They are used in physiological and other studies in laboratories and are easy to keep, surviving without food for up to 22 months. Adult eels are caught in Canada for export to Europe, particularly along the Gulf of St. Lawrence, using weirs, baited setlines, and pots, fyke nets, eel traps and hoop nets. Some are speared during winter when they are buried in mud. The catch in Lake Ontario reached 221,940 kg in 1978 and the total Quebec fishery for the same year was 527.9 tonnes and for the Maritimes about 320 tonnes. The total Canadian catch in 1988 was 1016 tonnes, worth about $2.3 million. Increased fishing pressure in Lake Ontario resulted in a decrease in average eel size. Elvers have been caught in Canada for raising in ponds in the U.S.A. and the Far East. Efforts to start such aquaculture in Canada have not met with extensive success but are potentially viable. Eels are exported live, on ice, or frozen. Live eels are used in making jellied eels which are popular in England. Smoked eel is an important, tasty and highly priced product. Eels should be cleaned with care as the blood has a neurotoxin which can affect humans but is destroyed in cooking. The Ontario Ministry of Natural Resources publishes a print and on-line "Guide to Eating Ontario Sport Fish" (www.mnr.gov.on.ca/MNR/) and has advisory limits for eating this species in the Mississippi River and Ottawa River. As these limits are apt to change, anglers consuming this fish should consult the most recent version.
Dymond (1939) records catches from 1881 onward in the general vicinity of the NCR but trends cannot be determined as fisheries data is recorded from different areas at different dates. For example, in 1898 the catch was 8172 kg in the Ottawa River from Carillon to Pontiac in Québec, the catch in 1933 from Hull, Labelle and Pontiac counties was 16,162 kg, and the catch in 1921 in Prescott, Russell, Carleton and Renfrew counties was 1800 kg, all the highest figures recorded. Generally catches were greater on the Québec side because there were more commercial fishermen there than on the Ontario side. Commercial fisheries for eels above and below Hull from the Québec side of the Ottawa River is documented by Pluritec (1982b). Lac Dollard des Ormeaux, the stretch of the Ottawa River form the Chaudière Falls to the Carillon Dam, had a harvest of 295 kg by Ontario commercial fishermen in 1999 but only 69 kg in 2000 (Haxton and Chubbock, 2002).
Blasting for a marina on the Ottawa River killed large eels around 1970. 

American Eel (Anguilla rostrata)

Other Names
Freshwater Eel
Anguilla and rostrata are both Latin, meaning "eel" and "beaked," respectively. The latter is probably a reference to the fish's snout. The American eel has a slender snakelike body with very small scales, and the fish may appear naked. A long dorsal fin usually extends for more than half the length of the body and is continuous with a similar ventral fin. Pelvic fins are absent. The back may be olive-green to brown shading to greenish-yellow on the sides and light gray or white on the belly.
Life History
Like the European eel, the American eel spawns during the winter in the Sargasso Sea, a tropical area northeast of Cuba. Adult eels spend most of their lives in freshwater, although the amount of time may vary among individuals. At some point, however, adults leave their freshwater habitats and move toward the Sargasso Sea. Neither adults or eggs have been collected in the vicinity of the Sargasso Sea, but newly hatched eels are found there. Presumably, spawning takes place in deep water and the adults die shortly thereafter. Young eels are transparent and leaf shaped. Years ago when they were first collected they were thought to be a new fish species and erroneously give the scientific name Leptocephalus. Within about a year, growing and moving toward the mainland, the American eels transform into more eel-like forms called "glass eels" or "elvers" and are ready to enter freshwater (European eels have a much longer journey and the process takes about three years). By the time American eels get close to the coast they are about 6 inches in length. The species begins to develop coloration only when the young reach nearshore areas. Once they reach freshwater, females continue to migrate deep inland as far up rivers and tributaries as they can. Males remain much closer to coastline areas. Eels tend to hide under rocks during the day, and venture out only at night to feed.
The American eel occurs in a variety of habitats. Known from Greenland to Brazil, it probably spans a wider range of latitudes than any other species in North America. American eels occur as far west as New Mexico, and are common throughout the Caribbean and the West Indies. Although it is native to much of Texas, the construction of dams, which impede upstream spawning migrations, has eliminated this species from most central and western areas of the state.
Although many anglers are put off by the snake-like appearance of eels and the prodigious amounts of slime they produce when captured, eels are in fact exceptionally good fish. In Texas, they are usually caught by anglers fishing for something else. The state rod & reel record is 6.45 pounds and 42 inches in length. The world record is 9.25 pounds.

Anguilla rostrata

The American eel, Anguilla rostrata, is a catadromous fish found on the eastern coast of North America. It has a snake-like body with a small sharp pointed head. It is brown on top and a tan-yellow color on the bottom. It has sharp pointed teeth but no pelvic fins. It is very similar to the European eel, but the two species differ in number of chromosomes and vertebrae.

The eel lives in fresh water and only leaves this habitat to enter the Atlantic ocean for spawning. It takes 9 to 10 weeks for the eggs to hatch. After hatching, young eels move toward North America and enter freshwater systems to mature. The female can lay up to 4 million buoyant eggs a year, but dies after egg-laying.
The eel is found around the Atlantic coast including Chesapeake Bay and the Hudson River. It prefers to hunt at night, and during the day it hides in mud, sand or gravel very close to shore, roughly 5 to 6 feet under.
American eels are economically very important to the East Coast and rivers where they travel. They are caught by fishermen and sold, eaten, or kept as pets. Eels help the Atlantic coast ecosystem by eating dead fish, invertebrates, carrion, insects, and if hungry enough, they will cannibalize each other.
Although many anglers are put off by the snake-like appearance of these catadromous fish, eels are in fact fit for human consumption. They are usually caught by anglers fishing for something else. The world record weight for the American eel is 9.25 pounds.

 Life cycle

The life stages of the American eel are leptocephali, glass eel, yellow eel, and silver eel. Leptocephali metamorphose into glass eel as they migrate toward land and bodies of freshwater. Glass eel develop pigmentation as they move into brackish water or freshwater. Usually by two years of age, small, pigmented eel make the transition into yellow eel. Yellow eel inhabit fresh, brackish, and saltwater habitats where they feed mostly on invertebrates and smaller fishes. Sexual maturity occurs around 10 to 25 years of age. When yellow eel become sexually mature, they begin a downstream migration toward the Sargasso Sea's spawning grounds. During this migration, yellow eel metamorphose into their adult silver eel phase, undergoing several physical changes. Adult silver eel are believed to spawn in the Sargasso Sea during winter and early spring.


American eel inhabit many different bodies of water throughout their lifetime and different life cycles, which makes them extremely hard to manage because of their frequent movement between jurisdictions.

 Sustainable consumption

In 2010, Greenpeace International has added the american eel to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."







美洲鰻鱺(American eel, Anguilla rostrata)為一種在北美東岸發現,降河迴游產卵(catadromous)魚類。牠有一個形身體及一個細小尖銳的頭部。背部為棕色而腹部為茶黃色。牠的牙齒銳利但沒腹鰭(pelvic fin)。牠與歐洲鰻鱺十分類似,但兩者的染色體脊椎骨(vertebra)數目都不相同。前者脊椎骨數103~111;後者為110~119。體長可達152公分。


雌性美洲鰻鱺在產卵(Spawn (biology)),並用9至10個星期令孵出。年幼鰻魚孵出後向北美移動,進入淡水系統後長成。雌性鰻魚可以每年生下4百萬浮起的蛋,但很多時在產卵後便死亡。鰻魚喜愛淡水,可以在大西洋岸邊發現,包括切薩皮克灣哈德遜河。鰻魚喜愛晚間獵食,在日間則在泥土、沙或砂礫中隱藏。





Eel Anguilla rostrata (LeSueur) 1817

[Jordan and Evermann, 1896-1900, p. 348, A. chrysypa Rafinesque 1817.]

Eel (Anguilla rostrata)
A, adult, Connecticut River, Massachusetts; 
from Goode, drawing by H. L. Todd; 
B, "Leptocephalus" stage, 49 mm.; 
C, "Leptocephalus" stage, 55 mm.; 
D, "Leptocephalus" stage, 58 mm.; 
E, transformational stage, 61 mm. B-E, after Schmidt.


In the common American eel the dorsal fin originates far behind the pectorals, this character is enough to distinguish it from the conger, from which it also differs in that the lower jaw projects beyond the upper or at least equals it in length, and its eyes are small and round. Furthermore, it develops scales as it grows, though these are so small that they might be overlooked. The eel, however, has a pointed snout, like the conger, a large mouth gaping back as far as the middle of the eye or past it; and its gill slits are set vertically on the sides of the neck, their upper corners abreast of the center of the base of the pectoral fin. It is very closely related to the European eel (Anguilla vulgaris), but has fewer vertebrae (average about 107 as compared with about 114 or 115 in the European species).


The colors of eels vary widely with the bottom on which they live. As a rule they are dark muddy brown or olive-brown above, more or less tinged with yellow on the sides; the lower surface paler brown and yellower, with dirty yellowish-white belly. It is common knowledge that eels are dark if living on dark mud but much paler on pale sand. And Parker[53] has found that they can change from pale to dark in about 11/2 hours and from dark to pale in a little more than 3 hours, if moved from a white background to a black or vice versa, under a strong light.


Eels are said to grow to 4 feet in length and to 161/2 pounds in weight. Full-grown females average only about 2 to 31/2 feet, however, and males are smaller. Any eel more than 18 inches long would probably be a female, and one more than 24 inches in length would certainly be one. The smallest mature males are about 11 to 12 inches long, females about 18 inches.


The life history of the eel remained a mystery until very recently. It has been common knowledge for centuries that young elvers run up into fresh water in spring, and adults journey downstream in autumn. A host of myths grew up to explain the utter absence of ripe eels of either sex, either in fresh water or along the seacoast. But it was only a few years ago that the breeding places of the European and American eels were discovered and the history of their larvae [page 152] traced, chiefly by the persevering researches of the Danish scientist, Johannes Schmidt.[54] Now we know that the life history of the eel is just the antithesis of that of the salmon, shad, and alewife, for eels breed far out at sea, but make their growth either in estuarine situations or in fresh water.
The young elvers, averaging from 2 to 31/2 inches in length, appear along our shores in spring. As yet we have few data on the exact date of their arrival on the Gulf of Maine coast. They appear as early as March at Woods Hole; by mid- or late April both in Narragansett Bay and in Passamaquoddy Bay at the mouth of the Bay of Fundy, while Welsh encountered a tremendous run in Little River, near Gloucester, on May 5, 1913, suggesting that they may be expected in the mouths of most Gulf of Maine streams during that month. And they are found ascending streams in the Bay of Fundy region during the summer. A run may last for a month or more in one stream, only for a few days in another. And there is a noticeable segregation even at this early stage, some of the elvers remaining in tidal marshes, in harbors, in bays back of barrier beaches, and in other similar situations, some even along the open coast, especially where there are beds of eel grass (Zostera); while others go into fresh water, some of them ascending the larger rivers for tremendous distances.[55]
It is now generally believed that most of the eels that are caught in fresh water are females. But some of the females remain in salt marshes and harbors, to judge from the large size of many of the eels that are caught there. And nothing is known as to what preference the males of the American eel may show in this respect.
It is no wonder that the ability of the elvers to surmount obstacles as they run upstream is proverbial, for they clamber over falls, dams, and other obstructions, even working their way up over damp rocks as Welsh saw them doing in Little River, where they were so plentiful on May 5 and 7, 1913, that he caught 1,500 in one scoop of a small dip net and 545 with a few grabs of his bare hand. Elvers, in equal multitudes have often been described in other streams, American as well as European. Eels can live out of water so long as to give rise to the story that they often travel overland. There is no positive evidence for this. But Sella[56] has proved, by experiments, with European eels marked so as to be recognizable if recaught, that they can carry out journeys as long as 31 miles (50 kilometers) along underground waterways. Doubtless it is this ability that explains the presence of eels in certain ponds that have no visible outlet nor inlet, a fact often attested.
It is true in a general way that eels seek muddy bottom and still water, as has been said so commonly. But this is not always so whether in salt water or in fresh. Thus the rocky pool at the outer end of the outlet from Little Harbor, Cohasset, on the south shore of Massachusetts Bay, is a good place to catch eels; and large ones are only too common in swift flowing, sandy trout streams on Cape Cod; we have had one follow and nibble at the trout we were dragging behind us on a line. The fact is, they can live and thrive wherever food is to be had, which applies to them in estuarine situations and in fresh water.
No animal food, living or dead is refused, and the diet of the eels in any locality depends less on choice than on what is available. Small fish of many varieties, shrimps, crabs, lobsters, and smaller crustacea, together with refuse of any kind (for they are scavengers) make up the bulk of the diet in salt, estuarine, and brackish water. Being very greedy, any bait will do to catch an eel. They are chiefly nocturnal in habit, as every fisherman knows, usually lying buried in the mud by day to venture abroad by night. But eels, large and small, are so often seen swimming about, and so often bite by day that this cannot be laid down as a general rule.
Eels tolerate a wide range of temperature. But it is common knowledge that those inhabiting the salt marshes and estuaries of our Gulf, and its tributary streams, mostly lie inactive in the mud during the winter.
Eels grow slowly. Hildebrand and Schroeder[57] concluded from a series of measurements taken at different seasons in lower Chesapeake Bay that those [page 153] 21/2 inches long in April are about 5 inches long a year later, or about 2 years after their transformation. The winter rings on the scales have shown that full grown adults of the European species are from 5 to 20 years old, depending on food supply, and other conditions; this is corroborated for the American species by the fact that Dr. Hugh M. Smith, former Commissioner of the United States Bureau of Fisheries, found that a female, on the way down the Potomac, was in her twelfth year.
At the approach of sexual maturity, which takes place in the fall, the eels that are in fresh water drop downstream, traveling mostly at night. They now cease feeding, as do those that have been living in the river mouths, bays, and estuaries; the color of the back changes from olive to almost black, the ventral side turns silvery, and the eyes of the males grow to twice their previous size. Both males and females then move out to sea, and it is not until after they reach salt water that the ovaries mature. In fact, no perfectly ripe female eel has ever been seen, and only one ripe male (of the European species).
So little is the life history of the eel understood by our fishermen that we again emphasize the undoubted fact that no eel ever spawns in fresh water.
The eels drop wholly out of sight when once they leave the shore;[58] no one knows how deep they swim, but they certainly journey out beyond the continental slope into the oceanic basin before depositing their eggs. Schmidt has been able to outline the chief spawning center of the American species (from the captures of its youngest larvae) as between latitudes 20° and 30° N. and between longitudes 60° and 78° W.; i. e., east of Florida and of the Bahamas south of Bermuda. But it may also spawn (always in deep water) farther north as well.[59]
The American eel spawns in midwinter, thus occupying one to two months in its journey from the coast to the spawning ground, for Schmidt found very young larvae (7 to 8 mm.) in February. Eels, like Pacific salmon, die after spawning, the evidence of this being that no spent eels have ever been seen and that large eels have never been known to run upstream again. Smith suggests that they probably "jellify" and disintegrate, as the conger does.
Eels (European) are among the most prolific fish, ordinary females averaging 5 to 10 million eggs and the largest ones certainly 15 to 20 million. It is doubtful whether eggs laid by the American eel have been seen, or of the European either, for that matter.[60] But it is generally supposed that they float in the upper or intermediate water layers until hatching. The larval, so-called "leptocephalus" stage, like that of all the true eels, is very different in appearance from the adult, being ribbon-like and perfectly transparent, with small pointed head; and it has very large teeth, though it is generally believed to take no food until the time of its metamorphosis. These leptocephali of our eel, living near the surface, have been found off our coasts as far north as the Grand Banks, but never east of longitude 50° W.
Inasmuch as the breeding areas of the American and European eels overlap, not the least interesting phase of the lives of the two is that the larvae of the American species should work so consistently to the western side of the Atlantic, and those of the European to the eastern side that no specimen of the former has ever been taken in Europe or of the latter in America.
The American eel takes only about one-third as long as the European to pass through its larval stage; i. e., hardly a year, as against 2 to 3 years. The leptocephali reach their full length of 60 to 65 mm. by December or January, when metamorphosis takes place to the "elver"; the most obvious changes being a shrinkage in the depth and length of the body but an increase in its thickness to cylindrical form, loss of the larval teeth, and total alteration in the aspect of head and jaws, while the digestive tract becomes functional.
It is not until they approach our shores, however, that the adult pigmentation develops or that the elver begins to feed, a change that is accompanied by a second decrease in size. How such feeble swimmers as the leptocephali find [page 154] their way into the neighborhood of the land remains a mystery. It seems certain, however, that all the young eels bound for the Gulf of Maine complete the major part of their metamorphosis while they still are far offshore. Thus we have never taken one in the leptocephalus stage in the Gulf of Maine in all our tow-nettings, whereas (more significant) the Albatross towed three young eels in the so-called "glass-eel" stage, 54 to 59 mm. long, of practically adult form but still transparent, during her spring cruise in 1920, one of them on Georges Bank, March 11; a second on Browns Bank, April 16; and one in the western basin of the Gulf off Cape Ann, February 23. Evidently they were intercepted on their way in to land. And since all three were on the surface, we may take it that glass eels, like leptocephali, keep to the uppermost water layers during their journey.

Gereral range—

Coasts and streams of West Greenland,[61] eastern Newfoundland[62] Strait of Belle Isle, and northern side of the Gulf of St. Lawrence south to the Gulf of Mexico, Panama, West Indies, and (rarely) to the northern coast of South America; also Bermuda; running up into fresh water but going out to sea to spawn p. 153.

Occurrence in the Gulf of Maine—

The occurrence of the eel around the periphery of our Gulf can be described in the one word "universal." There is, we believe, no harbor, stream mouth, muddy estuary, or tidal marsh from Cape Sable on the east to the elbow of Cape Cod on the west but supports eels in some numbers, and they run up every Gulf of Maine stream, large or small, from which they eventually find their way into the ponds at the headwaters unless barred by insurmountable barriers such as very high falls. Examples of long journeys by eels upstream, in New England rivers, are to the Connecticut Lakes, New Hampshire, at the head of the Connecticut River; to the Rangeley Lakes at the head of the Androscoggin, and to Matagamon Lake, at the head of the East Branch of the Penobscot. Eels are even caught in certain ponds without outlets, as noted above (p. 152). On the other hand, we have seen a few (and some large ones) along the open coast, at Cohasset, for example, but always close in to the shore line and in only a few feet of water, where flounder fishermen catch them from time to time.


Schmidt has suggested that the American eel is not as plentiful in actual numbers as the European, arguing from the facts that its larvae have not proven so common on the high seas, and that the American catch of eels (about 2,000 tons yearly) was but a fraction as large as the European catch (about 10,000 tons annually). But it is not safe to draw any conclusions from the statistics because the American catch is limited more by the fact that eels are not much in demand, than by the available supply. And the local demand is less for them today than it was 30 years ago, as is reflected in a decrease in the reported landings from about 305,000 pounds for Maine and about 240,000 pounds for Massachusetts in 1919 to about 19,000 pounds for Maine and about 32,000 pounds for Massachusetts in 1947. The yearly landings of eels along the Canadian shore of our Gulf and from the tributary fresh waters are 30,000-40,000 pounds nowadays.
Practically the entire coastwise catch is made in salt marshes, estuaries and stream mouths; the numbers captured up stream are negligible of recent years, except in New Brunswick where 16,000 pounds were caught in the lower sections of the St. John River System in 1950.[63] In Germany, however, where the demand for eels is much greater, the yearly catch is nearly four times as great for rivers and other fresh waters as it is for the coast. And many millions of elvers were transplanted, during the 1930's, from British rivers (the Severn in particular) to landlocked bodies of water in Central Europe which the young eels could not reach naturally.
The greater part of the catch is made in nets and eelpots; and some are speared, mostly in late autumn and winter, often through the ice.

[53] Jour. of Exper. Zool., vol. 98, 1945, No. 3, pp. 211-234.
[54] The life history of the eel is presented in more detail than is possible here by Schmidt (Philos. Trans. Roy. Soc. London, Series B, vol. 211 (1922) 1923, pp. 179-208, summarized in Nature, vol. 110, 1922, p. 716), and by Cunningham (Nature, vol. 113, 1924, p. 199). See also Schmidt (Rapp. et Proc.-Verb. Cons. Perm. Internat. Explor. Mer, vol. 5, No. 4, 1906, pp. 137-204, pls. 7-13); for a popular account see Smith (Nat. Geog. Mag., vol. 24, No. 10, October 1913, p. 1140).
[55] Eels are native in Lake Ontario which they reach by way of the St. Lawrence River; and up the Mississippi drainage systems even as far as North Dakota, Wisconsin, Ohio, and western Pennsylvania.
[56] Mem. R. Comit. Talassogr. Ital., vol. 158, 1929.
[57] Bull. U. S. Bur. Fish., vol. 43, 1928, p. 114.
[58] Large eels, on their seaward journey, have occasionally been caught by otter trawlers in the western part of the British Channel, but we know of no such occurrence on this side of the Atlantic.
[59] See Schmidt (Ann. Rep. Smithsonian Inst., (1924) 1925, pp. 279-314) for a readable account of the investigations which enabled him to chart the breeding places and seasons of the American and European eels.
[60] Four eggs taken on the Arcturus expedition near Bermuda in 1925 were provisionally identified as those of the American eel by Fish who has pictured them and the larvae hatched from one of them (Zoologica, New York Zool. Soc., vol. 28, 1927, pp. 290-293, figs. 103-107). But the date at which they were taken (July 15-17) makes it more likely that they belonged to some other member of the eel tribe.
[61] Jensen (Invest. of the Dana in West Greenland Waters, 1925, Extr. Rapp. et Proc.-Verb Cons. Internat. Expl. Mer, vol. 39, 1926, p. 101) records the American eel as one of the four fresh-water fishes known from the west coast of Greenland.
[62] Reported by Dr. G. W. Jeffers as common.
[63] Information from A. H. Leim.

The life cycle of the American eel involves several stages.
It begins in the ocean when the eel larva,
called the leptocephalus, hatches from the egg.
The leptocephalus, carried in the Gulf Stream,
changes into a glass eel (a more elongated, eel-like shape)
near the coast and migrates inland into streams, rivers,
and lakes to grow and evolve into the elver
(a small version of the adult eel).
In fresh water, the elver grows into the larger yellow eel
and then finally into the silver eel (almost full-grown).
The silver eel then migrates back to the Sargasso Sea and spawns,
thereby beginning the cycle once again. (created by Rob Slapkauskas)

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