Eel - definition of eel by The Free Dictionary Eel - definition of eel by The Free Dictionary (ēl) n. pl. eel or eels 1. Any of various long, snakelike, scaleless marine or freshwater fishes of the order Anguilliformes that lack pelvic fins and characteristically migrate from fresh water to salt water to spawn. 2. Any of several similar fishes, such as the lamprey and electric eel. [Middle English ele, from Old English ǣl.] eel (iːl) n 1. (Animals) any teleost fish of the order Apodes (or Anguilliformes), such as the European freshwater species Anguilla anguilla, having a long snakelike body, a smooth slimy skin, and reduced fins 2. (Animals) any of various other animals with a long body and smooth skin, such as the mud eel and the electric eel 3.

an evasive or untrustworthy person [Old English ǣl; related to Old Frisian ēl, Old Norse āll, Old High German āl] ˈeel-ˌlike adj (il) n., pl. (esp. collectively) eel, (esp. for kinds or species) eels. 1. any of numerous elongated, snakelike marine or freshwater fishes of the order Apodes, having no ventral fins. 2. any of several similar but unrelated fishes, as the lamprey. [before 1000; Middle English ele, Old English ēl, ǣl; c. Old Frisian ēl, Old Saxon, Old High German āl, Old Norse āll] eel′like, adj. eel (ēl) 1. Any of various fish having long, snake-like bodies without scales. Eels typically migrate from fresh to salt water to spawn. 2. Any of several similar fish, such as the lamprey.

ThesaurusAntonymsRelated WordsSynonymsLegend: A Guide to Eel Farming - The Fish Site A Guide to Eel Farming 23 March 2015 Eel farming is an aquaculture industry that takes place worldwide. It specialises in raising and growing eels, which provide a nutritious meat, to be sold at market. Growing young eels on until they are large enough to be sold for meat can be a lucrative business. It is estimated that the industry is worth over 1 billion US dollars, with eel farms producing around 60% of the eel meat consumed, writes Georgina Starmer for TheFishSite.com. Eels are fish that are characterised by their round, elongated and slender bodies. They are a carnivorous, long-living species that spend most of their life in fresh water, but return to the sea to breed. On average, the young eels live in the fresh water of rivers and streams for up to 12 years for males and up to 18 years for the females. Some species may reach even greater ages.

Then, as they reach sexual maturity their skin pigment becomes silvery, they put on weight and they migrate miles out into the seas to find the spawning grounds to breed. The eel only breeds once during its lifetime. The fertilised eggs are carried by the ocean current as they change into larvae, and then after around 18 months they have developed into ‘glass eels’. These are juvenile eels that have an under-developed, transparent appearance. When the glass eels reach 2-3 years old, the ocean currents have carried them towards the shores. Their pigmentation becomes darker and they resemble adult eels, only much smaller at around 8-20 cm in length. These young eels are called elvers. They have reached the estuaries, and now must migrate further up into the fresh water rivers to feed and grow for some years, beginning the cycle once more. Farming Eels Eel farms are found in many countries, and the significant producers are European countries, Scandinavian countries, China, Taiwan, Australia and Morocco, with the largest single producer being Japan. The farms begin by sourcing stock, usually obtained by purchasing the wild, glass eels which are sold on and used to replenish the stock on the farms.

Once the juvenile eels reach the glass eel stage of development, they are much closer to the shores and can be captured in nets. The young eels, sometimes called fingerlings, are sold and brought to the farms to restock the supply. It is important for them to be quarantined for several weeks and carefully inspected for any signs of pest or disease. Passing diseases on to the established eels could have a significant effect on the health and profitability of the farm. Eels are an ideal species of fish to be farmed because they are very tolerant of many conditions, including being kept in large numbers. After the fingerlings have been in quarantine, they can then be grown-on in ponds or in specialised tanks that recirculate the water. The temperature of the water must be kept between 23°C and 28°C to ensure optimal growth and health of the fish. This means that in hotter climates, growing eels in pond set-ups may be more suitable as the water will naturally be at a warmer temperature. In cooler climates, the most common way to farm is by using the tank system, although there are methods of heating the water in the ponds also, such as using solar or geo thermal heating methods.

Due to ponds generally being larger than tanks, they can produce a higher yield of eels and therefore more profit for the farm. For the most intensively farmed eels, tanks that incorporate recirculation systems are mostly used. The tank system requires access to a large amount of clean water, needed to recirculate around the tanks to keep them aerated and clean. An electricity supply is also required to heat the water to the optimal temperature and to pump the water around the system. The tanks are usually made from concrete or fibre glass, and the setup also features filtration systems to remove debris such as faeces and waste food particles from the water. Using a recirculation system means that the environment that the eels are in can be completely controlled, allowing the farmers to provide the best conditions for growth. Another way of cultivating eels is by a method called valliculture. Rather than using pond or tanks, farmers use the natural areas of the coast to grow the eels. This might be from making use of natural lagoons and by setting up a weir to keep the eels from escaping into the open waters, keeping them contained so that the can be harvested once they reach the desired size.

This method of farming eels is popular in the Mediterranean region. When growing eels on in ponds or tanks, regular grading must take place to reduce cannibalism and competition for food. Every 6 weeks, the eels must be graded and separated into different size categories. If all different sizes are kept together, the larger eels will eat the smaller eels. There are many designs of fish grading equipment commercially available, yet they all work using the same principle. The consist of an entrance that the fish swim into, and then there are different sized gaps that allow the smaller fish to return to the ponds or tanks, while retaining the larger fish that can be moved to other tanks or to be prepared for harvesting. Providing eels with the right food is important to their health and growth. Being meat eaters, protein is an essential requirement. Commercial foods are widely available, consisting of a protein paste for young eels and pellets for older eels. These foods consist of high quality fish proteins, oils and nutrients to produce optimal growth. The protein based food, and also the high volume of eels that are kept together, mean that the water in the ponds or tanks becomes dirty quickly.

Although very tolerant of many conditions, when the water becomes too dirty it can cause stress for the eels. This is another reason why access to lots of clean water is essential. Harvesting the eels is done by grading the sizes to make sure each eel is large enough to reach market value. It is important to keep stress to a minimum while grading, so as not to affect the health of the eel. The large eels that are ready for harvesting are put into tanks with clean water to flush out any possible impurities in their systems that could affect the taste. Their food is also stopped 1-2 days prior to harvest. Eels that are to be freshly consumed are chilled and put into bags that are filled with oxygen. There should also be enough water in the bag to keep their skin moist. They are then ready for transportation to market. Eels that are to be smoked are usually transported alive to the processors. Common Farmed Species of Eel Longfin eel (Anguilla reinhardtii) and the Shortfin eel (Anguilla australis) – found in brackish and fresh waters of Australia and New Zealand, and are the most commonly farmed species in the countries.

European Eel (Anguilla Anguilla) - found in fresh and brackish water in the UK, Ireland, Mediterranean, Northern Africa the Baltic Sea, and Iceland up to mid Norway. American eel (Anguilla rostrata) – found in brackish and fresh water on the eastern side of the United States, the south- east of Canada and the Gulf of Mexico. Japanese eel (Anguilla japonica) – most common in the fresh and brackish waters of Japan, Korea, China and Taiwan. This eel is particularly suited to pond cultivation in these countries as they are naturally acclimatised to higher water temperatures. Common Ailments and Treatment The young glass eels most commonly come from the wild, so they are more prone to carry parasites or diseases. It is important to quarantine the glass eels before introducing them to tanks with other fish. The change from salt to fresh water also helps to eliminate many parasites naturally. However, here are some parasites and diseases that need further attention. • Fungal Infections – symptoms include swellings on the body, gills or fins.

There can also be white or brown fibrous patches on the skin, which can cause the eel to die when on the gill area. Treatments include salt water solutions or the removal of the infected eel so the fungus does not spread to other eels. • Parasites – symptoms of a parasitic infection include an increase in mucus, frayed fins, lethargy, respiratory distress and white patches on skin. The eel may display changes in behaviour such as attempting to rub off parasites on the surface of the enclosure. Treatments for parasites include formaldehyde or salt solutions. • Red Fin – this is a bacterial disease that affects the fins. The symptoms are a rotting of the tail and fin areas. Treatment is with a salt solution. • Red Eel Pest – this bacterial disease causes symptoms of swelling, red spots and ulcerated lesions on skin. Treatment is with antibiotics. • Red Head – a viral disease that shows as haemorrhages that spread from the head to other parts of the eel’s body. Treatment is through vaccination of young fingerlings, salt water solutions and also by decreasing the temperature of the water.

During times of stress, such as when being handled, graded or if the water becomes poor quality, eels can also become more susceptible to infections. Care must be taken to keep the stress levels to a minimum at all times in order to produce healthy fish. Prevention is always better than cure, so regular maintenance and cleaning of equipment are recommended, and also routine inspections of eel stock. The Future of Eel Farming Eel farming has long been a worldwide industry. However, there is now concern over its sustainability, due the decreasing amount of elvers found in the wild. This is particularly significant for the European eel, whose numbers have dramatically declined in recent years. The reason for the decline is not yet known, although there are a few contributing factors. One reason could be from the over fishing of glass eels, meaning less eels reach maturity in rivers and streams, leading to the decline in the overall wild population. Another factor could be the increasing amount of flood defence construction, that prevent the elvers from being able to progress up the rivers and streams as they could do with ease before. Again this would affect the numbers of the wild population.

This means that in the future there may be regulations in place as to the quantities of elvers that can be caught for the purpose of restocking eel farms. There are programmes now in place in parts of the UK whereby 60% of all caught elvers can be sold to farms, and the other 40% are taken and released further upstream, in an effort to boost the population numbers. Because of the complex lifecycle of the eel, breeding stock in captivity is something that is not possible as yet. Eels spend months travelling to the spawning grounds to breed in the sea. So far, artificial ways of breeding eels for commercial farming purposes has not been successful. Until methods are discovered as to how to breed hatchings from the eel spawn, the industry will not be truly sustainable and will always depend on the supply of wild glass eels for its success. Also on this topic: 3. – Eels – Te Ara Encyclopedia of New Zealand Freshwater eels have a remarkable life cycle, which begins and ends in the ocean. Spawning has never been observed. Life cycle Adult eels: spawning at sea Adult eels probably spawn at some depth in warm seas.

New Zealand’s shortfin eels produce 1.5–3 million eggs, and the longfins 1–20 million eggs. Males fertilise the eggs. After spawning, the adults die. Larvae: drifting to land Fertilised eggs hatch at the surface and become leaf-shaped larvae, floating on ocean currents towards the coast. They have teeth, but it is not clear for what purpose – they may store calcium for bone development. Their skin may absorb nutrients, as researchers have not found food in the larvae. Glass eels: migrating into estuaries Once the larvae reach land, an extraordinary transformation takes place: they become slender, transparent eels, known as glass eels. They arrive at New Zealand’s coast from July to December, with numbers peaking in spring (August–October) – the time of whitebait migration. Glass eels migrate into river mouths or estuaries in astounding numbers. Up and over Hydroelectric dams are an obstacle to elvers (young eels) swimming upriver. Some dams have special passes, allowing them to get round the massive concrete walls. But they don’t always need this help.

Elvers can climb the 43-metre Arapuni Dam on the Waikato River, and the 75-metre Patea River dam in Taranaki. Elvers: swimming upriver Glass eels soon turn grey-brown, and in this form they are known as elvers. They migrate upriver, often in swarms and usually at night. Young elvers can climb waterfalls, but lose this skill as they grow. Adult eels Elvers become adults, with bigger heads and fatter bodies. After many years in fresh water, eels migrate back down the waterways to the sea. It is thought that males fertilise the eggs once the females spawn out at sea. Migration to the sea When they reach breeding size, eels change from ‘yellow-bellies’ to ‘silver-bellies’. The yellow-grey underside becomes grey-white, the head shape changes and the head, back and pectoral fins darken. Shortfin males migrate in February–March, and longfin males in April. The females soon follow, and both males and females die after spawning.

Studies show the species also migrate at different ages: Shortfin males at an average of 14 years (38–58 centimetres), females at 22 years (50–100 centimetres). Longfin males an average of 23 years (48–74 centimetres), females at 34 years (75–180 centimetres). It is not known how long the journey takes. One female longfin eel that was tagged took 161 days to swim from Canterbury’s Lake Ellesmere (Te Waihora) to a point 160 kilometres north-east of New Caledonia. Barriers across waterways have hampered their route. One estimate suggests that hydroelectric dams have blocked the longfin eel’s access to the sea in 35% of its habitat. Fish out of water As a young man, author David Graham worked on a Dannevirke dairy farm where eels slithered through wet grass from one waterway to another.

‘It was quite a common occurrence to leave home in the dark to bring the cows home to be milked and arrive back with several of these Eels, which were easily stunned with a blow on the head, and used for a meal.’ 1 Life cycle: a long-standing mystery For centuries, larval eels were thought to be a separate species: they occur in the ocean and look different from adult, freshwater eels. Then in 1896 the Italian zoologist Giovanni Grassi reported that Leptocephalus brevirostris, known as a saltwater fish, was in fact the larva of the European freshwater eel. But just where at sea they bred was a mystery. Searching for breeding grounds In a 1923 paper, Danish biologist Johannes Schmidt stated that American and European eels spawned in the Sargasso Sea, in the Atlantic. In 1926, after sailing his research vessel Dana II to Australia and New Zealand, he concluded that New Zealand eels probably bred somewhere east of New Caledonia. But the exact locations are still not fully known. Longfin eels At migration, longfin eels are more ready to reproduce than shortfin eels.

Scientists thought this meant their spawning grounds were closer to shore. However, a study showed that the longfin eel had the longest larval stage of any Pacific freshwater eel reported. This suggests that the larvae actually hatch further away from New Zealand, possibly near Tonga. They were also the biggest specimens when they reached coastal waters – so they may have been at sea longer, and travelled further. At first glance, all New Zealand freshwater eels look the same. But each species is unique in its own way. Learn about the differences between the species and how to tell them apart . About the longfin eel Habitat Longfin eels can be found throughout New Zealand. They live mainly in rivers and inland lakes but can be found in almost all types of waters, usually well inland from the coast. They are legendary climbers and have made their way well inland in most river systems, even those with natural barriers. Elvers (young eels) swimming up river will climb waterfalls and even dams by leaving the water and wriggling over damp areas. It is not unheard of for an eel to climb a waterfall of up to 20 metres.

Close up of longfin eel, Lake Pounui, Wairarapa Size When eels begin life, they are a tiny one millimetre in length. During their life, they can grow up to two metres long. Compared with many other fish, eels are slow growing - a longfin may grow only between 15-25mm a year. They can also live for many years. Large longfins have been estimated to be at least 60 years old. The biggest eels are usually old females that have been slow to reach sexual maturity and, for reasons that are not yet understood, have not migrated to sea to breed. The biggest longfin eels reported have weighed as much as 40 kg. Pictures of fishers and huge eels used to appear regularly in local newspapers. But today, you’ll seldom find an eel heavier than 10 kg. Commercial fishing has meant that a big proportion of our very large eels have now disappeared. Appearance In shape, eels are elongate, slender-bodied fishes, almost tubular. When they are small, they have relatively smooth heads but as they grow the head becomes bulbous, with a prominent muscular dome behind the eyes.

They change shape again when they get ready to migrate to their breeding grounds. The head becomes much more slender and tapered, almost bullet-like and the eyes enlarge to up to twice their normal size. Like all fish, eels have scales and fins. The longfin eel is so named because its top (dorsal) fin is longer than its bottom fin. While they have the appearance of being scaleless, tiny scales are embedded deeply within their thick, leathery skin. The eel’s skin is very sensitive to touch. This helps it to "see" in its watery environment. In colour, longfins are usually dark brown to grey black. Very occasionally, longfin eels found in the wild are partially or even wholly bright yellow in colour. Food Eels eat "live" food. Small longfin eels living amongst the river gravels will feed on insect larvae, worms and water snails. When they get bigger, they begin to feed on fish. They will also eat fresh-water crayfish and even small birds like ducklings. During the day, eels are secretive, hiding under logs and boulders or under riverbanks.

Occasionally, they may be seen out hunting for food but most of their hunting takes place at night. Eels hunt by smell rather than sight. Longfin eels have a well-developed sense of smell. They have tube nostrils that protrude from the front of their head, above their upper lip. They also have a very large mouth with rows of small, sharp, white teeth. The top teeth form an arrow shape on the roof of the eel’s mouth. Breeding Longfin eels breed only once, at the end of their life. When they are ready to breed, they leave New Zealand and swim 5000 kilometres up into the tropical Pacific to spawn, probably in deep ocean trenches somewhere near Tonga. When they reach their destination, the females lay millions of eggs that are fertilised by the male. The larvae are called leptocephalus and look nothing like an eel – they are transparent, flat, and leaf-shaped. The larvae reach New Zealand by drifting on ocean currents. Before entering fresh water, the leptocephalus change into a more familiar eel shape, although they remain transparent for up to a week after leaving the sea.

These tiny "glass" eels enter fresh water between July and November each year, often in very large numbers. Eels take many years to grow and it could be decades before an individual is ready to undertake the long migration back to the tropics to breed. The average age at which a longfin eel migrates is 23 years for a male and 34 for a female. The adults never return as they die after spawning. Threats While longfin eels are still relatively common, fishing has had a significant impact on the species. Europeans showed little interest in eels as a fishery until the 1960s when commercial catches rose steadily. In 1975, eels were the most valuable fish export after rock lobsters. Five years later, they were the fifth most valuable finfish export. This big increase in fishing effort led to significant stock reductions in some areas, with a marked decline in the average size of the eels caught. Habitat loss also affects eels. Changes caused by hydro development, drainage and irrigation schemes and river diversions affect eels by reducing their habitat and the water available for aquatic life.

Culverts and dams can also impact on eels by preventing their migration. Eel habitat is also impacted by pollution. Sewage and effluent from meat works and pulp and paper plants discharged into rivers can remove large quantities of oxygen from the water. The result of this oxygen depletion is that the fish will either die or move away. Report: Status and management of the longfin eel Longfin eel report welcomed - Media release 17 April 2013 Eels on the move Hydro dams stop eels moving freely up and done some rivers. To get around this problem eel passes have been built across some dams to help the eels complete their journey. Young eels may also be moved across the dams by hand. Activities for students Find out about the eel fishery in New Zealand and the problems associated with fishing a slow-growing, long-lived species. On a map, trace the journey of the longfin eel as it leaves New Zealand to breed. Work out how far it travels. Design a board game. You could call it "Eels and Ladders". Players move around the board, winning points for actions that protect the longfin eel and losing points for actions that harm it.

For example, one square could read "You go to the Environment Court to stop a company discharging toxic effluent into the river. Move ahead 5 squares." Another square could read "You drain a wetland, reducing the habitat for eels. Go back 6 squares". Discuss attitudes and feelings about eels. What do students think of when they hear the word eel? What does an eel feel like? Get students to make up poems about eels by putting up on a board all the words they associate with eels. . Hold a class debate on a proposed drainage scheme which would reduce the level of water in a river where eels live. Read Watercress Tuna and the Children of Champion Street by Patricia Grace. Have students write and illustrate their own stories about an eel. Activity sheet Elver | Define Elver at Dictionary.com elver a young eel, especially one that is migrating up a stream from the ocean. Expand 1630-40; variant of ellfare, literally, eel-journey.

See eel , fare Dictionary.com Unabridged British Dictionary definitions for elver Expand a young eel, esp one migrating up a river from the sea See also leptocephalus Word Origin C17: variant of eelfare migration of young eels, literally: eel-journey; see eel, fare Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Word Origin and History for elver Expand n. "young eel," 1640s, variant of eelfare (1530s), literally "passage of young eels up a river;" see eel + fare . Online Etymology Dictionary, © 2010 Douglas Harper Where have all the eels gone? Where have all the eels gone?

Printer Friendly Page By Ethan Nedeau EVERY AUTUMN, American eels (Anguilla rostrata) descend the Gulf of Maine's rivers on a journey toward the warm waters of the Sargasso Sea to spawn and die, returning to a birthplace they left as many as 30 years earlier. We do not know their path nor do we understand how they navigate vast distances. The moon, stars, magnetism and an exceptional homing ability may guide them through the dark waters. Eels have not revealed their spawning secrets; scientists do not know exactly where eels spawn, at what depth or how they behave when reunited at the spawning area. All eels from throughout their range, Greenland to Central America, converge on the spawning waters at about the same time. This is remarkable considering the vastly different distances they must travel. Northern fish leave much sooner to arrive �on time.� Despite the enormous geographic range of the species, all American eels comprise a single breeding population. After spawning is completed and eggs hatch, billions of tiny larvae become entrained in the Gulf Stream, Florida Current and Antilles Current. The larvae, called leptocephali, are transparent and shaped like a willow leaf.

They can orient themselves and change positions in the water column, but ocean currents dictate their path toward the continent. Some may get pushed southwest into the Gulf of Mexico and wander into estuaries of the Gulf Coast or Central America. Others will be whisked northward by the strong Gulf Stream, spin off into the Labrador Current and turn south toward Newfoundland and the Gulf of St. Lawrence, or north to southern Greenland. Every eel must be prepared to go where currents take it to warm tropical rivers, icy northern waters or anywhere in between. Leptocephali metamorphose into a more recognizably eel-like juvenile form called glass eels. They are so named because they are transparent and lack pigmentation. Glass eels are stronger swimmers and as currents take them close to the continental shelf and coastal waters, they will swim toward the coast and seek out estuaries. Once in estuaries, they become pigmented and are known as elvers; by this time they are 60 to 130 millimeters (2.5 to 5 inches) long. They swim up tidal rivers during flood tides and retreat to the bottom as tides ebb.

They forge upstream with each tidal cycle and gain strength until they can swim against strong currents. Elvers grow into yellow eels, the fourth stage of life. Over the next few years they may disperse within a watershed, often traveling hundreds of miles in stops and starts, depending on migration barriers and habitat along the way. Some will remain in estuaries and tidal freshwater habitats; these tend to be male fish and may only stay for a few years before returning to the sea. Others have wanderlust and may spend the next 30 years in a watershed - ascending rivers, crossing lakes and pushing toward headwaters. Eels that swim far inland - especially in the north - are mostly female and may grow to over four feet long, far larger than males. Eels toward the northern end of the range are the oldest and largest of their kind and females may produce two or three times more eggs than females from the mid-Atlantic region. Eels prey on or scavenge aquatic invertebrates, amphibians and fish. In turn, large predators such as bass, lake trout, fish-eating birds and mammals may eat them.

When the Sargasso finally calls them back, yellow eels turn to a blackish-bronze color, their eyes enlarge, they fatten and develop a thicker skin and their digestive tract degenerates. They are then silver eels - the fifth and last stage of their lives. Eels are negatively phototactic - they avoid light - and usually wait for the darkest nights to descend rivers. On nights when clouds shroud the moon and rivers swell from autumn rains, silver eels finally begin to swim toward the sea. Then they swim deep below the ocean's surface where light does not penetrate. The life cycle of an American eel A. After spawning is completed and eggs hatch, billions of tiny larvae become entrained in the Gulf Stream, Florida Current and Antilles Current. The larvae, called leptocephali, are transparent and shaped like a willow leaf. Leptocephali metamorphose into a more recognizably eel-like juvenile form called glass eels. B. The glass eels migrate into estuaries along the coast, where they become pigmented. These eels are known as elvers.

Some elvers remain in the estuaries, but others migrate varying distances upstream, often for several hundred miles, depending on migration barriers and habitat along their way. C. Now in their yellow eel phase, the American eels will remain in the brackish and fresh waters of the rivers for a few up to 30 years. Females reach a maximum length of five feet, and males grow as long as two feet. D. Before beginning its life-ending migration back to the waters of the Sargasso Sea to spawn, yellow eels turn to a blackish-bronze color, their eyes enlarge, they fatten and develop a thicker skin and their digestive tract degenerates. They are then silver eels - the last stage of their lives. Images � Ethan Nedeau Concern about eels Eels may be declining throughout their range, but most scientists agree that we need much better data. Since all eels come from a single breeding population and disperse somewhat randomly to coastal watersheds, declines in some areas are thought to reflect a range-wide decline.

In a 1994 review paper published in the Canadian Journal of Fisheries and Aquatic Sciences, scientists reported an 81-fold decline in yellow eel recruitment to Lake Ontario over an eight-year span, based on the number of fish passing an eel ladder at the R.H. Saunders Hydroelectric Dam on the St. Lawrence River. Research published in Fisheries magazine in 2000, found that seven of 16 long-term datasets reviewed showed a significant decrease in yellow eels and silver eels, and the other datasets showed no trend. In the United States, commercial landings for eels declined from a high of 1.8 million pounds in 1985 to a low of 649,000 pounds in 2002, according to a study released in 2004 by the Atlantic States Marine Fisheries Commission (ASMFC). It is difficult to demonstrate a significant decline in the eel population. Scientists can count silver eels leaving a river and estimate the number of elvers that return, but know almost nothing about the steps in between.

Eel recruitment (the number of juvenile eels returning to estuaries and rivers) can be cyclic and erratic and scientists do not understand long-term population dynamics well enough to put recent declines into perspective. Part of the problem is that, until recently, recruitment was not being measured at all in some areas. Commercial landings provided some evidence of a decline, but these data depend on market conditions and fishing intensity and may not necessarily reflect a declining population. Eels were just not on the radar screen of most fisheries management agencies until very recently, so agencies are now scrambling to develop more consistent monitoring programs for eels. ASMFC is spearheading this effort. In 2004, due to continued population declines, the ASMFC recommended that the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service consider designating the Atlantic coastal stock of American eels a species of concern. This action would prompt a status review to determine whether the species should be considered a candidate for federal listing under the Endangered Species Act. Eels may indeed be experiencing a drastic decline, as some evidence suggests. The perceived eel decline may be due to natural cycles or influenced by factors far beyond the scope of local or regional management agencies.

For example, scientists have demonstrated a strong correlation between European eel (Anguilla anguilla) recruitment and the North Atlantic Oscillation, sea-surface temperature anomalies and position of the Gulf Stream. If these hemisphere-scale factors strongly influence American eel recruitment, then we may need more realistic expectations about what local protection and restoration can accomplish. However, there are clear indications of how we affect eels and how we could reduce mortality, giving us some sense of control. Juvenile eels congregate at the foot of dams; we have severed their paths between the ocean and watersheds. Killed, maimed and stunned eels swirl in eddies below hydropower dams after unwittingly passing through the only downstream path we have provided, through the whirring blades of turbines. Adult eels from many watersheds have cancers, vertebral malformations and high levels of chemical contaminants accumulated during their long residence in polluted waters. Commercial weirs, nets and traps capture elvers trying to swim upstream, yellow eels while in freshwater, and silver eels trying to return to the ocean. In some cases, most or all of the eels that enter a river may never return to the Sargasso Sea to spawn.

Restoring eels There are ways to protect and restore eels in a given river, but unfortunately, it might make little difference to the population as a whole. Restoring eels in a particular river does not ensure that elvers will return in ensuing years. This is the challenge of trying to manage a species with an enormous geographic range that randomly breeds in an unknown location in the middle of the ocean. Unlike salmon that return to the rivers where they were hatched, young eels do not return to the same rivers where their parents lived. We may be able to restore eels in the Ipswich River in Massachusetts, but how much does this river contribute to the entire spawning stock of the species? Eels need access to more habitat, and though rivers like the Merrimack, Penobscot and Saint John may provide much more habitat than smaller rivers, all rivers are important. A 1998 USFWS report estimated that dams reduced potential eel habitat by 91 percent from Connecticut to Maine. The American eel population, wide-ranging and previously thought to be robust against local losses, may not be replacing itself.

Every river is important because the collective effort to restore rivers represents a culture of environmental concern and because every river restored does add up to more eel habitat. Restoration Options One of the best things we can do for eels is to allow them unrestricted access to coastal watersheds and safe passage back to the sea. Thus, we need to focus on man-made migration barriers, especially dams and culverts. With over 60 rivers, hundreds of small streams and perhaps more than 7,000 dams in the Gulf of Maine watershed, it is difficult to decide where to focus limited resources. Four factors may be important in selecting priorities: 1. Focus on hydropower dams that are up for relicensing, especially near the coast. Hydropower dams are relicensed for 30 to 50 years; so in our lifetimes, we may get one chance to allow eels to get past a particular dam. The relicensing process is an ideal time to consider eel passage because of the intense scrutiny given to the economic and ecological costs and benefits of dam operations. Sometimes eel passage should be provided even when there are no such passageways further downstream or upstream - it just depends on which dams come up for relicensing first.

2. Focus on dams that restrict access to the largest amounts of high - quality habitat. High-quality habitat for eels may include rivers, ponds and lakes with relatively undisturbed habitat, good water quality, few environmental threats and a good prey base. Low-gradient rivers that connect a series of lakes and wetlands are often very productive habitats. 3. Assess all migration barriers in a watershed and focus on dams that have few or no barriers further upstream. It makes sense to focus on the first impassable barrier that juvenile eels encounter after entering rivers, but the distance to the next barrier - and habitat quality in between - is also an important consideration. Some rivers have many dams and may require a comprehensive plan to address eel passage at all dams. 4. Evaluate upstream and downstream passage at each dam. It would seem counterproductive to install elver ladders to get eels upstream if there is not a safe way for them to get back downstream. However, after eels pass a dam they may spend 10 to 30 plus years in the watershed, and allowing upstream passage now can essentially �bank� eels in the watershed with the hope that safe downstream passage will be provided by the time these fish mature.

Properly designed fishways can allow eel migration. However, salmon or shad fishways typically are designed for strong adult fish that can swim very fast and ascend small drops. These fishways do not work for small juvenile eels that are weak swimmers and cannot leap. Water velocities in excess of their swimming speed may block migration, but eels are good climbers and may ascend vertical surfaces provided there is a wet, rough substrate for them to climb on. A common fishway design that is specifically intended for elvers is a ramp with baffles and a climbing material, such as artificial mesh or bottlebrushes. The ramp can be installed on the face of, or adjacent to, a dam. Some eel �ladders� actually trap the elvers in a container that volunteers carry above the dam and release. Very few elver ladders have been installed on Gulf of Maine's rivers, but this could be an effective way of restoring eels and involving citizens in restoration projects. Culverts are an important impediment to juvenile eels because they concentrate flow, create high water velocities that may exceed the swimming speed of eels and usually have a smooth surface that does not provide a flow refuge.

Some culverts are elevated at one or both ends, and drops of only a few centimeters may be enough to block juvenile eels. Problem culverts should be replaced with adequately sized culverts with natural bottom habitat and hydraulic conditions that do not restrict eel movement. Providing safe passage for ocean-bound eels is a different challenge than getting juveniles upstream. Dams do not necessarily hinder downstream migration, especially low-head dams where water flows over the top or through open gates. The main problem is hydroelectric dams where water passes through turbines. The most effective way of getting eels past a hydroelectric dam is to turn off the turbines or increase spill over a dam. Some hydropower companies have license articles that require them to turn off turbines at night during peak migration. Another effective way to get eels downstream is to remove dams altogether. Dam removal reconnects fragmented river systems, restores habitat for migratory and resident fish, restores natural flow regimes and may improve water quality. The American eel may lack the charisma of other species whose habitat spans the ocean, tidewaters and headwaters of the Gulf of Maine watershed.

We embrace Atlantic salmon, shad and sturgeon, but the American eel - snake-like and active on the darkest nights - receives a more reluctant welcome. Yet eels are one of the most interesting and poorly understood fish species in our region. They will test our ability and resolve to reconnect fragmented ecosystems for the benefit of all species, and to think locally and globally to protect our natural resources. Ethan Nedeau is a science translator for the Gulf of Maine Council. He can be reached at ethannedeau@comcast.net . As American as ... the American Eel | Yesterday's Island/Today's Nantucket July 11, 2013 | Filed under: Island Science and tagged with: Island Science , nature science , Sarah Oktay As we finish celebrating our country’s birth as a nation, everyone is in a patriotic mood and what could be more patriotic than, the American Eel. Okay, I am sure you can think of something more patriotic, but this is a nature column. We have an adorable baby eel swimming around in one of the field station aquariums right now and I am betting the Maria Mitchell aquarium has a couple of them also.

Eels are extremely interesting creatures that have fed Nantucketers (native Wampanoag to islanders today) for thousands of years. Eels live most of their life in fresh water, swimming to salt water to spawn in the opposite direction (salt to fresh) of the better known salmon migration. This two habitat lifestyle is called being catadromous from the greek “kata” for “down or away or off” and “dromous” from the Greek for the “act of running”. So catadromous fish run away from the coast and their freshwater homes to breed or away from their birthplace to live depending on one’s take on the matter. For comparison, river herring follow an anadromous life cycle, maturing at sea, then migrating up freshwater streams to spawn in freshwater ponds. The American Eel Anguilla rostrata was first described in 1817 by Charles Alexandre’ Lesueur. Anguilla is Latin for eel, and rostrata is a Latin word that can mean either “breaked or curved” or “long nose”.

The European eel (Anguilla Anguilla or “eel eel” – how original) was the eel that was studied most frequently by 18th and 19th century scientists. Where eels came from was a mystery for hundreds of years because fishermen never caught anything that looked like baby eels like the little guy swimming in my tank. The first person to study eels was Aristotle. “He stated that they are born of “earth worms”, which emerged from the mud with no fertilization needed — they grew from the “guts of wet soil”. For a long time, nobody could prove Aristotle wrong. In 1777, the Italian Carlo Mondini found the creature’s gonads (negating that whole virgin birth idea) and proved that eels are fish. In 1876, the young Austrian student Sigmund Freud dissected hundreds of eels in search of the male sex organs (that explains a lot). He had to concede failure in his first published research paper, and turned to other issues in frustration” (parts excerpted from .) American eels (Anguilla rostrata), hatch from eggs in the Sargasso Sea in the North Atlantic and migrate to freshwater systems.

First it was believed European and American eels were the same species due to their similar appearance and behavior, but research has shown that they differ in chromosome count and various molecular genetic markers, and in the number of vertebrae, Anguilla anguilla have 110 to 119 and Anguilla rostrata 103 to 110 (sounds like fun huh, counting vertebrae?). The spawning grounds for the two species are in an overlapping area of the southern Sargasso Sea, with A. rostrata spawning a bit westward of A. Anguilla. After spawning in the Sargasso Sea and moving to the west, the leptocephali (eel stage two, see more below) of the American eel exit the Gulf Stream earlier than the European eel and begin migrating into the estuaries along the east coast of North America between February and late April at an age of about one year and a length of about 60 mm. Their European cousins keep riding the Gulf Stream across to Europe where they proceed to travel up creeks and streams to live out their adult lives. American (and European) eels go through a total of six stages in their lives.

In October, sexually mature eels swim away from freshwater and brackish harbor, marshes, and bays up and down the east coast down to the Sargasso Sea, an area of the Atlantic Ocean west of the Bahamas. In some cases, the trip is thousands of miles as they eels instinctively head for their spawning grounds. In January, the eels spawn there, and then die. The next generation of eels begins their journey as eggs released by the females in the Sargasso Sea, floating around in buoyant bubbles with up to 4 million of their brethren. The second stage is so strange that for over a hundred years of years (until about 1893) scientists thought it was a separate species called Leptocephalus brevirostris. These transparent, leaflike two-inch (five cm) creatures of the open ocean were named from the Greek leptocephalus meaning “thin- or flat-head”.

In 1886, French zoologist Yves Delage kept leptocephali alive in a laboratory tank in Roscoff until they matured into eels, and in 1896 Italian zoologist Giovanni Battista Grassi observed the transformation of a Leptocephalus into a round glass eel in the Mediterranean Sea, and recognized the importance of salt water to the process. Despite this discovery, the name leptocephalus is still used for larval eel ( .) So this second stage is a flattened, very larval looking see through “leaf” with eyes and a small gut floating around the Atlantic Ocean. The third stage is when the eel, becomes more “eel -shaped” although it is still transparent and thin and ribbon-like, but looking like an honest to god eel and called a “glass eel” at this point. It takes almost a year before these tiny eel larvae reach the coast of the United States as they are carried by ocean currents. Many glass eels are eaten by predators before they ever reach fresh water. When glass eels reach the coast, they metamorphosize into a new body shape and they become pigmented.

These rounder, darker eels are now called “elvers” and they are on average about 2.4 inches long. As eels mature they go though at least 2 more stages of coloration. After a few months as they begin to enter coastal bays and harbors and estuaries, the elvers transform into the first adult “yellow eel” stage. For their final stage as full grown adults they will have a greenish, yellowish-brown or black/gray body with a white belly and a rounded tail. This final mature stage is known as a “silver eel”. Adults remain in freshwater rivers and streams for the majority of their lives. Once they reach sexual maturity, they return to the Sargasso Sea to spawn and die. Eels usually live for at least five years. Some eels can reach 15-20 years old and one lived in an aquarium for 85 years (!) ( ). American eels have a continuous fin stretching around the tail from the back to the belly. Like many animal species, the females are the larger specimen; on average the males grow to 2 feet long and females grow 3-5 feet long.

Eels are nocturnal, or active at night and not active in the day. I see the most eels around the Field Station marsh while doing the midnight horseshoe crab surveys in which they’ll slither around my waders in the grass or near the shore. In the daytime they usually bury themselves in sediments or hide in rocks or within vegetation. Eel predators include larger fish and fish-eating birds such as gulls, eagles and ospreys. I have seen several ospreys take eels from the area over by the Life Saving Museum. American eels are opportunistic eaters consuming everything from carrion (dead animals) to fish, crustaceans, bivalves, polychaete worms, aquatic insects, and things that fall In the water (but not voraciously like piranha so don’t get images of scary B grade horror movies stuck in your head). The color of eels depends on not only their age but sometimes their habitat. Older eels are usually dark brown or greenish, with yellowish-white bellies. Their color can change from light to dark within a few hours.

This helps them blend in with their surroundings (more gray for rocky areas and greenish for heavily vegetated bottoms). The scales of these fish are embedded in their skin in an interesting somewhat haphazard opposite direction parquet floor effect, and then covered with a thick mucus coating (“slippery as an eel”). American Eels have large heads. American eel are found in fresh, brackish, and coastal waters from the southern tip of Greenland to northeastern South America. The American eel can survive even on moist ground for a few hours and has been found in landlocked lakes, traveling either over short distance in moist sloughs or underground in groundwater plumes (or often transported there by helpful humans). This site has some amazing pictures of eels in all stages and quite a bit of great information about eels: . “As American Eels move upstream, they often have to navigate around obstacles. Eels can climb over rocks, dams, and even waterfalls. They have the ability to absorb oxygen through their skins to breathe. This allows them to survive out of water for several hours. If an eel is found doing this, it is most often on a damp, rainy night. Eels can also travel by underground waterways.

This explains how eels are found in ponds that don’t have a stream leading to it.” I was fascinated to learn of new citizen science projects called “eel ramps” which aim to restore the connection between fresh water and salt water so that eels can move freely between their homes and their spawning sites. More about a constructed eel ramp in Massachusetts can be found at . American eels are economically important in various areas along the East Coast as bait for fishing for sport fishes such as the striped bass, or as a food fish in some areas. Their recruitment stage, the glass eel, are also caught and sold for use in aquaculture in a few areas, although this is now restricted in most areas. Eels were once an abundant species in rivers, and were an important fishery for aboriginal people. The construction of hydroelectric dams, however, has blocked their migrations and locally exterminated eels in many watersheds. For example, in Canada, the vast numbers of eels in the St. Lawrence and Ottawa Rivers have dwindled.

The number of juvenile eels in the Lake Ontario area decreased from 935,000 in 1985 to about 8000 in 1993 and was approaching zero levels in 2001. Rapid declines were also recorded in Virginia, as well as in New Brunswick and Prince Edward Island in Canada” (from ). The following information is from Clint Andrew’s excellent and highly recommended article about historic methods of fishing for both Wampanoag and early settlers republished in the Historic Nantucket Vol. 43, Number 3. (Fall 1994) p. 70-73 ( ) and originally published in the Bulletin of the Massachusetts Archeological Society in 1986. “The Beginnings: Indian Fish and Fishing Off Coastal Massachusetts” By J. Clinton Andrews “People using primitive equipment depend on great concentrations of fish to be successful. When the surf breaks over the barrier beaches of the fresh or brackish water ponds, eels, white perch, and winter flounders swarm at the very edge of the sand, particularly at night.

Eels may be picked up by hand when they are left stranded between surges of the ocean waves crossing the beach. In fall, the inner beach is where the mature eels in breeding condition, with large eyes and bronze and silver coloring, cruise back and forth waiting for the storm swells to wash over the beach. These eels were called “eeshaws” by the Indians, and are still known by that name on the islands. This is one of the principal reasons leading us to believe that many of the fishing methods and much of the fishing gear originated with the Indians rather than with the European colonists. Eels were a staple food of the early settlers and, apparently, for the Indians as well. In winter eels hibernate in muddy areas where they can be speared through holes cut in the ice. The prongs of the island’s traditional eel spear terminate in hooks that grasp the eel when the spear is pulled up. This design differs from the European trident, which ends in sharp barbed points. There is a spring run of eels as well.

Beginning with the first warm rain after the ice has melted, eels that have wintered in the muddy bottoms of ponds and estuaries work their way to the salt water. They progress slowly and in the daytime, or when the temperature drops, they shelter in aquatic vegetation. Finding and catching eels during this migration is also very easy.” Nantucket would not be Nantucket without Eel Point, named for the eels often caught in the shallows there. Local historian and author Fran Karttunen has written about early eeling and Madaket ditch in Yesterday’s Island ). Using eels as bait for stripers (bass) is a long time practice and a variety of books and web sites describe how to best hook a large bass with live eel bait. The population of American eels has been declining in an alarming manner since the 1970s, and has been in decline since Europeans arrived centuries ago. Their multi-stage life history has made American eels particularly susceptible to both over-fishing and habitat destruction or obstruction. In the same manner as herring and salmon, eels can be easily obstructed from their travels by the construction of dams ( ).

In situ (in the water) measurements of glass eel migration are now being observed by data stations and observatories (Long term ecological research or LEO by Rutgers) in the Atlantic Ocean near New Jersey ( ). Many problems face eels today including the destruction of their freshwater habitats and the continued pollution of the oceans. In many parts of the world, a swim-bladder nematode called Anguillicola crassus has parasitized eels, causing them difficulty in migration. The harvest of Sargassum from the Sargasso Sea has also been implicated in eel population degradation. Sargassum is a combination of several species of large-bodied pelagic macroalgae which arise in the Sargasso Sea and drift into other portions of the Atlantic. Floating masses of sargassum are known to provide critical habitat for a wide variety of sea life including dolphin fish (Coryphaena hippurus) (also called mahi mahi), juvenile sea turtles, and seabirds and may represent the single most important fish habitat in the blue waters off the Atlantic Coast.

Last but not least, eels have very sensitive noses required for their migration and they are susceptible to low oxygen levels and confusing man-made water column chemical olfactory residual artifacts, both of which are exacerbated by dams, locks, and coastal pollution. American eels are currently managed under the Interstate Fishery Management Plan (FMP) for American Eel, approved in 1999. Long-term FMP objectives include: encourage protection of eel spawning, nursery and growth habitats; and protect and enhance inland and coastal water quality to protect the health of the eel population and to reduce bioaccumulation of toxic substances. Additional information is contained in the ASMFC’s Source Document for Diadromous Fish. Both documents can be found on the ASMFC website at or by contacting the ASMFC Habitat Specialist at (202) 289-6400. . More info on eels can be found at . Did you like this article? Share it with your friends!

Question: What is a young eel usually called ?
Answer: ELVER