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Diagnostic Description

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Anguilliform body; no scales; no pectoral and pelvic fins; dorsal, caudal and anal fins confluent and reduced to a skin fold; gill openings merged into single slit underneath the head (Ref. 27732). Rice paddy eels are red to brown with a sprinkling of dark flecks across their backs; large mouths and small eyes (Ref. 44091).
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Crispina B. Binohlan
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Diseases and Parasites

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Dentiphilometra Infestation. Parasitic infestations (protozoa, worms, etc.)
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Allan Palacio
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Diseases and Parasites

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Proleptinae Disease (general sp. larvae). Parasitic infestations (protozoa, worms, etc.)
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Diseases and Parasites

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Eustrongylides Disease (larvae). Parasitic infestations (protozoa, worms, etc.)
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Allan Palacio
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Diseases and Parasites

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Trypanosoma Infection. Parasitic infestations (protozoa, worms, etc.)
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Allan Palacio
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Diseases and Parasites

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Pallisentis Infestation. Parasitic infestations (protozoa, worms, etc.)
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Allan Palacio
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Life Cycle

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Male builds a large free-floating bubblenest among the submerged vegetation close to the shoreline; eggs are spat into the nest after being laid; male guards the nest and continues to guard the young after hatching till they are on their own (Ref. 44091). Spawning occurs in shallow water (Ref. 2060). Sex reversal is completed in 8-30 weeks (Ref. 34260).
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Tom Froese
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Migration

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Potamodromous. Migrating within streams, migratory in rivers, e.g. Saliminus, Moxostoma, Labeo. Migrations should be cyclical and predictable and cover more than 100 km.
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Susan M. Luna
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Threats

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Least Concern (LC)
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Trophic Strategy

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Found in several types of wetlands from hillstreams to lowland swamps and rice paddy field (Ref. 94495).
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Pascualita Sa-a
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Biology

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Found in hill streams to lowland wetlands (Ref. 57235) often occurring in ephemeral waters (Ref. 44894). Adults are found in medium to large rivers, flooded fields and stagnant waters including sluggish flowing canals (Ref. 12975, 12693), in streamlets and estuaries (Ref. 41236). Benthic (Ref. 58302), burrowing in moist earth in dry season surviving for long periods without water (Ref 2686). Occasionally dug out in old taro fields, in Hawaii, long after the field has been drained; more frequently observed in stream clearing operations using heavy equipment to remove large amounts of silt and vegetation where the eels are hidden (Ref. 44091). Nocturnal predators devouring fishes, worms, crustaceans, and other small aquatic animals (Ref. 44091); also feed on detritus. Are protandrous hermaphrodites. The male guards and builds nest or burrow (Ref. 205). Marketed fresh and can be kept alive for long periods of time as long as the skin is kept moist (Ref. 12693). Good flesh (Ref. 2686). Important fisheries throughout Southeast Asia (Ref. 57235).
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Importance

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fisheries: commercial; aquaculture: commercial; aquarium: commercial
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分布

provided by The Fish Database of Taiwan
廣泛分布於亞洲東部及附近之大小島嶼,西起東南亞,東至菲律賓群島,北起日本,南至東印度群島。臺灣西部淡水域皆有其分布。
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臺灣魚類資料庫
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利用

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為經濟性食用魚,一般以活魚販售,市場上的黃鱔多是人工養殖,以南部養殖較多。在臺灣多以切片油炒食之;在華人地區視為補血強壯劑。
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描述

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體細長而呈圓柱狀,頭部膨大,頰部隆起。吻短而扁平;口開於吻端,斜裂;上下頜均具齒。眼甚小,隱於皮下。鰓裂在腹側,左右鰓膜癒合。沒有胸鰭與腹鰭;背鰭與臀鰭也都退化成皮褶,而與尾鰭相連。體裸露無鱗片,富黏液;側線完全,沿體側中央直走。體背為黃褐色,腹部顏色較淡,全身並有不規則黑斑紋。
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棲地

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主要棲息於稻田、湖泊、池塘、河流與溝渠等泥質地的水域,甚至沼澤、被水淹的田野或濕地等皆可見其蹤跡。喜鑽洞穴居。夜行性,以水生昆蟲、蠕蟲及小魚等為食。口腔皮褶可行呼吸作用,故可直接呼吸空氣。冬季與乾季時,會掘穴深至地下1-2公尺,數尾魚共棲。
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Asian swamp eel

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The Asian swamp eel, swamp eel, rice eel, or white ricefield eel (Monopterus albus) is a commercially important, air-breathing species of fish in the family Synbranchidae. Originating in the waters of East and Southeast Asia, it has been identified as an invasive species in the North American Everglades.

Taxonomy and evolution

The Asian swamp eel is a freshwater eel-like fish belonging to the family Synbranchidae. This family is native to the fresh and brackish waters in temperate, subtropical and tropical parts of Asia, as well as Australia, West Africa, and Middle and South America.[2] Monopterus albus, as traditionally defined, is native to much of East and Southeast Asia, ranging west as far as India.[1] Its taxonomy, however, is incorrect. Though Monopterus albus was initially thought to be a single widespread species, four known populations of the “species” in the southeastern United States may actually be three distinct species or taxa,[3] each originating from a different area in Asia.[4]

Monopterus albus is placed in the class or subclass Actinopterygii. It arose from the Osteichthyes, the first bony fish, whose fossil record dates back to the Triassic period. In turn, the bony fish came from the Acanthodii class of bony and cartilaginous fish. The common name of M. albus is somewhat of a misnomer, as the Asian swamp eel is not an eel, per se. Eels are of the order Anguilliformes, while M. albus is of the order Synbranchiformes.

Characteristics

"
Close-up of the heads of Asian swamp eels from Mindanao, Philippines

The Asian swamp eel has a scaleless, anguilliform (snake-like) body that grows to a meter or less, typically 25 to 40 cm as an adult. As a swamp eel, it has a tapering tail and blunt snout, and lacks pectoral and pelvic fins. The dorsal, anal, and caudal fins are rudimentary, with the caudal fin often absent.[2] These fins serve to protect the swamp eel against rolling, and assist in sudden turns and stops. Its gill membranes are fused, but one v-shaped gill is located beneath the head. Such a shape prevents reverse flow. Its body and head are dark, with dark olive or brown dorsal coloring and light orange ventral coloring. This coloration camouflages the aquatic predator; however, some are brightly colored with yellow, black, and gold spots.

The mouth is large and protractile, and both upper and lower jaws have tiny teeth for eating fishes, worms, crustaceans, and other small aquatic animals at night.[3]

Life history

M. albus is an evasive nocturnal animal. Its diet includes other fish, shrimp, crayfish, frogs, turtle eggs, aquatic invertebrates such as worms and insects, and occasionally detritus. Unlike the traits of its diurnal counterparts, M. albus life history traits (e.g. absolute density and survival) are difficult to measure accurately and can require decades of data to detect trends, as expressed by the lack of data available on the topic.[5] This results in an increase in the population of the invasive species without adequate time for population control methods.[5] Hence its wide distribution.[6]

The Asian swamp eel has versatile motility and is even capable of moving over dry land for short distances. This behavior is used for relocation according to resource availability. In the absence of water and food, the Asian swamp eel is able to survive long periods of drought by burrowing in moist earth. If its home becomes unsuitable, M. albus simply crawls ashore and makes its way to a more suitable home by slithering over the land in a snake-like fashion. These characteristics enhance its ability to disperse widely.[7] The swamp eel is a voracious general predator, making it a threat to native fishes, amphibians, and aquatic invertebrates.[7]

The survivorship of a species or cohort can be found by calculating the number or proportion of individuals surviving at each age. Type I survivorship is characterized by high survival in early and middle life,[8] followed by a rapid decline in survivorship in later life because of physiological changes. Type II survivorship[9] exhibits a constant mortality rate regardless of age because of consistent environmental threats.[10] M. albus survivorship falls between Type I, physiological, and Type II, ecological. They exhibit a great deal of parental care,[3] indicative of physiological survivorship. Large males construct bubble nests at the mouth of burrows and guard the eggs and young. Additionally, eel populations are dependent upon resource abundance, making their survivorship partially ecological.

Lifecycle

The Asian swamp eel is hermaphroditic. All young are females. As juvenile fish begin to mature, some take on the masculine phenotype. Males are capable of changing sex, allowing them to replenish female populations when female densities are low. This change from one sex to another can take up to a year.[11]

Spawning can occur throughout the year. Eggs are laid in bubble nests located in shallow waters. These bubble nests float at the water's surface and are not attached to aquatic vegetation. Females produce up to 1,000 eggs, each, per spawning event.[12]

Distribution and habitat

M. albus is native to the tropical and subtropical areas of northern India and Burma to China, Asiatic Russia, Japan, and Indo-Malayan Archipelago. It is one of the common fish found mainly in Asia, from India, Southern China to Malaysia and Indonesia. The fish is an important protein source for people in the northeastern part of Thailand. In Asia, the swamp eel is wide-ranging, occurring in both tropical and temperate climates. Swamp eels live in ditches, ponds, streams, and rice paddies.

Native habitat

The preferred environment for the Asian swamp eel includes a wide variety of freshwater-like shallow wetlands, stagnant waters, marshes, streams, rivers, ditches, canals, lakes, reservoirs, and ponds. While they prefer fresh water, they are also able to tolerate brackish and saline conditions, as seen in their colonization of American marshlands. Depths of less than 3 m are optimal. M. albus also easily tolerates cold temperatures — well below 0 °C - and a wide range of oxygen levels. This fish can obtain up to 25% oxygen from air cutaneously if not using gills underwater. Factors that typically limit dispersal — temperature, oxygen, and salinity — do not limit the Asian swamp eel.

Nonnative habitats

"
Invasive Asian swamp eels from Georgia in the United States

The Asian swamp eels were first introduced to the Hawaiian Islands around 1900.[13] Locations in the southeastern United States were not colonized until the end of the 20th century.[7] As early as 1990, Asian swamp eels were introduced to several ponds at a nature center near Atlanta, Georgia, within the Chattahoochee River drainage basin; individuals have since migrated to an adjacent marsh of the Chattahoochee River.[14] As a general predator, the Asian swamp eel has disrupted the ecological balance of the Everglades. In 1994, eel specimen were collected in ponds at the Chattahoochee Nature Center north of Atlanta. Subsequently, eels were collected from Florida waters in 1997 at two widely separated areas: one in southeast and the other in west-central Florida.[15] Tens of thousands of swamp eels are estimated to inhabit nearly 55 miles of two water canal systems in southern Florida, one in the North Miami area and another on the eastern side of Everglades National Park. Two other populations of the eel have been discovered since 1993: one outside of Tampa, Florida, and one in southern Georgia near the Chattahoochee River.[16] One or more of the populations are believed to be the result of an intentional or accidental release of the creature from a home aquarium or fish farm. Some populations may have been the result of an attempt by a few local residents to establish the eels as a food source. Asian swamp eels pose a threat to the homeostasis of Everglades National Park [7] by disrupting the natural interactions between native species and their environment. The species has an incredible ability to survive in adverse conditions, and the Everglade food web presents no known natural predators. Swamp eels survive even in the dry season when other non-native species normally die. To combat Asian swamp eel resilience, the American Fisheries Society is investigating methods for control, containment, and possible eradication.[14]

Control

The United States Geological Survey (USGS) proposed and implemented several methods in controlling the Monopterus albus population in Southern Florida.[3] Having documented eel distribution, behavior, and biology, the USGS discourages catching and transporting the eel for use as bait, food, or aquarium pets.[3] Water management practices are also changing to combat the invasive species. Selected water-control structures near established swamp eel populations are not being opened to prevent or at least retard dispersal, particularly into the waters of Everglades National Park.[7] Adult and juvenile swamp eels are obligate air-breathers, while young absorb oxygen directly through the skin. As such, standard fish poisons or pesticides (e.g., rotenone and antimycin-A) that are transmitted across the gill membrane may not be effective.[14] Serial pesticide dilutions of antimycin-A were tested and found to be innocuous. No change in morbidity and mortality were observed.[14]

Since all individuals begin as females before maturation, it would be best to implement removal of the species at the juvenile stage of the life cycle so as to affect the largest number of the reproductive population.[7]

Cuisine

In Indonesia, Cambodia, China, Laos, Myanmar, Thailand, Vietnam, and other Asian countries, swamp eels are farmed in polyculture rice fields and sold as a food product with the rice crop.

Disease

Swamp eels are an important host for Gnathostoma spinigerum. Eating raw or undercooked swamp eel can cause gnathostomiasis, a common disease in Thailand, Laos, Burma, and Vietnam. [17][18][19] Neurognathostomiasis has been reported in the US, but a link to imported swamp eels has not been proven.[20]

Gnathostoma binucleatum (which is native to the Americas) has not been previously reported to cause neurognathostomiasis, suggesting that G. spinigerum has been introduced to the Americas, but a survey of isolates has not confirmed this.[21]

References

  1. ^ a b Froese, Rainer and Pauly, Daniel, eds. (2019). "Monopterus albus" in FishBase. March 2019 version.
  2. ^ a b Nelson, J.S. Fishes of the World. 3rd. New York City: John Wiley & Sons, Inc., 1994. Print.
  3. ^ a b c d e Fuller, P.L., L.G. Nico, and M. Cannister. ( 11 30 2010). "Asian swamp eel." Nonindigenous Aquatic Species. United States Geological Survey. Retrieved 15 Mar 2011.
  4. ^ Collins, Timothy M., Joel C. Trexler, Leo G. Nico, and Timothy A. Rawlings (2002). "Genetic Diversity in a Morphologically Conservative Invasive Taxon: Multiple Introductions of Swamp Eels to the Southeastern United States." Conservation Biology. 16.4: 1024-1035. Print.
  5. ^ a b Zweig, Christa, and Frank Mazzotti. "Body Condition Analysis ...for Use in Everglades Restoration." Joint Conference on the Science and Restoration of the Greater Everglades and Florida Bay Ecosystem. Greater Everglades Ecosystem Restoration. University of Florida, Palm Harbor, FL. 13 Apr 2003. Keynote.
  6. ^ M.albus distribution Archived September 28, 2011, at the Wayback Machine
  7. ^ a b c d e f McPherson, B.F., Miller, R.L., Haag, K.H., and Bradner, Anne. (2000) Water Quality in Southern Florida. Florida,1996–98: U.S. Geological Survey Circular 1207, 32 p.
  8. ^ Early stage Type I survivorship Archived September 10, 2011, at the Wayback Machine
  9. ^ Type II survivorship Archived September 10, 2011, at the Wayback Machine
  10. ^ Campbell, Neil A.; Reece, Jane B. (2005). Biology. Benjamin Cummings. pp. 1177 pp. ISBN 0-8053-7146-X.
  11. ^ Talwar, P.K. "Asian Swamp Eel." FishBase.org. Retrieved 13 Mar 2011.
  12. ^ Chivers, C.J. (1999). “Swamp aka Rice Eels.” Wildlife Conservation. 102.2: 18.
  13. ^ Clay, Keith (2003). "Parasites Lost". Nature. 421: 585–586. doi:10.1038/421585a.
  14. ^ a b c d Reinert, T. R., C. A. Straight, et al. (2006). "Effectiveness of atimycin-A as a toxicant for control of invasive Asian swamp eels." North American Journal of Fisheries Management 26(4): 949-952.
  15. ^ Shafland, Paul L., Kelly B. Gestring, and Murray S. Stanford (2010). "An Assessment of the Asian Swamp Eel (Monopterus albus) in Florida." Reviews in Fisheries Science. 18.1: 25-39. Print.
  16. ^ Daerr, Elizabeth G.(2000). “Asian swamp eel invades Florida.” National Parks. 74.5/6: 13-14.
  17. ^ Setasuban P; Nuamtanong S; Rojanakittikoon V; Yaemput S; Dekumyoy P; Akahane H; Kojima S. (1991). "Gnathostomiasis in Thailand: a survey on intermediate hosts of Gnathostoma spp. with special reference to a new type of larvae found in Fluta alba". Southeast Asian J Trop Med Public Health. 22 Suppl: 220–4. PMID 1822890.
  18. ^ Akahane H, Setasuban P, Nuamtanong S, Horiuchi S, Koga M, Kojima S (1995). "A new type of advanced third-stage larvae of the genus Gnathostoma in freshwater eels, Fluta alba, from Nakhon Nayok, central Thailand". Southeast Asian J Trop Med Public Health. 26 (4): 743–7. PMID 9139388.
  19. ^ Tran Phu Manh Sieu; Tran Thi Kim Dung; Nguyen Thi Quynh Nga; Tran Vinh Hien; Anders Dalsgaard; Jitra Waikagul; K. Darwin Murrell (2009). "Prevalence of Gnathostoma spinigerum Infection in wild and cultured swamp eels in Vietnam". Journal of Parasitology. 95 (1): 246–248. doi:10.1645/GE-1586.1. PMID 19245276.
  20. ^ Catalano M, Kaswan D, Levi MH (2009). "Wider range for parasites that cause eosinophilic meningitis". Clin Infect Dis. 49 (8): 1283. doi:10.1086/605687. PMID 19780663.
  21. ^ Almeyda-Artigas RJ, Bargues MD, Mas-Coma S (2000). "ITS-2 rDNA sequencing of Gnathostoma species (nematoda) and elucidation of the species causing human gnathostomiasis in the Americas". J Parasitol. 86 (3): 537–544. doi:10.1645/0022-3395(2000)086[0537:IRSOGS]2.0.CO;2.

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Asian swamp eel: Brief Summary

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The Asian swamp eel, swamp eel, rice eel, or white ricefield eel (Monopterus albus) is a commercially important, air-breathing species of fish in the family Synbranchidae. Originating in the waters of East and Southeast Asia, it has been identified as an invasive species in the North American Everglades.

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