Identification: The Family Anguillidae contains a single genus (Anguilla) with 15-18 species (Nelson 1995; Smith 1999).
Anguillid eels are elongate, cylindrical eels with small, well-developed pectoral fins and a lower jaw that projects beyond the upper jaw. The lips are well developed and fleshy. The dorsal and anal fins are continuous around the tail. The dorsal-fin origin is located between the pectoral fins and anus. The scales are small, oval-shaped, and embedded in the skin.
The giant mottled eel Anguilla marmorata is distinguished from all other anguillid species by its mottled colour and the position of the dorsal fin. Adults have brown or black marbling on their backs over a grey-yellow background and a white belly. The marbling is less visible in younger specimens (Froese and Pauly 2004). The origin of the dorsal fin is more anterior than other Anguilla, occurring closer to the gill opening than to the anus. See Smith 1999; Rainboth 1996.
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Anguilla marmorata are found here.
Table last updated 2/26/2021
† Populations may not be currently present.
Ecology: Anguillid eels spend their adult lives in freshwater or estuarine habitats, then migrate to the ocean (sometimes over long distances) to reproduce. The leaf-shaped larvae common to all anguillids (called a leptocephalus) is especially suited to long distance migration. The leptocephali of A. marmorata spend about 114-132 days drifting in the plankton before recruiting to river mouths (Arai et al. 2002). The larvae then undergo metamorphosis into elvers and move into freshwaters. One report from Reunion Island in the Indian Ocean (Robinet et al. 2003) documented year-round upstream migration of A. marmorata elvers (80-160 mm TL). Budimawan (1997) documented elvers recruiting into four Pacific estuaries at a mean size of 40-50 mm TL after an estimated 73-86 days at sea.
After migration to brackish or fresh waters, eels feed and grow for about 8-20 years before returning to sea for reproduction. In South China, females migrate to sea at a mean weight of 11 kg, a mean length of 150 cm and a mean estimated age of 15 years (Williamson and Boëtius 1993). The species is long-lived; individuals may reach up to 40 years in age (Froese and Pauly 2004).
Anguilla marmorata is nocturnal, feeding on a wide range of prey, especially crabs, fish and frogs (Skelton 1993).
Means of Introduction: Means of introduction unclear; possible food-fish escape, aquarium escape or waif arrival.
Anguillid eels are an important food source in many areas of the world, and are widely cultured. Large, live eels are especially sought-after by restaurateurs. In 1992, a typical 12 kg A. marmorata retailed for US $1,000 in China (Williamson and Boëtius 1993).
Because some anguillid species are capable of overland movement, especially during rainy periods (McCosker 1989), care should be taken to appropriately contain animals in aquaculture facilities.
References: (click for full references)
Arai, T.,M. Marui, M. J. Miller and K. Tsukamoto. 2002. Growth history and inshore migration of the tropical eel, Anguilla marmorata
, in the Pacific. Marine Biology 140: 309-316.
Budimiwan. 1997. The early life history of the tropical eel Anguilla marmorata (Quoy & Gaimard, 1824) from four Pacific estuaries, as revealed from otolith microstructural analysis. Journal of Applied Ichthyology 13: 57-62.
Froese, R. and D. Pauly. Editors. 2004. FishBase. World Wide Web electronic publication. www.fishbase.org, version (09/2004).
McCosker, J. E. 1989. Freshwater eels (Family Anguillidae) in California: Current conditions and future scenarios. California Fish and Game 75(1): 4-10
McCosker, J., R. Bustamante and G. Wellington. 2003. The freshwater eel, Anguilla marmorata, discovered in Galápagos. Noticias de Galápagos 62: 2-6.
Mundy, B. C. 2005. Fishes of the Hawaiian Archipelago. Bishop Museum Bulletin in Zoology, Number 6.
Nelson, J. S. 1994. Fishes of the World. 3rd Edition. John Wiley and Sons, Inc.
Okada, Y. 1960. Studies on the Freshwater Fishes of Japan. Prefectural University of Japan, Tsu, Mie Prefecture.
Rainboth, W.J., 1996. Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes. FAO, Rome, 265 p.
Robinet, Tony, Sylive Guyet, Gérard Marquet, Béatrice Mounaix, Jean-Michel Olivier, Katsumi Tsukamoto, Pierre Valade and Eric Feunteun. 2003. Elver invasion, population structure and growth of marbled eels Anguilla marmorata in a tropical river on Reunion Island in the Indian Ocean. Environmental Biology of Fishes 68: 339-348
Shiao, J. C., Y. Iizuka, C. W. Chang and W. N. Tzeng. 2003. Disparities in habitat use and migratory behaviour between tropical eel Anguilla marmorata and temperate eel A. japonica in four Taiwanese rivers. Marine Ecology Progress Series. 261: 233-242.
Skelton, P.H., 1993. A complete guide to the freshwater fishes of southern Africa. Southern Book Publishers (Pty) Ltd., 388 p.
Smith, D. G. 1999. Anguillidae. Freshwater eels. Pages 1630-1636 In: Carpenter, K. E. and V. H. Niem, (Eds.). FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volume 3. Batoid fishes, chimaeras and bony fishes par 1 (Elopidae to Linophrynidae).
Williamson, Gordon R. and Jan Boëtius. 1993. The eels Anguilla marmorata and A. japonica in the Pearl River, China, and Hong Kong. Asian Fisheries Science 6: 129-138.
Wright, W. 2003. 10-pound eel found on Maui could be harmful. Honolulu Advertiser; January 27, 2003.
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.