Japanese Eel (Anguilla japonica) Ecological Risk Screening Summary

U.S. Fish and Wildlife Service, March 2011 Revised, August 2018, November 2019 Web Version, 5/1/2020

Organism Type: Fish Overall Risk Assessment Category: Uncertain

Photo: H. T. Cheng. Licensed under CC BY-NC 4.0. Available: https://www.inaturalist.org/photos/8660994. (August 2018).

1 Native Range and Status in the United States Native Range From Froese and Pauly (2018):

“Asia: Japan to the East China Sea, Taiwan, Korea, China and northern Philippines.”

Status in the United States Although FAO (2018) reports Anguilla japonica as established in the wild in the United States, this could not be verified by any other source.

From FAO (2018):

“Anguilla japonica introduced to United States of America from Japan”

“Status of the introduced species in the wild : Established”

1

From Schofield and Fuller (2018):

“Because of potential impacts, California has made the importation, sale, or culture of live anguillids illegal.”

There is no indication that this species is in trade in the United States.

Means of Introductions in the United States From FAO (2018):

“Introducer : Unknown Reasons of Introduction : 1) unknown”

Remarks From Fuller et al. (2018):

“An adult eel was captured from the Sacramento-San Joaquin Delta, near Stockton, San Joaquin County, California, in 1964, but there is confusion surrounding its identity. The voucher specimen (SIO 64-219) is a skin only and was reported to be A. rostrata by Skinner (1971); however, the same specimen was reported as being either A. rostrata or A. anguilla by McCosker (1989), and as Anguilla sp. by Williamson and Tabeta (1991). […] Although not outside their native range, eels tentatively identified as this species have been used extensively for aquaculture in several areas, including Texas and South Carolina. The exact origin, and therefore positive identity of eels cultured in Texas has been somewhat uncertain. The Texas fish are believed to be native eels from the southeast coast, but there is a possibility that the fish actually may represent one of the foreign species, A. japonica or A. anguilla.”

From Schofield and Fuller (2018):

“There is still some uncertainty associated with the identification of the two California A. anguilla specimens. Because each had 114 vertebrae, Williamson and Tabeta (1991) indicated that these fish cannot be reliably distinguished from A. japonica.”

2 Biology and Ecology Taxonomic Hierarchy and Taxonomic Standing From ITIS (2018):

“Kingdom Animalia Subkingdom Bilateria Infrakingdom Deuterostomia Phylum Chordata Subphylum Vertebrata Infraphylum Gnathostomata Superclass Actinopterygii

2

Class Teleostei Superorder Elopomorpha Order Anguilliformes Suborder Anguilloidei Family Anguillidae Genus Anguilla Species Anguilla japonica Temminck and Schlegel, 1846”

From Eschmeyer et al. (2018):

“Current status: Valid as Anguilla japonica Temminck & Schlegel 1846. Anguillidae.”

Size, Weight, and Age Range From Froese and Pauly (2018):

“Max length : 150 cm TL male/unsexed; [Smith 1999]; common length : 40.0 cm SL male/unsexed; [Nichols 1943]; max. published weight: 1.9 kg [Okamura et al. 2002]”

From Jacoby and Gollock (2014):

“As with many eel species, the generation times for A. japonica are highly variable depending on sex, individual variation and locality/latitude. For example, Kotake et al. (2007) studied A. japonica from three different latitudes and found that the age of males at maturity ranged from 4 to 10 years and females from 3 to 17 years, but younger, small males were likely not adequately sampled. Other studies on the average age of silver-phase Japanese Eels, provide estimates of 6.9 and 7.8 years (Kotake et al. 2005) and 8.3 and 9.9 years (Yokouchi et al. 2009) for male and female eels, respectively, suggesting that the average generation length of A. japonica lies somewhere between 7 and 10 years.”

Environment From Froese and Pauly (2018):

“Marine; freshwater; brackish; demersal; catadromous [Riede 2004]; depth range 1 - 400 m [Shao and Lim 1991]. […] 4°C - 27°C [Baensch and Riehl 1995; assumed to be recommended temperature range in aquaria]”

From Jacoby and Gollock (2014):

“The species is catadromous, spending its lifetime in freshwater, estuaries and coastal environments, including rivers, streams and wetlands, but migrates thousands of kilometres to spawn.”

3

Climate From Froese and Pauly (2018):

“Subtropical; […] 46°N - 15°N, 105°E - 170°E”

Distribution Outside the United States Native From Froese and Pauly (2018):

“Asia: Japan to the East China Sea, Taiwan, Korea, China and northern Philippines.”

Introduced From FAO (2018):

“Anguilla japonica introduced to Germany from unknown”

“Anguilla japonica introduced to France from unknown”

“Anguilla japonica introduced to Italy from unknown”

“Anguilla japonica introduced to Brazil from Japan Date of introduction: 1977 onwards”

“Anguilla japonica introduced to Thailand from Japan, China Date of introduction: 1973”

“Anguilla japonica introduced to Guam from unknown”

“Anguilla japonica introduced to United Kingdom from Far East”

“Anguilla japonica introduced to Cambodia from [unknown]”

According to FAO (2018), the “Status of the introduced species in the wild” in all of these locations is “Not established”, except in Guam, the United Kingdom, and Cambodia, where it is “Unknown”. Froese and Pauly (2018) report A. japonica as “probably not established” in Guam and “probably established” in Cambodia. In contrast, Nuov et al. (2005) do not report A. japonica as introduced to Cambodia, and Suryati et al. (2019) depict A. japonica’s distribution in Southeast Asia as restricted to the Philippines.

From Silfvergrip (2009):

“[…] the Japanese eel (Kirk 2003) have been found in European natural waters and/or aquaculture but it is not likely that transplanted eels may hybridize with the native species or establish reproducing populations.”

4

Means of Introduction Outside the United States According to FAO (2018), “Reasons of Introduction” of Anguilla japonica to Germany, France, Italy, Brazil, Thailand, Cambodia, and Guam is “aquaculture”. In the United Kingdom, the reason is “accidental”.

Short Description From Jacoby and Gollock (2014):

“Typical diagnostic features of A. japonica include a fleshy and smooth elongate body that is cylindrical anteriorly and laterally compressed posteriorly. The mouth corner extends to the posterior margin of the eyes with the lower jaw slightly longer than the upper. The snout is depressed and stout and the distance between dorsal fin origin and vent varies from 9.0 to 13.5 % of total body length and the head length 11.2 to 11.9 % of the body length. The length of pectoral fin, at least during the yellow eel stage, is between 2.2 and 3.7 % of head length. The dorsal and anal fins are confluent with the caudal fin. The distance between origins of dorsal and anal fins is shorter than the head length. The body is covered with rudimentary embedded scales that are arranged in small groups and placed obliquely at right angles to those of neighbouring groups. Overall, A. japonica is plain-coloured and neither marbled or mottled (FAO).”

From Froese and Pauly (2018):

“Vertebrae: 114 - 118.”

Biology From Jacoby and Gollock (2014):

“Little is known about the marine component of anguillid life histories in general, but A. japonica stands alone in having a well-studied spawning ecology (Kimura and Tsukamoto 2006, Tsukamoto 2009, Tsukamoto et al. 2011). The Japanese Eel’s spawning area has been identified as the region along the western side of the seamount chain of the Mariana Ridge (Tsukamoto 1992, 2006, 2009; Tsukamoto et al. 2003). The eggs and the spawning adults were discovered in the west of Mariana Ridge (Chow et al. 2009, Kurogi et al. 2011, Tsukamoto et al. 2011). The depths where adults and newly hatched larvae were captured indicate that spawning occurs in shallower layers of 150–200 m and not at great depths (Tsukamoto et al. 2011).”

“Its larvae develop as leaf-shaped leptocephali in the pelagic ocean environment and over the course of five to six months they drift towards their estuarine recruitment areas (Kuroki et al. 2009, Shinoda et al. 2011) on oceanic currents and then metamorphose into transparent glass eels before becoming pigmented elvers in estuaries. Pigmentation stages of glass eels of A. japonica are described by Fukuda et al. (2013). Age upon arrival to estuaries is estimated between 154 and 182 days while age at metamorphosis as between 115-137 days. Therefore, time from metamorphosis to estuarine arrival is thought to be between 32 and 45 days. As such the total time between spawning and completion of metamorphosis is likely to be a principle factor in the long distance dispersal of this species (Cheng and Tzeng 1996). A full description of the timing of glass eel recruitment to different shores is given in the Geographic Range section. The

5

subsequent timing of upstream migration of glass eels depends on the water temperature, tidal current and moon phase (Tzeng 1985). In Korea, glass eels are caught in the Geum River when temperatures are between 5 and 15°C and the annual catch in this river is highly representative of catch throughout the rest of Korean freshwater habitat (T.W. Lee unpub. data).”

“Following this metamorphosis, a proportion of the population then moves upstream to feed and grow. However, some A. japonica never enter freshwater, but remain in estuaries or nearby marine habitats and have been referred to as marine residents or ‘sea eels’ (Tsukamoto et al. 1998). Analysis of the strontium;calcium ratios within the otoliths of maturing eels reveals a signature of the transition between these environments and it has been estimated that between 40-50% of the eels in some areas might be estuarine/marine residents (Kotake et al. 2005). This suggests that there is some flexibility in the continental migration of some A. japonica, which shows an ability to adapt to various habitats and salinities and implies that movement into freshwater is clearly not obligatory as evidenced by these different ecophenotypes. As such A. japonica are deemed facultatively catadromous (Tsukamoto and Arai 2001; Tzeng et al. 2002, 2003). During their growth phase, A. japonica feed mostly on invertebrates such as benthic crustaceans and insect larvae, and also on small fishes (Kaifu et al. [2013]).”

“As with many eel species environmental conditions may strongly influence recruitment and indeterminate growth rates and individual variability restrict our ability to predict how the Japanese Eel is likely to deal with environmental change.”

Human Uses From Jacoby and Gollock (2014):

“Together with A. anguilla (the European Eel), A. japonica has one of the longest histories of fishing, stocking and farming for consumption purposes of all the Anguilla species. Japanese Eels are utilized/traded fresh, smoked, canned and frozen and eaten steamed, broiled and baked and also to some extent in East Asian medicines. While consumption drives the main demand for this species, in both Japan and Korea, Anguilla spp. eel skin is also used in the manufacture of fashion accessories such as bags and wallets.”

“Anguilla japonica was historically caught in waters throughout its range, predominantly in Japan, mainland China, Taiwan and the Republic of Korea, with large eels caught destined directly for consumption or small eels destined for farming, from the early 1900s onwards (Ringuet et al. 2002). Globally, these are also the main eel farming, trading and consuming countries/ territories, with Japan in particular having a long tradition of consumption of A. japonica eels.”

“Global FAO catch data for Japanese eels is available for the period of 1950-2011. From the 1950s to 1986, annual catches fluctuated between 2,000 and 3,600 tonnes (in 1969), averaging 2,600 tonnes per year. From 1987 onwards catches gradually declined by a 50-100 tonnes on average per year, and in 2011 they were only 300 tonnes. Over 90% of these catches were reported by Japan, with Taiwan and Korea only reporting small quantities, and mainland China none. These catches include all life stages, except the oceanic larval stage (FAO 2013).”

6

Silfvergrip (2009) documented online Japanese eel sellers; the sellers reported their locations as Chile, Hong Kong, and the Philippines. Online Japanese eel buyers reported their locations as Southeast Asia, North America, South America, western Europe, eastern Europe, eastern Asia, Middle East, Africa, and Oceania. Silfvergrip (2009) reports global production (including capture and various forms of aquaculture) of A. japonica at 84,000 to 258,000 metric tons in the years from 1987 to 2006, according to FAO data.

Diseases No OIE-reportable diseases (OIE 2019) have been documented in this species.

Poelen et al. (2014) list the following as parasites of Anguilla japonica: Azgyia anguillae, Hebesoma violenteum, Gyrodactylus egusae, Gyrodactylus joi, Pseudodactylogyrus macrorchis, Cotylaspis chinensis, Phyllodistomum anguillae, Phyllodistomum macrobranchicola, Acanthocephalus gotoi, Longicollum alemniscus, Pallisentis cleatus, Bothriocephalus brachysoma, Bothriocephalus japonicus, Nybelinia anguillicola, Gyrodactylus nipponensis, Pseudodactylogyrus microrchis, Philometra sanguinea, Heliconema heliconema, Camallanus zacconis, Cucullanus anguillae, Cucullanus cyprinid, Cucullanus filiformis, Spinitectus gigi, Heliconema longissima, Rhabdochona minjiangensis, Cotylaspis sinensis, Rhipidocotyle illense, Azygia acuminate, Azygia anguillae, Bucephalus binidentacularis, Anguillotrema papillatum, Phyllodistomum sinense, Centrocestus formosanus, Genarchopsis anguillae, Genarchopsis goppo, Genolopa loborchis, Proctotrematoides anguillae, Proctotrematoides pisodontophidis, Opegaster lobulus, Plagioporus sinicus, Urorchis brachycaecum, Tubulovesicula angusticauda, Pseudodactylogyrus bini, Pseudodactylogyrus anguillae, Heliconema brevispiculum, Gyrodactylus anguillae, Anguillicola novaezelandiae, Anguillicola globiceps, Bothriocephalus claviceps, Gnathostoma hispidum, Anguillicola crassus, Gnathostoma spinigerum, Anguillicola novaezelandiae, Anguillicola globiceps, and Bothriocephalus claviceps (Strona et al. 2013; Benesh et al. 2017; Smithsonian Institution no date).

From Froese and Pauly (2018):

“Centrocestus Infestation, Parasitic infestations (protozoa, worms, etc.) Herpesviral Gill Filament Necrosis, Viral diseases Aeromonosis, Bacterial diseases Edwardsiellosis, Bacterial diseases Enteric Septicaemia of Catfish, Parasitic infestations (protozoa, worms, etc.)”

Threat to Humans From Froese and Pauly (2018):

“Harmless”

3 Impacts of Introductions No information was available on impacts of introduction of A. japonica itself, only on impacts of introduction of its parasites.

7

From Silfvergrip (2009):

“The eel parasite Anguillicola crassus originally infected the Japanese eel (Anguilla japonica), but is reported from European eel since an introduction due to a live eel import from East Asia in the early 1980s. The parasite is now reported from all over Europe, North Africa and eastern United States (Kirk 2003).”

From Knopf (2006):

“The swimbladder nematode Anguillicola crassus originates from Asia where it is a parasite of the Japanese eel Anguilla japonica. After its introduction to Europe about 25 years ago, the parasite spread rapidly within the indigenous populations of the European eel Anguilla anguilla and subsequently the prevalence and mean intensity appeared to stabilize. Under experimental and aquaculture conditions the naïve new host appears to be more susceptible to A. crassus compared to the original host.”

“Based on the present knowledge of the epidemiology and pathology of A. crassus in the European eel, and the host’s immune- and stress responses to this parasite, one must assume that A. crassus is a serious threat to indigenous eel populations, which are not adapted to this invasive parasite species (Sures & Knopf, 2004).”

“When migrating from the intestine to the swimbladder wall, A. crassus larvae damage tissues of the eel and induce inflammatory responses within 5h post-infection in European eels (Haenen et al., 1989).”

“Differences in the pathogenicity of A. crassus in the European and Japanese eels became obvious in the culture of both eel species in Japan: pathological changes in the swimbladder wall due to heavy infections with A. crassus are reported for farmed European eels, but the parasite causes ‘almost no serious damage’ to farmed Japanese eels (Egusa, 1979; Nagasawa et al., 1994).”

From Schofield and Fuller (2018):

“Because of potential impacts, California has made the importation, sale, or culture of live anguillids illegal.”

4 History of Invasiveness The history of invasiveness for Anguilla japonica is “Low.” Although A. japonica has been introduced to several countries outside its native range, there is no clear evidence that it has become established in any of these locations. Global trade in this species is substantial, with at least 84,000 metric tons of A. japonica produced in every year between 1987 and 2006. Therefore, the species meets the criteria for low history of invasiveness. However, it is important to note that introduction of a harmful eel parasite has been associated with the introduction of A. japonica outside its native range.

8

5 Global Distribution

Figure 1. Known global distribution of Anguilla japonica. Observations are reported from Japan, North Korea, South Korea, China, Taiwan, and the Pacific Ocean. Map from GBIF Secretariat (2017). Because RAMP climate matching analysis is not valid for marine waters, no marine occurrences were used in the climate matching analysis.

6 Distribution Within the United States No information available.

7 Climate Matching Summary of Climate Matching Analysis The climate match presented in here refers only to where the species can survive in freshwater and brackish environments and not in the open ocean, where it reproduces and juvenile stages live.

The overall Climate 6 score (Sanders et al. 2014; 16 climate variables; Euclidean distance) for the contiguous United States was 0.129, which is a high climate match (scores between 0.103 and 1, inclusive, are classified as high). Except for the West, Maine and coastal New England,

9

and the area around Lake Superior, where the climate match was low, most of the contiguous United States had a medium-low to medium climate match. There were high matches in parts of South Carolina and peninsular Florida.

Figure 2. RAMP (Sanders et al. 2018) source map showing weather stations in China, Japan, North Korea, South Korea, and Taiwan selected as source locations (red) and non-source locations (gray) for Anguilla japonica climate matching. Source locations from GBIF Secretariat (2017). Selected source locations are within 100 km of one or more species occurrences, and do not necessarily represent the locations of occurrences themselves.

10

Figure 3. Map of RAMP (Sanders et al. 2018) climate matches for Anguilla japonica in the contiguous United States based on source locations reported by GBIF Secretariat (2017). 0/Blue = Lowest match, 10/Red = Highest match.

The High, Medium, and Low Climate match Categories are based on the following table:

Climate 6: Overall (Count of target points with climate scores 6-10)/ Climate Match (Count of all target points) Category 0.000≤X≤0.005 Low 0.005

8 Certainty of Assessment Because of its monetary value, extensive information is available about the biology, life history, and trade history of Anguilla japonica. A. japonica has been introduced outside of its native range for aquaculture, although no established nonnative populations have been confirmed. The climate match for this species is only applicable to the phases of the lifecycle in fresh or brackish water. It is unknown whether A. japonica reproduction, which only occurs in marine

11

environments, could be completed offshore of the United States. For this reason, the certainty of this assessment is medium.

9 Risk Assessment Summary of Risk to the Contiguous United States Anguilla japonica, the Japanese Eel, is a catadromous eel species native to Japan, the East China Sea, Taiwan, Korea, China and the northern Philippines. It is highly valuable as a food fish and is both commercially harvested and used in aquaculture. It has been introduced to several countries outside of its native range through aquaculture, but no established nonnative populations have been confirmed. One source reports an established population in California, but this information could not be verified. California bans the importation, sale, or culture of live anguillids. History of invasiveness is low because of the combination of lack of confirmed establishment and substantial trade history. However, introduction of a harmful parasite, capable of infecting other eel species, has been associated with A. japonica introduction. This species has a high climate match with the contiguous United States for the portions of its lifecycle in fresh and brackish water. A. japonica needs a marine environment to reproduce. The certainty of this assessment is medium because only a portion of the lifecycle (non-reproductive) is included in the climate match. The overall risk assessment category is uncertain.

Assessment Elements  History of Invasiveness (Sec. 4): Low  Overall Climate Match Category (Sec. 7): High  Certainty of Assessment (Sec. 8): Medium  Remarks/Important additional information: Carrier of the parasitic swimbladder nematode Anguillicola crassus, which can infect and harm other eel species.  Overall Risk Assessment Category: Uncertain

10 Literature Cited Note: The following references were accessed for this ERSS. References cited within quoted text but not accessed are included below in Section 11.

Eschmeyer WN, Fricke R, van der Laan R, editors. 2018. Catalog of fishes: genera, species, references. Available: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp (August 2018).

[FAO] Fisheries and Agriculture Organization of the United Nations. 2018. Database on introductions of aquatic species. Rome: FAO. Available: http://www.fao.org/fishery/introsp/search/en (August 2018).

Froese R, Pauly D, editors. 2018. Anguilla japonica (Temminck & Schlegel, 1846). FishBase. Available: https://www.fishbase.de/summary/Anguilla-japonica.html (August 2018).

12

Fuller P, Nico L, Neilson M, Dettloff K, Sturtevant R. 2018. Anguilla rostrata (Lesueur, 1817). Gainesville, Florida: U.S. Geological Survey, Nonindigenous Aquatic Species Database. Available: https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=310 (August 2018).

GBIF Secretariat. 2017. GBIF backbone taxonomy: Anguilla japonica, Temminck & Schlegel, 1846. Copenhagen: Global Biodiversity Information Facility. Available: https://www.gbif.org/species/5213022 (August 2018).

[ITIS] Integrated Taxonomic Information System. 2018. Anguilla japonica (Temminck & Schlegel, 1846). Reston, Virginia: Integrated Taxonomic Information System. Available: https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=161 134#null (August 2018).

Jacoby D, Gollock M. 2014. Anguilla japonica. The IUCN Red List of Threatened Species 2014: e.T166184A1117791. Available: http://www.iucnredlist.org/details/166184/0 (August 2018).

Knopf K. 2006. The swimbladder nematode Anguillicola crassus in the European eel Anguilla anguilla and the Japanese eel Anguilla japonica: differences in susceptibility and immunity between a recently colonized host and the original host. Journal of Helminthology 80:129-136.

Nuov S, Viseth H, Vibol O. 2005. Present status of alien species in aquaculture and aquatic ecosystem in Cambodia. Pages 75-86 in Bhujel RC, Funge-Smith S, Olin PG, Phillips MJ, editors. International mechanisms for the control and responsible use of alien species in aquatic ecosystems. Rome: FAO. Report of an ad hoc expert consultation, Xishuangbanna, China, 27-30 August 2003.

[OIE] World Organisation for Animal Health. 2019. OIE-listed diseases, infections and infestations in force in 2019. Available: http://www.oie.int/animal-health-in-the- world/oie-listed-diseases-2019/ (June 2019).

Poelen JH, Simons JD, Mungall CJ. 2014. Global Biotic Interactions: an open infrastructure to share and analyze species-interaction datasets. Ecological Informatics 24:148-159.

Sanders S, Castiglione C, Hoff M. 2014. Risk Assessment Mapping Program: RAMP. U.S. Fish and Wildlife Service.

Schofield PJ, Fuller P. 2018. Anguilla anguilla (Linnaeus, 1758). Gainesville, Florida: U.S. Geological Survey, Nonindigenous Aquatic Species Database. Available: https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=308 (August 2018).

Silfvergrip AMC. 2009. CITES identification guide to the freshwater eels (Anguillidae) with focus on the European eel Anguilla anguilla. Version 1.1. Stockholm: Swedish Environmental Protection Agency.

13

Suryati NK, Pamungkas YP, Muthmainnah D. 2019. Addressing the issues and concerns on anguillid eel fisheries in Southeast Asia. Fish for the People 17:19-24.

11 Literature Cited in Quoted Material Note: The following references are cited within quoted text within this ERSS, but were not accessed for its preparation. They are included here to provide the reader with more information.

Baensch HA, Riehl R. 1995. Aquarien Atlas. Volume 4. Melle, Germany: Mergus Verlag GmbH, Verlag für Natur-und Heimtierkunde.

Benesh DP, Lafferty KD, Kuris A. 2017. A life cycle database for parasitic acanthocephalans, cestodes, and nematodes. Ecology 98:882.

Cheng PW, Tzeng WN. 1996. Timing of metamorphosis and estuarine arrival across the dispersal range of the Japanese eel Anguilla japonica. Marine Ecology Progress Series 131:87-96.

Chow S, Kurogi H, Mochioka N, Kaji S, Okazaki M, Tsukamoto K. 2009. Discovery of mature freshwater eels in the open ocean. Fisheries Science 75:257-259.

Egusa S. 1979. Notes on the culture of the European eel (Anguilla anguilla L.) in Japanese eel- farming ponds. Rapports et Proces-Verbaux des Réunions. Conseil International pour l’Éxploration de la Mer 174:51-58.

FAO. 2013. Capture and aquaculture production (1950-2011) and fisheries commodities production and trade (1976-2009) data.

Fukuda N, Miller MJ, Aoyama J, Shinoda A, Tsukamoto K. 2013. Evaluation of the pigmentation stages and body proportions from the glass eel to yellow eel in Anguilla japonica. Fisheries Science 79(3):425-438.

Haenen OLM, Grisez L, De Charleroy D, Belpaire C, Ollevier F. 1989. Experimentally induced infections of European eel Anguilla anguilla with Anguillicola crassus (Nematoda, Dracunculoidea) and subsequent migration of larvae. Diseases of Aquatic Organisms 7:97-101.

Kaifu K, Miyazaki S, Aoyama J, Kimura S, Tsukamoto K. 2013. Diet of Japanese eels Anguilla japonica in the Kojima Bay-Asahi River system, Japan. Environmental Biology of Fishes 96:439-446.

Kimura S, Tsukamoto K. 2006. The salinity front in the North Equatorial Current: a landmark for the spawning migration of the Japanese eel (Anguilla japonica) related to the stock recruitment. Deep-Sea Research II 53:315-325.

14

Kirk RS. 2003. The impact of Anguillicola crassus on European eels. Fisheries Management and Ecology 10:385-394.

Kotake A, Okamura A, Yamada Y, Utoh T, Arai T, Miller MJ, Oka H, Tsukamoto K. 2005. Seasonal variation in the migratory history of the Japanese eel Anguilla japonica in Mikawa Bay, Japan. Marine Ecology Progress Series 293:213-225.

Kotake A, Arai T, Okamura A, Yamada Y, Utoh T, Oka HP, Miller MJ, Tsukamoto K. 2007. Ecological aspects of the Japanese eel, Anguilla japonica, collected from coastal areas of Japan. Zoological Science 24:1213-1221.

Kurogi H, Okazaki M, Mochioka N, Jinbo T, Hashimoto H, Takahashi M, Tawa A, Aoyama J, Shinoda A, Tsukamoto K, Tanaka H, Gen K, Kazeto Y, Chow S. 2011. First capture of post-spawning female of the Japanese eel Anguilla japonica at the southern West Mariana Ridge. Fisheries Science 77(2):199-205.

Kuroki M, Aoyama J, Miller MJ, Yoshinaga T, Shinoda A, Hagihara S, Tsukamoto K. 2009. Sympatric spawning of Anguilla marmorata and Anguilla japonica in the western North Pacific Ocean. Journal of Fish Biology 74:1853-1865.

McCosker JE. 1989. Freshwater eels (family Anguillidae) in California: current conditions and future scenarios. California Fish and Game 75:4-10.

Nagasawa K, Kim YG, Hirose H. 1994. Anguillicola crassus and A. globiceps (Nematoda: Dracunculoidea) parasitic in the swimbladder of eels (Anguilla japonica and A. anguilla) in East Asia: a review. Folia Parasitologica 41:127-137.

Nichols JT. 1943. The freshwater fishes of China. Natural history of Central Asia. Volume IX. New York: American Museum of Natural History.

Okamura A, Yamada Y, Tanaka S, Horie N, Utoh T, Mikawa N, Akazawa A, Oka HP. 2002. Atmospheric depression as the final trigger for the seaward migration of the Japanese eel Anguilla japonica. Marine Ecology Progress Series 234:281-288.

Riede K. 2004. Global register of migratory species - from global to regional scales. Bonn, Germany: Federal Agency for Nature Conservation. Final report of the R&D-Projekt 808 05 081.

Ringuet S, Muto F, Raymakers C. 2002. Eels: their harvest and trade in Europe and Asia. TRAFFIC Bulletin 19(2):1-26.

Shao KT, Lim PL. 1991. Fishes of freshwater and estuary. Volume 31. Encyclopedia of field guide in Taiwan. Taipei, Taiwan: Recreation Press.

15

Shinoda A, Aoyama J, Miller MJ, Otake T, Mochioka N, Watanabe S, Minegishi Y, Kuroki M, Yoshinaga T, Yokouchi K, Fukuda N, Sudo R, Hagihara S, Zenimoto K, Suzuki Y, Oya M, Inagaki T, Kimura S, Fukui A, Lee TW, Tsukamoto K. 2011. Evaluation of the larval distribution and migration of the Japanese eel in the western North Pacific. Reviews in Fish Biology and Fisheries 21:591-611.

Skinner JE. 1971. Anguilla recorded from California. California Fish and Game 57(1):76-79.

Smith DG. 1999. Anguillidae. Freshwater eels. Pages 1630-1636 in Carpenter KE, Niem VH, editors. FAO species identification guide for fishery purposes. The living marine resources of the WCP. Volume 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophrynidae). Rome: FAO.

Smithsonian Institution. No date. U.S. National Parasite Collection Database. Available: http://invertebrates.si.edu/parasites.htm.

Strona G, Lourdes M, Palomares D, Bailly N, Galli P, Lafferty KD. 2013. Host range, host ecology, and distribution of more than 11800 fish parasite species. Ecology 94:544.

Sures B, Knopf K. 2004. Parasites as a threat to freshwater eels? Science 304:208-209.

Tsukamoto K. 1992. Discovery of the spawning area for Japanese eel. Nature 356:789-791.

Tsukamoto K. 2006. Spawning of eels near a seamount. Nature 439(23):929.

Tsukamoto K. 2009. Oceanic migration and spawning of anguillid eels. Journal of Fish Biology 74:1833-1852.

Tsukamoto K, Arai T. 2001. Facultative catadromy of the eel Anguilla japonica between freshwater and seawater habitats. Marine Ecology Progress Series 220:265-276.

Tsukamoto K, Otake T, Mochioka N, Lee TW, Fricke H, Inagaki T, Aoyama J, Ishikawa S, Kimura S, Miller MJ, Hasumoto H, Oya M, and Suzuki Y. 2003. Seamounts, new moon and eel spawning: the search for the spawning site of the Japanese eel. Environmental Biology of Fishes 66(3):221-136.

Tsukamoto K, Chow S, Otake T, Mochioka N, Miller MJ, Aoyama J, Kimura S, Watanabe S, Yoshinaga T, Shinoda A, Kuroki M, Oya M, Watanabe T, Hata K, Ijiri S, Kazeto Y, Nomura K, Tanaka H. 2011. Oceanic spawning ecology of freshwater eels in the western North Pacific. Nature Communications 2:179.

Tzeng WN. 1985. Immigration timing and activity rhythms of the eel, Anguilla japonica, elvers in the estuary of northern Taiwan, with emphasis on environmental influences. Bulletin of the Japanese Society of Fishery Oceanography 47:11-28.

16

Tzeng WN, Shiao JC, Iizuka Y. 2002. Use of otolith Sr: Ca ratios to study the riverine migratory behaviours of Japanese eel Anguilla japonica. Marine Ecology Progress Series 245:213- 221.

Tzeng WN, Iizuka Y, Shiao JC, Yamada Y, Oka HP. 2003. Identification and growth rates comparison of divergent migratory contingents of Japanese eel (Anguilla japonica). Aquaculture 216:77-86.

Williamson GR, Tabeta O. 1991. Search for Anguilla eels on the west coast of North America and on the Aleutian and Hawaiian Islands. Japanese Journal of Ichthyology 38:315-317.

Yokouchi K, Sudo R, Kaifu K, Aoyama J, Tsukamoto K. 2009. Biological characteristics of silver-phase Japanese eels, Anguilla japonica, collected from Hamana Lake, Japan. Coastal Marine Science 33:54-63.

17