Pac

New Caledonia, New Zealand

"Color abbreviations are P = plain, M = mottled.

6Zone abbreviations are Trop = tropical, Temp = temperate.

"Distribution abbreviations are ATL = Atlantic Ocean, IND = Indian Ocean, PAC = Pacific Ocean. dA. anguilla. A. rostrata, and A. japónica are closely related (9). eA. marmorata is the most widely distributed species (9). ^Synonymous (3).

"Color abbreviations are P = plain, M = mottled.

6Zone abbreviations are Trop = tropical, Temp = temperate.

"Distribution abbreviations are ATL = Atlantic Ocean, IND = Indian Ocean, PAC = Pacific Ocean. dA. anguilla. A. rostrata, and A. japónica are closely related (9). eA. marmorata is the most widely distributed species (9). ^Synonymous (3).

through early summer. The prelarvae grow to about 25 mm in June. They then attenuate in shape, and gradually grow into transparent, leaf-shaped leptocephalus. The leptocephali drift with the current away from the Sargasso Sea to the coasts of Europe in about three years. The leptocephalus can attain a body length of 50 mm after a year and about 75 mm at two years old. They metamorphose into slim transparent elvers (Fig. 2) at 2.5 years old. The elvers then head for the coast and enter estuaries.

Both the female and male European eels stay in rivers until they grow to 6-12 and 9-19 years old, respectively. When they become sexually mature, the eels migrate downstream and back to the Sargasso Sea to spawn. After spawning, the adults die.

American Eel

The American eel also spawns in the Sargasso Sea. The elvers only take about 1.5 years to reach the coastal area of North America (6).

Japanese Eel

The spawning ground of the Japanese eel is estimated to be within the eastern part of Taiwan and the southern part of the Ryukyu islands, which may extend to the northeastern part of the Philippines. The spawning season is estimated to be between June and July. At the latter part of their development, the leptocephali drift with the Ku-roshio current from the spawning ground and metamorphose into elvers when they reach the estuaries of Taiwan,

Figure 2. Elvers.

the People's Republic of China, Korea, and Japan after about 4-5 months. The migration time is estimated by the daily growth rings in the otolith. Using this index, the peak of elvers upstream migration is between December and January. The elvers enter the rivers and live and feed on small fish, shrimp, and aquatic insects for about 5-20 years until they reach adult size. They mature during autumn and winter (September-November). The pectoral fin, dorsal and ventral part of the mature males turn blackish and silvery. While mature males can weigh only about 500 g on maturity, the females can reach 2-3 kg. Sexually mature eels then migrate down the river into the ocean to spawn. Figure 3 illustrates the estimated spawning ground and life cycle of the Japanese eel (7). The Japanese eel is the most popular and most commonly eaten eel, particularly in Japan. Thus the following discussion focuses on the Japanese eel.

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