Figure 3. Estimated spawning ground and life cycle of the Japanese eel: (a) Leptocephalus, 5.5 cm T.L., drifted by current; (b) elver (ascending) migrates from estuary to river; (c) adult (descending) migrates from river to spawning ground. Source: Ref. 7.

the American eel, and the Japanese eel. From a marketing point of view, these species are similar in shape, growth, and behavior (8).

Elver Collection

The collection of the elvers is the starting point of eel culture. Attempts to propagate eels artificially have not been successful to date. In 1974, the Japanese succeeded in inducing artificial spawning of the eel and hatching the eel eggs. But attempts to rear the elver during the first three weeks of its life have not been as successful. Thus eel fry are still sourced entirely from the wild-caught elvers.

A growing concern within the eel culture industry in recent years is the diminishing number of large seaward running eels, as well as the elvers swimming upstream. This has been attributed mainly to pollution in estuaries, rivers, and streams and the overfishing of elvers. To rem edy this, captured elvers are now widely used not only for culturing eels for consumption, but also for restocking in the lower reaches of rivers and streams.

Elvers are usually captured at nighttime. Light is used to attract them (Fig. 4) and they are caught in scoop nets in shallow water, in a fine-mesh net set across the width of the river, or in trap nets set in the estuaries (10).

Elvers are quite hardy; nevertheless, great care is taken when handling them to prevent mortality due to injury. They are not handled directly. They are placed in boxes lined with wet muslin or hung in mesh cages in the river. These boxes or cages are taken to eel farms within a few hours. The high demand coupled with a supply shortage has resulted in a phenomenal increase in the price of elvers.

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