Japan, Europe, the United States and Canada are experiencing a sharp decline in eel populations due chiefly to overfishing, pollution and destruction of habitats because of river projects.
In the face of this, the European Union endorsed a proposal in June for a 60 percent cut in the catch of European eel fry by 2013. Its proposal to restrict their export was also approved by the Convention on International Trade in Endangered Species of Wild Fauna and Flora.
The EU decision is expected to cause a steep drop in Japan’s eel supply. European eel fry are raised on farms in China for export to Japan, where eels are a longtime delicacy.
The Japanese eat three species of eels — Japanese eels, found in East Asia and around Japan, European eels and American eels. They remain a precious foodstuff in Spain and other European countries.
Willem Dekker of the Institute for Marine Resources and Ecosystem Studies of the Netherlands said the population drop of each of the three species is serious, and especially serious is a decline in the number of European eels.
According to industry sources in Europe, the drop in the population of European eels became serious in and after 1990, when the catch of fry for export to China began to increase.
Kenichi Tatsukawa of the General Study Group for River Areas, said: “European measures about European eels should be considered in working to protect Japanese eels. Like European eels, the Japanese eel population is decreasing seriously.”
He said the drop in the Japanese eel population became conspicuous in the 1970s as their habitats began to deteriorate with the destruction of damp areas on coasts and river mouths covered over with concrete.
It has been noted in the U.S. that the turbine engines at hydraulic plants catch and kill parent eels going downriver to lay eggs. Some scientists are concerned that changes in currents and salt concentration due to global warming are confusing the mechanism that allows eels to migrate thousands of kilometers.
“The sighting of many egrets around fish farms is a sign of deterioration of the quality of water,” said Hung Chi-Feng, president of an eel farm in Tainan County, Taiwan. He is trying to raise eels without drugs for the first time. “You can raise eels with no drugs if you keep a sharp eye on changes in water and the environment.”
He said shrimp and small fish, which are sensitive to deteriorating water quality, come close to waterfronts, and egrets gather there to eat them. Birds and shrimp are an important indicator of pollution there.
“Drugs for eels kill even shrimp, which are important to preserve the quality of water,” Hung said.
The National Research Institute of Aquaculture under the Fishery Research Agency successfully raised eels from eggs to fry in 2003 for the first time.
One of the reasons for a decline in eel resources is the failure to commercialize technology to artificially pick eggs to raise into adult eels. All eels for global consumption, including those raised artificially, depend on natural eel fry, but the wholesale catch of fry going up rivers is liable to lead to overfishing.
This problem will be resolved if fry can be raised artificially.
“The rate of success is still low, and many obstacles remain before such raising can be commercialized,” said Hideki Tanaka, an official at the research institute. “To raise a large amount of eels, it is necessary to make them eat floating bait, but this is very difficult.”
Izumi Washitani, a professor at the University of Tokyo’s department of ecosystem studies, said, “For eels that live in lakes and around paddy fields after going up rivers via coastal areas from distant seas, it is necessary to maintain a healthy environment in river basins and networks. To recover the natural environment across the country, we have to review our own lifestyle.”