Impact of long-term habitat loss on the resource of Japanese eel, Anguilla japonica.

Abstract

Since the 1970s, the loss of temperate-zone anguillid eels, particularly Anguilla anguilla, Anguilla rostrata, and Anguilla japonica, has exceeded 90% based on estimate of glass eel recruitments; however, the cause of this decline has not been conclusively determined, although many factors have been proposed. In East Asia, the consequences of long-term habitat loss and deterioration of habitat quality on the sustainability of the Japanese eel resources are important. Impacts have already occurred and are expected to increase because hundreds of millions of people inhabit areas near estuaries and rivers that have undergone and are expected to continue to undergo substantial changes in land use. Driven by economic growth, these landscape changes have resulted in, and may continue to produce the large-scale destruction of eel habitats. We used chronological Landsat imagery to measure habitat reduction of the Japanese eel because of human activities in 16 rivers in East Asia, including Japan, Korea, Taiwan, and China. On average, 76.8% of the effective habitat area (Ae) has been lost in these 16 rivers from the 1970s to 2010s. Taiwan and China had the highest percentages of Ae loss, with declines of 49.3% and 81.5%, respectively. Extensive habitat loss may play an important role, together with regional climate phenomena such as the ENSO and overfishing, to the decline of the Japanese eel in East Asia. Measures targeting habitat restoration and protection may need to be integrated into management planning for Japanese eel resources, in an international rather than regional context.