Current status and concerns on tropical anguillid eel stocks

Abstract

@font-face { font-family: "ＭＳ 明朝"; }@font-face { font-family: "ＭＳ 明朝"; }@font-face { font-family: "@ＭＳ 明朝"; }@font-face { font-family: "Calibri"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0mm 0mm 0.0001pt; text-align: justify; font-size: 12pt; font-family: Calibri; }.MsoChpDefault { font-size: 11pt; font-family: Calibri; }.MsoPapDefault { margin-bottom: 6pt; }div.WordSection1 { } Freshwater eels of genus Anguilla have fascinated biologists for centuries due to the spectacular long-distance migrations between the eels’ freshwater habitats and their spawning areas far out in the ocean and the mysteries of their ecology. The spawning areas of Atlantic eels and Japanese eel were located far offshore in the Atlantic Ocean and the Pacific Ocean, respectively, and their reproduction took place thousands of kilometres away from their growth habitats. Phylogenetic studies have revealed that freshwater eels originated in the Indonesian region. However, remarkably little is known about the life histories of tropical freshwater eels despite the fact that tropical eels are key to understanding the nature of primitive forms of catadromous migration. Recently, the juvenile abundance has declined dramatically: by 99% for the European eel and by 80% for the Japanese eel. Recruitment of the American eel near the species’ northern limit has virtually ceased. Other eel species, including Australian and New Zealand eels, also show indications of decline. The main problem is that all young eels used in cultivation are wild juveniles (glass eels and elvers), which are captured in estuaries. Almost all (90 %) of the total world eel supply comes from aquaculture. Therefore, the supply of eel resources for human consumption is completely dependent on wild catch. Commercial eel industries are now considering tropical eels as possible replacement for European and Japanese eels to compensate for declining stocks. However, useful scientific research and information on the biology and stock assessments of tropical eels are lacking, a situation quite different from that for other temperate freshwater eels, which have been well studied for several decades with trends and recruitment patterns being on record. Nevertheless, the present tropical eel catch has been reported as being less than half that of 20 years ago. The present trends in eel stocks and utilization for human consumption suggest that all eel populations will decline to numbers that fall outside safe biological limits and will be seriously threatened with extinction without protection and conservation from strict enforcement of local and international laws.