Occurrence of migrating silver eels Anguilla japonica in the East China Sea

The seasonal occurrence of 72 silver phase Japanese eels Anguilla japonica collected in the East China Sea is described and their morphological features analyzed. These silver eels were captured with dip nets under lights around fishing boats at night near islands in the northeast region of the East China Sea over 7 yr. The eels had the typical morphological characteristics of silver eels, such as a black metallic body color and enlarged eyes. All females had started ovarian maturation with gonad somatic indices of 1.3 to 3.5. No eels smaller than 400 mm or yellow phase eels were collected or observed. Considering the limited seasonal occurrence of these eels, and that their morphological features were characteristic of silver phase migrating eels, these eels appeared to be passing through sampling areas on their spawning migration to the region just west of the Mariana Islands in the Philippine Sea.