Swimming performance and energetics of the Japanese eel (Anguilla japonica) across growth and early migratory phases remain poorly quantified. We used swim-tunnel respirometry to compare selected environmental and developmental contrasts in yellow and early silver eels from the Tone River estuary. Critical swimming speed (Ucrit), optimal swimming speed (Uopt), minimum cost of transport (minCOT), oxygen consumption at Uopt, and...

In the artificial seed production of Japanese eels, Anguilla japonica , the frequent occurrence of glass eels with jaw abnormalities has become a serious problem. To gain fundamental insights into this issue, we evaluated the effects of lower jaw abnormalities on survival during the glass eel stage and revealed that these abnormalities are lethal. Bone staining of glass eels and cartilage staining of leptocephali larvae showed...

Organogenesis of Japanese eels ( Anguilla japonica ) was investigated histologically from the late leptocephalus to the yellow eel stages. Early organogenesis, such as the formation of inner ears and the appearance of round blood cells that might be larval erythrocytes, had already begun at the late leptocephalus stage. During the first developmental phase (M1–M3 stages) of metamorphosing into early glass eels (G1 stage), the...

Downstream‐migrating ( n = 64) and non‐migrating ( n = 21) female Celebes eels Anguilla celebesensis were captured from the Poso Lake–River system on Sulawesi Island, Indonesia, and their reproductive physiological characteristics were examined. A histological observation of the ovaries revealed that most non‐migrating eels were at the perinucleolus (43%) or oil‐droplet (48%) stage, whereas most migrating eels were at the earl...