Diel vertical distribution ofAnguilla japonica leptocephali

Effects of water temperature changes on the endogenous and exogenous rhythms of oxygen consumption in glass eels Anguilla japonica

“…The present study shows that the endogenous physiological rhythms of glass eels migrating from the open ocean to continental waters can be deduced based on Leptocephali, therefore, are subjected to changes in water temperature that are greater than 1°C (Kajihara et al 1988, Otake et al 1998. Being subjected to such changes every 24 h probably affects exogenous physiological rhythms significantly.…”

“…The leptocephali migrate vertically during their drift in the open ocean (Kajihara et al 1988, Otake et al 1998. During this time, the metabolic activities of the larvae may display a circadian rhythm caused by the diurnal vertical migration.…”

Ontogenetic changes in phototactic behavior during metamorphosis of artificially reared Japanese eel Anguilla japonica larvae

“…However, this oceanic larval migration of leptocephali is probably not entirely passive, but includes some active behavioral components, such as vertical migration and swimming activity. Leptocephali appear to start vertical migration while moving west in the NEC, where individuals (10 to 20 mm TL) have been caught at depths of 50 to 100 m at night, and 100 to 200 m during daytime (Otake et al 1998). Moreover, large leptocephali were observed at shallower depths than were small leptocephali at night (Kajihara et al 1988), which suggests nighttime distribution becomes shallower with growth.…”

“…Error bars are SD. Significant differences (nonparametric Kruskal-Wallis test with Dunn's multiple comparison test, p < 0.05) are shown by different letters in each panel species from shallower depths in the upper 100 m at night to depths sometimes as deep as 250 to 300 m during the day (Schoth & Tesch 1984, Castonguay & McCleave 1987, Otake et al 1998, Kajihara et al 1988). The clear negative phototaxis observed in the leptocephali and metamorphosing larvae in the present study suggest that this behavioral response may be the overriding factor that causes their descending behavior, as has been suggested by studies on other types of zooplankton (Forward 1976, Ringelberg 1999.…”

“…Assuming, for example, that Japanese eel leptocephali are distributed in the upper 125 m layer in the daytime and in about the upper 75 m layer at night based on Otake et al (1998), leptocephali can dive into the lower layer at a swimming speed of ca. 1.6 cm s -1 within about 60 min from dawn and rise up to an upper layer at a swimming speed of ca.…”