1Hokkaido National Fisheries Research Institute, FRA, Akkeshi, Hokkaido 088-1108, 2Miyako Station, National Center for Stock Enhancement, FRA, Miyako, Iwate 027-0097, 3Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
The transition from endogenous to exogenous feeding, starvation tolerance, and effect of starvation on growth and swimming performance were examined in hatchery-reared larvae of the Japanese sandfish Arctoscopus japonicus. Most newly hatched larvae (12.3 mm in standard length and 2.47 mg in dry weight) commenced feeding at 2 days after hatching (DAH) and completed yolk sac absorption at about 25 DAH. However, no differences in the larval size and swimming speed between feeding and non-feeding groups were observed at 8 DAH (dry weight), 10 DAH (standard length) and about 10 DAH (cruising speed). The 50% lethal time (Ltime50) of 0 DAH larvae under starvation conditions was 23-25 days. Ltime50 was shortest (4 days) when starvation conditions were initiated at 25 DAH and after that the tolerance gradually increased. This suggests that the larvae have a long overlap of endogenous nutrition and exogenous feeding period (2-25 DAH) and mainly depend on endogenous nutrition until 8 DAH. The completion period of yolk absorption is also a critical time for starvation. Although endogenous nutrition is important for growth and survival, exogenous feeding may be required at least before 8 DAH because the influence of starvation on growth appeared after 8 DAH.