Comparison of escape behavior of wild and hatchery-reared juvenile Japanese flounder Paralichthys olivaceus

Abstract

: The escape behavior of wild and hatchery-reared juvenile Japanese flounder Paralichthys olivaceus from a dummy predator, gray goblinfish Minous monodactylus, was investigated under artificial light in an experimental tank. When the dummy predator approached, both the juveniles quickly emerged from the sand, escaping primarily by swimming close to the bottom (benthic swimming) rather than off the bottom (off-bottom swimming). It is suggested that juvenile flounders might escape in this manner from a diurnal visual feeder in the daytime, owing to the flounder being virtually undetectable visually when close to the bottom. The average escape swimming speed of an individual of 9.3 total length (TL)/s in wild fish and 9.8 TL/s in hatchery-reared fish was similar to the maximum speed of many fish species. Juvenile flounder escaped more quickly and had a higher swimming speed (v cm/s), when their distance (d cm) to the dummy predator decreased (v = −2.7d + 82.1, r = −0.33; anova, P < 0.02).