Abstract: Abstract： Two indoor trials were conducted to study effects of various light intensities and colors on aggregation of juvenile sea cucumber（Apostichopus japonicus Selenka） with body weight of 0.10-0.17 g. In the first trial, the sea cucumber was stocked into a white plastic tank（50 cm × 40 cm× 30 cm）, 7 cm apart from one end of which 15W, 25W, 40W, 60W, and 100 W bulbs were displaced and covered with black plastic sheet for 24 h. The aggregation of the sea cucumber was observed and recorded in different regions of the tank at water temperature of 9.0-16.0℃ in a 2 hour interval for 24 h with triplication. In the second trial, 50 healthy individuals of sea cucumber were stocked into a flowing sea water plastic tank consisted of a large compartment connected to six small compartments by a 1.5 cm height crevice. There was red （wave length of 639 nm）, yellow （wave length of 587 nm）, green （wave length of 548 nm）, blue（wave length of 435 nm）, or white bulb on the 5 small compartments and no any bulb on the rest small compartment as control. During the second trial, the recycling water tank was covered by a thick paper plate with a photoperiod of 12 h light： 12 h dark, and the number of the sea cucumber was observed and recorded in a 3 hour interval for 24 h with octoplication. The results showed that more sea cucumber were found in the farthest region IV in the tanks, the maximum in the tanks exposed to the 40 W bulb withlight intensity of 12~ 19 lx. More sea cucumber was showed to aggregate in the small compartment exposed to red light than in the small compartments exposed to other light colors, very significantly between in the red compartment and blue and white compartments （P 〈 0.01）, significantly between in the red compartment and in the control compartments （P〈0.05）, significantly between in the white compartment and in the green compartment （P〈0.05）, indicating that the sea cucumber was very sensitive to red light.

Key words: sea cucumber (Apostichopus japonicus Selenka), light intensity, light color, aggregation