THE PREFERABLE LIGHT INTENSITY AND COLOR FOR DARKBARBEL CATFISH AND SILVER CARP

We studied the preferable light intensity and light color for wild darkbarbel catfish and farmed silver carp. In the light intensity experiment, the subjects were exposed to four light intensities (010, 1030, 100200 and 700800 lx) in which the subjects had free access to. Similarly in the light color experiment, they were exposed to four colors (red, white, blue and green). The percentage of time spent in each area was recorded and compared. The results showed that darkbarbel catfish spent (% of total time) (78.336.66)%, (10.002.65)%, (7.334.04)% and (4.334.04)% in 010, 1030, 100200 and 700800 lx respectively. The percentage of time in the area with light intensity of 010 lx was significantly higher than that of the other three groups (P0.05). However, silver carp did not show significant difference in the percentage of time among the four groups of light intensity (P0.05). In the light color selection experiments, darkbarbel catfish did not show significant difference in the percentage of time spent in areas with four different colors (P0.05). In the contrast the percentage of time silver carp spent was (12.675.03)% (red), (30.335.13)% (blue), (35.674.73)% (white) and (21.333.06)%. Silver carp exhibit noticeable preference for green light and red light (P0.05). This research is expected to contribute to the theory of phototaxis research of fish.