Abstract
The effects of lunar phase and habitat depth on the vertical migration patterns of the sergestid shrimp Acetes intermedius were examined based on seven field observations in coastal waters off south-western Taiwan. The results indicate that the pattern of nocturnal vertical movement of A. intermedius depends on the lunar phase. The shrimp evaded moonlight during the ascending period andthen the moon was used as a trigger for resuming an ascent towards the sea surface or descending towards the 10 m water layer. During the descending period, A. intermedius moved rapidly to the bottom or to a middle water depth at 50-80 m before sunrise. However, A. intermedius in waters of deep Kaoping Canyon can also perform a slow descending migration thatcoincides with photosynthetically active radiation of 4 μmol/s per m2. Because the density of A. intermedius on the surface layer is affected by moonlight, the lunar phase is one of the factors affecting the catch rate of large-skimming nets during the night in waters off south-western Taiwan.
