FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

The purpose of this study was to investigate the aggregating behavior of zooplankton under fish attracting lamps using a commercial stick-held net fishing boat. The experimental design was divided into 2 parts. The first part used fixed power at 8 Kw for fish attracting lamps both above and under the water level. Zooplankton specimens were sampled by a closing net (with a 51-cm mouth diameter) at depth layers of 0~10, 10~20, 20~30, 30~40, and 40~50 m, after the fish attracting lamps were turned on at 5, 35, 65, and 95 min, respectively. In the other part, the power for lamps under the water was maintained at 8 Kw, but power for lamps above the water varied at 16, 24, 32, 40, and 48 Kw. Zooplankton specimens were sampled at the same depth layers as used in the first part, while the luring time was up to 30 min.Based on the 2 factors of luring time and the power of fish attracting lamps in this study, zooplankton slowly aggregated when lights were turned on, and it took about 35 min to complete this aggregating procedure, and then the zooplankton gradually dispersed. The results also showed that the average numbers of individuals/m3 of the chaetognatha, mysidacea, copepoda, amphipoda, etc. were affected by the power of lamps.