IDENTITY AND ABUNDANCE OF SURFACE-DWELLING, COASTAL COPEPODS OF SOUTHWESTERN TAIWAN

Abstract

Day and night abundance of copepods in the coastal waters off southwestern Taiwan was studied during a cruise an 26-28 December 1997. A total of 14 zooplankton samples (7 daytime and 7 nighttime) was taken at seven stations using a one-meter mouth opening net with 333 Pm mesh, and a Hydrobios flowmeter mounted in the centre of the mouth. The mean numerical abundance of copepods was 123 +/- 69 ind./m(3). In all, 67 species of copepods belonging to 16 families and 31 genera were identified. Among these, Paracalanus aculeatus (32% of the numerical total of copepods), Acrocalanus gracilis (31%), and Oncaea venusta (11%) were the most dominant species and occurred at every station. Most species were more abundant during the day than at night. Both the index of species diversity and that of species number of copepods were higher at the northern stations and decreased toward the southern stations at night, but behaved in the opposite manner during the day. From the results of cluster analysis, four station groups were formed: daytime northern stations, daytime southern stations, nighttime northern stations, and nighttime southern stations. The daytime northern station group was most distinct from the others. Four copepod groups were also distinguished and are herein discussed.