Thesis (M.Sc.)--Chulalongkorn University, 1992

Biological study of Acrocalanus gibber was carried out at Phuket Marine Biological Center, Thailand, with two main objectives ; 1) seasonal variation in egg production, abundance, biomass and secondary production, in relation to environmental factors, and 2)roles of A. gibber in pelagic marine food web by determination of ingestion rate, stomach content of fishes and relationship within the zooplankton community. The study was conducted within one year period from July 1990 to July 1991. Length-weight relationship of copepodid stages of A. gibber, size range between 53.7 an^micrometers, was expressed by the equation :W = (1.188 X 10 ) L. Egg production of A. gibber ranged between 6.2-52.0 eggs per female per day. Secondary production of A. gibber showed seasonal pattern with peaks in February and May. The minimum production was 4.62 microgram carbon per cubic meter of water per day recorded in January 1991 and the maximum was 187.54 microgram carbon per cubic meter of water per day recorded in May 1991. The main factor effecting egg production and secondary production of A. gibber is food availability. Ingestion rate of A. gibber adult female increased with food concentration, ranged from 1.98 to 13.08 microgram carbon per cubic meter of water per day at the algal concentration of 50 and 1,500 microgram carbon per liter, respectively. From stomach content analysis, A. gibber was consumed by 13.9 per cent of fish species observed around the study area. Thus, even the copepod, A. gibber, is only a small fraction, 2 per cent, of the whole zooplankton population at PMBC pier, it can be concluded from this study that it plays an important linkage between the primary producer, within the zooplankton community, and the higher trophic level.