| From 1990's, the development of marine fish aquaculture has been widely acknowledged as important to meet the increasingly worldwide demand for sea food. However, compared with wild species, cultured fishes usually exhibit inferior qualities in terms of vitality and taste. Feedstuff plays an important role in the alteration of fish qualities. Since zooplankton especially copepods, are the main food source of most marine fishes in nature, they have been considered as the potentially high quality living food for marine fish cultivation. In order to select the suitable species as potential fish food, verify the availability of such a species, feasibility for mass culture and the possibility to improve fish products quality, etc., numerous basic exploiting research work are needed such as biological and ecological characters of copepods.The purpose of this paper is to select a copepod species which would be easier to establish in cultures and might be suitable for mass culture as live food for marine fish culture.Copepods were collected in the Jiaozhou Bay from October 2003 to September 2004. All the samples, which included Acartia bifilosa, Paracalanus parvus , Paracalanus. crassirostris , Calanopia thompson , Acartia pacifica , Labidocera euchaeta , Schmackeria poplesia , Centropages mcmurrichi , Eurytemora pacifica , Labidocera.bipinnata , Centropages. Tenuiremis, were reared at the same condition in the laboratory to compare their survival abilities. Acarita bifilosa was proved to be the best candidate among the collected copepods for fish diets. Focused on this species, for the future exploitation, its basic biological characters as well as optimal culture conditions were studied and then preliminary population propagation was carried out in the laboratory. As we had not found resting eggs in the laboratory experiments, which is vital for clarifying its over summer strategy in Jiaozhou Bay, ecological characters as the effects of high temperature and food concentration were studied to supplement the in situ survey results. The followings are the main results:Selection: Among the 11 collected copepod species, Acartia bifilosa , Paracalanus. crassirostris , Calanopia thompson and Eurytemora pacifica are easier to be maintained in our culture conditions than the other 7 species. Further studies on the endurance to varying temperature or salinity of the above four species showed that: Paracalanus. crassirostris larva can not live over 11 days at 18℃when salinity exceeded 20; Calanopia Thompson females can not live over 10 days when tempreture is lower than 20℃and when salinity is under 20‰,females and larva of Calanopia Thompson can not live beyond 9 and 7 days respectively. Eurytemora pacifica are hardly maintained at temperature over 20℃. Acartia bifilosa keeps the survival rate of 24-85% at 8-24℃, both the adults and the larva are ready to live in the range of salinity 10-35 which made it the only species to be further studied.Reproduction: Effects of food and temperature on the reproduction of Acartia bifilosa were studied in laboratory. Results showed that: Among the 6 microalgae: Nannochloropsis oculat, Chlorella.sp, Isochrysis galbana, Phaeodactylum tricornutum, Platymonas subordiformis, Skeletonema costatum that applied in our experiments, Platymonas subordiformis, Skeletonema costatum and the mixture of them are proved to be better for the reproduction than the other four microalgae; Pre-starved treatment had a strong influence on reproduction of females which need a relatively long time to resume to their peak egg production states and always keeping a low egg production rates; Suitable temperature for the reproduction is in the range of 15-20℃; but there was no significant difference in average egg production between 10-25℃.Growth and development: As the larval stage food, Nannochloris oculata (1-2μm) was proved to be the ideal -sized first feeding food in contrast to other experimental microalgae; Later staged nauplii should feed on large-sized microalgae (> 4μm) to compensate the large amount of energy spent on hunting at high temperatures. Food consists of Nannochloropsis oculata, Platymonas subordiformis, Skeletonema costatum are better for cultivation lower 22℃, whereas Isochrysis galbana should be added for cultivation over 22℃.Generation time: Effect of different temperatures on the development of Acartia bifilosa under the same food condition showed: in the temperature range of 15-25℃, development rates increased with the increasing temperature which resulted in a decreasing generation time.Populaiton cultivation: Based on the biological characters research, the effects of algal species ration and total food concentration on the population propagation were investigated. Results showed that: a proportion of 2:1:1 (Platymonas subordiformis: Skeletonema costatum: Nannochloropsis oculata) in terms of carbon content and total food concentration in the range of 1.0-4.0μg C ml-1 were optimal for the population cultivation at 20℃; A proportion of 2:1:1:2 (Platymonas subordiformis: Skeletonema costatum: Nannochloropsis oculata: Isochrysis galbana, ) in terms of carbon content and total food concentration of 1.0μg C ml-1 concentration were optimal for the cultivation at 25℃, concentrations lower or higher than 1.0μg C ml-1 have negative effects on the output.Over summer strategy: In order to make a clear understanding of the oversummering life history strategy of Acartia bifilosa in Jiaozhou Bay, effects of high temperature and food concentration simulating in situ summer conditions on the reproduction and development of A. bifilosa was studied in the laboratory to supplement the survey results in situ . Results showed that: food concentration had significant influence on the reprodction of A. bifilosa; Females keep producing eggs at the highest experimental food level 15μg Chla l-1 even at 28℃; and hatching success of the produced eggs was mostly high, varing between 50%and 90%, indicating that there is no resting egg produced; Nauplii can develop to adults in the two high food level treatment of both 15μg Chla l-1 and 10μg Chla l-1, whereas in 5μg Chla l-1 treatment, nauplii can not develop to C1 at 28℃and can only develop to C4 at 25℃. We do not discover resting eggs both in our experiments and in situ survey which strongly suggest that Acartia bifilosa population in Jiaozhou Bay could sustain the high temperature seasons independent of producing resting eggs.
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