Abstract:Based on the planktons sampled in the Jiaozhou Bay during the time period from January to December 2003,totally 28 species of planktonic copepods and 6 species of the larva are identified. The spatial\|temporal distribution and variation of the species, and their relationships to the environmental factors of the sea area are analyzed. As it is shown by the results from the analysis and the comparison with the historical data, the species composition can be clearly simplified and mainly characterized by their ecological features of the typical species living in the low\|salinity water of the near\|shore sea in the warm temperate zone. The planktonic copepod abundance variates from month to month with its peak of 181.61 ind./m3 in July, the lowest of 23.53 ind./m3 in December, and the annual mean of 71.42 ind./m3.The planktonic copepod abundance is inhomogeneous in its horizontal distribution, with the densest of 132.62 ind./m3 at Station 5 and the sparsest of 40.45 ind./m3 at Station 8. In general, the abundance tends to be denser in the north of the sea area than in the south. The spatial\|temporal distribution of the dominant species and the seasonal variation of their abundances keep less changeable in the 20 years. Although the time for the peak abundance appearance is different from year to year, this difference depends upon the temperature seasonal or annual variation. In fact, the spatial\|temporal distribution of the planktonic copepod abundance are closely related to thermohaline distribution, even more closely to temperature than to salinity. Furthermore it is evidenced by means of the investigation data the Jiaozhou Bay that planktonic copepod population depends upon the phytoplankton abundance, and the latter provides food for the former growing and breeding.