湛江港近江牡蛎的生态研究

STUDIES ON THE ECOLOGY OF Crossostrea rivularis (Gould) IN ZHANJIANG BAY

湛江港石门海区的近江牡蛎Crassostrea rivularis(Gould)养殖,出现苗种大批死亡、生产不稳定等现象。本文对该海区近江牡蛎的生活环境和个体生态进行了调查研究,并对它的采苗、养成、生物敌害的防除等问题作了初步探讨。

Crassostrea rivularis is cultured in Zhanjiang Bay which is located at 110°24/-110°32/E and 21°18/-21°24/N, mainly from the mid-tidal zone to 2 meters below low tide; temperature ranges from 14to 31.8℃, sea water salinity is between 7.52 to 30.02%, pH is 7.1 to 8.1, transparency 0.7 to 2.5m, and current speed 0.214-0.912m/s. It belongs to an irregular semidiurnal tide with a tidal difference of 1.2 to 4.0 m, and has a silt bottom.Planktonic biomass counts 30242-1 239 600 ind/m3, in which phytoplankton has 31 species (Table 3), a biomass of 3084-554 718 ind/m3; zooplankton include Copepoda, Cladocera, Coelenterata, Protozoa, Am-phipoda, Chaetognatha, Tunicata and other animal planktonic larvae, biomass amounts to 22 240-251196 ind/m3; benthic diatom include Coscino-discus, etc. (Table 5), which gross biomass is 47880-143998 ind/m3.C.rivularis grows rapidly during the first three years and slows down gradually. The majority of its food comes from Coscinodiscus sp., Nitzschia sp. and Cyclotella sp. The reproductive season is between April and June, most of the attached seeds can be obtained on the shade sides of the sedentary medium.Apart from C .rivularis, bivalvia growing in the area involves Sacco-strea glomerata, Corbicula fluminea, Anomia cyteum, etc. Harmful organisms include Thais gradata and Balanus sp., the former is harmful to the one-year-old oysters, and the latter competes for sedentary medium and feed. The extermination of T .gradata can be carried out by catching them or their egg capsules.