综述国外养殖机械和设备

养殖机械化是提高产量、降低饲料系数，减轻劳动强度和提高劳动效率的有效途径。养殖业历史悠久，但，近几十年来发展较快，国外已出现了机械化养殖场和现代化的养殖工厂，养殖生产过程日趋机械化、自动化，劳动生产率有较大提高。如池塘养鱼业，日本每个劳动力年产7．5吨；苏联600亩的湖泊，亩产迭534斤，日本145亩的水库，亩产达1130斤，新兴的工业化养鳗亩产能达40，000斤。这充分显示了机械化的优越性。

Macroalgae Blooms and their Effects on Seagrass Ecosystems

Seagrass decline caused by the macroalgae blooms is becoming a common phenomenon throughout temperate and tropical regions. We summarized the incidence of macroalgae blooms throughout the world and their impact on seagrass beds by direct and indirect ways. The competition for living space and using resources is the most direct effect on seagrass beds when macroalgae are blooming in an aquatic ecosystem. The consequence of macroalgae blooms(e.g., light reduction, hypoxia, and decomposition) can produce significant indirect effects on seagrass beds. Light reduction by the macroalgae can decrease the growth and recruitment of seagrasses, and decomposition of macroalgae mats can increase the anoxic and eutrophic conditions, which can further constrict the seagrass growth. Meanwhile, the presence of seagrass shoots can provide substrate for the macroalgae blooms. Controlling nutrient sources from the land to coastal waters is a general efficient way for coastal management. Researching into the synergistical effect of climate change and anthropognic nutrient loads on the interaction between searsasses and macroalgae can provide valuable information to decrease the negative effects of macroalgae blooms on seagrasses in eutrophic areas.

Comparative study of brine shrimp bioassay-based toxic activities of three harmful microalgal species that frequently blooming in aquaculture ponds

Typical harmful micro-algal species constantly occurred in high density in marine aquaculture ponds in Xiangshan and Sanmen Bay, Zhejiang Province. Fates of the microalgal cells influenced by activity of the cultured animals largely determined the ef fects of the harmful microalgae. However, it is difficult to detect the in situ process. In this paper, toxic activities of three harmful microalga, namely P rymnesium parvum, Pleurochrysis elongata, Karlodinium veneficum, which were isolated from the local ponds, were comparatively studied based on brine shrimp toxic bioassays. Diff erent lethal activities of live cells, cell debris, cellular extracts, and cell free mediums prepared by different process were analyzed. The results showed that,(1) all of the three microalgal species had density and time dependent lethal ef fects on A rtermia nauplii, while P. parvum was the most toxic one and had acute lethal eff ects in 5 h. No such acute lethal eff ects were observed in P. elongata or K. veneficum;(2) live cells, cell debris and cellular extracts of P. parvum had the same lethal pattern. Prymnesins, toxin from P. parvum, is probably not exotoxic active; For P. elongata, toxic activity mainly came from live cells and cell debris; For K. veneficum, toxic activity was relatively lower compared with the other two species. However, Karlotoxin, toxin from K. veneficum, is exotoxic active. Physical disturbance triggered K. veneficum cells actively releasing toxins, which made it an active predator.