一秋龄性成熟中华绒螯蟹的生物学─2.生殖、越冬行为及脱壳的可能性

本文对池塘育成的一秋龄成熟中华绒螯蟹生殖行为的观察表明,其具有生殖洄游习性,当年１０月是其活动高峰期,而湖泊放流育成的早熟河蟹其活动高峰在当年１０月及翌年３月,在湖泊淡水水体中少数个体有交配的行为,翌年３月份发现部分雌蟹的纳精囊内有精液。     

船舶使用岸电的经济性分析

文中构建了船舶使用岸电的经济性分析模型,并以挂靠上海港洋山三期码头的欧洲航线典型集装箱船为例进行了实证分析。结果表明,在基准情景其他条件不变的情况下,若不提供任何补贴,无论是否征收环保税,船舶使用岸电的成本均高于辅机发电,此时船舶使用岸电不具经济性。为使船舶使用岸电具有经济性,船舶剩余寿命不宜少于5年,岸电使用补贴不宜低于0.55元/(kW∙h),仅征收环保税时税率提高幅度不宜低于当前设定税率的458%,岸电使用率不宜低于39%,单次供电时间不宜低于11.8 h。若岸电收费标准≥1.73元/(kW∙h),或燃油消耗率低于158.70 g/(kW∙h),或合规燃油价格低于2841元/t,则船舶几乎不可能使用岸电。     

Biology of three Malacostraca (Decapoda) in a Mediterranean lagoon with particular emphasis on the effect of rapid environmental changes on the activity (catchability) of the species

The activity of three Malacostraca (Decapoda), Crangon crangon, Carcinus aestuarii and Paleamon squilla, was studied following rapid environmental changes in a Mediterranean lagoon linked temporarily with the sea. Nekton was sampled every 2–3 days using fixed fyke nets. A canonical analysis and a stepwise multiple regression were computed to determine which factor(s) can predict or account for the catch of these three decapods. In spite of rapid environmental changes no exceptional mortality was observed in each of the three species. Temperature is the environmental factor with major impact on the activity of C. crangon. Activity of P. squilla is controlled by water depth. At a depth of less than 20 cm two factors, salinity and phase of the moon, have a significant influence on the activity of this species. At depths deeper than 20 cm the activity is inhibited. There is only a weak relationship between the catch of C. aestuarii and salinity. Additional data on the life cycle of these species are given. The limitations of a monthly sampling period are discussed and the need for more short-term, consecutive sampling periods is stressed in order to understand the dynamics of systems with rapid environmental fluctuations.     

中华绒螯蟹人工育苗若干技术问题的探讨

本文对中华绒螯蟹亲蟹的选择、促产以及亲蟹培育、幼体培育、环境控制、饵料投喂及病害防治等技术进行了探讨．     

Seasonal abundance, distribution and recruitment of mud crabs (Scylla spp.) in replanted mangroves

The abundance and distribution of mud crabs were studied in a replanted mangrove forest in Buswang, Aklan, Philippines. Two fishing gears, lift nets and bamboo traps, were used to monitor relative abundance of Scylla spp. populations from March 2002 to December 2003 inside the mangrove forest. A third gear, a stakenet set across a creek, was used to monitor crabs migrating out of the mangroves during the ebb tide. Scylla olivacea formed 99.3% and 70.3% of the catch in the mangrove and the stakenet, respectively. The percentage of Scylla tranquebarica increased from <1% in the mangrove catches to 29% in the stakenet. Scylla serrata was present at very low levels in both catches. The lack of modal progression in the size–frequency plots and the year-round catch rate of gravid females suggested that recruitment was constant throughout the year. Even though relative abundance decreased over the study period indicating that the stock is being over-exploited, mud crab production is more than equivalent to that of most natural mangroves.     

东海南部海域蟹类种类组成及分布特征

本文根据1998年5月(春)、8月(夏)、11月(秋)和1999年2月(冬)在东海南部海域的蟹类资源调查资料,结合近年相关渔业调查数据,研究分析了该渔场蟹类的种类组成、地理和区系分布及其数量分布的特点.结果表明该渔场蟹类有63种,隶属13科、38属,以热带和亚热带暖水性种为主,属印度-西太平洋区系中的中-日亚区,与南海关系最为密切,而与黄、渤海关系较为疏远.蟹类分布遍及整个调查海区,但时空分布差异明显,调查海区东南部和沿27°45′N一带海域,平均资源密度指数以夏季最高,达276.8kg/km2,秋季最低,仅为40.1kg/km2;同时蟹类数量分布与水深有较大的关系,以水深100~120m海域数量最大,这与主要种类细点圆趾蟹的分布海域区域明显相关;具有开发利用价值的经济种类有十几种,其渔获量占蟹类总渔获量83%,在渔业产量中占主导地位的为细点圆趾蟹、光掌、锈斑和武士等.