Population parameters and dynamic pool models of commercial fishes in the Beibu Gulf, northern South China Sea

Length-frequency data of eight commercial fish species in the Beibu Gulf （Golf of Tonkin）, northern South China Sea, were collected during 2006-2007. Length-weight relationships and growth and mortality parameters were analyzed using FiSAT II software. Five species had isometric growth, two species had negative allometric growth, and one species had positive allometric growth. Overall, the exploitation rates of the eight species were lower in 2006 2007 than in 1997-1999： for four species （Saurida tumbil, Saurida undosquamis, Argyrosomus macrocephalus, and Nemipterus virgatus） it was lower in 2006-2007 than in 1997 1999, for two species （Parargyrops edita and Trichiurus haumela） it remained the same, and for the other two species （Trachurus japonicus and Decapterus maruadsi） it was higher in 2006~007 than in 1997-1999. The exploitation rates might have declined because of the decline in fishing intensity caused by high crude oil prices. The optimum exploitation rate, estimated using Beverton-Holt dynamic pool models, indicated that although fishes in the Beibu Gulf could sustain high exploitation rates, the under-size fishes at first capture resulted in low yields. To increase the yield per recruitment, it is more effective to increase the size at first capture than to control fishing effort.

Feeding ecology of hairtail Trichiurus margarites and largehead hairtail Trichiurus lepturus in the Beibu Gulf, the South China Sea

We evaluated the feeding ecology of largehead hairtail (Trichiurus lepturus) and hairtail (T. margarites). We collected specimens from fishing ports in the Beibu Gulf (Gulf of Tonkin) from October 2008 to September 2009 and analyzed their gut contents. We collected 857 T. lepturus and 666 T. margarites samples. The number of stomachs examined in this study was sufficient to describe the monthly and ontogenetic diet shifts for the two species, as indicated by the trophic diversity curves. T. lepturus was a general omnivore, feeding primarily on Bregmaceros rarisquamosu, Decapterus maruadsi, and Acetes chinensis. Conversely, T. margarites preyed primarily on D. maruadsi, B. rarisquamosus, B. nectabanus, and A. chinensis. Both species exhibited distinct ontogenetic diet shifts. Although the two hairtail specie fed on similar sources in the same habitat, the diet overlap was relatively low. Our results suggest that hairtail play an important role in controlling small pelagic and benthic fish populations in the gulf. This trophic correlation shall be used for developing a marine ecosystem model for the Beibu Gulf.

Roles of fishing and climate change in long-term fish species succession and population dynamics in the outer Beibu Gulf,South China Sea

A prevailing,controversial hypothesis is that fishing pressure has played a greater role than climatic and environmental drivers,in changing fish species succession and biomass fluctuation in the South China Sea(SCS).Based on otter trawl survey data from 1959 to 2010 in the outer Beibu Gulf(OBG),northern SCS,large seasonal and interannual variation is reported for fish species composition,the proportional abundances of dominant taxa,and fish biomass.Generalized additive models are developed to quantify relationships between fish biomass and the external factors of fishing pressure and climate change.Fishing pressure proved to be the main driver of sharp declines in demersal fish stocks,with high-value species being replaced by low-value ones over time.Abrupt decreases in fish biomass during the years of 1993 and 1998 correspond to El Nino events,with climate change possibly the main driver of proportional representation of pelagic species in fisheries trawl catch.The need to differentiate impacts of fishing and environmental drivers on fish species with different life history strategies is stressed to better understand fish community dynamics.

Sea Breeze Front Storm and Its Composite Analysis in Beibu Gulf

[Objective] The aim was to study the sea breeze front storm and its composite analysis in Beibu Gulf. [Method] By dint of routine observation data, ground automatic meteorology data and European numerical mode grid data, rainstorm caused by sea breeze in Guangxi during 1990 and 2007 and the strong convection triggered by sea breeze on June 5 in 2008 were expounded. The main characteristics of the configuration of circulation in the low and high latitude of breeze front of middle scale were summarized. [Result] Sea breeze front storm system was an important middle scale sea breeze front system that triggered storm in the Beibu Gulf. Sea breeze in Beibu Gulf occurred most easily during the southwest monsoon eruption period. Case study pointed out that after sunrise, the continental and island temperature in Beibu Gulf turned from warm-ocean-cold-island into warm-island-cold-ocean. The southerly airstream of high temperature and high humidity met with the relatively low temperature and dry northerly airstream in Beibu Gulf, and triggered vertical circulation and stimulated ground middle scale sea breeze front system. Composite analysis referred to the circulation characteristics of the ocean and continental temperature in Beibu Gulf. The upper air of south China was in strong divergence center. The air pressure was high in the east and low in the west. Beibu Gulf was in the southerly torrent belt in front of the trough and after the latitude in cyclonic circulation convergence area. The strata unstable structure of the divergence in the upper air and the convergence in the lower layer and the 'pumping effect' provided upward dynamics for the ocean circulation development. The southerly brought rich water vapor to the Beibu Gulf, which was conductive to the formation of strong convective cloud system in the lower layer and the generation of precipitation. [Conclusion] The research provided references for the study on the characteristics of middle scale convective system.

Estimation of potential distribution of gas hydrate in the northern South China Sea

Gas hydrate research has significant importance for securing world energy resources, and has the potential to produce considerable economic benefits. Previous studies have shown that the South China Sea is an area that harbors gas hydrates. However, there is a lack of systematic investigations and understanding on the distribution of gas hydrate throughout the region. In this paper, we applied mineral resource quantitative assessment techniques to forecast and estimate the potential distribution of gas hydrate resources in the northern South China Sea. However, current hydrate samples from the South China Sea are too few to produce models of occurrences. Thus, according to similarity and contrast principles of mineral outputs, we can use a similar hydrate-mining environment with sufficient gas hydrate data as a testing ground for modeling northern South China Sea gas hydrate conditions. We selected the Gulf of Mexico, which has extensively studied gas hydrates, to develop predictive models of gas hydrate distributions, and to test errors in the model. Then, we compared the existing northern South China Sea hydrate-mining data with the Gulf of Mexico characteristics, and collated the relevant data into the model. Subsequently, we applied the model to the northern South China Sea to obtain the potential gas hydrate distribution of the area, and to identify significant exploration targets. Finally, we evaluated the reliability of the predicted results. The south seabed area of Taiwan Bank is recommended as a priority exploration target. The Zhujiang Mouth, Southeast Hainan, and Southwest Taiwan Basins, including the South Bijia Basin, also are recommended as exploration target areas. In addition, the method in this paper can provide a useful predictive approach for gas hydrate resource assessment, which gives a scientific basis for construction and implementation of long-term planning for gas hydrate exploration and general exploitation of the seabed of China.

Two new species of Leodamas Kinberg, 1866 (Annelida, Orbiniidae) from China seas

Two species of Leodamas(Annelida,Orbiniidae)from China seas are described based on both material of the Marine Biological Museum(Chinese Academy of Sciences,Qingdao),and newly collected specimens.Leodamas robustus sp.n.is characterized by having uncini arranged in two short rows,anterior row with 3-5 uncini,increasing in size,with uncini on posterior chaetigers thicker,heavier and more curved than those on precedent chaetigers;posterior row with 2-5 uncini,thin and delicate,nearly the same size on all chaetigers,with 2-3 thin capillaries dorsally to two rows of uncini.Leodamas weizhouensis sp.n.is characterized by having delicate pocket-like membrane below and posterior to neuropodia,neuropodia of thoracic chaetigers with fi ve dense rows of uncini.A key to all species of Leodamas from China seas is also provided.

北部湾多齿蛇鲻摄食习性及随生长发育的变化

2008年10月至2009年9月,对北部湾多齿蛇鲻逐月采样共749尾(实胃数408个),通过胃含物分析法研究其摄食习性及随生长发育的变化。结果表明,北部湾多齿蛇鲻捕食种类包括鱼类、头足类以及虾类等饵料生物,其中可鉴定出的鱼类种类有17种。以相对重要性指数百分比为指标,鱼类为最主要饵料(98.8%),其中优势饵料种类有蓝圆鲹(34.9%)、少鳞犀鳕(26.6%)、长颌棱鳀(4.30%)和条鲾(2.5%)。多齿蛇鲻摄食强度、饱满指数和成熟系数的月份差异十分显著,而以Brillouin指数表征的各月份营养多样性则无显著差异。一年中呈现3个产卵高峰期(3-4月、6月及11月),产卵期间摄食强度没有降低,仍然强烈索饵。随着体长的增长,北部湾多齿蛇鲻饵料生物个数变化较小,但平均单个饵料生物质量却明显增加。聚类分析表明,北部湾多齿蛇鲻各体长组间食物组成相近,其中136～255mm各体长组相似性系数均大于60%。

南海北部陆架北部湾盆地古湖泊与烃源条件

利用地震资料对整个盆地的追踪和对比 ,结合钻井资料 ,对北部湾古湖进行分析发现 :古湖发育始于古新世 ,到始新世流沙港期进入鼎盛时期 ,湖泊规模最大达 5 0 0 0km2 ,沉积了巨厚沉积物 ,最大沉积厚度达 4 70 0m。井资料分析显示 ,在始新统流沙港三段、二段各古湖沉积物中浮游藻类和沉积有机质含量高 ,说明该两段具有较高的生物生产力 ;流一段和涠洲组沉积物中仅在涠西南古湖和乌石古湖内浮游藻类和沉积有机质具有较高的含量 。

南海北部湾全新世以来沉积物地球化学特征及物源分析

为探讨全新世以来南海北部湾沉积物的沉积环境变化,对北部湾海域的SO-31沉积物柱状样进行了元素地球化学分析。根据元素地球化学的垂向分布特征,将SO-31沉积柱划分为3个单元,反映了全新世不同时期的区域海平面波动以及沉积物物源的变化。SO-31沉积柱的稀土元素配分曲线和La/Co与La/Sc散点图分析表明：111 400-12 800 a BP（全新世前期）,研究区海平面较低,红河、其他周边河流及海岸侵蚀物均为本区的主要物源;28 500-1 1400 a BP（全新世早期）,随着海平面的逐渐上升,河口和岸线逐渐后退,各物源供给区对本区沉积物的贡献量也发生了相应变化,相对而言红河贡献率有所下降;30-8 500 a BP（中全新世至今）,区域海平面持续上升导致了琼州海峡打开,北部湾水动力环境和物源供给发生了剧变,红河对本区的物源贡献逐渐变小,而来自北部湾东部的物质成为本区沉积物的主要物源。

北部湾东北部海区污着生物研究

1986年6月至1987年6月，在北部湾东北部离岸分别为40和3．6nmile处布设了BZ，B3两个浮标调查站，以了解该海区的污着生物生态特点。调查结果表明，该水域的污着生物主要为热带、亚热带海域沿岸常见种类，其中无柄蔓足类在近岸的B3站处于绝对优势的地位；至于远岸的BZ站；不仅珍珠贝和牡蛎等双壳类软体动物的生物附着量（湿重）高于B3站，而且还有少量的茗荷Lepasanatifera、鹅茗荷L．anserdera等外海性种类出现。

1960-2017年北部湾珊瑚礁区海洋热浪增强原因分析

在全球气候变化、区域气候因素的共同作用下,海洋热浪频发,北部湾珊瑚礁正处于快速退化之中。探究海洋热浪逐年增强的机制,对预测珊瑚礁未来生长环境具有重要意义。根据北部湾东部4个海洋站(北海、涠洲、海口、东方)实测海表温度历史资料和该海域的相关气候资料,选取SSTA、DHM、DHW、DHD 4种指标,采用相关分析和对比分析法探讨该海域近58年海洋热浪的变化趋势及原因,结果表明:(1)1960-2017年北部湾东部珊瑚礁区海洋热浪爆发的强度及频率逐年波动上升;(2)海洋热浪逐年增强源于全球性的厄尔尼诺事件增多、区域性的高压系统增强及风场减弱等多因素共同作用;(3)全球变暖背景下造成的海洋热浪爆发对北部湾东部海域的珊瑚礁生态系统已经造成不利影响。

用温盐资料研究夏季南海水通过琼州海峡进入北部湾的特征

夏季琼州海峡水交换向来存在两种观点:一种认为在西南风作用下,琼州海峡水交换从西向东;另一种观点则和上述相反。我们通过琼州海峡东部水域温盐分布和沿岸海洋站同步观测资料的对比发现,夏季北部湾的涠州岛盐度变化规律和琼州海峡东部、琼州海峡中部变化规律一致。由此证明,夏季南海水通过琼州海峡进入北部湾的事实。北海略受影响。而远离琼州海峡的龙门和白龙尾两站,则更多反映夏季陆地水文规律。由此证明,夏季南海水通过琼州海峡进入北部湾的事实。

南海北部湾主要鱼类食物网

1997～2000年在南海北部湾渔场调查中搜集了49种鱼,共计2080尾.对其食性分析,并依其食料生物的生态类群以及消化器官特点,将其划分为5种食性类型:浮游生物食性、底栖生物食性、游泳动物食性、浮游生物兼底栖生物食性、底栖生物兼游泳动物食性.根据食物网中各营养级的相互关系,初步将这49种鱼划分为3个营养级:(1)草食性动物和杂食性动物,营养级分别为1.0～1.3级和1.4～1.9级.(2)低级肉食性动物和中级肉食性动物,营养级分别为2.0～2.8级和2.9～3.4级.其中,属于低级肉食性营养级的种类数量最多,共有30种;属于中级肉食性营养级的种类较少,共有12种.(3)高级肉食性动物,营养级为3.5～4.0级.属于该营养级的种类数量最少,只有7种.

南中国海及泰国湾渔业资源过度利用现状及保护对策

南中国海及泰国湾具有丰富的浅海和热带的生物多样性,支持着一个世界重要的渔场,同时南中国海及泰国湾周边的国家还是目前亚洲太平洋地区工业化和经济快速增长的中心,关系着东南亚及相邻地区的政治和经济的稳定。过去对渔业资源的过度开发利用,造成了该海区渔业资源减少,海岸环境退化严重。虽然南中国海及泰国湾周边国家过去都实施了相应的海洋环境保护行动计划,然而缺乏区域协调措施大大降低了这些行动的有效性。文中对南中国海及泰国湾渔业资源过度利用现状进行了诊断分析,识别了渔业资源过度利用造成的环境问题以及这些环境问题的跨境影响,以便能在双边或区域的层面上共同协作,采取适当的措施去扭转南中国海及泰国湾的环境退化趋势。

“南海一号”与宋代广西北部湾的对外交往

宋代中国南海海上贸易空前繁荣,留给后人的最直接航海物证就是"南海一号"古沉船。在汉代海上丝绸之路开辟与广西北部湾港口形成的基础上,随着宋代南海海上丝绸之路航线的改变,广西北部湾主要以安南等东南亚小国为交往对象,中心港口移至钦州,钦州博易场等地成为主要的贸易场所。"南海一号"发掘地所在的阳江外海面是商船从广州、福建港口经由北部湾到南海各国的经过地,也是广州与钦州间来往商船的经过地。广西北部湾港口特别是钦州港的对外交往是宋朝海外交往繁荣发展的一个缩影。

北部湾经济圈的形成和开发设想

随着中越关系的改善以及南昆铁路即将通车，大西南与北部湾的联系日渐密切。以北部湾为中心，将迅速形成区域合作体系──经济圈。文中分析了北部湾的战略区位及其形成经济圈的区域环境和条件，认为其区位优越，且无论是国际大环境还是区域内部小环境都有利于经济圈的形成；还分析了北部湾经济圈形成所必需的物质基础，认为其具有大储量的现代工业资源、曲折的海岸线和众多的优良港湾、丰富的热带亚热带作物资源和海洋生物资源以及特有的热带海洋。在此基础上提出了对北部湾经济圈进行开发建设的设想，认为其将成为与渤海湾南北对峙的国际瞩目的经济圈。

酸洗+气举诱喷技术在涠洲6-1油田石炭系储层的应用

介绍了一套适合于南海北部湾海域涠洲6-1油田石炭系灰岩储层的酸洗工艺,对涠洲6-1-A1h/A2h井酸洗原理、处理依据、施工工艺进行了详细说明,针对这两口井实施的酸洗+气举诱喷技术均取得了成功并获得了理想的产量,对今后南海类似油田的开发具有一定的借鉴意义。

南海北部湾真鲷的捕捞现状研究

南海北部湾真鲷的捕捞渔具以刺网、钓具、桁杆拖网、笼壶为主。本文根据在北部湾北部渔场（北纬20°30＇N以北）布置的18艘调查渔船获取的真鲷捕捞生产资料,通过统计这四种主要捕捞类型的产量及真鲷的渔获比例,评估了该海区真鲷的捕捞产量及结构、资源量和主要渔汛期。结果表明：2015年北部湾北部真鲷的捕捞产量为546 864 kg。其中,刺网产量为449 961 kg、钓具为62 783 kg、桁杆拖网为14 587 kg、笼壶为14 260 kg、其它渔具为5 272 kg。真鲷的最主要捕捞月份为11月和12月,这两个月的月度产量分别占全年产量的29.45%和21.38%;4～5月真鲷个体平均质量和体长的生长速率为全年最高。研究结果可为改善北部湾真鲷资源状况和捕捞管理,提高北部湾真鲷资源开发水平,促进真鲷增殖放流工作的开展提供科学依据。

试论南宁区域性国际城市的建设

南宁建设成区域性国际城市就是要建成为东南亚区域的国际化大都市。通过分析南宁建设区域性国际城市的有利条件,提出了南宁在建设区域性国际城市中应采取的六项措施,并对未来南宁区域性国际城市进行了描述。