南沙群岛珊瑚礁区黑斑鹦嘴鱼(Scarus globiceps)食性分析

鹦嘴鱼科(Scaridae)鱼类参与珊瑚礁生态系统诸多关键生态过程,在维持珊瑚礁生态系统稳定与平衡中发挥着重要作用。由于以往研究手段的限制,对鹦嘴鱼的食物来源及生态功能价值认识不足,在其功能定位方面存在较多争议。本研究选择珊瑚分布的典型区域—南沙群岛中的东门礁和南薰礁为研究海域,对该海域鹦嘴鱼优势种类黑斑鹦嘴鱼(Scarus globiceps)摄食的藻类多样性进行全面分析。通过18S rDNA和16S rDNA多基因条形码技术,分别对黑斑鹦嘴鱼肠含物的真核藻类和原核藻类DNA进行高通量测序分析。18S rDNA的测序结果发现,黑斑鹦嘴鱼类的肠含物中真核藻类以甲藻(Dinoflagellata)、红藻(Rhodophyta)、绿藻(Chlorophyta)、褐藻(Ochrophyta)为主,共计77个OTU(operational taxonomic units)。甲藻相对序列丰度和多样性较高,序列比例占真核藻类序列总数的51.42%,其中网甲藻科(Suessiaceae)OTU_5在东门礁和南薰礁的样品中均超过20%。16S rDNA测序鉴定发现肠含物含有原核藻类(蓝藻)的序列,共计21个OTU,其中以念珠藻目(Nostocales)的相对序列丰度最高,达到39.33%。本研究表明,黑斑鹦嘴鱼在摄食过程中会摄入一定量大型藻类,但微藻(甲藻)序列占据优势地位,蓝藻在肠含物中也有较高的检出率,说明需要重新考虑微藻(甲藻和蓝藻)在鹦嘴鱼食源中的重要贡献以及对珊瑚礁生态系统结构与功能的影响。

西沙群岛10种鹦嘴鱼鱼体形态学研究

为探究鹦嘴鱼鱼体形态的主要种间差异及其在物种鉴别中的重要作用,于2019—2022年在西沙群岛海域采集到10种鹦嘴鱼,选取24个形态学性状对其进行测量,采用多元分析方法对鹦嘴鱼物种进行形态差异判别分析。单因素方差分析结果表明,鹦嘴鱼种间所有形态学指标均存在显著性差异(P<0.05);主成分分析提取了7个特征值大于1的形态学指标,累积方差贡献率为66.86%,各物种间的形态差异主要表现在反映食性和游泳能力的特征上;采用判别分析方法对所有鹦嘴鱼样本进行判别,综合判别率为81.1%;10种鹦嘴鱼的形态学聚类结果与鱼类分类结果一致,与已有研究的进化树结果差异显著,说明鹦嘴鱼的表型特征除了受遗传因素控制外,也会受环境因素影响。

西沙群岛鹦嘴鱼科耳石形态学物种鉴定的可行性研究

研究于2018—2021年在西沙群岛海域采集鹦嘴鱼样本,通过传统形态测量法选取的19个耳石形态指标和椭圆傅里叶分析法选取的77个椭圆傅里叶系数对其进行鉴别分析,探究耳石形态在鹦嘴鱼科物种鉴别中的可行性。结果表明,仅使用耳石形态指标鉴别鹦嘴鱼时综合判别率为56.8%,低于仅使用椭圆傅里叶系数的63.1%和两种参数结合的75.7%;而结合两种参数对其4个属的综合判别率为88.6%,其中绚鹦嘴鱼属的判别率达到100%;15种鹦嘴鱼的耳石形态聚类结果与已有研究的进化树结果基本一致,特别是属层面的聚类,呈现高度一致,证实了耳石形态具有遗传的属性,也说明了耳石形态学用于鱼类物种鉴定的可行性。研究结果将为西沙群岛鹦嘴鱼的基础研究提供科学资料,为鹦嘴鱼资源的保护与开发提供理论依据。

条石鲷鳔器官早期发育的组织学观察

应用石蜡切片技术和显微测量法,对条石鲷(Oplegnathus fasciatus)鳔的早期发生、分化和形成过程进行了连续观察。结果显示:条石鲷为闭鳔鱼类,在水温为23.5℃±0.5℃的条件下,鳔的形成过程可分为鳔原基出现、鳔管形成、鳔腔充气、鳔管退化及气腺形成4个时期。1日龄(孵化后第2天)仔鱼,在食道与肠的交界处分化出鳔原基;4日龄,鳔管原基出现;5日龄,气腺原基出现;6日龄,迷网出现;8日龄,鳔管形成;10日龄,鳔开始充气;17日龄,鳔充气完毕,鳔管开始退化;20日龄左右,鳔管从幽门处完全脱离;25日龄,气腺迷网发育完全;30日龄,鳔管完全消失,鳔的发育基本完善。在条石鲷的苗种培育过程中,鳔器官的发育影响到条石鲷仔鱼的成活率。

野生波纹唇鱼Cheilinus undulates营养成分分析与评价

该研究测定了野生波纹唇鱼Cheilinus undulates肌肉的营养成分。结果显示,波纹唇鱼肌肉(鲜样)的水分、粗蛋白、粗脂肪和粗灰分的含量分别为80.97%、18.38%、0.10%和0.49%。肌肉中含有18种氨基酸,总量为15.70%(鲜重),必需氨基酸含量占氨基酸总量的39.37%,必需氨基酸的组成符合FAO/WHO的标准。氨基酸的支/芳值为2.5654,接近正常人的支/芳值;依据氨基酸评分(AAS)结果,第一限制性氨基酸为苏氨酸(Thr),第二限制性氨基酸为色氨酸(Trp);必需氨基酸指数(EAAI)为68.46;4种鲜味氨基酸(SAA)的总量为31.85%。脂肪酸中二十碳五烯酸(EPA)+二十二碳六烯酸(DHA)的含量为21.86%。含有人体所必需的钠、钾、钙、镁、铁、铜、锌等元素,表明波纹唇鱼具有较高的营养价值。

新型流化床生物滤器处理海水养殖废水性能研究

为提升流化床生物滤器的水处理性能,优化滤器的工艺运行参数,研制了新型流化床生物滤器,并以玻璃珠为填料,将该生物滤器应用于斑石鲷循环水养殖系统,探讨了其对养殖水体中营养盐和有机物的去除效果。结果表明:新型流化床生物滤器实现了床层高度的稳定,避免了滤料的流失,优化了滤器内部的流态。在海水养殖工况下,新型流化床生物滤器经过一个月的自然挂膜,可实现滤器的成功启动。通过扫描电镜观察,挂膜前后生物膜载体表面发生了显著的变化。流化床生物滤器的硝化作用主要发生于床层的底部,表层对其贡献率不显著。在稳定工况下,新型流化床生物滤器对TAN、NO_2^--N、BOD_5和SS的去除率分别达到了(48.7±5.23)%、(64.28±9.88)%、(59.19±4.98)%和(40.06±10.21)%,对TAN的平均去除负荷达到了(245.2±50.5)g/(m^3·d)。本生物滤器硝化性能及稳定性优于常规生物滤器,可为该滤器在循环水养殖系统中的高效运行和应用提供一定的技术支撑。

Composition Changes and Movements in Mixed-Species Groups of Algae Grazing Fish in Jamaica and Grand Cayman Island. Part II

Although Caribbean mixed-species herbivorous fish groups are an important component to the reef community by helping to crop algae that often overgrow and kill corals, little is known of how they organize their foraging groups. In spite of a highly flexible membership, the basic structure of these groups consists of a “core species,” that leads the group and often is either the striped parrotfish (Scarus iserti) or the ocean surgeon (Acanthurus tractus). These species lead their groups to open areas where they feed largely on low profile turf algae. Other members prefer macro algae and are termed “associate species,” of which the two common species we studied were the stoplight parrotfish (Sparisoma viride) and the redband parrotfish (Sparisoma aurofrenatum). In spite of the large difference in group sizes between Jamaica and Grand Cayman Islands, the relationships between movement patterns and compositional changes were largely consistent. There was no support for the hypothesis that these dramatic and continuous group changes were related to foraging success. Instead, we speculated that these group changes perhaps were designed to maintain cohesion among a membership that was spread over a wide area. We also examined if associates species may be more than just passive followers of core species but rather instigated the attracting or the building of core groups. Both associate species do attract striped parrotfish in open areas and thus appear active in initiating mixed-species groups. Finally, given that associate species seem to derive little foraging benefit from following core species, we tested the hypothesis that associate species joined core groups to gain protection against predators. Associate species do not selectively join the larger groups of striped parrotfish but appear to join core species randomly and the groups they joined resembled the wide assortment of core groups available in the area. Thus, while associates may be joining core groups for protection, this protection was not based on sizes of core groups.

Fatty Acid Profiles of Livers from Two Marine Fishes Inhabiting Sudanese Red Sea Coast

Fish livers a good source of long-chain polyunsaturated fatty acids and omega 3, are usually discarded as a waste when fish are processed for human consumption in Sudan. Highly fresh Triaenodon obesus and Hipposcarus harid fish were purchased from Port Sudan fish central market during December 2014. The fatty acid profiles of the livers of these commercially important fish were determined. The polyunsaturated and saturated fatty acids ratio in the livers oil of T. obesus and H. harid was 1:2.2 and 1:1.38, respectively. The Palmatic (16:0), Pentadecenoic (12:0) and Arachidic acids were the highest in both species. The poly chain unsaturated fatty acids Linolenic (18:3n - 3), Eicosapentaenoic (20:5n - 3) and Docosahexaenoic (22:6n - 3) were detected in the liver of both species. The highest values of above poly chain unsaturated fatty acids were detected in T. obesus.

南海典型岛礁的鹦嘴鱼群落结构组成

明确人类活动对鹦嘴鱼群落结构的扰动作用,可为鹦嘴鱼的保护和开发提供科学依据。根据2020年7月在南海典型岛礁的调查数据显示,共发现鹦嘴鱼4属20种,其中,美济礁和晋卿岛均为14种,海南陵水9种。生物多样性指数(物种多样性指数H、均匀度指数J和丰富度指数D)均呈现美济礁(3.09、0.81、2.50)>晋卿岛(2.32、0.61、2.27)>海南陵水(1.66、0.52、1.44)的变化趋势。远海岛礁到近岸人口密度增加和生物多样性指数降低,表明美济礁、晋卿岛和海南陵水受到捕捞强度依次增强。另外,摄食功能群中易受到人类干扰的生物侵蚀类(excavators)鹦嘴鱼的数量和重量百分比依次为美济礁(28.96%、26.27%)>晋卿岛(15.86%、10.60%)>海南陵水(1.15%、0.51%);同样,对过度捕捞敏感的牧食类(browsers)也表现为美济礁(1.64%、0.82%)>晋卿岛(1.29%、0.76%)>海南陵水(0、0),摄食功能群结构组成的空间变化也反映了各区域捕捞压力的差异。进一步将各摄食功能群的鹦嘴鱼体长进行标准化处理后(即体长与Fishbase数据库中对应物种的最大体长的比值),发现晋卿岛>美济礁>海南陵水(P<0.05),该结果符合中度干扰假说,中度捕捞能降低物种的种内竞争,有利于晋卿岛的鹦嘴鱼获取更多的空间和食物资源,但长期的过度捕捞容易导致鹦嘴鱼个体减小。