【作者】 颜云榕；

【导师】 金显仕；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋生态学， 2010， 博士

【摘要】 海洋鱼类的摄食生态和食物关系是海洋生态营养动力学的重要内容,而北部湾为热带、亚热带半封闭海湾,是中越两国渔民传统的作业海域,在该海域开展主要鱼类摄食生态和食物关系研究,具有重要的学术和实践价值。本研究通过2008年10月至2009年9月的北部湾主要渔港逐月采样,结合2010年2月北部湾海域现场拖网调查,以传统胃含物分析方法为基础,并结合碳、氮稳定同位素技术对北部湾海域主要鱼类的饵料组成、营养级和摄食习性随长度的变化进行研究,主要结果如下:(1)北部湾带鱼(Trichiurus lepturus)捕食种类包括鱼类、头足类、底栖甲壳类以及浮游动物等43种饵料生物。摄食强度与饱满指数的季节差异十分显著(P<0.001),食物多样性全年平均为1.97。带鱼在达到50%性成熟肛长值190 mm时出现食性转换。(2)北部湾珠带鱼(Trichiurus margarites)捕食种类包括鱼类、头足类、底栖甲壳类以及浮游动物等33种饵料生物。其中,蓝圆鲹为最主要的种类。珠带鱼的平均饱满指数在各月份之间变动显著。珠带鱼平均饱满指数随性腺发育呈正相关,而空胃率则呈负相关。不同肛长组间的饵料生物质量与个数、摄食习性差异极显著。(3)带鱼主要摄食少鳞犀鳕、蓝圆鲹和中国毛虾,珠带鱼主要摄食少鳞犀鳕、银腰犀鳕和中国毛虾。虽然两种带鱼属种类在北部湾均有分布,但两者的食性重叠却相对较低。(4)北部湾多齿蛇鲻(Saurida tumbil)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,主要为蓝圆鲹、少鳞犀鳕、长颌棱鳀和条鲾等。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%。(5)北部湾宝刀鱼(Chirocentrus dorab)既摄食小型中上层鱼类,又摄食底栖鱼类、虾蟹类和头足类,属于广食性动物食性鱼类。以相对重要性指数百分比(%IRI)为指标,表明鱼类为其最主要饵料(99.7%),其中优势饵料生物为犀鳕属、小公鱼属、小沙丁鱼属和圆鲹属等。宝刀鱼摄食强度和饱满指数的月份差异十分显著(P<0.001),而以Brillouin指数表征的各月份营养多样性则无显著差异。雌性性腺成熟度指数显示北部湾宝刀鱼1年中呈现1个产卵高峰期(5—8月),与北部湾中上层水温高峰趋势相符,表明宝刀鱼产卵高峰与水温密切相关,且产卵期间摄食强度没有降低。随着叉长的增长,北部湾宝刀鱼饵料生物个数变化较小,但平均单个饵料生物重量却明显增加。以δ15N计算所得宝刀鱼各叉长组的平均营养级为3.4。(6)斑鳍白姑鱼(Pennahia pawak)鳞片的年轮显示为空白型窄带,边缘增长率MGI计算结果表明,年轮主要在9-11月形成,为一年一个周期;性腺成熟指数GSI表明繁殖期为4-8月份,年轮形成于繁殖期之后。Logistic生长方程为最适生长模型,主要参数分别为:L∞= 220.32 mm,K = 0.58,t0 = 0.905。摄食种类包括鱼类、甲壳类计27种饵料生物,其中甲壳类占43.0%,鱼类占57.0%。摄食的优势种类有少鳞犀鳕(6.55%)、银腰犀鳕(6.80%)、中国毛虾(5.27%)。摄食强度与饱满指数的季节差异十分显著(P<0.001),食物多样性无季节性显著差异(P>0.05)。北部湾斑鳍白姑鱼食性转换的体长值为130mm,略大于50%性成熟体长115mm。(7)δ13C值随着生物栖息水层的深度而增加,饵料生物中的中上层鱼类蓝圆鲹和底栖鱼类粗纹鲾分别具有最低(-17.830‰)和最高值(-14.925‰)。带鱼δ13C值与肛长不呈明显线性相关,反映其在各个生长阶段于各水层均有摄食活动。根据食物质量比例及δ15N计算的北部湾带鱼营养级平均值和周年平均值均为3.7。真空冷冻干燥与恒温烘干进行样品预处理δ13C差异不显著,而δ15N则差异极显著。更多还原

【Abstract】 Marine fish feeding ecology and food relationships are the main contents of marine ecotrophic dynamics studies. The Beibu Gulf of the South China Sea, a tropical and subtropical semi-closed bay, is the traditional fishing ground of China and Vietnam. Studies on the fish ecology and foraging associations in this sea area are of significant academic and practical value. Based on monthly sampling in the main fishing ports of the Beibu Gulf from October 2008 to September 2009 and on the fishery-dependent trawl survey in February 2010,stomach contents analysis and stable isotope analysis were used to study the prey category,trophic position and ontogenetic feeding habit shifts of the main fishes in the Beibu Gulf,South China Sea. The main results are as follows:(1) Trichiurus lepturus mainly feeds on 43 species of prey. Among them, Bregmaceros rarisquamosu was the principal prey component of the diet, accounting for 37.99% of the contents on the Index of Relative Importance. Small pelagic fish, Decapterus maruadsi, and crustacean, Acetes chinensis, with the percentages of 16.42% and 10.03%, respectively, were also relatively important in the diet of this fish, whereas the other 40 prey species, including pisces, cephalopoda, benthic crustacean and zooplankton, were only present in lower percentages.Since Decapterus maruadsi and Anchoviella heteroloba appeared throughout the Beibu Gulf area year-round, they could serve as index species for the largehead hairtail migration and fishing ground distribution. The feeding intensity and stomach fullness indexes differed significantly from month to month (P<0.001). However, niche width, measured by Shannon-Weiner diversity index H′, indicated no significant seasonal differences (P>0.05). H′reached its peak in autumn and had an average value of 1.97. Cluster analysis, measured with Bray-Curties similarity index, revealed a clear diet shift at preanal length 190mm, i.e. at 50% of maturity length. It was concluded that ontogenetic development was synchronized with the changes in feeding habits from small benthic, zooplankton and pelagic fishes for juvenile largehead hairtail to predominantly larger fish and cephalopoda for adult hairtail. (2) Stomachs of 666 hairtail, Trichiurus margarites Li 1992, ranging in size from 121 mm to 561 mm in preanal length (PL), were sampled monthly in the Beibu Gulf of the South China Sea, and analysis of their stomach contents showed Decapterus maruadsi to be the primary prey components of the diet, averaging 23% by number, 34% by weight and 49% by Index of Relative Importance (IRI). Small benthic fish, Bregmaceros rarisquamosus and B. nectabanus, and crustacean, Acetes chinensis, with IRI percentages of 8%, 4% and 3%, respectively, were also relatively essential in the diet of this fish, whereas the other 30 species of prey were only present in comparatively lower percentages. The research findings revealed that the mean repletion index varied considerably by month, while trophic diversity, calculated by Brillouin index Hz, proved to be relatively consistent throughout the year. Mean repletion index increased in accordance with the gonad maturity stages of hairtail. On the other hand, the proportion of empty stomachs decreased with the stages, being the highest at Stage I with 60.9% and the lowest at StageⅥwith 41.6%. The 14 PL classes demonstrated significant differences with respect to prey weight and numbers. The tendency of mean prey number and weight increased with the body size. Using PRIMER 5.2 software, the cluster analysis, based on IRI values for the above PL classes, showed that the feeding habits of hairtail were relatively heterogeneous among different sizes. In conclusion, the diet of hairtail, T. margarites varied significantly by month and ontogenetic development. These findings may later assist in the development and improvement of marine ecosystem modeling for the Beibu Gulf, South China Sea.(3) As each curve of trophic diversity calculated with the Brillouin index reached an asymptote, the number of stomachs examined in this study was sufficient to describe the monthly and ontogenetic diet shifts for Trichiurus lepturus and T. margarites. T. lepturus is a general omnivore, feeding mainly on Bregmaceros rarisquamosu, Decapterus maruadsi and Acetes chinensis, while T. margarites preys primarily on D. maruadsi, B. rarisquamosus, B. nectabanus and A. chinensis. Both species showed distinct ontogenetic diet shifts in the studied periods. Even though the two examined hairtail feed on similar resources in the same habitat, the diet overlap was relatively low. The results in this study indicated that hairtail played an important role in controlling small pelagic and benthic fish population in the Beibu Gulf area. This trophic correlation may later assist in the establishment of marine ecosystem modeling for the Beibu Gulf of the South China Sea.(4) Stomachs of 749 greater lizardfish, ranging in size from 124 mm to 375 mm in standard length (SL), were sampled monthly in the Beibu Gulf of the South China Sea, and analysis of their stomach contents showed Decapterus maruadsi to be the primary prey components of the diet, averaging 9.7% by number, 55.5% by weight and 34.9% by percentage of Index of Relative Importance (IRI). Small benthic fish, Bregmaceros rarisquamosus and pelagic fish, Thryssa setirostris and Leiognathus riviulatus, with IRI percentages of 26.6%, 4.3% and 2.5%, respectively were also relatively essential in the diet of this fish, whereas the other species of prey were only present in comparatively lower percentages. The research findings revealed that the mean repletion index and mean maturity coefficient varied considerably by month, while trophic diversity, calculated by Brillouin index Hz, proved to be relatively consistent throughout the year. Mean repletion index (RI) was highest (RI = 7.61%) at the stage ofⅥ-Ⅱindicating that this group of greater lizardfish reverted from StageⅥto StageⅡincreased their food input to compensate for energy loss during reproduction. On the other hand, the proportion of empty stomachs reached its peak with 61.5% while mean RI reached the second highest position with 5.98% at StageⅤ, indicating that during the reproduction periods from March to April, and in June and November, greater lizardfish cease feeding until digestion of the prior meal was completed or near completion. The 12 SL classes demonstrated significant differences with respect to prey weight but showed relative consistency in prey numbers. The tendency of mean prey weight increased with the body size following the improvement of the feeding organs and swimming ability of greater lizardfish. Using PRIMER 5.2 software, the cluster analysis, based on IRI values for the above SL classes, showed that the feeding habits of greater lizardfish were generally homogeneous among different sizes, and particularly among the 136~255mm SL classes, with similarities of more than 60%. In conclusion, the diet of greater lizardfish, Saurida tumbil varied significantly by month and ontogenetic development. These findings may later assist in the development and improvement of marine ecosystem modeling for the Beibu Gulf, South China Sea.(5) A total of 645 (344 stomachs with contents) dorab wolf-herring, ranging in size from 193 mm to 782 mm in fork length, were randomly sampled through trawl and gillnet commercial fishing. The results showed that the dorab wolf-herring of the Beibu Gulf was omnivorous and predated not only on small pelagic fish but also on benthic fish, shrimps, crabs and squids. Pisces were the primary prey components of the diet with a percentage of Index of Relative Importance (%IRI) of 99.7%. Among these, 24 species were identified. Genera such as Bregmaceros sp., Thryssa sp., Sardinella sp. and Decapterus sp. were dominant in the dorab wolf-herring food constituent. The small fish, Stolephorus zollingeri, Bregmaceros rarisquamosus, Sardinella jussieu, Decapterus maruadsi, Stolephorus commersoni and Caranx mate, were also relatively important in the diet of this fish, with the weight percentages of 10.27%, 9.36%, 4.72%, 4.11%, 2.77% and 2.73%, respectively, whereas the other species prey were only present in lower percentages. The research findings revealed that the mean repletion index and vacuity coefficient varied considerably by month, while trophic diversity, calculated by Brillouin index Hz, proved to be relatively consistent throughout the year. The spawn peak, from May to August, was recognized by the female gonad somatic index (GSI). Furthermore, the peak periods were consistent with the surface water temperature,20m and 30m layers provided by France CATSAT fisheries remote sensing system. It can be safely concluded that spawning and reproduction of dorab wolf-herring, one of the pelagic fishes, correlate with the sea surface temperature. Mean repletion index (RI) was highest (RI = 2.50%) at the stage ofⅤindicating that this group of dorab wolf-herring maintained strong feeding intensity during the reproduction periods. Meanwhile the vacuity coefficient was almost lowest (VC = 0.75%) at the stage ofⅥ-Ⅱindicating that the fish reverting from StageⅥto StageⅡincreased their food input to compensate for energy loss during reproduction. The 12 fork -length classes demonstrated significant differences with respect to prey weight and prey numbers. The tendency of mean prey weight and number increased with the body size following the improvement of the feeding organs and swimming ability of dorab wolf-herring. Using PRIMER 5.2 software, the cluster analysis, based on %IRI values for the above fork-length classes, showed that the feeding habits of dorab wolf-herring could be classified into three groups: under 380mm, between 381 to 530mm, and above 531mm. The absence of a significant linear correlation between the fork length andδ13C lead to the conclusion that dorab wolf-herring were feeding all the water layers during the major part of their biological life cycle. With an average value of 3.4, the trophic level of dorab wolf-herring calculated byδ15N varied not significantly from the fork length. It can be concluded that stable isotope analysis will play an import role in evaluating the fish feeding ecology and in constructing the marine food web.(6) The annulus of Pennahia pawak in the scales were of the vacant type, which indicated that they formed once a year, during September– November by monthly changes in the marginal growth increment (MGI )of the scales, just after the spawning had occurred from April to August. A maximum likelihood estimation procedure was used to fit the von Bertalanffy, Logistic, Gompertz and generalized von Bertalanffy growth functions to the length-at-age data. ARSS indicated that there were no significant differences in growth between sexes in the four growth models (P>0.05), and the Logistic growth function was selected as the most appropriate growth model according to Akaike’s Information Criterion (AIC), AIC differences( ) and Bayesian information criterion(BIC.The estimated parameters for Logistic growth function were LΔi∞= 220.32 mm,K = 0.58,t0 = 0.905. P. pawak showed rapid growth before the 3rd year, after which the growth tended to slow down; therefore, the starting age of 3 was proposed the best stage of exploitation and utilization for this resource. Pennahia pawak preyed mainly on benthic organisms. Analysis of their stomach contents showed that by Index of Relative Importance (IRI), fish and crustacean were the primary prey components of the diet, accounting for 57.0% and 43.0%, respectively. Bregmaceros rarisquamosus, B. nectabanus and Acetes chinensis were the dominant species in the 27 prey species, making up 6.55%, 6.80% and 5.27% respectively. Solenocera crassicorni and Thryssa setirostris also appeared in all seasons. The feeding intensity and repletion index differed significantly according to seasons (p<0.001), while food diversity had no considerably shifts during the whole year (p>0.05). Cluster analysis based on %IRI values showed that the feeding habits of P. pawak shifted at the standard length of 130mm, which is a little bigger than the 50% sex maturity length (115mm).(7) Small pelagic fish,Decapterus maruadsi,Sardinella jussieu,Stolephorus heteroloba,benthic Bregmaceros rarisquamosus and cephalopoda,Loligo chinensis, were also relatively important in the diet of this fish,with the weight percentages of 26.19%,10.21%,9.94%,7.20% and 6.07%,respectively,whereas the other species prey were only present in lower percentages. Theδ13C signatures increased negative (depleted) values for pelagic species to more enriched values for benthic species. As expecte, D. maruadsi displayed the lowest value (-17.830‰) while benthic Leiognathus lineolatus displayed the highest value (-14.925‰). The absence of a significant linear correlation between the preanal length andδ13C leads to the conclusion that T. lepturus are feeding all the water layers during the major part of their biological life cycle. Both the average trophic level and its annual mean value were calculated by prey weight percentages andδ15N are 3.7. The trophic level of T. lepturus varied not significantly with the preanal length,despite the fact that in the same sea area T. margarites and T. minor increased notably. Two samples of dehydration undertaken prior to the analytical determination of stable isotope ratios were tested and resulted in the observation that vacuum freeze-drying and drying in an oven at constant temperature showed significant variance inδ15N but not inδ13C. Undoubtedly,SIA will play an import role in evaluating the fish feeding habits and trophic positions. At the same time,the following three key points should be taken into account: (a) SIA must be combined with the stomach contents analysis; (b) an appropriate baseline organism has to be selected and its exact trophic position determined; (c) attention needs to be paid to the uncertainty of SIA application in the ontogenetic diet shifts and trophic position variations.更多还原