Seasonal patterns in feeding ecology of three small fishes in the Biandantang Lake, China

Feeding ecology of three small fish species, Hypseleotris swinhonis, Ctenogobius giurinus and Pseudorasbora parva was studied seasonally in the Biandantang Lake, a small, shallow lake in central China. Gut length, adjusted for total body length, was significantly higher in spring than in other seasons for all the three species. Seasonal changes in gut length were not associated with changes in food quality. Weight of fore-gut contents, adjusted for body weight, was significantly higher in winter and spring than in summer and autumn in H. swinhonis and C. giurinus, and significantly higher in autumn than in spring and summer for P. parva. Percentage of empty fore-guts was highest in summer and lowest in spring for I-I. swinhonis and C. giurinus, and highest in winter and lowest in autumn for P. parva. Diet of the three small fishes showed apparent seasonal changes, and these changes reflected partly the seasonal fluctuations of food resources in environment. Diet breadth was high in winter and low in autumn for H. swinhonis, high in winter and low in spring and summer for C. giurinus, and high in autumn and low in spring for P. parva. Diet overlaps between pairs of species were biologically significant in most cases, except between H. swinhonis and P. parva in summer and autumn and between C. giurinus and P. parva in autumn. (C) 2000 The Fisheries Society of the British Isles.

Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: Adaptations to a marginal environment

The diet and feeding ecology of a wild subpopulation of black-and-white snub-nosed monkeys (Rhinopithecus bieti) were studied at Xiaochangdu in Honglaxueshan Nature Reserve, Tibet. This region is climatologically harsher than any other inhabited by non-human primates. Black-and-white snub-nosed monkeys fed on 48 parts of 25 plant species, at least three species of lichens and seven species of invertebrates. The number of food items exploited varied markedly among seasons, with dietary diversity being greatest in spring and summer. In winter, black-and-white snub-nosed monkeys had to subsist on fallback foods such as dried grass and bark. Ubiquitous lichens formed a major dietary constituent throughout the year, contributing about 75% of feeding records. Even though lichens act as a staple, our findings signify that the monkeys at Xiaochangdu prefer feeding on foliage, which is higher in protein content than the former. We provide evidence that black-and-white snub-nosed monkeys are able to cope with an array of food items other than lichens and hence can be regarded as feeding generalists. We discuss the results with reference to previous studies on other subpopulations living in habitats that are floristically more diverse and offer more plant food items than the marginal habitat at Xiaochangdu.

塔城黑白仰鼻猴（Rhinopithecus bieti）的觅食生态学和社会

从 1999 年4 月至2002 年六月间，对黑白仰鼻猴种群(Rhinopithecus bieti ) 的分布和生境状况进行了调查。与十年前的调查结果相比，本次调查新发现了4 个亚种群（指存在生境走廊的若干群体），但有5 个以前存在的群已经消失，现 存猴群数量为13 群，总体数量约为1200-1700 只。从西藏的芒康到云龙的龙马 山，随着海拔的降低，猴群可利用的植被类型也随之多样化。但由于砍伐、放牧、 开矿等因素的影响，猴群生境破碎化程度较高，连接猴群的生境走廊状况极差， 多数猴群孤立分布，并且存在小种群问题，生境走廊的维护和恢复已成为该物种 保护成功与否的关键。种群的总体数量下降了32%（不含4 个新发现的亚种群）， 其中4 群数量下降，4 群持平，1 群有所增长，5 群消失，这不容乐观的状况给 我们保护敲响了警钟。此外，基于以前的研究结果，暗针叶林、针阔混交林和栎 树林均为其适宜生境，夏季高山牧场则是由当地居民为放牧而砍伐、焚烧高海拔 带的暗针叶林而形成的林间空地。我们使用了1997 年的卫星影像和1958 年的航 拍地图来估算适宜生境和夏季高山牧场的面积。结果表明；1）在1997 年，黑白 仰鼻猴的适宜生境面积为4169 km2，夏季高山牧场的面积为1923 km2。2）在近 40 年中，黑白仰鼻猴的适宜生境面积下降了31％（约1887 km2），而夏季高山牧 场的面积则增加了204％（约1291 km2）。3）森林斑块的平均面积从15.6 km2 下降到5.4 km2。此外，夏季高山牧场的面积与当地居民的人口数量增长之间呈 正相关关系 (R2 ≥ 0.53，p < 0.05)。除非当地居民的人口数量增长模式或者传统 的生产生活方式发生改变，这种破碎化趋势将继续下去。 从1999 年三月至2000 年十二月对云南塔城(99o18’E, 27 o36’N, 活动范围在 2,700 – 3700 m asl)的一群黑白仰鼻猴收集了食性和时间预算的数据。通过状态 行为扫描的方式，主要记录了树冠中单雄组食用植物种类—部位。同时用显微镜对每个月的粪便样本进行了显微分析，以此作为食性的补充数据。仰鼻猴食用属 于28 科、42 属的59 种植物，共计90 个食用的植物种类—部位，其中冬季利用 21 个植物种类—部位，春季38 个，夏季39 个，秋季47 个。另一方面，该群年 平均花费日活动时间的35％进食，33％休息，15％移动，13％社会行为。日活 动时间预算分配、摄食不同食物类别的时间、粪便中食物残留物及食用植物种 类―部位的数目存在着季节性变化。食物种类与时间分配之间和之内的相关显然 是为了最大化觅食效率与最小化能量消耗。考虑到来自北面与南面的群的相关报 道，这个种对生境的适应性似乎与其他疣猴没什么区别，并无特化之处。因此， 这个种的最终生存预期要比以前乐观。 我们利用整个塔城猴群沿地面通过开阔地或喝水的机会，使我们能记录野外 种群的大小和组成（如性比等）以及通过分析依次经过个体间的时间间隔以量化 反映社会组织单元之间和之内的空间距离，用统计分析的方式来量化描述社会组 织的模式，发现塔城猴群由9 个单雄单元（OMUs）、5 个多雄单元（MMUs）和2 个全雄单元（AMUs）组成， 单雄单元、多雄单元和全雄单元内的个体分别约占 总数的58％、34％和8％，无论在开阔峡谷地域或水潭旁，单元内的时间间隔显 著短于单元间的时间间隔（开阔峡谷地域：非配对 t 检验，df = 49; p < 0.01， 水潭：非配对t 检验，df = 35; p < 0.01）。 在单雄单元的成年不等性比和成 年雌性与婴猴的比例显著大于多雄单元（开阔峡谷地域：非配对t 检验，df = 40; p < 0.05，水潭：非配对t 检验，df = 16; p < 0.05）。在全雄单元中有大量的 性别不明的未成年个体。此外，加之某些个案描述，论述了多雄单元存在的可能 性及与全雄单元和单雄单元之间的关系。

海洋桡足类摄食生态及其对浮游植物的摄食压力

该文利用肠道色素法,对中国近海(渤海、黄海、东海、莱州湾、潍河口)和南大洋(普里兹湾及邻近海域)浮游桡足类在自然海区的摄食状况及其对浮游植物及初级生产力的摄食压力进行了研究.主要内容包括:近海:桡足类肠道色素含量随个体的增大而增加,但是肠道排空率与个体大小没有相关性.桡足类通常存在着一定的昼夜摄食节律,摄食高峰出现在夜间,另外河口海区桡足类的摄食节律与潮汐有关.南大洋:南极夏季边缘浮冰区微型浮游动物是浮游植物的主要摄食者,纽鳃樽在形成一定的种群密度时也对浮游植物起到重要的控制作用,而桡足类对浮游植物生物量的变化影响相对较小.

Ecology of macrozoobenthic communities in two plateau lakes of Southwest China

Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytoplankton (Chl a=99.76 +/- 24.01 mu g/L), and Yangzong Lake (YL), a mesotrophic lake. Sampling was carried out from October 2002 to May 2004. Altogether 23 benthic taxa were identified in XL and 21 taxa in YL. The density of benthos in XL was much lower than that in YL, but the biomass was about equal in the two lakes, being 1 423 ind/m(2) and 8.71 g/m(2) in XL and 4 249 ind/m(2) and 8.60 g/m(2) in YL. The dominant species were Limnodrilus hoffmeisteri, Branchiura sowerbyi, Aulodrilus pluriseta and Chironomus sp. in XL and Limnodrilus hoffmeisteri, Aulodrilus pluriseta and Bellamya sp. in YL. Seasonal fluctuation occurred, showing richer species in summer and winter, but the density and biomass varied in different ways in the two lakes. Analyses on functional feeding groups indicate that collector-gatherers were predominant, but the relative abundances of other groups were different. Stepwise multiple regression analysis demonstrated that the water depth, conductivity and chlorophyll a were the key factors affecting macrozoobenthic abundance in the lakes.

Distribution, feeding and body condition of four small fish species in the near-shore and central areas of Liangzi Lake, China

Small fish abundance is usually high in heavily vegetated habitats in Yangtze lakes, China. Visual and swimming barriers created by dense macrophytes beds could reduce feeding efficiency and growth of small fishes. We tested the hypothesis that small fishes in habitats with dense macrophytes would show decreased feeding efficiency and reduced growth rates by comparing feeding efficiency (measured as the relative weight of fore-gut contents), total length, and condition factor of four small young-of-the-year fishes collected in the near-shore (heavily vegetated) and central (less vegetated) areas of Liangzi Lake. Feeding efficiency, total length, or condition factor were each significantly reduced in the near-shore area compared with the central area for Ctenogobius giurinus, Pseudorasbora parva and Carassius auratus auratus. This supports our hypothesis that vegetation abundance may mediate feeding efficiency and growth of small fishes. Although Hypseleotris swinhonis did not show significant decreases in feeding efficiency or growth in the near-shore area, there was not any reversed tendency, i.e. increased feeding rate or growth in the near-shore area compared to the central area.

Food habits and feeding rhythm of the early juvenile Chinese mitten crab (Eriocheir sinensis) in experimental tanks

Gastric mills were examined from 98 early juvenile Chinese mitten crabs (Eriocheir sinensis) from experimental tanks. Recognizable food items were macrophytes, algae, oligochaetes, and detritus; their percent frequencies of occurrence were 94.6%, 86.5%, 10.7%, and 18.3%, respectively. The crabs had a diet feeding rhythm.

Impacts of filter-feeding fishes on the long-term changes of crustacean zooplankton in a eutrophic subtropical Chinese lake

Long-term changes In the crustacean zooplankton community (calanoid and cyclopoid copepods and cladocerans) were studied in Lake Donghu, a shallow and eutrophic Chinese lake. This lake had been earlier stocked with two pump Alter-feeding Ashes, silver carp (Hypopthalmichthys molitrix) and bighead carp (Aristichthys nobilis). During the 1950s and the mid-1980s, the ratio of copepods to cladocerans was relatively stable but showed a general increase thereafter. From the early-1980s to the 1990s, calanoid/cyclopoid ratios decreased obviously. In the 1990s, Cyclops vicinus, Diaphanosoma brachyurum, and Moina micrura were dominant the abundance of C. vicinus and M. micrura increased significantly; and D, brachyurum showed a substantial decrease. The study shows that under extremely high pressure of Ash predation, the species which could recover rapidly from fish predation would be the most likely to survive and increase their numbers.

Feeding, morphological changes and allometric growth during starvation in miiuy croaker larvae

We investigated the effects of the timing of first feeding (larvae in F0, F1, F2, F3 and S were first fed on day 3, 4, 5, 6 days after hatching (DAH) and unfed, respectively) on feeding, morphological changes, survival and growth in miiuy croaker larvae at 24A degrees C. The fed larvae initiated feeding on 3 DAH and reached point of no return (PNR) on 6 DAH. Larvae in F0 and F1 groups survived apparently better than F2 group at the end of the experiment on 36 DAH. High larval mortality occurred from 3 to 7 DAH in all feeding groups, accounting for 40% (F0, F1 and F2 groups) to 90% (F3 and S groups) of the total mortality. Larvae in F0 and F1 groups grew better than F2 group throughout the experiment. Eye diameter, body height, head height and mouth gape of the first feeding larvae were more sensitive to starvation than other morphometrics and could be used as indicators for evaluating their nutritional status. Results indicated that delayed first feeding over 1 day after yolk exhaustion could lead to poor larval survival and growth. To avoid starvation and obtain good growth in culturing, larvae feeding should be initiated within 1 day after yolk exhaustion at 24A degrees C.

Observations on the nocturnal activity and feeding behavior of Anguilla japonica glass eels under laboratory conditions

Glass eels of the temperate anguillid species, Anguilla japonica, clearly showed a nocturnal activity rhythm under laboratory conditions. Light-dark cycle was a determinant factor affecting their photonegative behavior, nocturnal locomotor activity, and feeding behavior. Under natural light conditions, glass eels remained in shelters with little daytime feeding, but came out to forage during darkness. They moved and foraged actively in the following dark, and then their activity gradually declined possibly because of food satiation. They finally buried in the sand or stayed in tubes immediately after the lights came on. Under constant light, glass eels often came out of the shelters to forage in the lights but spent little time moving outside the shelters (e.g. swimming or crawling on the sand). Glass eels took shelter to avoid light and preferred tubes to sand for shelter possibly because tubes were much easier for them to take refuge in than sand. Feeding and locomotor activities of the glass eels were nocturnal and well synchronized. They appeared to depend on olfaction rather than vision to detect and capture prey in darkness. Feeding was the driving force for glass eels to come out of sand under constant light. However, in the dark, some glass eels swam or crept actively on sand even when they were fully fed. The lunar cycles of activity rhythms of glass eels that have been observed in some estuarine areas were not detected under these laboratory conditions.

Summer feeding activities of zooplankton in Prydz Bay, Antarctica

Grazing of dominant zooplankton copepods (Calanoides acutus. and Metridia gerlachei), salps (Salpa thompsoni) and microzooplankton was determined during the austral summer of 1998/1999 at the seasonal ice zone of the Prydz Bay region. The objective was to measure the ingestion rates of zooplankton at the seasonal ice zone, so as to evaluate the importance of different groups of zooplankton in their grazing impact on phytoplankton standing stock and primary production. Grazing by copepods was low, and accounted for less than or equal to 1% of phytoplankton standing stocks and 3.8-12.5% of primary production for both species during this study, even the ingestion rates of individuals were at a high level compared with previous reports. S. thompsoni exhibited a relatively high grazing impact on primary production (72%) in the north of our investigation area. The highest grazing impact on phytoplankton was exerted by microzooplankton during this investigation, and accounted for 10-65% of the standing stock of phytoplankton and 34-100% of potential daily primary production. We concluded that microzooplankton was the dominant phytoplankton consumer in this study area. Salps also played an important role in control of phytoplankton where swarming occurred. The grazing of copepods had a relatively small effect on phytoplankton biomass development.