鲥鱼的驯养与生物学研究Ⅰ.O~+龄幼鱼的生长与食性

本文主要描述池塘养殖条件下鲥鱼幼鱼的生长与食性。1)1987—1989年8月至11月幼鱼生长迅速,快于同期珠江天然个体的生长速度;2)体长26.6—94.9mm的幼鱼主要摄食浮游动物,轮虫和浮游植物出现率随个体增大而减少。食物共有18个属种,摄食频度为100％;3)幼鱼的平均饱满指数为75.70‰。各类食物重量百分比的顺序为:桡足类>枝角类>无节幼体>虾类溞状幼体>轮虫>藻类。     

鲥鱼仔幼鱼食性与生长的初步研究

本文主要描述鲥鱼仔幼鱼阶段有关摄食、消化器官的发育、不同大小仔幼鱼食物组成特点、摄食量及其昼夜摄食节律。此外,还就仔幼鲥鱼人工饲养条件与天然状况下的生长作了比较。结果表明,只要供饵正常,孵化环道内生活的仔幼鲥生长速度可以略快于鄱阳湖同期天然生长个体的速度,为今后人工培育仔幼鲥进行放流和增殖提供资料。       

叉尾斗鱼仔鱼饵料选择与摄食强度

采用实验生态学方法,研究了叉尾斗鱼仔鱼对不同类别饵料的选择及其摄食强度。结果表明,2—3 日龄刚开口摄食的仔鱼对桡足类无节幼体有明显正选择,对轮虫表现为明显的负选择,而对枝角类和桡足类则完全不摄食。4—6 日龄仔鱼主要以桡足类无节幼体为食物,7—11 日龄的仔鱼主要以枝角类为食物,而12—25 日龄仔鱼则主要摄食桡足类。仔鱼口宽或全长与摄食饵料个体大小呈线性或曲线正相关。2 日龄仔鱼开口摄食发生率达47%,而3 日龄以上则保持100%;2 日龄仔鱼平均摄食量仅为0.0017 mg,而25 日龄仔鱼平均摄食量已达0.3795 mg。最高饱食率出现在25 日龄,达到60%,而消化道饱满系数以5日龄最大,达13.13%。但之后消化道饱满系数逐步下降,11—25 日龄仔鱼消化道饱满系数在1.46%—2.79%之间波动。     

鲥鱼仔幼鱼食性与生长的初步研究

本文主要描述鲥鱼仔幼鱼阶段有关摄食、消化器官的发育、不同大小仔幼鱼食物组成特点、摄食量及其昼夜摄食节律。此外,还就仔幼鲥鱼人工饲养条件与天然状况下的生长作了比较。结果表明,只要供饵正常,孵化环道内生活的仔幼鲥生长速度可以略快于鄱阳湖同期天然生长个体的速度,为今后人工培育仔幼鲥进行放流和增殖提供资料。     

单宁酸对根田鼠断乳幼体生长和存活的影响

在食物中含10％和20％蛋白质条件下,测定了单宁酸对根田鼠幼体在断乳后20d内的生长和存活的影响。结果表明,食物中含蛋白质为10％的条件下,摄食含3％和6％单宁酸食物的试验个体生长速率分别为-0．135g/d和-0．25g/d,食物利用效率均显低于对照组,断乳后20d内平均存活天数较对照组分别下降26．23％和49．36％。在食物蛋白质为20％的条件下,摄食含3％和6％单宁酸食物的试验个体生长速率分别为0．134g/d和-0．116g／d,摄食6％单宁酸食物的试验个体食物利用效率显低于摄食3％单宁酸食物的试验个体和对照组个体,断乳后20d内的平均存活天数较对照组下降39．41％,摄食3％单宁酸食物的试验个体较对照组略有下降,但不显。上述结果验证了单宁酸能显影响植食性小哺乳动物生长和存活的假设。     

蜓和蓝尾石龙子幼体食物同化的热依赖性

用采自安徽滁州琅琊山的蜓(Sphenomorphus indicus,头体长42.8-54.4 mm,n=12)和蓝尾石龙子(Eumeces elegans,头体长43.9-57.3 mm,n=10)幼体,研究温度(24-32℃)对蜓和蓝尾石龙子幼体食物通过时间、摄食量、表观消化系数(ADC)、同化效率(AE)和生长的影响。结果显示,24-30℃范围内,蜓和蓝尾石龙子幼体的食物通过时间随温度的升高而缩短,超过30℃则基本不变。蜓幼体：30和32℃摄食量和生长小于24-28℃;24-30℃ ADC、AE随温度升高而下降,但32℃时又升高。蓝尾石龙子幼体：24-26℃摄食量随温度升高而增加,26℃后随温度升高显著下降;24-28℃ ADC、AE大于30和32℃,呈现出随温度升高而下降的趋势;26℃生长最快。结果表明,蜓和蓝尾石龙子幼体的摄食和同化能力均低于相应的成体。     

两品系萼花臂尾轮虫摄食强度的比较研究

对广州和芜湖两品系萼花臂尾轮虫的摄食强度及其与食物浓度、食物种类和培养时间之间的关系进行了比较研究.结果表明,食物浓度、食物种类和培养时间均对轮虫滤水率和摄食率有显著影响.两品系轮虫滤水率和摄食率均随培养时间的延长而减小;20 h内,两品系轮虫的总滤水率均与食物浓度呈曲线相关,而两品系轮虫总摄食率均与食物浓度呈直线相关.广州和芜湖两品系轮虫均在以小球藻为食物时有较大的滤水率,分别为0.0029±0.0001和0.0039±0.0008ml·ind.^-1·h^-1;广州品系轮虫以小球藻为食物时的摄食率(0.3992×10⁴±0.00850×⁴ cell·ind.-1·h^-1)显著地大于以栅藻为食物时的摄食率(0.170×⁴±0.0370×⁴ cell·ind.^-1·h^-1),而它们均与以混合藻为食物时的摄食率无显著差异;芜湖品系轮虫摄食率不受食物种类影响.轮虫滤水率和摄食率因食物浓度、食物种类和培养时间的不同而在品系间存在着差异.     

长江口中华鲟幼鱼的食物组成及摄食习性

分析了2004年5-9月长江口水域中华鲟幼鱼的食物组成及摄食的月份变化.结果表明:长江口中华鲟幼鱼以底栖小型鱼类、多毛类和端足类为主要食物,兼食虾类、蟹类及瓣鳃类等小型底栖动物.幼鱼的摄食率和摄食强度较高,且摄食强度存在着月份变化.主要饵料生物组成有明显的月变化,且食物个体有逐渐增大的趋势,其中5月主食多毛类和蟹类,6月主食鱼类和端足类,7月为鱼类和多毛类,8月样本较少且为空胃,9月为鱼类和虾类.与历史资料进行比较发现,曾是幼鱼重要饵料的鲬类所占比例极小,其质量百分比仅占1.81%;而以前未曾记录的虾虎鱼类在食物中所占比例较高, 其质量百分比达50.54%;等足类以前也未曾记录,其出现频率达10.07%.     

入侵早期食蚊鱼仔幼鱼食物组成、摄食策略及营养状况分析

饥饿是影响鱼类仔鱼早期存活的关键因素,入侵鱼类仔鱼耐饥饿能力对其种群增长与扩散意义重大。本文对滇池流域食蚊鱼Gambusia affinis奠基种群仔幼鱼摄食及仔鱼营养状况进行深入分析,初步了解了饥饿因素在食蚊鱼入侵早期种群增长中的影响。研究结果显示,该种群食蚊鱼仔幼鱼主要以枝角类、桡足类为食物,同时能够广泛利用栖息地食物资源,包括种类较为丰富的水生昆虫幼体、弹跳虫等,具有广食性的摄食策略,许多个体食物多样性指数>1。这些特点与其口裂较大、发育较为完善的特点密切相关。尽管如此,仍有高达73.27%的食蚊鱼仔鱼存在饥饿胁迫问题,可能与奠基种群自身生物学特点、仔鱼群体内部竞争、行为特点及环境资源差异化分布格局等因素密切相关。对奠基种群而言,入侵早期仔幼鱼面临陌生的栖息地生境,其摄食与营养状况对种群的定殖有关键影响。     

在人工饲养条件下鲥鱼仔鱼期开口摄食的观察

受精卵孵化后的仔鱼开口摄食阶段是鱼类早期发育的关健时期,经常引起仔鱼的大量死亡,缺乏充足的适口外源性饵料可能是造成死亡的重要原因之一。1982—1983年,利用赣江产卵场人工授精的鲥鱼受精卵在室内孵化环道中孵出的仔鱼,投喂捞取的天然浮游生物饵料进行了仔鲥有关开口摄食方面的观察,其主要结果如下:仔鱼在孵化后2.5—6.5日为开口摄食期,个体全长为4.5—7.4毫米,仔鱼通常残留多少不等的卵黄物质,为混合性开食营养类型;开口摄食期间的饵料以轮虫,桡足类及其幼体(无节幼体与挠足幼体)为主要种类,适口饵料宽度为仔鱼口宽的39—81％左右,约占仔鱼全长比例的1.5—3.8％;肠内一次饵料量为平均体重的6.72％。     

Nutritional importance of detritivory in the growth and condition of gizzard shad in an Ohio reservoir

Synopsis Gizzard shad,Dorosoma cepedianum, in Acton Lake, Ohio, ingested foods of varying nutritional quality during the 1981–1983 growing seasons. Adult (ages 2–4) fish fed on a mixed diet (ORG>30%; C:N<7:1) of zooplankton and organic detritus in early summer, and on detrital materials (ORG<16%; C:N>11:1) during the remainder of the growing season. Age 0 (<35 mm standard length) fish ingested only detrital materials. The nutritional quality (ORG = 10 – 20%; C:N<11:1) of these foods displayed little seasonal variation, but was higher than that of organic detritus taken by adult fish in late summer and autumn. Growth and condition of gizzard shad were poor when the diet consisted of detrital materials; however, age 4 fish (1983) grew rapidly and condition improved when zooplankton were consumed. These results suggest that ingestion of poor-quality detritus can reduce the growth and condition of gizzard shad in Acton Lake, whereas the seasonal inclusion of high-quality zooplankton in the diet can result in rapid growth and improved condition.     

Seasonal variation in condition, growth and food habits of walleye in a Great Plains reservoir and simulated effects of an altered thermal regime

Catch rates in gillnets and relative weight ( W _r) of walleye Stizostedion vitreum , in Glen Elder Reservoir, Kansas, were lowest during the summer (June–August) and highest during the autumn (September–November). Approximately 80% of their annual growth in length and mass was attained during late summer and autumn. Growth was minimal during winter (January–February) and spring (March–May). The number of walleye with empty stomachs was highest during the summer. Invertebrates (Cladocera, Chironomidae) were common in walleye stomachs during the summer and spring, but contributed little to the ingested biomass. Gizzard shad Dorosoma cepedianum dominated walleye diets (per cent by mass) throughout the year. A bioenergetics model predicted that the proportion of maximum consumption ( P _c) was highest during the autumn and was probably due to spatial overlap of walleye and gizzard shad once water temperatures were <22° C. The bioenergetics model predicted that walleye would lose up to 65% of their body mass during the summer if water temperature increased by 10% (as predicted by some global warming models). Growth during the autumn, winter and spring was enhanced up to 150% by increased temperatures. The results of this study indicate that lower condition, reduced consumption and slow growth are a generalized response of walleye to extreme temperatures. Elevated temperatures may have a net positive effect on walleye growth if they can survive the high thermal stress during summer.     

Assessing the quality of four inshore habitats used by post yolk‐sac Alosa sapidissima (Wilson 1811) in the Hudson River: a prelude to restoration

Habitat restoration within large rivers to enhance early life stages of fish is an emerging field. Prior to restoration, assessment of what constitutes “good” habitat is needed. We exemplify this with a study of larval Alosa sapidissima (American shad) in the Hudson River estuary in New York State, United States, which examines the quality of four main shallow water habitat types that have been reduced greatly by dredging activities. The larval stage has been identified as a sensitive period in need of mortality reduction. Habitats were examined as nursery habitat by comparing ambient conditions to known suitability indexes and by comparing relative abundance, loss rate, daily growth, and relative condition among habitats. Areas of lower velocity had greater abundances of shad ≤15.0 mm in length and shad growth was significantly higher. As shad became larger, those in areas of higher velocity had significantly higher relative condition, suggesting a shift in habitat use as larvae metamorphose into the juvenile stage. Contiguous backwater and secondary channel habitats had reduced loss rates during 2011 when there was high river discharge. No single habitat type examined in this study was found to be overall poor quality, and it is recommended that restoration sites be examined on an individual basis. More broadly, habitat diversity appears needed both for within‐year ontogeny as well as for longer‐term resiliency in the face of disturbance, such as storm‐driven high flows.     

Length–weight and length–length relationships for four shad species along the western Black Sea coast of Turkey

This study investigates length–weight and length–length relationships of four shad species (Alosa caspia caspia, Alosa immaculata, Alosa maeotica, Alosa tanaica) captured in the western Black Sea coast of Turkey. A total of 686 specimens, 355 females and 331 males, were caught by gill net, trammel net and longline from 2006 through 2007 along the western Black Sea coast of Turkey. The relationships of total length (TL), fork length (FL) and standard length (SL) are presented for inhabiting in the Black Sea four shad species and the relationships between total length (TL) and body weight (BW) from the two localities, Sile and Karasu in the western Black Sea coast of Turkey. The Length–weight relationships generally indicated positive allometric growth in Alosa species for both males and females and an isometric growth for A. immaculata females. The coefficient b ranged from a minimum 2.97 for females of A. immaculata to a maximum 3.75 for both sexes A. c. caspia. Results indicated that the length–length relationship between the three length measurements were highly correlated (r² > 0.99, P < 0.001).     

Length and restriction site heteroplasmy in the mitochondrial DNA of american shad (alosa sapidissima)

Restriction endonuclease analysis was used to assess mitochondrial DNA (mtDNA) variation in American shad (Alosa sapidissima) collected from 14 rivers ranging from Florida to Quebec. Two types of heteroplasmy were observed, one involving a major length polymorphism and the other a single restriction site. Shad mtDNA occurred in two principal size classes, 18.3 and 19.8 kb. Of 244 shad examined, 30 were heteroplasmic and carried both size classes of mtDNA in varying proportions; the remainder were homoplasmic for the smaller size class of mtDNA. The large mtDNA variant occurred most frequently at the southern end of the range, and except for two individuals from Nova Scotia, was not detected among shad from rivers north of the Delaware. In contrast, ten shad heteroplasmic for a SalI restriction site originated from rivers ranging from South Carolina to Nova Scotia. DNA mapping and hybridization experiments indicated that the length polymorphism is in the D-loop-containing region and consists of a tandemly repeated 1.5-kb DNA sequence occurring in two and three copies, respectively, in the two major size classes of shad mtDNA. Continuous length variation up to approximately 40 bp occurs among copies of the repeat both within and among individuals. Restriction site data support the conclusion that both forms of heteroplasmy in shad mtDNA have originated more than once.     

Effect of threadfin shad density on production of threadfin shad and gizzard shad larvae in a Tennessee reservoir

Production of larvae by threadfin shad, Dorosoma petenense, and gizzard shad, D. cepedianum, varied over two orders of magnitude and was regulated by adult threadfin shad abundance over five years in Normandy Reservoir, Tennessee. Significantly more larvae of both species were produced in years following winterkills of threadfin shad (repeated-measures ANOVA, df=4, 75; F > 21.44, p=0.0001). Peak geometric mean catch of threadfin shad larvae in neuston samples was inversely related to biomass (kg ha^–1; r = – 0.91; p=0.031) and density (no. ha^–1; r=– 0.89; p = 0.043) of adult (> 70 mm total length) threadfin shad in mid-summer cove samples. Peak geometric mean catch of gizzard shad larvae was also inversely related to adult threadfin shad biomass (r = – 0.93; p=0.022) and density (r=– 0.88; p=0.046) in cove samples. Winterkills of threadfin shad were size selective, killing all fish under 60 mm total length but allowing some unknown percentage of larger fish to survive. When threadfin shad stocks were reduced by winterkills, surviving threadfin shad and gizzard shad may have taken advantage of less competition for food resources in early spring and increased condition enough to spawn successfully.     

Caspian Anadromous Shad Alosa kessleri kessleri (Grimm, 1887) from the Akhtuba River,Lower Volga River Basin: Biological and Morphological Features

Data on the dynamics of anadromous migration, age composition, body length, body weight, and morphometric characteristics of Caspian anadromous shad from the Akhtuba River are presented. Currently, Caspian anadromous shad from the Akhtuba River is monomorphic; no temporal groups have been identified. The population is represented by medium-sized young early-maturing (age of 2–3 years) fish with life longevity less than 5 years. Generally, according to the most important diagnostic signs, first and foremost, to the number of gill stamens and some plastic signs, Caspian anadromous shad from the Akhtuba River falls within the range of the diversity that is typical for the form.     

Biology and traits of the formation of stock of big-eyed shad Alosa saposchnikowii

Special traits of distribution, reproduction, growth, feeding, and population abundance of the big-eyed shad Alosa saposchnikowii are discussed. In investigations of the formation of abundance, the focus is on the strategy of observations on the stock in the absence of fishery statistics data. The informational representativeness of two monitoring methods is noted: trawl survey of the annual abundance of underyrearlings and census of the relative abundance of spawners recalculated per 100 nets. The big-eyed shad was a secondary commercial species. At present it prospers and occupies a leading position among herrings. In the observed period of sea transgression, in the northern Caspian Sea where principal spawning grounds of herrings are situated, the freshened zone has considerably widened, with conditions favorable to the spawning of big-eyed shad. As a result, its abundance has increased. In spite of the increase in species abundance, its linear and weight growth also increased. The latter is attributed to the change in the diet of the big-eyed shad, namely, its transition to consumption of food consisting mainly of fish.