美洲鲥的资源变动及修复

美洲鲥在美国渔业史上曾起到重要作用,但从19世纪初期开始,建闸筑坝、水域污染以及人们的过度捕捞,造成美洲鲥种群数量急剧下降,目前,美洲鲥在很多地区已经绝迹.然而,经过人们不断的努力,美洲鲥资源渐渐得到修复,每年在切萨皮克地区举行的鲥鱼节,让人们在庆祝这一自然文化财富的同时加深了对美洲鲥的了解.     

美洲鲥(Alosa sapidissima)的资源变动及修复

美洲鲥在美国渔业史上曾起到重要作用。然而从十九世纪初期开始,建闸筑坝、水域的污染以及人们的过度捕捞造成美洲鲥种群数量急剧下降,目前美洲鲥从很多地区已经绝迹。然而,经过人们不断的努力,美洲鲥资源渐渐得到修复,每年在切萨皮克地区举行的鲥鱼节,让人们在庆祝这一自然文化财富的同时加深了对美洲鲥的更多了解。     

美洲鲥的生物学特征及资源状况

美洲鲥(Alosa sapidissima),隶属于鲱形总目,鲱形目,鲱科,西鲱属.别名有Common shad,Susquehanna shad,Delaware shad,Connecticut river shad,Potomac river shad,White shad,Buck shad,和Atlantic shad等.作为一种有较高经济价值和美味的溯河产卵洄游性鱼类,美洲鲥曾被很多地区引种和驯养,导致了其广泛的分布.不同河流的种群不仅显示出诸如尾叉长、鳞片数目、椎骨数目等形态学上的不同,还显示出基因上的差异,因此可以视为不同的地理种群.Evpifanio(1995)和Brown(1996)通过mtDNA分析将北美洲的美洲鲥分为17个不同种群.目前,在国内也有单位在进行美洲鲥驯养试验,但还没有关于它的报道.     

美洲鲥工厂化养殖技术初探

为研究美洲鲥低能高效的温室工厂化养殖新技术,于2010年6月~2013年6月进行了温室工厂化养殖试验,同时探索了物联网技术在美洲鲥工厂化养殖生产中的应用。通过智能化管理,共生产美洲鲥商品鱼11084 kg,年平均单产10.14 kg/m2,年平均养殖效益达7353.69元/m2。     

美洲鲥苗种绿色生产试验

采用由美国的野生美洲鲥亲本人工繁育而来的子一代亲本进行苗种绿色生产试验,孵化育苗用水经过严格的消毒、过滤等处理,尾水通过水循环系统净化后排放,开口饵料以自行扩培的方式生产,并在种鱼养殖和苗种培育过程中使用经绿色生产资料认证的饲料.试验结果显示:养殖和育苗用水符合NY/T 391—2013《绿色食品产地环境质量》,排放水...     

美洲鲥肌肉营养成分分析与评价

采用常规的生化分析方法对美洲鲥的肌肉营养组成分进行了测定。结果表时，美洲鲥肌肉鲜样中粗蛋白含量为18．88±0．41％，粗脂肪含量为6．80±0．27％，水份70．23±0．37％，灰份1．96±0．30％；肌肉含有17种氨基酸，总量占鲜样的15．27％，其中7种人体必需氨基酸（除色氨酸外）含量占鲜样的6．27％，与非必需氨基酸的比值（EAA／NEAA）为69．67％，其必需氨基酸构成比例基本符合FAO／WHO的标准；根据AAS，美洲鲥的第一限制性氨基酸为苏氨酸，第二限制性氨基酸为蛋＋胱氨酸；而根据CS，第一限制性氨基酸为蛋＋胱氨酸，第二限制性氨基酸为苏氨酸：必需氨基酸指数（EAAL）为56．11，支链氨基酸与芳香族氨基酸的比值（F值）为2．43，4种鲜味氨基酸占鲜样的5．76％：不饱和脂肪酸质量分数为66．1％，高于其他经济鱼类：微量元素含量丰富，有较高的钙镁含量，铜，铁，锌的比值较为合理。美洲鲥是一种营养价值和经济价值都较高的鱼类。     

美洲鲥帆布池塘大棚养殖试验

为探索池塘大棚养殖美洲鲥的可行性,采用GLP-832型标准蔬菜大棚、直径6 m的帆布池、黑白遮阳膜和通风控制系统等构建美洲鲥帆布池塘大棚养殖系统,利用河道水开展了美洲鲥养殖试验,通过自动温度记录仪每隔2h记录水温数据,并对该模式的养殖成本和效益进行了分析.结果表明,帆布池塘大棚养殖系统能够保持养殖池水温在9.9～30....     

美洲鲥

美洲鲥（Alosa sapidissima）是生活在北美洲东西沿岸河流和海洋中的一种具有较高营养价值和经济价值的溯河产卵洄游性鱼类,属鲱形目,鲱科,鲥亚科,西鲱属,与中国鲥同属一个亚科、不同属的两个种,在分类地位上十分接近。     

工厂化养殖美洲鲥幼鱼的生长特性及消化酶活性变化

在工厂化养殖条件下,将初始体长为(54.04±6.07)mm、体质量为(2.03±0.75)g的4 000尾美洲鲥幼鱼放在有效体积约300 m³的养殖池中饲养84 d,研究美洲鲥幼鱼养殖过程中的生长特性及生长过程中消化酶活力的变化特点。结果显示:美洲鲥体长(L)、体质量(W)均与养殖时长(t)呈指数相关(L＝56.568e0.008 8t,W＝2.463 3e0.027 4t),体长与体质量呈幂函数相关(W＝7×10-6L3.158 2),试验期间美洲鲥幼鱼的生长类型为等速生长;总体上,肥满度随着幼鱼的生长发育而明显提高,试验初期(养殖14 d时)显著提高,之后有所降低,在42 d时显著下降(P＜0.05),之后幼鱼的肥满度保持着较快的增长,随着时间的推移显著提高(P＜0.05),并在试验结束时达到最高值。美洲鲥幼鱼胃蛋白酶活力随着幼鱼的生长显著升高(P＜0.05);幽门盲囊的淀粉酶活力随着幼鱼生长显著下降(P＜0.05),而蛋白酶和脂肪酶活力总体呈升高趋势(P＜0.05);肠道中淀粉酶的活力随着幼鱼生长而显著降低(P＜0.05),蛋白酶和脂肪酶活力总体呈上升趋势,最大值均出现在第84天(P＜0.05)。研究结果表明,工厂化养殖美洲鲥幼鱼的生长类型为等速生长,本试验的养殖条件适宜美洲鲥幼鱼生长;养殖过程中应根据消化酶的变化规律,适时调整饲料中营养成分的含量或添加生物酶制剂,以提高饲料的利用效率,提高养殖效益。     

美洲鲥室内人工育苗技术初探

为探究美洲鲥室内人工育苗的技术方法,对其受精卵孵化及苗种培育进行了初步的研究。在美洲鲥苗种培育过程中,用空气能制冷制热机组将受精卵孵化温度控制在17～19℃,苗种培育温度控制在19.0～20.5℃,并以池塘培养的生物饵料(轮虫、枝角类和桡足类等)作为仔鱼的开口饵料。试验结果:2017—2019年连续3年,每年4—8月收集美洲鲥卵,数量分别为277.96万、471.48万、2 226.32万粒,获得的受精卵分别为18.58万、74.47万、195.85万粒,受精率分别为6.68%、15.80%、8.80%;受精卵孵化后,仔鱼经30～50 d的室内水泥池培育,最终分别获得体长30～50 mm并已成功驯化摄食配合饲料的幼鱼9 392、40 083、78 600尾,育苗成活率分别为11.01%、15.00%、15.72%。试验获得了1套适合上海地区美洲鲥室内人工育苗的模式,可以为美洲鲥后续的人工育苗研究和规模化苗种培育生产提供技术参考。     

美洲鲥(Alosa sapidissima)胚胎发育形态学及组织切片观察

通过显微镜及连续切片技术,研究了美洲鲥(Alosa sapidissima)胚胎发育过程中的形态学及组织学特征.结果显示,在孵化温度为(21.0±0.5)℃的条件下,美洲鲥受精卵经过71 h 15 min大量孵化出膜,其胚胎发育阶段主要分为6个时期.受精卵第1-5次卵裂均为经裂,第6次卵裂(64细胞期),纬裂出现,胚盘被分为外部的包被层和内部的深层细胞两部分.受精6 h 2 min,内外卵黄合胞体层形成.受精7h 40 min,囊胚腔出现.受精10 h 39 min,胚盘下包30％,胚盾形成;受精14 h 50 min,下包50％,三胚层形成;受精17 h 33 min,下包75％,神经板形成;受精21 h 13 min,下包90％,脑原基、视囊、脊索原基和体节出现;受精24h 15 min,完全下包,神经胚、听囊、前脑、中脑及后脑出现.受精24 h 55 min,克氏囊形成.受精35 h 44 min,心脏和消化管出现;42h50 min肾小管形成;47 h 35 min克氏囊消失;60 h 15 min角膜出现.70h 15 min,仔鱼大量出膜,初孵仔鱼具有一个大而均质的卵黄囊,上面布有明显的色素.美洲鲥胚胎发生发育的特征与大多数报道的硬骨鱼类类似,但在分化发育的时序上具有较大的差异.     

Skeletal development and abnormalities of the vertebral column and fins in larval stage of hatchery‐reared American shad,Alosa sapidissima

The present study describes the skeletal development and the occurrence of deformities in American shad, Alosa sapidissima, larvae from hatching to 45 days after hatching (DAH). The ontogeny of the vertebral column started at 16 DAH (days after hatching), with the formation of the posterior neural and haemal arches, and was complete at 28 DAH. In comparison, the vertebral centra started to form at 16 DAH, with ossification being visible in all centra at 38 DAH. The pectorals were the only fins that formed before the onset of feeding (at 2 DAH), with ossification being complete at 45 DAH. The caudal fin formed at 5 DAH, with ossification being complete at 40 DAH. Dorsal and pelvic fin development began at 6 DAH and 20 DAH respectively. The ossification of both the dorsal and pelvic fins was visible at 45 DAH. The anal fin began forming at 14 DAH, and was complete at 30 DAH. The ossification of the anal fin was complete at 45 DAH. Overall, 22 types of skeletal deformities were detected in about 41% of individuals. Most anomalies were detected in the haemal region, while the fewest anomalies were detected in the anal fin. In addition, the frequency of deformities gradually increased with fish age at the different developmental stages. Our results are expected to contribute baseline information on how rearing conditions impact skeletal development, in addition to identifying potential causative factors of skeletal deformities.     

美洲鲥(Alosa sapidissima)眼睛早期发育的组织学观察

应用石蜡切片及HE染色的方法对美洲鲥(Alosa sapidissima)早期发育过程中眼睛的发生、分化和形成过程进行了系统的观察.结果显示,受精后21 h 13 min,视泡出现;受精后26h 23 min,视泡发育成视杯;受精后35 h 44 min,原始视网膜和晶状体形成;受精后60h 15 min,角膜在视网膜前缘处形成,由单一的立方上皮构成;2日龄仔鱼,巩膜分化完成,由软骨组织和弹力纤维构成,脉络膜出现;3日龄仔鱼,虹膜出现,视网膜分化完全,由外向内的色素层、视觉细胞层、外界膜、外核层、外网膜层、内核层、内网膜层、视神经节细胞层、视神经纤维层和内界膜10层构成,此时视觉细胞层中视杆细胞出现;14日龄仔鱼,角膜分化完全,由自外向内的复层扁平上皮、前弹性层、基质层、后弹性层和内皮层5层构成;22日龄仔鱼,脉络膜腺出现;26日龄稚鱼脉络膜分化完全,由外向内依次为银膜层、血管层和色素层,虹膜也完全分化,由外向内依次为虹膜内皮层、前缘层、基质层、后缘层和色素层;45日龄幼鱼,视网膜内核层分化成两层水平细胞.此时美洲鲥眼睛的各个结构均发育完善.     

Lipid content and fatty acid composition in female American shad,Alosa sapidissima,at different stages of ovarian development under reared conditions

The fatty acid accumulation in broodstock influences the fecundity of spawners as well as egg quality. A comprehensive understanding of the lipid and fatty acid changes in broodstock during the reproductive period can increase our knowledge of the nutritional requirements in artificial breeding programs. The study assessed the lipid and fatty acid compositions of muscle, liver and ovary of American shad at different stages of reproductive development under reared conditions. The results indicated that there were significant differences in lipid content among ovary, liver and muscle. Mean total lipid levels in ovary, liver and muscle were 15.92%–10.87%, 13.62%–6.89%, 10.39%–6.11% respectively. During the development season, the total lipid content in muscle in stages V and VI were significantly lower than those in stages II and III. The total lipid content in liver in stages IV, V and VI was significantly lower than in stages II and III, whereas the total lipid content in the ovary increased significantly as the gonad developed and reached its highest value at stage V. From II to VI stage, the liver content of docosahexaenoic acid (DHA) decreased and the ovarian content of DHA increased, whereas the content of eicosapentaenoic acid (EPA) remained relatively constant. The content of C16:0 and C18:1n‐9 decreased in muscle and liver, but significantly increased in ovary. It is therefore suggested that the lipids were preferentially transferred from muscle and liver to ovary beginning in stage IV as the gonad matured. At stage IV, the lipid transfer accelerated, and saturated and unsaturated fatty acids, such as C16:0, C18:1n‐9, DHA, EPA and arachidonic acid, were selectively transferred to and conserved in ovaries.     

Predator response to releases of American shad larvae in the Susquehanna River basin

Abstract— Predation on American shad ( Alosa sapidissima ) larvae within the first two hours of release was examined from 1989 to 1992 on 31 occasions at stocking sites in the Susquehanna River basin. Twenty-two fish species consumed shad larvae; the dominant predators were spotfin shiner ( Cyprinella spiloptera ), mimic shiner ( Notropis volucellus ) and juvenile smallmouth bass ( Micropterus dolomieu ). The number of shad larvae found in predator stomachs ranged from 0 to 900. Mortality of shad larvae at the stocking site was usually less than 2%. The greatest mortality (9.6%) occurred at the highest stocking level (1.5 million larvae). Highly variable predation rates and release levels of shad insufficient to achieve predator satiation hindered the ability to determine a specific type of functional response of predators. Predator numbers increased with stocking density, indicating short-term aggregation at the release site. Because of practical problems associated with releasing the large numbers of larvae that would be required to satiate predators, routine stocking at these levels is probably unreasonable. Releases of 400,000 to 700,000 larvae may reduce predation by offsetting depensatory mechanisms that operate on small releases and the effects of increased predation due to predator aggregation on large releases. Night stocking may reduce predation on larval shad at the release site.     

Digestion of larval American shad by cyprinids

Cyprinids have pharyngeal teeth for grinding food before swallowing and a continuous gut with no discrete stomach. This digestive tract structure, as well as the feeding behavior traits shown by cyprinids, makes it difficult to identify and measure the amount of food consumed by these fishes. The relations among quantity of food in cyprinid gut, time after feeding and predator size were described by log-linear multiple regression. The number of intact American shad (Alosa sapidissima (Wilson)) larvae eaten in laboratory experiments was estimated by extrapolating the regression for the amount of food in the gut over time for predators of various size. The numbers of larval American shad in guts of fish captured in the Juniata River, Pennsylvania, were not significantly different from those estimated with the equations derived from laboratory data. In view of their abundance in rivers and their potential digestion rate for larval fish, cyprinids can be expected to have a marked influence on reducing the numbers of larval American shad.