鲥鱼在中国东南近海生殖洄游期间性腺发育的研究

鲥鱼是名贵的溯河洄游性鱼类,每年春夏之交,沿我国东南近海作生殖洄游,并溯入长江、钱塘江和珠江繁殖。对长江和钱塘江鲥鱼性腺发育的研究,国内已有一些报导,如陆桂等曾记述过钱塘江鲥鱼Ⅳ期和Ⅴ期性腺的外形特征,作者等曾注意过鲥鱼在近海和钱塘江洄游期间的性腺发育。     

钱塘江鲥鱼的自然繁殖及人工繁殖

一、钱塘江鲥鱼的自然繁殖(一)钱塘江鲥鱼渔业生物学Ⅰ．材料和方法;Ⅱ．产卵洄游的动态及其资源概况;Ⅲ．亲鱼群体组成;Ⅳ．鲥鱼产卵群体的性腺发育状况和丰满系数;Ⅴ．幼鲥的栖息场所及其成长与降河。     

东莞市池养鲥鱼三周年

一九八七年，东莞市水产局和长江水产研究所分别接受省科委和农业部的任务，共同合作，开晨珠江鲥鱼的上岸养殖和全人工繁殖试验。经过三周年的攻关，在鲥鱼的生物学、养殖生态学、幼鱼索饵场的发现和人工采苗、鉴别技术，以及池塘养鲥鱼试验，后备亲鱼的培育和性腺发育的研究等方面，均取得了可喜的阶段性成果．一九八七年捕捞的当年鱼苗，     

池养鲥鱼全人工繁殖的机理↑（*）

本研究首次成功地在盐度０．５～１２的咸淡水池塘中驯养鲥幼鱼至６龄，并提出池养鲥鱼全人工繁殖机理。采用外源内分泌药理学和生态学的方法刺激鲥鱼早春脂肪积累和血清中的１７β－Ｅ２的合成与分泌，启动性腺发育和诱导成熟，４、５、６龄雌鱼的成熟率分别达８３．３％、８７．５％和１００％；在催产过程中采用神经介质抑制剂和可的松对抗剂，克服池养鲥鱼排卵机制障碍和产卵前紧张反应的副效应，获得约８００００粒的受精卵，受精率约７５％，从而突破了池养鲥鱼不育症。     

赣江鲥鱼产卵场生殖群体生物学的研究

本文主要报导江西省赣江鲥鱼产卵场江段鲥鱼生殖群体生物学的测定和解剖，并描述其形态特征和性腺发育成熟等情况。鲥鱼[Macrura reevsii(Richardson)]属鲱形目、鲱科、鲥属、为溯河性鱼类，每年一度由海入江进行生殖洄游，在长江形成渔讯。长江鲥鱼产量1974年曾达157．5万公斤，由于近十多年来工业排污和水利设施以及围湖造田、酷渔滥捕等人为因素的影响，致使鲥鱼产量每况愈下，到1986年止，长江鲥鱼捕获量只有1万公斤。赣江鲥鱼产量也由历史上最高产量12328公斤降到1986年的249．5公斤。关于鲥鱼生物学方面的调查测定，前人巳有过研究，见参考文献(1)、(2)、(3)、(4)，但上述的测定与描述仅在生态因子，自然繁殖及人工繁殖方面的探索，而在生物学方面的测定尚无完整的描述和统计。到1971年以后鲥鱼攻关小组的方向还在人工繁殖及养殖试验方面的研究，由于受财力、人力、技术水平等条件的限制，有关基础理论方面研究得较少，所以至今仍在探索之中。1986年江西省水产科学研究所根据农牧渔业部水产局下达的课题精神，在进行鲥鱼人工繁殖试验的同时，有目的地对亲鲥生殖群体有关生物学方面的材料进行系统全面的收集整理。这次共测定试验材料192尾，旨在取得更有代表性的数据，以便对鲥鱼有一个较全面、完整的描述。同时，本文还对赣江鲥鱼产卵场亲鲥的生长发育历年来的变化作了一些探讨。     

长江鲥鱼卵巢的发育特点及怀卵量

鲥鱼是长江下游的名贵经济鱼类之一。每年4—5月由海入江上溯产卵,形成了一年一度的渔汛期。了解鲥鱼生殖腺发育的特点及怀卵量的变化,掌握其生殖腺成熟时撞、繁埴地点以及繁殖的生态条件等,为长江鲥龟资源增殖提供可靠的生物学依据。将收集到的生殖腺材料进行整理。由于条件的限制,鲥鱼在海洋里的生殖腺标本,采集到的较少,有待今后补充。鲥鱼入江后的精巢发育不像卵巢那样复杂,在此不详加     

长江鲥鱼卵巢的发育特点圾怀卵量

鲥鱼是长江下游的名贵经济鱼类之一。每年4—5月由海入江上溯产卵，形成了一年一度的渔汛期。了解鲥鱼生殖腺发育的特点及怀卵量的变化，掌握其生殖腺成熟时间、繁殖地点以及繁殖的生态条件等，为长江鲥鱼资源增殖提供可靠的生物学依据。     

鲥鱼消化器官的形态与特征

研究了鲥鱼 Macrua reeuesii(Rich.)消化系统主要消化器官的形态与特征,观察了体长2. 2～79.00毫米仔、稚、幼鲥鱼发育过程中各阶段主要消化器官形态的变化.     

虾蟹类营养繁殖研究进展

甲壳动物亲体在性腺发育过程中的营养需要和生长需要不同,必须给予适当的营养物质才能使亲体的性腺正常发育。亲体性腺发育状况直接影响胚胎和幼体的发育。本文综述了蛋白质、脂肪、维生素等对虾蟹类亲体性腺、胚胎、幼体发育的影响。     

黄山浦溪河光唇鱼的性腺发育周年变化

采用组织切片法,对黄山浦溪河光唇鱼(Acrossocheilus fasciatus)的性腺发育、产卵时间和产卵类型等进行了研究。结果显示:其性腺的发育分为六6个时期,卵母细胞的发育分为5个时相。产卵时间始于四月,持续到八月。光唇鱼属于一次性产卵类型,每年成熟一次。在整个性腺发育过程中,雌性个体右侧性腺先于左侧性腺发育;雄性个体右侧性腺在整个发育过程中一直处于优势。     

Threadfin Shad Dorosoma petenense Effects on Water Quality, Phytoplankton, and Channel Catfish Production in Ponds

Threadfin shad Dorosoma petenense are often stocked into commercial catfish ponds for biological control of algae. It is thought that the fish will alter the phytoplankton community, improve water quality, and enhance channel catfish production. Co-stocking of shad and catfish is a common practice, although there is limited information regarding the effects of threadfin shad on pond dynamics and catfish production. To evaluate the influence of shad in catfish ponds, this study was conducted in ten 0.04-ha experimental earthen ponds near Auburn, Alabama. All ponds were stocked in April with 600 fingerling channel catfish Ictal-urus punctatus (13,200/ha) with a mean length of 10.4 cm (4.1 in). Additionally, five of these ponds were randomly chosen and stocked with 70 adult threadfin shad (1,750/ha) weighing a total of 3.3 kg (16.5 kg/ha). At harvest in November, an average of 1,284 threadfin shad (32,100/ha), weighing a total of 55 kg (1,375 kg/ha) were collected from each shad pond. Water quality was improved with the addition of threadfin shad to channel catfish ponds. Mean total ammonia-nitrogen was significantly lower and less variable in the shad treatment. Observed mean nitrite concentrations, though not significant, were lower in the shad treatment. The phytoplankton community of the shad treatment had significantly higher density, more taxa, and smaller organisms. Pond water in the shad treatment had higher projected early morning dissolved oxygen levels requiring less aeration. Channel catfish had significantly higher survival in the shad treatment, furthermore, though not statistically significant, observed mean fish production was higher and feed conversion ratio was lower than in the no-shad treatment.     

人工生态条件下鲥鱼保种越冬的试验研究

在低盐度人工生态条件下鲥鱼保种越冬获得成功。在总密度为56.13尾/米~2(鲥鱼0.37尾、淡水白鲳55.76尾/米~2)的条件下,鲥幼鱼成活率达92.0％,3龄鱼达100％;在鲥鱼密度为8.99尾、淡水白鲳密度为7.80尾/米。的条件下,鲥幼鱼成活率达89.4％,3龄鱼达100％。试验表明,鲥鱼越冬期间可摄食人工饲料,无需投喂浮游生物;鲥鱼的商品化养殖越冬是可行的。     

Channel Catfish Polyculture with Fathead Minnows or Threadfin Shad: Effects on Pond Plankton Communities and Catfish Fillet Flavor,Color, and Fatty Acid Composition

Threadfin shad, Dorosoma petenense, or fathead minnows, Pimephales promelas, were co‐cultured with channel catfish, Ictalurus punctatus, in earthen ponds to determine the effects of planktivory on plankton community dynamics and catfish fillet quality. Fathead minnows had no effect on the plankton community structure or catfish fillet flavor, color, and fatty acid composition. Fillet color was also unaffected by the presence of threadfin shad. Small differences were found in fillet fatty acid composition for catfish from ponds with shad, but these differences probably have no biological significance. Threadfin shad did, however, have important impacts on the plankton community structure and catfish flavor. Size‐selective filter‐feeding by shad reduced cyanobacterial abundance relative to ponds with catfish‐only and fathead minnows. Relative abundance of smaller phytoplankton in the groups Chlorophyta, Cryptophyta, Bacillariophyceae, and Euglenophyta increased in ponds with shad. Relative abundance of small zooplankton (rotifers) also increased in shad ponds. Reduced abundance of large, colonial cyanobacteria that are known to produce odorous metabolites caused a corresponding reduction in off‐flavor prevalence and intensity in catfish from ponds with threadfin shad when sampled in September. Although threadfin shad dramatically reduced catfish off‐flavor prevalence during the warm season, they apparently caused a high prevalence of “fishy” off‐flavors in the February sample. This undesirable flavor appeared to be caused by catfish foraging on shad killed during a preceding period of exceptionally cold water temperatures. Use of threadfin shad for phytoplankton biomanipulation therefore presents a dilemma: catfish–shad polyculture reduces prevalence of cyanobacteria‐related off‐flavors in warm months but may cause undesirable forage‐related off‐flavors in the colder months. Catfish farmers must consider these benefits and risks when deciding to use threadfin shad as a management tool.     

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。     

Association of Aeromonas sobria with mortalities of adult gizzard shad, Dorosoma cepedianum Lesueur

Abstract. This report describes an epizootic in a natural population of spawning females of gizzard shad, Dorosoma cepedianum Lesueur, which occurred in the Potomac River (Maryland, USA). Microbiological analysis of moribund shad revealed the presence in pure culture in all the organs examined of one bacterium which was identified as Aeromonas sobria by conventional tube and plate tests. The different API-systems used to attempt for a rapid diagnosis of the disease yielded false negative and positive reactions in important differential tests such as ornithine decarboxylase, arabinose fermentation, gelatinase, urease, indole and production of H₂S which gave an erroneous identification of the shad isolate. The virulence assays in rainbow trout revealed that A. sobria was pathogenic with a mean LD₅₀ of 2 × 10⁵. Bacterial extracellular products also displayed fish lethality and were cytotoxic for poikilothermic and homeothermic cell-lines. Although the source of shad infection is unknown, the physico-chemical conditions of the river, together with the stress associated with the spawning could have been contributing factors in the proliferation of A. sobria inducing this epizootic.     

Genetic characterisation of the Rhodanian twaite shad, Alosa fallax rhodanensis

Abstract  Data on the genetic characteristics of the rhodanian shad, Alosa fallax rhodanensis Roule, using three Mediterranean populations (rivers Rhône, Aude and Hérault) and seven protein markers are presented. Allelic frequency distribution, and absolute and relative genetic diversity show a genetically homogeneous structure in the Mediterranean populations. Results when compared with allis ( Alosa alosa Linné) and twaite ( Alosa fallax fallax Lacépède) shad Atlantic populations confirm that the Rhodanian shad belongs to the Alosa fallax Roule species. Furthermore, genetic characteristics of the twaite shad Mediterranean group were quite different from Atlantic populations but remained close to the most southern Atlantic population in the Oued Sebou (Morocco). These findings suggest that Rhodanian shad should be considered a well identified homogeneous group within Alosa fallax rather than a subspecies because of the low genetic distance and some relatively different biological characteristics between the Atlantic and Mediterranean twaite shad groups.     

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。     

From salmon to shad: Shifting sources of marine‐derived nutrients in the Columbia River Basin

Like Pacific salmon (Oncorhynchus spp.), nonnative American shad (Alosa sapidissima) have the potential to convey large quantities of nutrients between the Pacific Ocean and freshwater spawning areas in the Columbia River Basin (CRB). American shad are now the most numerous anadromous fish in the CRB, yet the magnitude of the resulting nutrient flux owing to the shift from salmon to shad is unknown. Nutrient flux models revealed that American shad conveyed over 15,000 kg of nitrogen (N) and 3,000 kg of phosphorus (P) annually to John Day Reservoir, the largest mainstem reservoir in the lower Columbia River. Shad were net importers of N, with juveniles and postspawners exporting just 31% of the N imported by adults. Shad were usually net importers of P, with juveniles and postspawners exporting 46% of the P imported by adults on average. American shad contributed <0.2% of the total annual P load into John Day Reservoir, but during June when most adult shad are migrating into John Day Reservoir, they contributed as much as 2.0% of the P load. Nutrient inputs by American shad were similar to current but far less than historical inputs of Pacific salmon owing to their smaller size. Given the relatively high background P levels and low retention times in lower Columbia River reservoirs, it is unlikely that shad marine‐derived nutrients affect nutrient balances or food web productivity through autotrophic pathways. However, a better understanding of shad spawning aggregations in the CRB is needed.     

Threadfin shad impacts phytoplankton and zooplankton community structures in channel catfish ponds

Plankton community structure and chlorophyll a concentration were compared in twelve 0.1 ha earthen ponds co‐stocked with channel catfish (Ictalurus punctatus Rafinesque, 1818) in a multiple‐batch culture (initial biomass=5458 kg ha^?1) and a planktivore, threadfin shad (Dorosoma petenense Güther, 1867; initial biomass=449 kg ha^?1), during the April–November growing season. We used a completely randomized design in a 2 × 2 factorial arrangement to test the planktivore level (presence or absence of threadfin shad) and channel catfish feeding frequency (daily or every third day). Channel catfish were fed a 32% protein feed to apparent satiation on days fed. The presence of threadfin shad affected phytoplankton and zooplankton community structure more than did feeding frequency, and the impact in ponds was more pronounced after 1 July. The numbers of all major groups of zooplankton were lower in ponds with threadfin shad, but were unaffected by the feeding frequency. Chlorophyll a concentration before 1 July was higher in ponds with threadfin shad and unaffected by the feeding frequency, whereas after 1 July it was higher in ponds without threadfin shad and that were fed daily. Phytoplankton community structure after 1 July was dominated by nuisance algal bloom genera of cyanobacteria in ponds without threadfin shad and by Bacillariophyceae in ponds with threadfin shad.     

Environmental DNA reveals the temporal and spatial extent of spawning migrations of European shad in a highly fragmented river basin

1. Artificial barriers on lowland rivers impede the spawning migrations of anadromous fishes, preventing access to historical spawning areas. In the cryptic European shads Alosa alosa and Alosa fallax (‘shad’ hereafter), this has resulted in population declines across their range. Conservation programmes aim to facilitate the passage of migrators over these barriers and so require baseline information on the spatial and temporal extent of current migrations.
2. Here, a shad-specific environmental DNA (eDNA) assay was used to quantify the spatial extent of shad spawning migrations in the River Severn basin, western England. This basin is characterized by the presence of multiple barriers in the lower catchment. In 2017, the eDNA assay was piloted in the River Teme, an important shad spawning tributary, and then applied in 2018 and 2019 across the lower Severn basin.
3. In all years, shad DNA was detected between mid-May and mid-June, with the maximum spatial extent of shad distribution being in early June when shad eDNA was detected upstream of weirs that were generally considered as impassable. In 2018, this included the detection of shad above the most upstream weir on the main River Severn that required individual fish to have passed six weirs.
4. Although barriers inhibit the spawning migrations of shad, this eDNA assay showed that some highly vagile individuals might be able to ascend these barriers and migrate considerable distances upstream. This suggests that efforts to increase the permeability of these barriers could result in relatively high numbers of migrating shad reaching upstream spawning areas. These results demonstrate that this eDNA assay could also be used across their range, to further quantify the spatial extent of their spawning, including in highly fragmented rivers and those where shad are believed to spawn only occasionally and are rarely observed.