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.     

长三角地区美洲鲥工厂化养殖水温管理措施

长三角地区是我国美洲鲥引种、繁育和养殖的发源地,一直以来都是国内美洲鲥的主要养殖区,常见于池塘养殖和工厂化养殖。工厂化模式不但能够较好地满足美洲鲥的养殖条件要求,而且非常适合该地区土地资源稀缺、价格昂贵的特点,因而被养殖户广泛采用。根据养殖经验,美洲鲥鱼种养殖水温应控制在10~32℃,鱼苗和成鱼养殖阶段温度耐受范围更窄。     

江苏地区美洲鲥“两段式养殖”模式探索

正目前,美洲鲥养殖以工厂化温室养殖为主,然而温室造价大,产能低,养殖成本高,因此尽管美洲鲥引进我国已经近20年,但养殖产量依然没能满足消费市场的需求。本试验利用工厂化温室和室外土池塘、室外网箱相结合进行美洲鲥"两段式养殖"模式的探索,在工厂化温室进行美洲鲥鱼苗阶段的培育,经过越冬后放至室外土池或     

水库网箱美洲鲥养殖试验

<正>美洲鲥(Alosa sapidissima)属鲱形目,鲱科,鲥亚科,西鲱属,分布在北美洲大西洋西岸从加拿大魁北克省到美国的佛罗里达州河流和海洋中,与中国鲥(Tenualosa reevesii)同属一个亚科,是一种有较高营养和经济价值的溯河产卵洄游性鱼类[1,2]。由于目前中国鲥鱼资源的急剧减少,但人们对鲥鱼需求的热情不减,因此我国从2003年开始从美国引进美洲鲥,希望能够在中国驯养成功,以供市场之需。经过10年的驯化养殖摸索,美洲鲥的养殖水平不断提升,养殖成活率也得到一定的提高[3,4]。中国     

美洲鲥亚成鱼池塘大棚越冬养殖试验

为弥补美洲鲥对水温耐受性较差的缺陷,使其在上海乃至江浙地区能自然过冬,2016-2019年通过在养殖池塘上搭建保温棚,开展了美洲鲥2龄鱼种越冬养殖试验。试验结果:2016-2017年、2017-2018年、2018-2019年3年越冬期间,美洲鲥的体长相对增长率分别为26.58%、5.63%、11.87%,体质量相对增长率分别为96.21%、27.46%、49.6%,养殖成活率分别为93.1%、70.5%、95.0%,饲料系数分别为2.36、3.51、2.21。结果表明,水温在12℃以上时,2龄美洲鲥摄食良好,越冬期仍然是其重要的生长期,在池塘上搭建越冬保温棚能够使美洲鲥安全过冬。建议在江浙沪等地区搭建越冬棚养殖美洲鲥,越冬放养密度控制在1000~1200尾/亩(15亩=1 hm^2,下同)。     

美洲鲥池塘养殖试验

<正>为了更好地在南通地区推广美洲鲥的养殖,2022年5月开始笔者在南通市通州区五接镇开沙村里沙养殖场开展了美洲鲥池塘养殖试验,至2023年11月生产商品美洲鲥15.1吨,平均亩产1 760千克,亩效益3.04万元。现将试验情况总结如下。一、养殖设施及材料1.养殖池塘本试验的养殖塘口为里沙养殖场8号,池塘长110米,宽52米,面积8.58亩。池塘水泥护坡,池塘深度4.0米(主要方便美洲鲥越冬和渡夏)。养殖池上方建有大棚设施,方便冬季美洲鲥越冬。     

美洲鲥人工繁殖再获新突破

近日,由中国水产科学研究院珠江水产研究所朱新平研究员主持的“美洲鲥人工驯养项目》获得新突破。4月底至5月初,项目研究小组对池养2冬龄美洲鲥进行了多次人工繁殖试验,最终以生态调控方式,成功促使池养美洲鲥亲鱼自然产卵,获得美洲鲥受精卵10万余粒,孵化出美洲鲥仔鱼1万余尾。这是继2009年度该项目组在美洲鲥苗种培育与养殖中取得苗种培育成活率达到85％,养殖成活率达90％成绩基础上的又一突破。     

美洲鲥专题系列讲座 美洲鲥人工养殖技术

<正>我国美洲鲥的养殖规模日益扩大,主要集中在长三角及湖北、四川等地,每年苗种的放养量在250万～350万尾。养殖美洲鲥的常用模式有集约化养殖、大水面网箱养殖、遮阳池塘养殖等。近几年,长三角地区逐渐兴起大棚结构池塘养殖,该模式具有养殖要求低、能耗较低、成本可控、管理方便等优点。现将美洲鲥的大棚结构池塘养殖模式介绍如下。     

从鲥鱼洄游路径的分析探讨美洲鲥养殖的温度管理

综合国内外有关文献,比较中华鲥(Tenualosa reevesii)和美洲鲥(Alosa sapidissima)两种鲥鱼洄游路径中对温度的适应性特征,结合笔者多年来在美洲鲥养殖及技术研发过程中所观察到的美洲鲥在繁殖、育苗和养殖阶段的温度适应性变异现象,提出适合美洲鲥养殖的温度和水质管理方案,以期降低高温缺氧综合症(thermal hypoxemia)和低温水霉病引发的养殖风险,促进其养殖产业的健康发展。     

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.     

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 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.     

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.

     

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。     

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.     

人工诱导池养3+龄鲥鱼性腺发育的初步试验与探讨

通过模似鲥鱼性腺发育的自然生态条件和埋植 LHRH-A 和 Testosterone 缓释放颗粒激素,诱导池养3~+龄鲥鱼性腺发育季至第1期,成熟系数达0.9%。试验摸索出麻醉操作鲥鱼不死的有效方法。对今后鲥鱼全人工繁殖的前景及有关问题进行了探讨.     

A simplified approach for estimating age‐0 gizzard shad prey supply and predator demand

Gizzard shad, Dorosoma cepedianum (Lesueur), often compose a majority of the prey biomass in southern US reservoirs. Previous studies suggest prey limitation frequently occurs in these systems, suggesting that fisheries managers need tools to evaluate the production potential of the populations they manage. Bioenergetics modelling was used to quantify the abundance of age‐0 gizzard shad necessary to sustain multiple piscivore species with diverse growth rates, population sizes, mortality rates and diets. Gizzard shad biomass at the 50th percentile of published values was insufficient to support seven piscivore species in 69% of the simulations, suggesting that above‐average prey biomass is required to support multiple piscivore populations at high abundance and growth rates. To help guide management, estimates of the gizzard shad biomass needed to sustain piscivore communities are provided for management situations in which coarse‐scale (low, medium or high) growth, population size and percent of shad in diet data are available.     

Lactococcus lactis,causative agent of an endocarditis valvularis and parietalis thromboticans in the allis shad,Alosa alosa (L.)

Since the 1940s, the anadromous allis shad, Alosa alosa (L.), has suffered population declines throughout its distribution range in Europe. In context of EU‐LIFE projects for the reintroduction of the allis shad in the Rhine system, a comprehensive study was started in 2012 to investigate infectious diseases occurring in allis shad. In course of the study, 217 mature and young‐of‐the‐year allis shad originating from the wild population from the Gironde–Garonne–Dordogne system (GGD‐system) and the Rhine system as well as 38 allis shad from the breeding population were examined by use of bacteriological and histological methods. In 2012 and 2014, an endocarditis valvularis thromboticans caused by a coccoid bacterium was detected in 16% and 25% of mature allis shad originating from the GGD‐system. Results of microbiologic examinations, including biochemical characteristics, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) and 16S rRNA gene sequence analysis, revealed Lactococcus lactis as causative agent of this infection. This is the first report of an endocarditis valvularis and parietalis thromboticans caused by Lactococcus lactis in fish. Possible sources of infection as well as the impact for the reintroduction programme are discussed.