克氏原螯虾两种养殖模式的食物网结构及其食性比较

为比较克氏原螯虾(Procambarus clarkii)精养模式和稻虾共作模式下的食物网结构及其食性差异, 对两种养殖模式的基础食源与消费者的δ13C和δ15N进行了分析, 并借助SIBER考察了各自的食物网结构, 定量计算不同饵料对克氏原螯虾食物的贡献率。结果显示: 在采集的19种样品中, 消费者的δ13C值介于–34.22‰—–25.34‰, δ15N值介于2.33‰—8.05‰, 营养级介于1.46—3.64; 在精养模式下克氏原螯虾的营养级(2.34)高于共作模式(1.79)。食物网结构参数对比表明, 两种模式下克氏原螯虾的生态空间利用率接近, 但共作模式的食物网营养结构多样性较高, 群落的营养生态位范围较宽, 食物网的营养冗余程度较低, 不同物种竞争激烈程度较低; 食性分析显示, 在两种模式下克氏原螯虾的δ15N值与其体长、体重具有线性正相关关系, 说明克氏原螯虾营养级随着其体型增大而提高, 另外克氏原螯虾在两种养殖模式中均偏向于摄食动物性饵料, 共作模式中克氏原螯虾饵料来源分布较精养模式更均匀, 其植物性饵料贡献率较精养模式更高。研究表明: 精养模式的物质能量从基础食源传至克氏原螯虾的传递损耗较共作模式要高; 与精养模式相比, 稻虾共作模式中克氏原螯虾更偏向植食性。     

河蟹、克氏原螯虾、黄鳝摄食生态的研究

通过疫区围网养殖河蟹、黄鳝、克氏原螯虾试验,解剖观察食性表明:河蟹、黄鳝、克氏原螯虾都可以摄食钉螺、蚊幼虫.为进一步验证它们的这一食性及其摄食量,通过模拟网栏养殖模式的数据统计表明:河蟹每天每只能摄食蚊幼虫2.4尾、钉螺4.8个;克氏原螯虾每天每只能摄食蚊幼虫17.尾、钉螺0.9个;黄鳝每天每尾摄食蚊幼虫8.1尾、钉螺0.7个;河蟹、克氏原螯虾、黄鳝摄食生态的研究为生物灭螺、灭蚊提供新的途径.       

克氏原螯虾的入侵生态学研究进展

克氏原螯虾(Procambarus clarkii)原产于美国南部和墨西哥北部,是一个著名入侵物种,作为一种水产经济资源物种在世界各地扩散。克氏原螯虾抗逆性强,所具有的广泛生境适应性、生长迅速、高生殖率等特点使它们迅速建立野生种群。近10余年的研究认为,克氏原螯虾通过捕食和资源竞争等机制严重威胁引入地的水生植物、无脊椎动物、两栖类等的生存,显著降低引入地的生物多样性。当前,由于克氏原螯虾的经济价值高,它会借助于人力的作用而继续扩散。为认清和减少克氏原螯虾对引入地的生态影响,应加强以下方面的研究:1)在中国开展克氏原螯虾的生态危害的调查和研究;2)克氏原螯虾种群调节和控制对策研究;3)被入侵地的生态恢复工作。     

植物蛋白替代鱼粉对克氏原螯虾生长和繁殖的影响

为了探究复合植物性蛋白(豆粕﹕菜粕=1﹕1)替代鱼粉对克氏原螯虾(Procambarus clarkii)生长以及繁殖性能的影响, 实验以豆粕和菜粕为植物性蛋白源配制了6组不同替代水平的等氮等能的饲料并选取其中替代水平较高的3组添加蛋氨酸和赖氨酸, 进行为期10周的养殖实验。实验结果表明: 随着饲料中植物蛋白水平的提高, 克氏原螯虾增重率和绝对繁殖力均显著下降(P<0.05)。与对照组相比, 添加适量的植物性蛋白(33.8%)能显著提高克氏原螯虾的生长性能的同时对其绝对繁殖力和性腺指数无明显影响(P<0.05)。此外, 在饲料中添加高水平的植物蛋白抑制克氏原螯虾的生长并且降低其繁殖能力, 而在饲料中补充赖氨酸和蛋氨酸可以很好地改善这一状况。另外, 尽管每组饲料的处理方式不同, 但是克氏原螯虾性腺指数与绝对繁殖力变化一致。     

不同施肥模式对克氏原螯虾稻田养殖水体浮游植物群落结构的影响

为探讨在克氏原螯虾(Procambarus clarkii)稻田养殖水体中施用不同肥料对浮游植物群落结构的影响,以湖北省荆州市太湖农场稻虾模式试验基地为场所,于2019年4—5月进行试验,设置施化肥、施有机肥和施有机-无机复混肥3个处理.每块稻田中克氏原螯虾的放养密度为2.30ind/m2.结果发现,施化肥、施有机肥和...     

安徽地区克氏原螯虾白斑综合征的诊断及朔源

[目的]诊断安徽地区养殖的克氏原螯虾发生疫情的病原,追踪感染源,为疫病的防控提供依据.[方法]采集病料,参照OIE推荐的套式PCR法检测白斑综合征病毒(WSSV).将病螯虾鳃丝组织研磨后离心,取上清液接种健康克氏原螯虾.透射电镜观察病原特征.综合流行病源学及病原检测,分析养殖地区的可能感染源.[结果]发病螯虾感染了WSSV,动物实验可见和发病螯虾相同的临床症状,证实该病原引起养殖螯虾发病.电镜观察可见典型的白斑综合症病毒颗粒.流行病学调查显示,水产颗粒膨化饲料和冷冻饲料甲壳类检测阳性.[结论]该地区养殖的克氏原螯虾近年爆发的疫病病原为WSSV,推断地区性克氏原螯虾WSSV的感染并流行与污染的饲料有关.     

桂林地区克氏原螯虾对泽蛙蝌蚪的捕食

克氏原螯虾（Procambarus clarkii）已入侵我国江苏、湖北、江西、安徽等多个省（市）。为研究克氏原螯虾对其生境中主要两栖动物泽蛙（Rana limnocharis）的影响,我们于2006年5-6月对广西桂林地区自然生境中克氏原螯虾和泽蛙蝌蚪的数量和密度进行了调查,7月在室内进行了克氏原螯虾对泽蛙蝌蚪和饰纹姬蛙（Microhyla ornata）蝌蚪的捕食实验。野外调查结果表明克氏原螯虾的密度与泽蛙蝌蚪的密度呈显著负相关。室内实验结果表明克氏原螯虾对泽蛙蝌蚪的捕食强度与克氏原螯虾体长呈显著正相关,且对泽蛙蝌蚪的捕食强度高于饰纹姬蛙蝌蚪。表明克氏原螯虾对两栖类幼体有比较严重的危害,应加强监测,采取相应措施预防和控制其危害。     

长江下游地区4个克氏原螯虾群体的遗传多样性分析

为了对长江下游地区克氏原螯虾(Procambarus clarkii)群体的遗传多样性状况进行本底调查, 本文利用17对微卫星引物对南京(NJ)、盱眙(XY)、合肥(HF)、南昌(NC)4个克氏原螯虾地理群体进行了遗传多样性研究。结果表明, 4个地理群体的平均观测杂合度为0.4322–0.4826、平均期望杂合度为0.4024–0.6121、平均多态信息含量为0.3408–0.5624, 4个克氏原螯虾群体的遗传多样性处于中等水平, 其中南京群体遗传多样性最高, 合肥群体最低; 4个克氏原螯虾群体的基因流为1.3729–5.9161, 遗传分化指数为0.0405–0.1540, 群体间基因流水平较高, 群体间遗传分化程度较小。聚类结果显示4个群体可分为2支: 南京、南昌、盱眙三个群体聚为一支, 合肥群体独自成一支。以上结果将为克氏原螯虾遗传育种、资源保护和利用提供一定的理论依据。     

两种绿藻辅助饲喂对克氏原螯虾生理活性的影响

以克氏原螯虾为研究对象, 测定了在正常投喂人工颗粒饲料的基础上辅助添加小球藻、刚毛藻饲喂克氏原螯虾的生理活性。结果表明: 试验期间添加小球藻(1.0×106-1.0×107 cells·L-1)、刚毛藻(0.06-0.08 g·L-1)对克氏原螯虾的生长与存活率均无显著影响(P >0.05), 但肌肉超氧化物歧化酶(SOD)和肝胰脏酸性磷酸酶(ACP)的活性显著降低(P <0.05); 机体的血细胞密度显著增加(P <0.05), 外骨骼和肌肉中虾青素的含量极显著增加(P <0.01); 单独添加刚毛藻肌肉虾青素含量也显著提高(P <0.05), 血清、肝胰脏和肌肉碱性磷酸酶(AKP)的活性极显著提高(P <0.01), 肝胰脏酸性磷酸酶的活性极显著降低(P <0.01)。摄食小球藻和刚毛藻对于克氏原螯虾的抗逆活性和免疫能力具有促进作用, 养殖水体中适度添加小球藻和刚毛藻有助于克氏原螯虾的健康与活力。     

洞庭湖克氏原螯虾肌肉成分分析及品质特性分析

通过对洞庭湖克氏原螯虾肌肉成分进行分析, 并与其他产地克氏原螯虾进行比较, 进而较为科学的评定其品质特性。结果表明: 克氏原螯虾含肉率为20.21%, 水分和灰分含量分别为79.46%和1.17%, 粗蛋白和粗脂肪含量分别16.67%和0.77%; 对肌肉的质构特性分析表明克氏原螯虾肌肉硬度小, 易咀嚼; 肌肉中含18种氨基酸, 其中包括8种必需氨基酸, 必需氨基酸指数为80.02%, 氨基酸总含量为16.06%, 鲜味氨基酸含量为5.98%; 依据氨基酸化学评分, 克氏原螯虾的第一限制性氨基酸是含硫氨基酸(甲硫氨基酸和胱氨酸), 第二限制性氨基酸是缬氨酸。测定了克氏原螯虾肌肉中15种脂肪酸占肌肉鲜质量的含量, 其总脂肪酸含量为6.66‰, 其中不饱和脂肪酸含量为4.94‰, n-3与n-6多不饱和脂肪酸比值为1.73。综上所述, 洞庭湖克氏原螯虾具有较高的食用价值和养殖价值。     

The vulnerability of juvenile signal crayfish to perch and eel predation

1. We conducted laboratory experiments to determine how juvenile signal crayfish (Pacifastacus leniusculus) responded to two predators with different foraging behaviours (European eel Anguilla anguilla and European perch Perca fluviatilis), and whether these responses affected their vulnerability. 2. By accelerating a model predator towards crayfish which had been temporarily blinded, we assessed whether crayfish had to see predators in order to escape. Blind crayfish escaped later than did sighted crayfish attacked in the same manner. 3. Both eels and perch elicited similar evasive behaviour when approaching and attacking sighted crayfish. Crayfish usually escaped these initial attacks but perch chased and caught more crayfish than did eels. 4. In a third experiment, perch preyed more rapidly on a population of crayfish than did eels. By the end of the experiment, however, crayfish survival rates were similar in response to eel and perch predation. 5. Our results show that crayfish are well adapted to evade predatory attacks based on rapid responses to both visual and/or mechanical stimuli. The results also suggest that behaviourally, crayfish are more vulnerable to attacks by perch than by eels. We discuss these findings in relation to other factors that affect the vulnerability of crayfish to these predators.     

Biological control of invasive populations of crayfish: the European eel (<Emphasis Type="Italic">Anguilla anguilla</Emphasis>) as a predator of <Emphasis Type="Italic">Procambarus clarkii</Emphasis>

The red swamp crayfish, Procambarus clarkii, is a paradigmatic invader of freshwater systems. Several attempts have been made to mitigate its multiple impacts but none was successful. Among the different methods proposed, the use of the European eel (Anguilla anguilla) as an indigenous predator is promising but the available information about its predatory ability on crayfish is to date scanty. To fill this gap in knowledge, we ran three experiments in wetlands and irrigation ditches in Italy. The first experiment, in the laboratory, was aimed at quantifying the extent of predation by eels on crayfish, the second, in enclosures, the size classes of crayfish mainly preyed and the possible effect of the eels on P. clarkii behaviour, and the third, in the field, its ability to effectively reduce crayfish populations. Results showed that eels prey on small-sized or soft crayfish, attacking them from the back; an indirect effect was to reduce crayfish trophic activity, which in turn might increases crayfish mortality due to starvation and decreases impact on the community. However, as shown in the field, the use of eels should be appropriately calibrated to the context of application. Taken together, our results show that eels might be used as a complement to the traditional trapping method. However, additional studies are necessary to understand the adequate number of eels to be introduced and to develop appropriate methods for quantifying such effects.     

Movement of exotic plants into coastal native forests from gardens in northern New Zealand

The anti-predator behaviours of a New Zealand freshwater crayfish (Paranephrops zealandicus) to the native long-finned eel (Anguilla dieffenbachii) and the introduced brown trout (Salmo trutta) were investigated. Crayfish modified their behaviour in the presence of both trout and eels. However, a significantly greater number of defensive chela displays and swimming responses were made to eels than trout. Crayfish were able to use chemical cues from skin mucus to detect eels but not trout. Paranephrops zealandicus is able to make some appropriate defensive behavioural responses to the introduced brown trout as well as to its native predator, the long-finned eel. However, crayfish may be at greater risk from the introduced predator because of their apparent inability to detect trout using non-contact chemical cues. This may be a reflection of the different co-evolutionary histories crayfish have had with trout and eels.     

Temporal changes in digestive enzyme activities in the gastrointestinal tract of European eel (Anguilla anguilla) (Linneo 1758) following feeding

Changes occurring after feeding in the digestive enzyme activities of European eel were investigated to provide some insights into the digestive physiology of this fish. Total and specific proteases, amylase and lipase activities were measured using standard biochemical assays over a 24 h cycle in fed eels, compared to starved ones, under the same rearing conditions. In the gastrointestinal tract of fed eels quantitative changes started 4 h after feeding and continued later on; conversely, in starved eels enzyme activities remained unchanged over time. In fed eels, total and specific protease activities showed an overall increasing trend in the intestine, while in the stomach they progressively decreased to values 22–50% lower than those measured at the pre-feeding time; this behaviour probably reflected the progression of digesta along the intestinal tract. The prolonged secretory response of European eel to food ingestion proved its extended activity in the digestive process.     

The role of a freshwater tidal area with controlled reduced tide as feeding habitat for European eel (Anguilla anguilla,L.)

Implementation of the Controlled Reduced Tide (CRT) technique could increase the total surface of tidal freshwater marshes in Europe and ease implementation of restoration projects in coastal defense and riverine ecosystems. The goal was to determine whether a regularly flooded area connected to a freshwater tidal river could act as an important foraging area for European eel, and if so, to what extent the diet of eels in this flooding area differed from that of eels foraging in the river itself. The stomach contents of eels from the River Schelde were compared with eels from the Lippenbroek, an adjacent CRT area. Prey diversity (H′) of individual eels was about four times higher in the Lippenbroek than in the River Schelde. Moreover, 12 prey categories in eel stomachs from the Lippenbroek were found whereas only three categories were retrieved from eels in the River Schelde. In the Lippenbroek, eels fed on terrestrial organisms (lumbricids, caterpillars and other insects), but also on fish and fish eggs and to a lesser extent on other aquatic prey (Lumbricullidae, chironomids and Hirudinea). In contrast, eels from the main river fed mainly on tubificids, fish, and some gammarids. Consequently, eels in the Schelde estuary are opportunistic feeders, but with a preference for large benthic prey. The number and weight of aquatic organisms ingested by eels in the Lippenbroek is not significantly different from the River Schelde. However, eels foraging in the Lippenbroek area had consumed significantly more terrestrial prey. Furthermore the total caloric value estimated for the ingested prey of eels from the Lippenbroek (derived from the literature) was about twice as high as that for eels from the River Schelde. While the condition index remained inconclusive, an Ancova revealed that eels captured in the Lippenbroek were significantly heavier for a given length than eels captured in the Schelde. The study showed that with a controlled reduced tide to restore lateral connectivity of large tidal rivers with their adjacent floodplains, high quality habitats for the European eel are created. These measures could significantly contribute to the production of eels in better condition, which have better chances to reproduce successfully. Hence, wetland restoration could enhance the recovery of the European eel stocks.     

Shark Predation on Migrating Adult American Eels (Anguilla rostrata) in the Gulf of St. Lawrence

In an attempt to document the migratory pathways and the environmental conditions encountered by American eels during their oceanic migration to the Sargasso Sea, we tagged eight silver eels with miniature satellite pop-up tags during their migration from the St. Lawrence River in Québec, Canada. Surprisingly, of the seven tags that successfully transmitted archived data, six were ingested by warm-gutted predators, as observed by a sudden increase in water temperature. Gut temperatures were in the range of 20 to 25°C—too cold for marine mammals but within the range of endothermic fish. In order to identify the eel predators, we compared their vertical migratory behavior with those of satellite-tagged porbeagle shark and bluefin tuna, the only endothermic fishes occurring non-marginally in the Gulf of St. Lawrence. We accurately distinguished between tuna and shark by using the behavioral criteria generated by comparing the diving behavior of these two species with those of our unknown predators. Depth profile characteristics of most eel predators more closely resembled those of sharks than those of tuna. During the first days following tagging, all eels remained in surface waters and did not exhibit diel vertical migrations. Three eels were eaten at this time. Two eels exhibited inverse diel vertical migrations (at surface during the day) during several days prior to predation. Four eels were eaten during daytime, whereas the two night-predation events occurred at full moon. Although tagging itself may contribute to increasing the eel''s susceptibility to predation, we discuss evidence suggesting that predation of silver-stage American eels by porbeagle sharks may represent a significant source of mortality inside the Gulf of St. Lawrence and raises the possibility that eels may represent a reliable, predictable food resource for porbeagle sharks.     

饲料中不同EPA和DHA含量对黄鳝脂类代谢、生长及繁殖性能的影响

为研究EPA和DHA对黄鳝脂类代谢、生长及繁殖性能的影响, 用添加有EPA和DHA比例相同(EPA/DHA=0.35)但水平不同(EPA和DHA总量分别为0.00%、0.35%、0.70%)的3种等氮等脂肪饲料, 在常温(2230 ℃)下, 分别喂养平均体重为(21.710.54) g的黄鳝7周, 分析黄鳝脂类代谢和生长性能, 然后每组取15尾继续养殖至性腺发育成熟用于繁殖性能分析。结果表明:在饲料中添加0.70%的EPA和DHA 能促进黄鳝生长, 显著提高黄鳝的特定生长率(SGR)及肌肉粗蛋白含量, 降低肝体指数(HSI)及肌肉、肝脏中的粗脂肪含量(P0.05), 显著提高亲鳝的性体指数(GSI)、产卵量、孵化率、幼苗的存活指数(SAI)(P0.05)。添加0.35%的EPA和DHA能显著降低肝脏中粗脂肪含量(P0.05)。综合分析表明:EPA和DHA能促进黄鳝的脂类代谢, 显著提高其生长及繁殖性能; 饲料中添加0.70%的EPA和DHA较为适宜。       

黄鳝饲料蛋白质需求量的研究

为确定黄鳝(Monopterus albus)对饲料蛋白质的需求量, 试验分7组, 每组4个重复。每个重复放养初始体重为(17.1±0.2) g的幼鳝25尾, 分别以鱼粉和酪蛋白为主要蛋白源, 配制蛋白质含量为32.74%(T1)、38.50%(T2)、42.26%(T3)、48.35%(T4)、52.65%(T5)、57.87%(T6)和62.31%(T7)的7种等能不等氮饲料, 养殖期为60d。以生产性能、蛋白质保留率和生理生化指标等综合评价确定蛋白质的需求量。结果: (1)随饲料蛋白质含量升高, 饲料系数呈先降低后升高; 增重率(WGR)、特定生长率(SGR)、蛋白保留率(PRR)与蛋白质效率(PER)先升高后降低; 饲料蛋白质含量57.87%组获得最好的生长性能, 52.65%组蛋白质保留率最高。(2)随饲料蛋白质含量升高, 黄鳝血清中尿素氮(BUN)含量升高, 谷丙转氨酶(ALT)和谷草转氨酶(AST)的活性先降低后保持稳定, 总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白(HDL-C)、低密度脂蛋白(LDL-C)及血糖(GLU)含量降低; 丙二醛(MDA)含量呈现先降低后升高的趋势, 在52.65%时最低。(3)随饲料蛋白质含量升高, 黄鳝肝胰脏、胃和肠蛋白酶活性先显著上升后呈缓慢上升趋势; 肝胰脏脂肪酶活性先显著下降后呈缓慢下降趋势, 胃和肠脂肪酶活性各试验组之间无显著性差异; 胃淀粉酶活性无显著差异, 肝胰脏和肠呈先显著下降后缓慢降低的趋势。综上: 当饲料蛋白质含量低时, 黄鳝会加大摄食量满足蛋白质需求, 在饲料蛋白质含量过高时, 氧化应激增加, 黄鳝通过降低摄食量减少蛋白质摄入。以WGR、PER、SGR及饲料系数(FCR)为评价指标确定幼鳝对饲料蛋白质的适宜需求量为48.51%—52.60%。     

Timing and pattern of annual silver eel migration in two European watersheds are determined by similar cues

Many animals perform long‐distance migrations in order to maximize lifetime reproductive success. The European eel migrates several thousand kilometers between their feeding habitats in continental waters (fresh‐, brackish, and sea water) and their spawning area in the Sargasso Sea. Eels residing in freshwaters usually initiate their spawning migration as silver eels during autumn, triggered by diverse environmental cues. We analyzed the time series of silver eel downstream migration in Burrishoole, Ireland (1971–2015), and Imsa, Norway (1975–2015), to examine factors regulating the silver eel migration from freshwater to the sea. The migration season (90% of the run) generally lasted from 1 August to 30 November. Environmental factors acting in the months before migration impacted timing and duration of migration, likely through influencing the internal processes preparing the fish for migration. Once the migration had started, environmental factors impacted the day‐to‐day variation in number of migrants, apparently stimulating migration among those eels ready for migration. Both the day‐to‐day variation in the number of migrants and the onset of migration were described by nearly identical models in the two rivers. Variables explaining day‐to‐day variation were all associated with conditions that may minimize predation risk; number of migrants was reduced under a strong moon and short nights and increased during high and increasing water levels. Presence of other migrants stimulated migration, which further indicates that silver eel migration has evolved to minimize predation risk. The onset of migration was explained mainly by water levels in August. The models for duration of the migration season were less similar between the sites. Thus, the overall migration season seems governed by the need to reach the spawning areas in a synchronized manner, while during the actual seaward migration, antipredator behavior seems of overriding importance.     

Qualitative assessment of the diet of European eel larvae in the Sargasso Sea resolved by DNA barcoding

European eels (Anguilla anguilla) undertake spawning migrations of more than 5000 km from continental Europe and North Africa to frontal zones in the Sargasso Sea. Subsequently, the larval offspring are advected by large-scale eastward ocean currents towards continental waters. However, the Sargasso Sea is oligotrophic, with generally low plankton biomass, and the feeding biology of eel larvae has so far remained a mystery, hampering understanding of this peculiar life history. DNA barcoding of gut contents of 61 genetically identified A. anguilla larvae caught in the Sargasso Sea showed that even the smallest larvae feed on a striking variety of plankton organisms, and that gelatinous zooplankton is of fundamental dietary importance. Hence, the specific plankton composition seems essential for eel larval feeding and growth, suggesting a linkage between eel survival and regional plankton productivity. These novel insights into the prey of Atlantic eels may furthermore facilitate eel larval rearing in aquaculture, which ultimately may replace the unsustainable use of wild-caught glass eels.