Getting cosy in freshwater: Assumed to be brackish pike are not so brackish after all     

Kim Birnie‐Gauvin  Lasse Birch Hjrup  Theis Kragh  Lene Jacobsen  Kim Aarestrup 《Ecology of Freshwater Fish》2019,28(3):376-384

Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.  相似文献   

麦蚜对吡虫啉的敏感性及吡虫啉有效用量的评价   总被引：1，自引：0，他引：1  

刘爱芝  王晓军  李素娟  武予清  李巧丝 《植物保护》2002,28(3):15-18

室内测定结果表明 ,禾谷缢管蚜对吡虫啉的敏感性比麦长管蚜高 ,其LC₅₀之比为1∶3左右。田间试验结果明确 ,吡虫啉持效性好 ,其持效期与吡虫啉用量和麦蚜种类有关。小麦穗蚜发生始盛期是吡虫啉防治麦蚜的最佳时期 ,防治禾谷缢管蚜最佳有效用药量为1g/667m²,麦长管蚜为2g/667m²。  相似文献   

Turbidity‐induced changes in emergent effects of multiple predators with different foraging strategies     

Matthew M. VanLandeghem  David H. Wahl 《Ecology of Freshwater Fish》2011,20(2):279-286

Abstract – In natural systems, prey frequently interact with multiple predators and the outcome often cannot be predicted by summing the effects of individual predator species. Multiple predator interactions can create emergent effects for prey, but how those change across environmental gradients is poorly understood. Turbidity is an environmental factor in aquatic systems that may influence multiple predator effects on prey. Interactions between a cruising predator (largemouth bass Micropterus salmoides) and an ambush predator (muskellunge Esox masquinongy) and their combination foraging on a shared prey (bluegill Lepomis macrochirus) were examined across a turbidity gradient. Turbidity modified multiple predator effects on prey. In clear water, combined predators consumed in total more prey than expected from individual predator treatments, suggesting risk enhancement for prey. In moderately turbid water, the predators consumed fewer prey together than expected, suggesting a risk reduction for prey. At high turbidity, there were no apparent emergent effects; however, the cruising predator consumed more prey than the ambush predator, suggesting an advantage for this predator. Understanding multiple predator traits across a gradient of turbidity increases our understanding of how complex natural systems function.  相似文献   

南疆棉田十一星瓢虫对棉蚜的生态控制   总被引：2，自引：0，他引：2  

王林霞  田长彦  吕昭智 《干旱地区农业研究》2006,24(4):222-226

通过对南疆尉犁县两处棉田,4个品种十一星瓢虫的种群动态、人工诱集和棉蚜防治效果测试观察,发现:在南疆不同品种的棉田中,十一星瓢虫是棉田棉蚜的主要天敌,约占棉田瓢虫总数的80%左右;十一星瓢虫与棉蚜种群数量呈显著的跟随关系,发生期比棉蚜滞后1周左右。人工诱集十一星瓢虫的数量与诱集箱放置的位置和箱内的诱集物有关。放置在棉田周围林带中的诱集箱诱集的十一星瓢虫数量最多,其次是棉田埂箱,棉田内诱集的数量最少;诱集箱放入蜂蜜和花粉蜜诱集的十一星瓢虫数量最多,放入花粉诱集的十一星瓢虫数量次之,不放任何诱集物诱集的十一星瓢虫数量最少。越冬后的十一星瓢虫早期释放到棉田中心蚜株上可以有效防治蚜虫危害,中心蚜株株高比未释放瓢虫处理的增高59.5%,果枝数增加20.3%、蕾数增加100%、铃数增加81.4%,单株产量增加81.1%。  相似文献   

紫外线系统净化文蛤中大肠杆菌的研究   总被引：2，自引：0，他引：2  

乔庆林  蔡友琼  徐捷  姜朝军 《海洋渔业》2008,30(4)

文蛤经人工方法使其体内积累埃希氏大肠杆菌达到5个对数值后,放入小型紫外线循环净化系统中,通过正交试验来研究各种环境因子对文蛤自身净化能力的影响。经36 h净化处理后,贝肉中埃希氏大肠杆菌减小约3个对数值。方差分析结果表明,影响文蛤净化效果的因子依次为水交换率、贝水比和温度;最佳的净化条件为:换水率3次/h、贝水比为1∶4、温度15℃。文蛤的净化生产证明,这些净化条件是合适的。  相似文献   

不同类型林分青杨虎天牛发生状况研究     

毛若智  吴立秋  董希文 《防护林科技》2007,(4):26-27,34

通过调查分析,得到青杨虎天牛在各种杨树及其它阔叶树种的纯林、混交林以及不同类型林分、、树干不同部位的发生状况,选择出相对抗青杨虎天牛及易受青杨虎天牛危害的杨树品种及其它阔叶树种,为利用生态方法控制青杨虎天牛的传播和蔓延提供了科学依据。  相似文献   

β-1,3-葡聚糖及其羧甲基衍生物对海湾扇贝免疫功能的影响   总被引：3，自引：0，他引：3  

杨文鸽 《水产学报》2006,30(3):383-389

2003年3月和2004年4月，新疆某养殖场和西安灞桥区某养殖场的白斑狗鱼（Esox lucius Linnaeus）相继爆发“败血症”。从具有明显症状的濒死病鱼体表病灶和内脏组织分离得到12株优势菌株，经人工感染试验表明：其中10株分离菌为致病菌。对分离菌株进行形态、培养特征、生理生化试验鉴定，认为该病原菌为杀鲑气单胞菌史氏亚种（Aeromonas salmonida subsp．smith）。血清学试验表明各分离菌株具有相同的保护性抗原。组织病理学研究表明：患病狗鱼病灶肌纤维明显肿胀断裂，肌纤维束之间出现间隙；肝胰组织严重坏死，细胞核溶解消失，细胞浆崩解；肾小管绝大部分均已坏死，细胞破裂，胞浆呈红色团块状流失于管腔。脾脏细胞大量坏死，髓质内含铁血黄素沉积。代表菌株EL0304-1药敏试验结果为：对供试24种抗菌药物中的磺胺二甲嘧啶钠、磺胺二甲嚯唑钠等不敏感；庆大霉素、卡那霉素等中度敏感；对氧氟沙星、培氟沙星、新霉素等高度敏感。  相似文献   

“红肉病”文蛤的组织病理学   总被引：9，自引：0，他引：9  

任素莲 《水产学报》2003,27(5):462-467

利用组织学和组织化学方法,在光镜水平下研究了患“红肉病”文蛤(Meretrix meretrix Linnaeus)的组织病理学变化特征。结果显示,患病文蛤的病理学变化主要表现为组织结构紊乱,上皮膨大、脱落,鳃、外套膜、消化盲囊等组织发现异常结构及寄生物,如嗜碱性的包涵体、嗜酸性颗粒及寄生性原生动物等。另外,组织化学研究结果显示,病蛤在糖含量、磷酸酶活性等方面也有明显变化,表现为消化盲囊、肠等部位吸收细胞内糖含量增加。消化盲囊、消化管各处酸性磷酸酶(ACP)活性减弱,碱性磷酸酶活性(AKP)增强。鳃组织ACP活性增强,AKP活性减弱等。  相似文献   

溶藻胶弧菌脂多糖对大菱鲆白细胞吞噬活性的影响   总被引：1，自引：0，他引：1  

叶海斌  朱安成张涛 李天保 《齐鲁渔业》2006,23(3):34-35

针对溶藻胶弧菌脂多糖在增强大菱鲆非特异性免疫功能、提高机体抗病能力方面的作用机理,开展了研究工作。实验中以浓度为2．4mg／ml 溶藻胶弧菌脂多糖,通过口服和注射的方式接种平均体重47．2g 大菱鲆幼鱼,接种后第7、15、 30天,分别采血根据血细胞吞噬作用检测结果计算吞噬百分比和吞噬指数。结果显示,溶藻胶弧菌脂多糖对白细胞吞噬活性有明显促进作用,在增强白细胞的吞噬能力方面作用不显著。  相似文献   

Changing of fat content and fatty acid profile of reared pike (Esox lucius) fed two different diets     

Balázs Kucska  László Pál  Tamás Müller  Márk Bódis  Ádám Bartos  László Wágner  Ferenc Husvéth  & Mikós Bercsényi 《Aquaculture Research》2006,37(1):96-101

Fat content and fatty acid profile of two pike yearling groups grown on two different diets were compared. The groups originated from culture on artificial feed. One group (cultured pike fed first pellet then prey‐fish (PF)) was fed with natural food, live prey‐fish, while the other one (cultured pike fed exclusively pellet (PP)) by trout feed through a 3‐month experimental period. Growth of pike was lower with PP than with PF. The trout feed resulted in an increase of the fat content of fillet and the formation of abdominal fat depots. Feeding of natural food decreased the fat content. The proportion of the saturated fatty acids in fillet was higher in the (PF) group. The n‐6 fatty acids (arachidonic C20:4n‐6 and docosatetraenic C22:4n‐6 acids) were lowest in PP‐fed pike. Regarding total n‐3 fatty acids ratio there was no significant difference between the groups, but the level of α‐linolenic (C:18:3n‐3) acid showed significant difference among groups.  相似文献