Microsatellite polymorphism in Italian populations of northern pike (Esox lucius L.)

Northern pike (Esox lucius) is not considered an endangered species in Italy, but since recent studies indicate the decline of this population, conservation and management strategies based on the genetic differentiation of natural northern pike populations are needed. In this paper, genetic diversity was analysed in 10 Italian and 2 East European northern pike populations by means of seven microsatellite loci. Data indicated an appreciable genetic differentiation, in spite of a low genetic variation, and agreed with the low level of genetic polymorphism already observed for this species in North America and North Europe. Results of statistical tests revealed genetic peculiarities of the Italian populations, even though signals of recent contact between populations were found and discussed in relation to anthropic impacts, particularly to the stocking practice. This investigation represents the first approach to the knowledge of the genetic variability of Italian pike populations using microsatellite markers, and reported results could be of interest for future management and conservation programmes of this species in Italy.     

东北地区池塘养殖条件下白斑狗鱼肌肉营养成分分析

[目的]为评价在不同地区养殖白斑狗鱼的营养品质提供依据。[方法]从新疆地区引进白斑狗鱼夏花鱼种,在东北地区池塘养殖条件下对白斑狗鱼的肌肉营养成分进行分析。[结果]白斑狗鱼的鲜样肌肉水分、灰分、粗蛋白和粗脂肪含量分别为78.58%、2.20%、18.36%和1.32%,肌肉干样的灰分、粗蛋白、粗脂肪含量为87.83%、85.70%和6.16%。18种氨基酸总量为15.12%(占鲜样),其中人体必需的8种氨基酸含量为6.07%(占鲜样),占氨基酸总量的40.18%;4种鲜味氨基酸含量为5.75%。必需氨基酸指数(EAAI)为103。DHA和EPA含量丰富,占脂肪酸总量的23.74%,特别是DHA含量占脂肪酸总量的22.97%。[结论]在池塘养殖条件下白斑狗鱼仍属于一种高蛋白、低脂肪的优质鱼类,具有较高的开发养殖价值。     

白斑狗鱼含肉率及肌肉营养成分分析

测定了贵州地区池塘养殖白斑狗鱼的含肉率及其肌肉生化成分。试验结果表明,白斑狗鱼的含肉率为59.64%;其肌肉生化成分(鲜质量百分比),水分77.5%、蛋白质18.3%、脂肪1.2%、灰分1.2%。肌肉中含有17种氨基酸,总含量为16.55%;7种必需氨基酸含量为6.79%,占氨基酸总含量的41.03%;4种鲜味氨基酸总量为5.077%,占总氨基酸含量的30.67%;必需氨基酸指数为77.24,赖氨酸含量丰富(1.914%),占氨基酸总量的11.56%,蛋氨酸、胱氨酸和缬亮氨酸为限制性氨基酸。     

Ovulation induction in northern pike Esox lucius L. using different GnRH analogues, Ovaprim, Dagin and carp pituitary

The traditional GnRH analogue treatments applying the chemicals in pure form proved to be ineffective in inducing ovulation in northern pike (Esox lucius L). Neither mGnRHa ([D‐Ala⁶, Pro⁹NEt]‐mGnRH) nor sGnRHa ([D‐Arg⁶, Pro⁹‐Net]‐sGnRH) administered alone or together with pimozide (mGnRHa), metoclopramide (mGnRHa) or domperidone (sGnRHa) induced ovulation in females, whereas in groups receiving a carp pituitary injection most females ovulated. Spawning‐inducing agent Dagin did not induce ovulation, whereas all but one female ovulated in the carp pituitary‐treated group. Treatment with another preparation, Ovaprim, resulted in similar or lower ovulation ratio than treatment with carp pituitary. After the Ovaprim treatment, time to ovulation was not as predictable as after the carp pituitary injection. The mean fertilization rate was relatively low and similar in the groups treated with Ovaprim (54.7 ± 12.3% and 58.7 ± 19.1% for the first and second experiment respectively) and with carp pituitary (53.7 ± 10.5% and 58.9 ± 14.9%). The mean pseudogonadosomatic index (PGSI) was also similar between the Ovaprim‐treated group (14.5 ± 6.1%) and the carp pituitary‐treated one (17.9 ± 4.1%). In the present experiments, treatment with Ovaprim was less effective than that with carp pituitary.     

黑斑狗鱼形态性状对体重的影响效果分析

选取0^＋龄～4^＋龄黑斑狗鱼332尾,对其体长、体高、体宽、尾柄长、尾柄高、头长、头高、头宽、吻长、眼间距、口裂宽、口裂长和体重等13个性状进行测量。采用多元分析法分析体重和形态形状的关系。结果表明,黑斑狗鱼除0^＋龄头长与体重之间的相关系数未达到显著水平（P〉0．05）外,其它各形态性状与体重的相关系数均达到显著水...     

Is scuba sampling a relevant method to study fish microhabitat in lakes? Examples and comparisons for three European species

Abstract – We compared fish microhabitat use patterns in the littoral zone of a lake using a new direct method (point abundance sampling by scuba, PASS) and the widely used point abundance sampling by electrofishing technique (PASE). We collected microhabitat data for age 0+ roach ( Rutilus rutilus L.), perch ( Perca fluviatilis L.), and pike ( Esox lucius L.). The two methods yielded different results for fish assemblage structure and microhabitat patterns. Using PASE, fish were mainly found in "shelter habitats" such as shallow waters and dense vegetation. It is likely that this behavior is caused by the disturbance of the observer stamping around. Using PASS, fish escapement behavior was rarely observed. Therefore, we concluded that this direct and nondestructive sampling technique can be used to provide an accurate microhabitat estimation of a fish community and is assumed to be more suitable than PASE for fish habitat studies.     

白斑狗鱼胚胎和卵黄囊期仔鱼的发育

连续观察了7批白斑狗鱼胚胎及卵黄囊期仔鱼的发育状况并进行比较分析。结果显示:(1)白斑狗鱼在水温7～13℃时,胚胎期需248h,有效积温100～120℃·d;水温11～13℃时,卵黄囊期需10d,有效积温110～130℃·d。(2)白斑狗鱼出膜前期可见眼球色素、出膜期可见体色素。白斑狗鱼胚胎卵黄囊表面有许多小油滴分布。白斑狗鱼出膜前期胚体头尾绕卵黄囊超过一周。(3)白斑狗鱼胚胎颜色随着发育进程由起始的淡黄色转为绿黄色,最终出膜前转变为棕褐色。胚胎发育不同步,仔鱼出膜数百分比第1天、第2天、第3天、第4天分别是20%、50%、20%、10%,为避免互相残食,对分批出膜的仔鱼即使是同批受精卵也应分开饲养。     

温度对白斑狗鱼耗氧率、窒息点及主要生化指标的影响

在不同温度下,测定了平均体重为(597.2±96.3)g的白斑狗鱼(Esox lucius)的呼吸耗氧率、窒息点及主要生化指标。结果显示:在水温为3℃、8℃、13℃和18℃下,白斑狗鱼的耗氧率随着温度的升高而显著上升(P<0.05)。3℃时耗氧率最低;为(0.0047±0.000017)mg/g.h,18℃时耗氧率最高;为(0.029±0.0011)mg/g.h。当水温在13℃时,白斑狗鱼的昼夜平均耗氧率在(0.020±0.0031)mg/g.h,15:00耗氧率最低,11:00耗氧率出现最高值。Q10值的变化显示白斑狗鱼的耗氧率对温度具有敏感性,13～18℃时,Q10最小,此温度为白斑狗鱼的较适生长温度。在高温下(18℃),白斑狗鱼呼吸急促,呼吸频率达到(68.50±3.58)次/min;在低温下(3℃),白斑狗鱼呼吸缓慢,呼吸频率下降到(29.00±4.31)次/min。白斑狗鱼的窒息点随着水温的升高而增大,水温为13℃,其窒息点最高为1.68 mg/L,水温为3℃时,其窒息点最低为0.82 mg/L。随着水温的不断上升,白斑狗鱼的肝糖元含量、肝胰脏中的乳酸含量显著减少(P<0.05)。肝糖元含量由(67.70±6.66)mg/g降至(41.83±3.72)mg/g。乳酸含量由(0.36±0.0041)mmol/gprot降至(0.15±0.0034)mmol/gprot。肝胰脏中的碱性磷酸酶、酸性磷酸酶的酶活力随着水温的升高而小幅缓慢下降,分别由(21.51±0.69)U/gprot和(22.34±0.43)U/gprot降至(19.04±0.62)U/gprot和(18.10±0.41)U/gprot。     

饥饿和再投喂对白斑狗鱼生长性能和生化组成的影响

选用体重196.77±7.60g的白斑狗鱼（Esox Lucius Linnaeus）为研究对象,试验设置饥饿14d、21d、28d、35d、42d组和正常投喂对照组,各组饥饿结束后恢复饱食投喂,试验周期为56d,水温为22～26℃,研究了饥饿和再投喂对白斑狗鱼生长性能、体生化组成和肌肉、肝脏RNA/DNA比值的影响。结果表明：饥饿再投喂后各处理组均出现补偿生长现象,在恢复生长结束后,饥饿14d组体重显著高于对照组（P＜0.05）,其他各饥饿处理组体重与对照组无显著性差异（P＞0.05）;随着饥饿时间的延长,饥饿各处理组肌肉的脂肪含量显著下降（P＜0.05）,水分含量显著升高（P＜0.05）,恢复投喂结束时各饥饿处理组蛋白质和水分含量恢复到对照组水平;在恢复投喂初期各处理组的特定生长率、摄食率和食物转化效率显著高于对照组水平（P＜0.05）,随着恢复生长时间的延长,逐渐恢复到对照组水平（P＞0.05）;肌肉和肝脏的RNA/DNA比值均随饥饿时间的延长呈逐渐下降的趋势,在恢复投喂结束时,RNA/DNA比值均在饥饿28d组达到最大值。由此表明饥饿14d组的白斑狗鱼在恢复生长过程中出现了超补偿生长效应,21d组、28d组、35d组和42d组出现了完全补偿生长效应,该补偿效应是由摄食率和食物转化效率升高共同作用的结果。     

Estimation of northern pike population sizes via mark–recapture monitoring

Abstract Estimates of population size are needed in populations targeted by recreational fisheries, to determine their conservational status and to formulate fishing regulations. Mark–recapture monitoring is a promising tool for this because of the increased popularity of catch‐and‐release angling. Northern pike, Esox lucius L., population sizes were estimated in four lakes based on experimental mark–recapture fishing using a hierarchical Bayesian model that also estimated natural mortality. The approach was compared with output from traditional Petersen’s population size estimates. Despite intensive fishing with multiple gears, the population size estimates suggested that a substantial proportion of individuals remained unobserved by fishing. Petersen’s estimates depended on the assumed rate of natural mortality, and no mortality rate scenario matched with the Bayesian estimates. Consequently, the number of individuals caught by recreational anglers is a poor proxy of population size for which estimations should be carried out using a modelling approach that also estimates natural mortality.