Development of hatchery technology for the silver pomfret Pampus argenteus (Euphrasen): effect of microalgal species on larval survival

The silver pomfret Pampus argenteus (Euphrasen) is a new candidate for aquaculture and there is not much information available on its larval rearing. Investigations carried out using microalgae alone in the culture system for the initial feeding of the silver pomfret larvae showed that Chlorella, Isochrysis and Nannochloropsis without rotifers are not conducive to the survival of newly hatched larvae. At 6 days after hatching (DAH), a maximum survival of 3% (1.8 ± 1.69%) was observed with Isochrysis followed by Nannochloropsis (0.35 ± 0.21%) and Chlorella (0.25 ± 0.21%). All control larvae died at 6 DAH without microalgae. Further investigations using the above microalgae with rotifers and a mixture of these same microalgae with rotifers showed that significantly higher (P < 0.05) survival could be achieved in the mixture of microalgae with rotifers in the culture system. At 12 DAH, the larval survival was 9.73 ± 1.39% in mixed species of algae compared with that of Isochrysis (6.93 ± 1.86%), Nannochloropsis (6.83 ± 0.61%), Chlorella (5.93 ± 2.76%) and seawater without microalgae or the control (0.73 ± 0.31%). The first incidence of feeding on rotifers at 4 DAH was significantly higher (P < 0.05) in all treatments with microalgae than that of the control. The incidence of feeding in mixed species of algae at 4 DAH (60.0 ± 0.00%) and in Isochrysis (55.0 ± 35.36%) was significantly higher (P < 0.05) than that of Chlorella (40.0 ± 0.00%) and the control (25.0 ± 7.07%). Prey consumption of individual larvae increased significantly (P < 0.01) at 8 DAH compared with that at 4 DAH. During this period, predation on rotifers by larvae was significantly higher (P < 0.05) in mixed species of algae (12.85 ± 5.73 rotifers larva^?1) than that of the control (6.75 ± 1.20 rotifers larva^?1). The fatty acid composition of rotifers used during this investigation shows that significantly higher (P < 0.05) ω3 HUFA was present in rotifers treated with mixed algae plus commercial enrichment media ‘Super Selco’ and ‘DHA Protein Selco’. Rearing of silver pomfret larvae up to the juvenile stage using mixed species of microalgae in the hatchery has been discussed. During 38 days of the larval rearing period, it was possible to achieve 3.6–4.2% larval survival with a mean of 3.9 ± 0.42%, which was considerably higher than in previous attempts (survival up to 1.5%).     

银鲳人工育苗技术研究

2005~2006年,在舟山海域银鲳繁殖季节(4~5月),随流刺网和张网捕鱼船出海,捕捞性腺成熟的银鲳进行人工授精,把胚胎运回岸上在孵化桶中继续孵化,得到初孵仔鱼并移入水泥池中进行培育。在水温19.0~24.0℃、盐度25.0~28.0的人工育苗条件下培育苗种。饵料为轮虫、卤虫无节幼体和配合饲料,孵化后3 d仔鱼开始开口摄食。银鲳初孵仔鱼~12日龄为仔鱼期,13~40日龄为稚鱼期,41日龄起转为幼鱼期。经50 d培育,获得20~27 mm叉长的银鲳幼鱼。育苗成活率为5%~14%。     

养殖与野生银鲳精巢发育形态学和组织学的初步比较

采用组织学与形态学等方法研究养殖与野生银鲳(Pampus argenteus)精巢结构、细胞形态、发育过程的异同点。结果表明:银鲳精巢结构为典型的小叶型结构,由精小叶、精小囊、小叶间质、小叶腔和输出管构成;生殖细胞可划分为5类;精巢发育与其他海水鱼类一样,可划分为6个时期。通过实验得知,养殖银鲳个体普遍小于野生银鲳的个体,且同等大小个体的养殖银鲳的精巢发育也不如野生银鲳精巢饱满,推测可能由于营养和环境温度的差异所造成。     

银鲳亲鱼不同组织的氨基酸及其随性腺发育的变化

测定了海捕银鲳亲鱼肌肉,肝脏和性腺组织的氨基酸,并分析了不同性腺发育阶段的氨基酸变化。结果表明,雄性V期亲鱼精巢中的牛磺酸含量最高（27.8mg/g）,显著高于肌肉和肝脏组织,而雄性V期亲鱼氨基酸总量在肌肉中最高（631.4 mg/g）,其次是精巢（544.8 mg/g）和肝脏（468.0 mg/g）组织。雌性亲鱼肝脏中的牛磺酸含量（13.7 mg/g）显著高于卵巢和肌肉组织。在卵巢从III期发育到V期过程中,雌性亲鱼肌肉和肝脏中的氨基酸总量在V期下降显著,而卵巢氨基酸总量维持稳定。在总氨基酸的组成上,肌肉中含量高的氨基酸为Glu,Lys, Asp,Leu和Arg;肝脏中含量高的为Glu,Lys, Asp,Val和Leu;精巢中含量高为Glu,Asp, Lys, Arg和Val;卵巢含量高中为Glu,Lys,Leu,Val和Asp。性别和性腺发育阶段对亲鱼肌肉总氨基酸组成无影响。游离氨基酸含量在III 、IV和 V期卵巢中的含量分别为17.7 mg/g ,41.5 mg/g和29.6 mg/g,且其组成随性腺发育阶段的不同而有显著差异。     

不同饲料对银鲳幼鱼增重率、肝脏脂酶及抗氧化酶活性的影响

利用营养学与生物化学的方法,研究分析了不同饲料对银鲳幼鱼增重率、饲料系数、肝脏脂酶及抗氧化酶活性的影响。试验共设4组不同饲料,依次为饲料1(新鲜鱼肉糜)、饲料2(新鲜鱼肉糜+饲料)、饲料3(新鲜鱼肉糜+饲料+蛏子肉糜)和饲料4(新鲜鱼肉糜+饲料+蛏子肉糜+桡足类)。试验用银鲳幼鱼的平均体重为(4.80±0.11)g,每组饲料设3重复,试验周期为9周。研究结果显示,不同饲料可显著影响银鲳的增重率,各饲料组中以饲料1组的增重率最低,并显著低于其它各饲料组;饲料4组的增重率最高,并显著高于饲料2、3组的增重率(P<0.05)。饲料系数以饲料1组最高,且显著高于其它3组饲料组;饲料2、3、4组饲料系数间并无显著性差异(P>0.05)。饲料1组肝脂酶与总脂酶活性均显著低于其它3组饲料组(P<0.05),但饲料2、3、4组间肝脏脂蛋白脂酶、肝脂酶和总脂酶活性均未有显著性差异(P>0.05)。各组间肝脏超氧化物歧化酶(SOD)与谷胱甘肽过氧化物酶(GSH-PX)活性均未有显著性差异(P>0.05),但均以饲料1组最低、饲料4组最高;饲料1、2、3组间肝脏过氧化氢酶(CAT)活性未有显著性差异(P>0.05),但饲料4组CAT活性显著高于饲料1组的CAT活性(P<0.05)。分析结果表明,单纯利用鱼肉糜作为饲料不利于银鲳的生长;饲料中添加桡足类不但有助于促进银鲳的生长,也可提高其抗氧化能力。     

渤海银鲳成熟卵巢生化成分分析

采用现代生化分析方法,研究了渤海银鲳卵巢组织的生化成分。结果表明:卵巢水分平均含量为68.83%,蛋白质平均含量15.45%,脂肪平均含量12.37%,灰分平均含量1.21%,糖类(碳水化合物)平均含量1.82%;卵巢组织的17种氨基酸中以谷氨酸含量最高,天冬氨酸次之,赖氨酸居于第三位;卵巢脂质中的主要脂肪酸排列顺序如下:C18∶1(n9&7)>C16∶0>C22∶6n3>C16∶1n7>C20∶5n3,饱和脂肪酸(SFA)占脂肪酸总量的18.95%~25.28%,单烯酸(MUFA)占24.67%~31.87%,多不饱和脂肪酸(PUFA)占19.72%~24.26%,EPA和DHA之和占16.27%~20.08%。     

饲料组成对银鲳幼鱼生长率及肌肉氨基酸、脂肪酸组成的影响

研究分析了饲料组成对银鲳(Pampus argenteus)幼鱼特定生长率(SGR)及肌肉氨基酸与脂肪酸组成的影响。实验共设4组不同的饲料组成,依次为饲料A(鱼肉糜)、饲料B(鱼肉糜+配合饲料)、饲料C(鱼肉糜+配合饲料+蛏子肉糜)和饲料D(鱼肉糜+配合饲料+蛏子肉糜+桡足类)。实验用银鲳幼鱼的平均体重为4.80±0.11 g,每组饲料设3重复,实验周期为9周。研究结果显示,不同饲料组成可显著影响银鲳的特定生长率,饲料A组的特定生长率最低,并显著低于其它各饲料组;饲料D组的特定生长率最高,且显著高于饲料B、C组的特定生长率(P<0.05);但饲料B、C组间银鲳特定生长率无显著性差异(P>0.05)。银鲳肌肉氨基酸与脂肪酸的分析结果显示,4组饲料组成对银鲳肌肉氨基酸的组成及含量并无显著性影响(P>0.05),但可显著影响肌肉脂肪酸的组成及含量(P<0.05)。饲料D组的多不饱和脂肪酸(PUFA)、高度不饱和脂肪酸(HUFA)及n-3HUFA含量均分别显著高于饲料A、B和C组(P<0.05),饲料B和C组的PUFA、HUFA及n-3HUFA均分别显著高于饲料A组(P<0.05),但饲料B、C组间并无显著性差异(P>0.05)。综合分析得出,丰富的饲料组成以及饲料中较高的HUFA含量均有利于银鲳幼鱼的生长。     

Changes in lipid composition of different tissues of common octopus (Octopus vulgaris) during short‐term starvation

In this work, we study the variations in concentration (mg 100 g^?1 dry weight) and total content (mg individual^?1) of different lipid classes in muscle and the digestive gland of Octopus vulgaris during an 8‐day starvation period. In all the samples analysed, polar lipids (PL) predominated in muscle (267.3–337.2 mg 100 g^?1) compared with neutral lipids (66.9–104.7 mg 100 g^?1). A significant positive tendency was observed in muscle for the content and concentration of monoglycerides as a consequence of starvation (P < 0.05). Furthermore, a higher cholesterol (CHO) content was detected in this tissue after the fourth day of starvation compared with the fed animals (P < 0.05). Neutral lipids predominated in the digestive gland (12 958–14 151 mg 100 g^?1) compared with PL (3157–6517 mg 100 g^?1), with triglycerides, free fatty acids and monoglycerides being the major lipid classes. The concentration of PL and monoglycerides showed a positive trend with starvation, while the triacylglycerol showed a negative tendency (P < 0.05). The results suggest that triglycerides and CHO are transported simultaneously from the digestive gland to the muscular tissues during starvation and the preferential use of PL and CHO during growth phases. It was estimated that lipids contributed 26% of the energy costs of the animals during starvation, mainly in the form of triglycerides from the digestive gland.     

Effects of short‐term starvation on the rhythmic expression of microRNAs in skeletal muscle of goldfish (Carassius auratus)

Molecular oscillators exist in peripheral tissues such as in skeletal muscles and diet is a dominant factor to affect Zeitgeber for peripheral clocks. MicroRNAs (miRNAs) play an important role in muscle cell proliferation and differentiation. However, the knowledge of starvation effects on miRNA rhythmic expression remains limited in teleost. In this study, the circadian expression pattern of miRNAs was investigated in goldfish muscle upon restricting feeding treatment. The data showed that 15 miRNAs exhibited a daily rhythmicity among the 70 miRNAs assayed in muscles of normally fed goldfish. While after 7‐day and 15‐day fasting treatment, 23 and 18 miRNAs showed circadian rhythmicity in goldfish muscles respectively. Only 4 miRNAs (miR‐23a, miR‐29, miR‐199a‐3p and miR‐455) exhibited a daily rhythmicity in all three groups of different nutrient treatments. Correlation analysis of the circadian‐miRNAs indicates different feeding stimulation could alter the circadian‐miRNA components and their expression profile in skeletal muscle upon short‐term feed deprivation. These miRNAs may play important roles in regulating circadian expression of genes involved in muscle cell differentiation and growth by nutritional alteration, thus having a potential application in fish aquaculture.     

Dietary n‐3 LC‐PUFAs affect lipoprotein lipase (LPL) and fatty acid synthase (FAS) activities and mRNA expression during vitellogenesis and ovarian fatty acid composition of female silver pomfret (Pampus argenteus) broodstock

We studied the effects of dietary n‐3 LC‐PUFAs on the activities and mRNA expression levels of tissue lipoprotein lipase (LPL) and fatty acid synthase (FAS) during vitellogenesis and ovarian fatty acid composition in female silver pomfret broodstock. Broodstock were fed one of four experimental diets for 185 days: FO (100% fish oil), FSO (70% fish oil + 30% soybean oil), SFO (30% fish oil + 70% soybean oil) or SO (100% soybean oil). The results revealed that hepatic LPL and FAS and ovarian FAS activities and mRNA expression levels significantly increased at vitellogenesis and postvitellogenesis relative to previtellogenesis, with no significant differences between these two stages, except for hepatic LPL mRNA expression. Dietary n‐3 LC‐PUFAs decreased tissue FAS and increased LPL activities and mRNA expression levels. The ovarian concentrations of 20:4n‐6 (ARA), 20:5n‐3 (EPA), 22:6n‐3 (DHA) and n‐3 LC‐PUFAs were directly influenced by n‐3 LC‐PUFA levels. Total n‐3 LC‐PUFA concentrations in SO were 57% lower than those in FO, while 18:2n‐6 concentrations in SO were 4.7 ×  higher than those in FO. These results revealed that high dietary n‐3 LC‐PUFAs levels significantly affected tissue lipid metabolism in female silver pomfret broodstock during vitellogenesis by upregulating LPL and downregulating FAS.     

灰鲳仔稚鱼消化系统的发育

对出膜后1~35 d灰鲳仔稚鱼的消化系统进行了形态学和组织学观察。初孵仔鱼具有很大的卵黄囊,消化管为一简单的直形盲管。2日龄仔鱼消化系统中肠区首先开始分化,内面可见纹状缘。3日龄仔鱼胃区膨大,卵黄消失,肠道分化出小肠和直肠。侧囊在4日龄仔鱼时出现分化。5日龄仔鱼观察到幽门盲囊的初始结构,油球消失,从内源性营养向外源性营养过渡基本完成。6日龄仔鱼摄食主动。14日龄稚鱼肝脏分为两叶,体积增大,胰脏体积增大,胃弯曲呈"U"形,幽门盲囊指状分支已增加到几十个。22日龄稚鱼肠道弯曲更多,在胸腹腔中肠道盘曲程度已接近幼鱼。28日龄稚鱼侧囊背腹形成一纵隔,出现角质剌。35日龄稚鱼胃腺已十分丰富,侧囊结构也已完善,标志着灰鲳消化系统更趋完善。     

银鲳ghr和igfbp1基因表达特征、组织分布及操作胁迫对其的影响（英文）

为探讨急性操作胁迫对银鲳生长的影响,首次克隆了3种生长调控相关基因-生长激素受体1(ghr1)、生长激素受体2(ghr2)和胰岛素样受体1(igfbp1),并对3种基因在银鲳肝脏、心脏、性腺、肌肉和肾脏等不同组织中的表达进行了比较。定量表达结果表明3种基因均广泛分布于所研究的各个组织中,而其中肾脏、性腺和心脏中的表达量较其它组织低。在银鲳受到外界操作胁迫刺激后,3种基因呈现不同的表达模式:其中ghr2和igfbp1的表达下调,而ghr2的表达量与对照组无显著性差异。结果表明,ghr2和igfbp1在银鲳生长调节中起到重要的作用;在胁迫环境中,外界刺激可通过下调生长相关基因表达以影响鱼体的生长。     

低盐度和不同硫酸铜浓度对银鲳鳃离子调节酶和肝抗氧化功能的影响

开展银鲳(Pampus argenteus)试养海域的盐度易随气候降低, 且受到一定程度Cu等重金属污染, 研究低盐条件下硫酸铜对银鲳的影响十分必要。本实验首先进行银鲳幼鱼低盐度适应, 将盐度以4的幅度从24逐步降低至12。稳定后进行硫酸铜胁迫, 在盐度12下CuSO₄·5H₂O浓度梯度设为0、0.1、0.3、0.5 mg·L^–1, 盐度24下CuSO₄·5H₂O浓度梯度设为0、0.5 mg·L^–1, 胁迫持续144 h。通过检测两种鳃离子调节酶: Na⁺/K⁺-ATP酶(NKA)和V-H⁺-ATP酶(VHA), 以及3种肝抗氧化活性物质－还原型谷胱甘肽(GSH)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT), 探究低盐条件下铜离子对银鲳幼鱼上述指标的影响。结果显示, 盐度逐步降低后, NKA与VHA活力呈上升后下降的变化, 之后NKA活力随硫酸铜浓度增加而减弱; VHA活力加入硫酸铜后都出现显著下降, 其中CuSO₄·5H₂O 0.3 mg·L^–1与0.5 mg·L^–1组在72 h时下降更为明显; 盐度24硫酸铜组NKA和VHA活力都在24 h时增强而后减弱。GSH含量和SOD活力在盐度降低时出现跃升, CAT活力则呈波动变化, 加入硫酸铜后, 0.3 mg·L^–1与0.5 mg·L^–1组GSH含量持续下降后显著上升而后回落; 各硫酸铜组SOD活力都出现增强后回落的变化; 0.3 mg·L^–1与0.5 mg·L^–1组CAT活力在72 h有显著增强。本实验表明, 铜离子对NKA与VHA有抑制作用, 盐度降低时其作用更强; GSH、SOD和CAT的变化能反映低盐度和铜离子对银鲳的伤害程度。银鲳对水体铜离子有一定的抗性, 但在盐度降低等环境变化时, 应当密切注意水体中铜等重金属浓度。

     

银鲳卵黄发生期间组织中抗氧化水平的变化及饲料n-3 LC-PUFA对其的影响

研究了银鲳(Papus argenteus)肝及卵巢组织中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性、总抗氧化能力(T-AOC)及丙二醛(MDA)含量在整个卵黄发生过程中的变化情况,并分析了饲料n-3 LC-PUFA对卵黄发生期间组织中抗氧化水平的影响。分别以100%鱼油(FO组)、70%鱼油和30%大豆油(FSO组)、30%鱼油和70%大豆油(SFO组)、100%大豆油(SO组)为脂肪源,配制了4组等氮、等能及等脂的试验饲料。以1年龄雌性银鲳为试验对象,每组饲料设3重复,试验周期185 d。研究结果表明,肝与卵巢组织SOD、CAT活性、T-AOC水平及MDA含量在卵黄发生过程中均呈现逐渐升高的趋势,且卵黄发生后期各指标水平均显著高于卵黄发生前期(P0.05)。肝SOD(除SO饲料组外)、CAT活性、T-AOC水平及MDA含量在卵黄发生中期与前期之间未表现出显著性差异(P0.05),而卵黄发生中期FO与FSO饲料组卵巢SOD、CAT活性及T-AOC水平则均显著高于卵黄发生前期(P0.05)。FSO饲料组肝与卵巢SOD、CAT活性在卵黄发生过程中均为最高值,且在卵黄发生中、后期均显著高于SO饲料组(P0.05),但与FO饲料组无显著性差异(P0.05)。各饲料组间肝与卵巢T-AOC水平在卵黄发生前期均未表现出显著性差异(P0.05),而在卵黄发生后期,FO与FSO饲料组肝与卵巢T-AOC水平均显著高于SO饲料组(P0.05),但FO与FSO饲料组间无显著性差异(P0.05)。肝与卵巢中MDA含量随着饲料n-3 LC-PUFA含量的升高而呈现出升高趋势,且这种升高趋势在肝组织中表现更为明显,卵巢组织MDA含量在卵黄发生中、后期仅FO饲料组表现出显著性升高趋势(P0.05),其他各饲料组在卵黄发生各期均未表现出显著性差异(P0.05)。统计分析表明,银鲳卵黄发生过程中组织中抗氧化水平逐渐升高,适宜的饲料n-3 LC-PUFA含量(4.01%,FSO饲料组)可明显改善银鲳卵黄发生中期与后期组织中的抗氧化水平。双因素方差分析结果表明,试验饲料与卵黄发生时期对银鲳组织抗氧化水平均具有极显著性影响(P0.01),且两者对肝T-AOC水平与MDA含量存在显著性的交互作用(P0.05)。     

饲料中大豆油替代鱼油对银鲳(Pampus argenteus)幼鱼血清溶菌酶活性及组织抗氧化能力的影响

银鲳(Pampus argenteus)是沿海重要的经济鱼类,本研究针对养殖银鲳幼鱼进行人工配合饲料研发,降低饲料成本、增强鱼体体质、提高存活率等.通过配制以100％鱼油(FO)、70％鱼油和30％大豆油(FSO)、30％鱼油和70％大豆油(SFO)、100％大豆油(SO)为脂肪源的4组饲料,检测银鲳幼鱼血清溶菌酶(LZM)和组织抗氧化性能的变化情况,以探究饲料大豆油替代鱼油对银鲳幼鱼健康的影响.结果显示,SFO组血清LZM水平最高,SO组最低,但各组间差异不显著(P＞0.05).FSO和SFO组的肌肉丙二醛(MDA)含量显著高于FO和SO组(P＜0.05),肝脏MDA含量则是FO和FSO组较高(P＜0.05).血清和肌肉超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活力最高的均为SFO组,而SO组活力较低.相对地,肝脏SOD和CAT活力均是FO组最高(P＜0.05).肌肉和肝脏总抗氧化能力(T-AOC)均是FO和FSO组较高,而血清T-AOC是SO组较高.研究表明,豆油替代30％和70％鱼油,对银鲳幼鱼免疫和抗氧化能力都略有促进作用,但完全使用豆油会对机体产生负面影响.     

Effects of dietary carbohydrate and lipid levels on growth performance,feed utilization,body composition and non‐specific immunity of large yellow croaker (Larimichthys crocea)

The present study was conducted to investigate the effects of dietary lipid, carbohydrate and their interactions on growth performance, feed utilization, body composition and non‐specific immunity of large yellow croaker (Larimichthys crocea). The experimental fish were fed the diets with graded levels of dietary crude lipid (80, 110 and 140 g/kg diet) and dietary carbohydrate (60, 90 and 120 g/kg diet) for 7 weeks. Results showed that the specific growth rate decreased significantly as dietary carbohydrate increased, which partly resulted from the progressively reduced feed intake and protein efficiency ratio. Meanwhile, the result of postprandial glucose content confirmed glucose intolerance of the croaker. However, the specific growth rate was not significantly altered by dietary lipid, but the feed intake was remarkably reduced. The different growth performance and feed utilization of croaker in response to dietary lipid and carbohydrate resulted in the variation of body composition. In addition, the activity of lysozyme and classical complement pathway was significantly improved in croaker fed the diet with 110 g/kg lipid. In above, dietary carbohydrate and lipid of large yellow croaker should be maintained at 60 and 110 g/kg diet, respectively, based on the above indices.     

Antibiotics,Penicillin and Sreptomycin improve semen quality indices of endangered Caspian brown trout,Salmo trutta caspius (Kessler, 1870) during in vitro short‐term storage

In this study, we examined the effects of 500 IU mL^?1 penicillin + 500 μg mL^?1 streptomycin sulphate on semen quality indices of endangered caspian brown during 12 days short‐term storage at 4°C. Twenty‐four millilitre semen samples with good quality were considered for the experiment. The semen samples were then stored in the presence and absence of 500 IU mL^?1 penicillin + 500 μg mL^?1 streptomycin sulphate. The semen quality parameters including percentage and duration of sperm motility were measured 0, 3, 6, 9 and 12 days after storage. In the antibiotic receiving group, the values of percentage and duration of sperm motility reduced 3 and 6 days after storage respectively and reduced to lowest levels at day 12. In the antibiotic‐free group, the duration and percentage of sperm motility decreased significantly after 3 days of storage and reached to lowest values at day 12. Also, percentage and duration of sperm motility in each storage time were significantly higher in the antibiotic receiving group than in the antibiotic‐free group. The overall values of percentage and duration of sperm motility for all storage periods were higher in the antibiotic receiving group than in the antibiotic‐free group. In conclusion, our results demonstrated that 500 IU mL^?1 penicillin + 500 μg mL^?1 streptomycin sulphate improves the viability of caspian brown trout during short‐term storage.     

The effects on some non‐enzymatic antioxidants and oxidative stress of Astacus leptodactylus (Esch., 1823) of starvation periods

This study investigated the effect of starvation (78 days) and refeeding (33 days) on the oxidative stress [malondialdehyde (MDA)] and the non‐enzymatic antioxidants [vitamin E (VE), vitamin C (VC), vitamin A (VA), beta carotene (βC) and reduced glutathione (GSH)] in the hepatopancreas, muscle and gill tissues of freshwater crayfish (Astacus leptodactylus). Crayfish were divided into three experimental groups: control (fed), starved (not fed) crayfish for 78 days and refeeding crayfish for 33 days after 78 days of starvation. The biochemical analysis of the tissues was conducted at 3, 18, 33, 48, 63 and 78 days of starvation and feeding and at 3, 18 and 33 days of refeeding. It was determined that crayfish can withstand starvation period of 78 days. In all of the periods, the MDA levels were significantly higher in the tissues of starved crayfish when compared with the control. The findings of this study demonstrate that starvation has a negative effect on the VE, VC, VA, βC and GSH levels in the crayfish. The measured parameters returned to control values after 33 days of the refeeding. Additionally, the starvation resulted in decreased levels of VE, VA and βC in the abdomen muscle of crayfish consumed by humans.     

Estimation of production and long‐term changes in the population of European eel Anguilla anguilla (L.) in an Irish lake

Monitoring of yellow‐phase and silver‐phase Anguilla anguilla during their continental life history is necessary for evaluation of stock recovery measures. Eel population data for an Irish lake (Lough Sheelin) were compiled for the period 1993–2014. Catch data from 2009 to 2014 provided minimum estimates of recent silver eel production ranging annually from 0.79 to 1.84 kg/ha. Long‐term changes in yellow eel abundance and silver eel size structure were assessed as part of a fishery monitoring programme. Yellow eel catch per unit effort (CPUE) in the lake (from longline surveys) was considerably higher in the 1990s (52.2–62.1 eels/100 hooks) than 2002–2008 (1.9–15.8 eels/100 hooks). Conversely, during 1993–2014, the mean size of silver eels migrating from the lake increased significantly (p < .001), from 659 mm to 838 mm. The results suggest that in the absence of direct yellow eel abundance data, interannual variation in silver eel size structure may be a useful monitoring tool for local eel stocks as part of Eel Management Plans (EMP's).