长江野生和池塘养殖河蟹(Eriocheir sinensis)蟹种早期养殖性能、抗病力和非特异性免疫性能的比较

本研究采用养殖性能评价、攻毒实验和非特异性免疫指标分析方法,比较了2个种群河蟹(Eriocheir sinensis)扣蟹在成蟹阶段的早期养殖性能[第1次蜕壳间隔时间、成活率(SR)和增重率(WGR)、特定生长率(SGR)]、攻毒后的死亡率和免疫性能。结果显示,(1)池塘养殖扣蟹第1次蜕壳间隔时间和SGR显著短于野生扣蟹(P0.05),而2种来源扣蟹的SR和WGR均无显著差异(P0.05);(2)野生扣蟹攻毒后的累计死亡率一直低于池塘养殖扣蟹,攻毒96 h后,野生扣蟹累计死亡率(28.3%)明显低于养殖扣蟹(50.0%);(3)比较肝胰腺组织非特异性免疫指标发现,无论雌蟹还是雄蟹,野生扣蟹碱性磷酸酶(ALP)活性显著低于养殖扣蟹,野生雄蟹的总抗氧化能力(T-AOC)活性和NO含量显著高于养殖雄蟹,而野生雌蟹的丙二醛(MDA)含量显著低于养殖雌蟹;(4)比较血清中非特异性免疫指标发现,野生扣蟹NO含量显著高于养殖扣蟹,而养殖扣蟹酸性磷酸酶(ACP)活性显著高于野生扣蟹。此外,野生雌蟹血清中的血蓝蛋白(Hc)含量、T-AOC及谷胱甘肽还原酶(GR)等活性显著高于养殖雌蟹,而ALP、γ-谷氨酰转移酶(γ-GT)及谷胱甘肽过氧化物酶(GSH-Px)等活性显著低于养殖雌蟹。综上所述,2种来源蟹种各有优势,池塘养殖扣蟹具有较好的早期养殖性能,野生蟹种具有较强的免疫性能,有关其质量差异形成原因有待进一步深入研究。     

中华绒螯蟹2龄早熟、晚熟选育群体和非选育群体蟹种免疫性能的比较

免疫性能是评价中华绒螯蟹(Eriocheir sinensis,以下简称河蟹)蟹种质量的重要指标,采用攻毒实验和非特异免疫指标测定方法,以常规养殖未经遗传选育的养殖群体蟹种为对照组,评价了河蟹2龄早熟、晚熟选育群体第2代(G2)扣蟹的攻毒成活率和非特异性免疫指标。结果显示:(1)嗜水气单胞菌攻毒注射后,整体上未选育组扣蟹的死亡率略高于两选育群体,但是雌雄个体间具有一定的性别差异,2龄晚熟群体雄蟹和2龄早熟群体雌蟹攻毒后死亡率分别最低;(2)就肝胰腺中非特异性免疫指标而言,无论雌蟹还是雄蟹,2龄早熟群体肝胰腺中的碱性磷酸酶(ALP)活性显著高于对照组(P0.05),酸性磷酸酶(ACP)活性显著高于2龄晚熟组(P0.05);此外,两个选育组雄体肝胰腺中的总抗氧化能力(T-AOC)和过氧化物酶(POD)活性均显著高于对照组,2龄早熟G2雌体肝胰腺中的丙二醛(MDA)和谷胱甘肽过氧化物酶(GSH-Px)均显著高于其它两组雌体;(3)就血清中非特异免疫指标而言,无论雌蟹还是雄蟹,2龄早熟G2扣蟹血清中的ACP活性均显著高于对照组,2龄晚熟G2扣蟹血清中的谷胱甘肽还原酶(GR)活性均显著低于其它两组扣蟹,此外,2龄早熟G2雌蟹血清中的γ-谷氨酰转移酶(γ-GT)和T-AOC活性均显著高于2龄晚熟G2。综上,两个选育群体子二代扣蟹具有较强免疫性能及抗病力,其中2龄早熟群体扣蟹的免疫性能和抗氧化能力略强于2龄晚熟选育群体。     

中华绒螯蟹二龄早熟和晚熟品系选育第四代在扣蟹阶段养殖性能和免疫性能的评价

本研究以中华绒螯蟹2龄早熟和晚熟群体选育第四代(G4)的扣蟹为对象,并以未经选育的养殖群体扣蟹为对照组,采用养殖实验、免疫指标测定和攻毒实验等方法,从生长性能和免疫抗病性能的角度分析并评价不同群体的蟹种质量。结果显示:①养殖实验中两选育群体的最终体质量和特定增长率(SGR)均优于对照组,且2龄早熟群体在8-11月的平均体质量始终低于晚熟群体,但差异不显著;②养殖效果方面,三群体成活率和最终产量由大到小依次为早熟G4、晚熟G4和对照组,三群体1龄早熟率的大小次序与之相反,其中雌体产量和1龄早熟率差异显著;③免疫指标方面,两选育组碱性磷酸酶(AKP)和酸性磷酸酶(ACP)活性以及总抗氧化能力(T-AOC)水平均高于对照组,其中雄体肝胰腺中AKP活性以及雌体血淋巴中T-AOC水平差异显著;④两选育群体在攻毒实验中最终死亡率均较低,分别比对照组低29.50%和22.94%。研究表明,选育G4扣蟹的生长性能和免疫抗病相关生理指标都表现出了比未选育群体优良的特性,市场应用和产业化前景广阔。     

长江和黄河水系中华绒螯蟹扣蟹在黄河口成蟹阶段生长性能的比较

为探讨长江和黄河水系中华绒螯蟹(Eriocheir sinensis)在黄河流域生长性能，本实验2021年3-11月在东营黄河口地区以长江和黄河水系中华绒螯蟹扣蟹为实验对象，对两水系中华绒螯蟹扣蟹在成蟹阶段的养殖性能和性腺发育进行比较。结果显示：(1)在相似或相同养殖环境下，养殖前期(3-5月),两水系中华绒螯蟹平均体质量变化无明显差异。但在养殖后期(7-9月)长江蟹雌体的平均体质量显著高于黄河蟹。两水系中华绒螯蟹特定生长率(SGR)和增重率(WGR)的变化趋势类似，长江蟹雌体在5-7月SGR和WGR均显著高于黄河蟹。(2)就生殖蜕壳而言，黄河蟹生殖蜕壳要提前长江蟹10～15 d左右，但两水系成蟹雌、雄个体生殖蜕壳高峰期相似，分别出现于8月底和9月初。(3)长江蟹最终成蟹规格显著大于黄河蟹，但黄河蟹成活率高于长江蟹，故两水系中华绒螯蟹的最终成蟹产量基本一致。综上，在黄河口地区养殖的长江蟹具有成蟹规格大，性腺成熟略晚等特点，而黄河蟹则具有性腺成熟较早，早上市等特点。     

2种饵料模式对稻田养殖中华绒螯蟹幼蟹养殖性能和生理代谢的影响

为优化稻田养殖中华绒螯蟹(Eriocheir sinensis)幼蟹的饵料模式,本研究分别采用配合饲料和传统饵料(豆粕、麸皮、玉米和小麦)投喂稻田养殖中华绒螯蟹幼蟹152 d,每种投喂组各3个重复,比较2种饵料模式对幼蟹养殖性能、蛋白质代谢、消化酶、抗氧化和免疫指标的影响。结果显示,配合饲料组的雌蟹和雄蟹体质量均高于传统饵料组,但差异不显著(P>0.05);就养殖性能而言,2种饵料模式下,配合饲料组正常幼蟹的平均体质量及产量、1龄早熟蟹平均体质量及其产量、总产量和成活率均略高于传统饵料组,饵料系数显著低于传统饵料组(P<0.05);就蛋白质代谢而言,配合饲料组雌蟹和雄蟹血淋巴中的总蛋白含量显著高于传统饵料组(P<0.05),而传统饵料组雄蟹血淋巴中的尿素氮含量和肝胰腺中的谷草转氨酶活力显著高于配合饲料组(P<0.05);配合饲料组雌蟹和雄蟹肝胰腺中的脂肪酶均显著高于传统饵料组(P<0.05),而雄蟹的α-淀粉酶活力显著低于传统饵料组;配合饲料组的雌蟹血淋巴中总抗氧化能力、碱性磷酸酶、酸性磷酸酶活力和肝胰腺中酸性磷酸酶活力均显著高于传统饵料组(P<0.05)。综上所述,投喂配合饲料可以提高稻田扣蟹的养殖性能、促进蛋白质沉积和脂类吸收、增强幼蟹抗氧化和免疫能力、提高蟹种质量。     

辽河和闽江水系中华绒螯蟹扣蟹在成蟹阶段的养殖性能比较

2018年3—11月,将体质量(7.83±0.72)g和(7.53±0.39)g的雌雄辽河水系中华绒螯蟹Eriocheir sinensis扣蟹和体质量(5.06±0.74)g和(5.21±0.49)g雌雄闽江水系中华绒螯蟹扣蟹饲养在42m×35m×1.2m、种植伊乐藻Elodea nuttallii的两口池塘中,密度约为1.2～1.3只/m2,常规方法养殖,比较辽河和闽江水系绒螯蟹扣蟹在成蟹阶段的养殖性能。结果显示:辽河蟹平均终体质量大于闽江蟹,成活率和产量较高;3—5月和7—9月闽江蟹增重率(WGR)和特定生长率(SGR)高于辽河蟹。辽河雌蟹全部完成生殖蜕壳时间早于闽江蟹一个月,而雄蟹则提前半个月左右。9—11月,闽江蟹性腺指数(GSI)增加量高于辽河蟹。11月初辽河蟹总可食率(TEY)显著高于闽江蟹(P0.05),但出肉率(MY)无显著差异(P0.05)。闽江蟹中体质量50g的雌蟹和≥200g的雄蟹的百分比较高。综上所述,辽河蟹全部完成生殖蜕壳时间早于闽江蟹。虽然闽江蟹性腺发育较晚,但其性腺发育速度较快。本实验为进一步挖掘优异种质资源和新品种培育奠定了理论和实践基础。     

中华绒螯蟹1龄性早熟自交和1龄性早熟与2龄正常成熟杂交F1养殖性能及可食率比较

中华绒螯蟹(Eriocheir sinensis)1龄性早熟是目前产业发展中面临的重要问题,为全面了解中华绒螯蟹 1龄性早熟性状对其子代相关性状的影响,本研究构建了 1 龄性早熟自交家系(PI)和 1 龄性早熟与 2 龄正常成熟杂交家系(PHN),综合评估其养殖性能和可食率。结果表明:(1)在扣蟹养殖阶段, PI 组 F1扣蟹平均体重始终大于 PHN 组;PI组 F1雌体的增重率(WGR)、特定生长率(SGR)和早熟率均高于 PHN组,雄体则较低,但均无显著性差异(P>0.05);PI组 F1雌体成活率显著低于 PHN 组(P<0.05),雄体略低于 PHN 组;PHN 组总产量较高,但无显著差异(P>0.05)。扣蟹终体重呈正态分布, 3.00~8.99 g 终体重扣蟹比例较高。(2)在成蟹养殖阶段,生长前期(3 5 月)PI 组平均体重低于PHN 组,生长后期(7 9 月)则以 PI 组为高;3 5 月和 7 9 月 PHN 组 F1WGR 和 SGR 均高于 PI 组,而 5 7 月则以 PI组为高;PI组 F1生殖蜕壳和性腺发育略早于 PHN组,无显著性差异(P>0.05);总体来看, PI组 F1成活率和产量均高于 PHN组,但饵料系数显著低于 PHN组(P<0.05);PHN组 F1体重<125.00 g和≥250.00 g的成蟹百分比较高,两组体重<125.00 g 的成蟹存在显著性差异(P<0.05)。(3)就总可食率(TEY)而言, PI 组 F1TEY 高于 PHN 组;就肥满度(CF)而言, PI组 F1雌体高于 PHN组,雄体则较低,但两组无显著性差异(P>0.05)。综上, 1龄早熟自交组 F1具有扣蟹平均体重大、早熟率略高,成蟹生殖蜕壳较早、成活率和产量高的特点;而 1 龄早熟与 2 龄正常成熟杂交组F1则具有扣蟹成活率和产量高,成蟹生殖蜕壳略晚、饵料系数低的特点。     

池塘养殖和野生长江水系中华绒螯蟹扣蟹形态学及生化组成的比较研究

采用形态学测量和生化分析等方法,比较了野生和池塘养殖条件下长江水系中华绒螯蟹扣蟹的形态学、肝胰腺指数(HSI)、常规生化组成和脂肪酸组成。结果发现:野生和池塘养殖扣蟹的形态学特征差异较大,雌雄个体均有4个贡献较大的主成分(PC1,PC2,PC3,PC4),其中PC1的贡献率均远高于其他主成分,两者PC1分别由16和19个主要影响变量构成;所测36个形态学指标中,两群体雄蟹和雌蟹分别有25和22个形态学指标差异显著,进一步筛选判别贡献率较大的4~5个指标分别建立判断方程,综合判别准确率达95%以上;野生扣蟹的HSI、组织中总脂、躯体肌肉的16:0、18:1n9和20:4n6含量均高于池塘养殖扣蟹,后者组织中水分含量、躯体肌肉中的18:0、20:5n3和22:6n3高于前者。研究表明,野生和池塘养殖扣蟹的形态学和生化组成均存在较大差异,可以根据两群体扣蟹的形态学差异和判别方程鉴别两种扣蟹蟹种。     

不同规格中华绒螯蟹亲本子一代在扣蟹阶段养殖性能的比较研究

为探究中华绒螯蟹(Eriocheir sinensis)亲本规格对其子代在扣蟹阶段养殖性能的影响,本试验在相同的养殖环境下将4种规格河蟹亲本(规格I:雌90~110 g、雄140~160 g;规格Ⅱ:雌115~135 g、雄160~180 g;规格Ⅲ:雌140~160 g、雄220~240 g;规格Ⅳ:雌190~210 g、雄290~310 g)所产的大眼幼体养殖至扣蟹,并比较各组扣蟹的体质量、增重率、特定生长率、成活率及最终产量差异。试验结果显示:(1)不同规格的河蟹亲本,其子一代在大眼幼体至豆蟹阶段的平均体质量、成活率以及增重倍数均无明显差异(P>0.05);(2)在豆蟹至扣蟹养殖阶段,各组幼蟹的生长速度差异大体上与其亲本规格的差异相一致,其中Ⅰ组幼蟹在8—10月期间的平均体质量均显著低于Ⅳ组(P<0.05);(3)养殖效果方面,各组扣蟹平均规格和最终产量均随着亲本规格的提高而提高,其中Ⅳ组扣蟹的最终平均体质量显著高于Ⅰ组扣蟹(P<0.05);(4)就规格分布而言,Ⅳ组扣蟹2.00~3.99 g规格的比例显著低于另外3组,而≥6.00 g规格的比例显著高于另外3组(P<0.05)。结果表明,中华绒螯蟹亲本规格对其后代的养殖性能存在影响,大规格河蟹亲本子一代在扣蟹生产阶段生长速度快、养殖效果好,因此建议在生产上选择大规格亲本的后代用于扣蟹养殖。     

中华绒螯蟹二龄早熟和晚熟品系选育第五代(G5)的生长性能和性腺发育评估

为评估中华绒螯蟹(Eriocheir sinensis)二龄早熟(EM)和晚熟(LM)品系第五代选育效果,本研究以未选育群体作为对照组,比较了两选育品系与对照组在扣蟹及成蟹养殖阶段的生长性能和性腺发育差异,结果显示：(1)两选育品系在扣蟹养殖阶段的平均体质量与增重率(WGR)均高于对照组,其中8月和10月时LM雄体平均体质量显著高于对照组,且7-9月期间LM品系雌雄扣蟹的WGR均显著高于对照组;(2)两选育品系在成蟹养殖阶段的平均体质量一直高于对照组,且两选育品系中LM品系平均体质量一直高于EM品系,但两选育品系之间并无显著差异;(3)雌雄个体在成蟹养殖阶段的生殖蜕壳高峰期分别为7月25日-9月5日和8月15日-9月25日,在此期间EM品系的生殖蜕壳率高于对照组,LM品系的生殖蜕壳率低于对照组,其中EM品系雌雄个体在8月15日的生殖蜕壳率均显著高于LM品系;(4)就性腺发育而言,EM品系在性腺发育期间的性腺指数(GSI)始终较高,LM品系的GSI始终较低,其中在10月25日EM品系雄体的GSI显著高于LM;综上,经过连续多代选育,中华绒螯蟹二龄EM和LM品系在扣蟹和成蟹阶段的生长性能较...     

不同繁育方式蟹苗对1龄蟹种培育效果的影响

采用♀亲蟹平均规格分别为158.9g、132.8g,♂亲蟹平均规格为180g、150g两种群体繁育的蟹苗培育的1龄蟹种,其群体规格分别为128只/kg、160只/kg。在面积相同、放养密度相同、饲养条件相同的条件下,采用天然海水土池繁育的蟹苗培育的1龄蟹种成活率为5.1%、亩产蟹种8064只;而采用天然海水工厂化繁育的蟹苗,育种成活率为2.24%、亩产蟹种3609只;在蟹苗来源相同、饲养管理相同,培育池面积为19亩的培育池蟹种产量低于面积5亩的池塘。     

Dietary phospholipids requirement of the early juvenile (C1) swimming crab,Portunus trituberculatus

A 30‐day experiment was conducted to investigate the effect of phospholipids (PLs) on growth performance, survival, fatty acid profile and gene expression of the early juvenile (C1) swimming crab (Portunus trituberculatus). Five semi‐purified diets were formulated with graded PLs levels (0%, 1%, 2%, 4% and 8%). Each diet was fed to four replicates of crabs (30 crabs per replicate, initial weight: 8.4 ± 0.1 mg). In this study, crabs fed diets with 2%, 4% and 8% PLs had significantly higher survival rates than crabs fed with 0% and 1% PLs. Crabs fed diets with 0% and 1% PLs had significant lower weight gain (WG) than crabs fed with 8% PLs. But crabs fed with diets containing 2%, 4% and 8% PLs showed no significant difference in WG. Besides, the content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in whole body was higher than that in diets, but the monounsaturated fatty acids (MUFA) content showed an opposite trend. The EPA and DHA content in whole body increased with the increase in dietary PLs. Moreover, the moulting number increased with the increasing dietary PLs levels, the lowest moulting number was observed in crabs fed diets without supplementation of PLs. The ecdysteroid receptor (EcR) was found to be significantly up‐regulated by PLs levels. This study demonstrated that 2% PLs could meet the requirement of early juvenile (C1) swimming crab based on the growth and survival. And 4%–8% PLs supplemented in diets could reduce the leaching of feed.     

Evaluation of palygorskite on pellet quality,growth, antioxidant status and mineral contents of Chinese mitten crabs (Eriocheir sinensis)

This study evaluated the palygorskite inclusion effects on the pellet quality, growth, antioxidant status and mineral contents of Chinese mitten crabs. Crabs (n = 640; initial average weight, 1.36 ± 0.02 g) were allocated into four groups with eight replicates of twenty crabs. A basal diet supplemented with 0, 10, 20 and 40 g/kg palygorskite was fed to crabs for 8 weeks respectively. Results exhibited that dietary addition of palygorskite enhanced the pellet process electrical energy consumption, improved the hardness and durability (p < .05), reduced percentage of fines and dissolved weight loss of pellets (30, 60, 120, 240, 480 min; p < .05) in the water. Crabs had no differences on the weight gain, specific growth rate, feed conversion ratio, abdominal meat ratio and edible viscera index among the groups (p > .05). Palygorskite inclusion decreased the MDA contents of edible viscera and abdominal meat (p < .05) of Chinese mitten crabs. The ether extract contents of edible viscera in palygorskite inclusion groups were lower than that of the control group (p < .05) in Chinese mitten crabs. Furthermore, palygorskite addition linearly increased the Fe level in the edible viscera and reduced tissue Pb and Cr (p < .05) accumulations of Chinese mitten crabs. In conclusion, palygorskite inclusion could improve pellet quality, enhance the antioxidant capacity and Fe content of edible viscera, decrease the edible viscera ether extract level and tissue Pb and Cr accumulations without impairing the growth performance of Chinese mitten crabs, but increased the electrical energy consumption of pelleting.     

长江和辽河水系中华绒螯蟹湖泊放养生长性能的比较

对长江水系和辽河水系中华绒螯蟹（Eriocheir.sinensis)在长江下游湖泊生长性能研究的结果：（1）生长速度在3－8月长江蟹稍低于辽河蟹,但差异不显著（P＞0．05）;9－10月长江蟹则快于辽河蟹,差异极显著（P＜0．01）。（2）青春期蜕壳时间辽河蟹比长江蟹提前30－40d,生殖洄游期也相应提前30－40d。（3）养成的商品蟹规格、增重倍数和回捕率,长江蟹优于辽河蟹,差异极显著（P＜0．01）。综合分析认为,长江蟹在长江下游湖泊的生长性能指标优于辽河蟹。     

中华绒螯蟹“六月黄”与成蟹肝胰腺营养成分比较

对同一年度、同一饲养环境下的中华绒螯蟹"六月黄"和后期成蟹雌、雄个体肝胰腺组织的营养成分进行了测定和比较分析。结果显示,"六月黄"的肥满度与雌性成蟹间没有显著性差异(P0.05),但肝胰腺指数极显著高于成蟹(P0.01)。"六月黄"肝胰腺中水分和灰分的含量极显著高于成蟹(P0.01),而粗脂肪含量极显著低于成蟹(P0.01),两种蟹的粗蛋白质含量没有显著差异(P0.05)。在检测到的17种氨基酸中,除"六月黄"雄蟹肝胰腺中丙氨酸的含量显著低于其雌蟹及雌、雄成蟹外(P0.05),其他16种氨基酸在"六月黄"与成蟹间均不存在显著差异(P0.05)。"六月黄"和成蟹的肝胰腺中含量最高的4种脂肪酸均为C18:1n9c、C18:2n6c、C16:0和C16:1,其总和分别占"六月黄"和成蟹肝胰腺中总脂肪酸的72.13%和69.02%(雌、雄蟹平均值)。"六月黄"的饱和脂肪酸总量显著低于成蟹(P0.05),但其单不饱和脂肪酸总量(ΣMUFA)和多不饱和脂肪酸总量(ΣPUFA)均显著高于成蟹(P0.05)。"六月黄"肝胰腺中Σn-6 PUFA的含量也极显著高于成蟹(P0.01),而Σn-3 PUFA含量二者不存在显著差异,因此"六月黄"的Σn-6/Σn-3 PUFA比率(1.42～1.44)低于成蟹(0.85～0.92)。结果表明,从总体上看,"六月黄"的营养价值较高,其肝胰腺的营养品质好于成蟹,"六月黄"养殖具有一定的产业发展前景。     

Development of performance indices for the Newfoundland and Labrador snow crab (Chionoecetes opilio) fishery using data from a vessel monitoring system

This study investigates the potential for using data from a vessel monitoring system (VMS) to create indices of commercial fishery performance that may be used in monitoring snow crab resource status. Fishing hours were screened from hourly positional signals to create an index of fishing effort (hours fished) for comparison with that derived from logbooks (number of trap hauls). Similarly, a VMS-based fishing catch per unit of effort (CPUE) index was developed for comparison with CPUE derived from logbooks. Analysis of these indices showed that VMS-based fishing effort and CPUE indices can be interpreted to provide reliable complementary or alternative indices to logbooks for assessment of fishery performance in the Newfoundland and Labrador (NL) snow crab (Chionoecetes opilio) fishery. We also developed a VMS-based index of fishing efficiency and illustrate how it can be applied toward understanding various behaviors and anomalies in the fishery. VMS data may offer other potential applications for snow crab assessment and management. Our approach and methods are applicable to other commercial fishery resources worldwide that are monitored using vessel monitoring systems.     

中华绒螯蟹蜕皮抑制激素基因单核苷酸多态与性早熟的关联性分析

该研究以中华绒螯蟹MIH基因编码区序列的10个单核苷酸多态位点(SNPs)为研究目标,采用性状-基因型分析方法研究了MIH基因变异与河蟹性早熟性状之间的相关性。结果表明,位于MIH基因内含子(Intron2)上一个SNP位点(SNP g.2466 C>T)与中华绒螯蟹性早熟之间存在着较具统计学意义的相关性(OR=0.459,95%CI 0.223-0.944,P=0.034)。     

Effects of dietary phospholipid and cholesterol levels on growth and fatty acid composition of juvenile swimming crab,Portunus trituberculatus

The objective of this study was to evaluate the effects of different phospholipids (PL) and cholesterol (CH) levels on the growth, moulting and fatty acid composition of juvenile swimming crab, Portunus trituberculatus. Six diets were designed to contain three PL levels (0, 10 and 20 g/kg) and two CH levels (2 and 8 g/kg). Juvenile swimming crabs (3.48 ± 0.02 g/crab) were reared for 8 weeks. The weight gain (WG) was significantly (p < .05) increased by supplementation of 8 g CH/kg of diet. However, no significant interaction between dietary PL and CH levels was found on the growth performance (p > .05). The moulting frequency (MF), protein efficiency ratio (PER) and feed efficiency ratio (FCR) were not significantly (p > .05) affected by the dietary treatments. The serum total cholesterol (TCH) significantly (p > .05) increased with increasing dietary PL level. The C20:4n‐6 and C20:5n‐3 content of the whole body of crabs increased with the addition of PL to the diet containing 2 g/kg CH of diet. An interaction was observed between PL and CH on certain saturated and unsaturated fatty acid concentrations of body.     

Effects of dietary DHA/EPA ratios on growth performance,survival and fatty acid composition of juvenile swimming crab (Portunus trituberculatus)

This study was conducted to investigate the effects of dietary docosahexaenoic to eicosapentaenoic acid (DHA/EPA) ratios on growth performance, survival and fatty acid composition of juvenile swimming crab (Portunus trituberculatus). Four isonitrogenous and isoenergetic experimental diets were formulated to contain different DHA/EPA ratios (0.70, 0.84, 1.06 and 1.25). There were three replicates (15 crabs per replicate) for each diet treatment. The crabs were fed (about 6–8% body weight) twice daily for 8 weeks. A good growth performance and feed utilization were observed in swimming crabs fed the diets with DHA/EPA ratios of 0.70 and 0.84. Crabs fed diet with 0.70 DHA/EPA ratio showed a significantly higher weight gain (WG) compared with the crabs fed the diet with DHA/EPA ratio of 1.25 (P < 0.05). The result of this study showed that the survival increased with decreasing the ratio of DHA/EPA. The DHA/EPA ratios in polar lipid from tissues were influenced by the dietary DHA/EPA ratios. Results of this study indicated that the growth performance and survival of juvenile swimming crab are correlated to the DHA/EPA ratio in the diets, and the best growth performance and survival were achieved with the ratios of 0.70–0.84.     

Improved hatchery‐rearing techniques for juvenile production of blue swimming crab,Portunus pelagicus (Linnaeus, 1758)

The effects of tank colour, larval stocking density, antibiotic administration and water exchange on survival and moulting of blue swimming crab, Portunus pelagicus, were determined. Circular 4‐m³ experimental larval‐rearing tanks were used in triplicate for all treatments. White, dark grey, blue and brown were tested as tank background colours. The stocking densities tested were 10, 20, 40, 60, 80 and 100 larvae L^?1. The effect of oxytetracycline was estimated by comparing a treatment with oxytetracycline to a treatment without oxytetracycline administration. The daily water exchange rates tested were 0%, 25%, 50% and 100% of the tank volume. In all treatments, the larvae were fed with Artemia nauplii, rotifers and encapsulated Spirulina. The highest percentage survival was observed in the dark‐grey tanks when the stocking density of larvae was 20 larvae L^?1. No larva reached the juvenile crab size in white tanks. No significant difference in survival was found between treated and non‐treated larvae with oxytetracycline when the daily water exchange rate was more than 50%.