Effects of Supplemental Feeding on Harvest of Red Swamp Crawfish,Procambarus clarkii,in Forage‐based Ponds

Procambarid crawfish aquaculture in the USA relies on an established forage‐based system for providing sustenance for growing crawfish. These systems may become inadequate at times for providing sufficient nourishment to support maximum growth of the population. Supplemental feeding is not routinely used because management recommendations for the cost‐effective use of supplemental feeds in ponds are not available. Because crawfish under confinement readily consume and grow well when fed single feedstuffs, such as rough rice seed and whole, raw soybeans, this study was initiated to investigate the use of these readily available low‐cost feedstuffs as supplemental feeds in aquaculture ponds. Earthen ponds (0.2 ha), constructed and managed to simulate commercial crawfish ponds, were used over three consecutive production seasons to evaluate the effects of supplemental feeding on yields and size of crawfish. Treatments for Seasons 1 and 2 consisted of (a) hull‐on rough rice seed, (b) whole raw soybean, (c) formulated 25% crude protein pellet, and (d) no supplementation and were replicated in four and three ponds for Seasons 1 and 2, respectively. Treatments for Season 3 consisted of (a) whole raw soybean and (b) no feed, with 10 replicated ponds each. Feeding frequency was established each year, and feeding rates were adjusted according to predetermined guidelines and monitoring of feeding trays. Crawfish harvesting was conducted by baited wire‐mesh traps and all harvested crawfish were subjected to a mechanical grader and sorted into three size classes. Results show that supplemental feeding, while trap‐harvesting operations are underway, can reduce yields and generate a negative economic benefit, perhaps as a result of residual feed within the pond rendering the baited trap less effective.     

克氏原螯虾的生态养殖⑤ 上海海洋大学克氏原螯虾生态养殖课题组协办 克氏原螯虾高效生态养殖模式

近年来,克氏原螯虾的养殖发展迅猛,已在全国各地形成各具特色的高效生态养殖模式,前面介绍的池塘生态养殖和稻田生态养殖只是众多模式中的一部分,下面介绍其它几种养殖模式,供广大养殖户借鉴.     

克氏原螯虾的池塘生态养殖(三）克氏原螯虾的池塘生态养殖

池塘饲养克氏原螯虾,对水体水质和池塘条件没有特别的要求,只要水质无工业污染,水中有机质丰富,即可进行粗放饲养.但如果要充分利用水体,提高单位水体的产量,则要对池塘进行一些必要的改造,辅以投喂饲料和日常管理,进行池塘精养.     

Double-Cropping Malaysian Prawns,Macrobrachium rosenbergii,and Red Swamp Crawfish,Procambarus clarkii

Prawns, "Macrobrachium rosenbergii," and crawfish, "Procambarus clarkii," were alternatively grown in ponds to determine if they were compatible and if total production could be increased. Brood crawfish were stocked into replicated ponds at rates of 0,60, 120 or 180 kg/ha on 18 April. Water was removed to encourage burrowing. Following this, rice was planted as forage. Post-larval prawns (0.02 g) were stocked 3 July in all ponds at 17,500/ha. Prawns in half the ponds were fed and those in the other ponds were not. Ponds were drained from 7 to 11 October. Prawn production ranged from 157 to 248 kg/ha; survival ranged from 69% to 88%, and average size ranged from 11 to 7 g. There was no significant difference (P > 0.05) between fed and non-fed treatments. The ponds were reflooded and crawfish were harvested by trapping from 15 January to 15 May. The average yield of crawfish ranged from 746 to 1,266 kg/ha. Stocking rate had no effect of crawfish yields (P > 0.25). Total yield, with prawns and crawfish combined, ranged from 1,037 to 1,237 kg/ha. Overall, prawns and crawfish were compatible in rotation. Prawns were a good size for soft shell production during months when crawfish are not available for soft shell production.     

The Effect of Five Stocking Densities on Growth and Yield of Red Swamp Crawfish Procambarus clarkii

A 34-day study was conducted to estimate the effect of stocking density on growth, biomass, and yield of harvestable animals in red swamp crawfish, Procambarus clarkii (Girard). Juvenile crawfish were stocked at l, 2, 4, 8, and 16 crawfish per m² into plastic-lined metal pools planted with rice ( Oryza sativa ) with three replicate pools at each density. Crawfish averaged 35 ± 1.5 mm (SE) total length at the time of stocking.
Growth in total length and weight was significantly affected by density ( P < 0.01), ranging from 91.5 mm and 20.7 g for crawfish stocked at 1 per m² to 62.5 mm and 6.3 g for crawfish stocked at 16 per m². The total crawfish biomass ranged from 20.7 g per m² for crawfish stocked at 1 per m² to 88.7 g per m² at 16 per m². The portion of that biomass made up of harvestable sized animals (>75 mm total length) ranged from 100% at 1 per m² to 0.7% at 16 per m². Gross revenues per ha were projected for crawfish yields at each stocking density with and without a graded product.     

角落空间与克氏原螯虾生活状况的关系

通过试验法研究了不同角落数与克氏原螯虾个体数比例的空间资源环境,对存活率、蜕壳率和SOD值的影响.试验结果表明,角落空间对克氏原螯虾的生存有影响,克氏原螯虾在角落资源合适时(角落数∶虾数=1～1.2∶1)生存较好,角落资源过多或过少对克氏原螯虾的生存都有负面影响.本试验结果利用了克氏原螯虾是一种具有优势等级序列的社会性动物的基本规律,表明空间资源过剩有可能升高其建立和维持其等级低位的能量代价.     

Substitution of Soybean Protein for Fish Protein in Formulated Diets for Red Swamp Crawfish Procambarus clarkii1

A 10 week laboratory growth trial was conducted with red swamp crawfish Procambarus clarkii to determine the amount of soybean protein that could be substituted for fish protein in formulated crawfish diets without reducing growth. Crawfish received 32% crude protein, isocaloric diets in which protein was supplied by soybean (soy) meal, menhaden fish meal or an isonitrogenous mixture of soybean and fish meal calculated to provide graded levels of each protein source. Dietary protein was provided as: 1) 100% soy protein; 2) 75% soy protein: 25% fish protein; 3) 50% soy protein: 50% fish protein; 4) 25% soy protein: 75% fish protein; and 5) 100% fish protein. Crawfish fed soy protein: fish protein (SP:FP) mixtures or fish protein alone exhibited better (P < 0.05) weight gain than crawfish fed a diet containing soy protein as the only protein source. Diets containing 25% soy protein: 75% fish protein (1:3 ratio) and 50% soy protein: 50% fish protein (1:1 ratio) produced greater (P < 0.05) weight gains than a diet in which fish protein was the sole protein source. Survival, feed efficiency ratio, maturation rate, net protein and energy retention, and body composition of crawfish did not differ (P > 0.05) among diets with SP:FP ratios of 1:3, 1:1 and 3:1. However, maximum (P < 0.05) weight gain occurred in crawfish fed the 1:3 SP:FP ratio. Although crawfish fed SP:FP ratios of 1:1 and 3:1 had lower weight gains in the laboratory than crawfish fed a 1:3 SP:FP ratio, SP:FP ratios of 1:1 and 3:1 might be adequate for supplemental diets fed to pond-reared crawfish that have access to natural sources of food.     

克氏原螯虾的营养保健功能及相关食品的研究与开发

综述了克氏原螯虾(俗称小龙虾)的营养保健功能以及小龙虾虾尾罐头、冻煮小龙虾仁、整肢冻煮熟小龙虾、小龙虾酱油等食品的加工技术,以期引起食品科技工作者对开发小龙虾食品的重视,供小龙虾养殖、加工企业同仁们参考,促进小龙虾产业链的形成.     

克氏原螯虾人工育苗技术初步研究

采用大棚土池人工育苗技术,进行了克氏原螯虾的亲虾培育和人工育苗试验,育苗池总面积为2744 m2.2007年9月份共收捕亲虾1 368 kg(其中雄虾342 kg、雌虾1 026 kg),规格25～40 g.设置了两种亲虾投放密度(分别为10尾/m2和20尾/m2),雌、雄性比均为3:1.试验结果:从9月份亲虾培育管理起到翌年3月份出苗,亲虾死亡率为58.6%;共计出苗50余万尾,平均单位产苗量为203尾/m2.高密度亲虾组的虾苗数量并未相应增加.     

Effects of Density Reduction and Supplemental Feeding on Stunted Crayfish Procambarus clarkii Populations in Earthen Ponds1

Density reduction, supplemental feeding, and a combination of two treatments were evaluated as means to alleviate stunting of red swamp crayfish Procambarus clarkii in earthen ponds. Mean total yield of crayfish in low density control ponds averaged 1,218 kg/ha and was 1.5 to 2 times higher (P≤ 0.05) than either the high density control or treatment ponds. Mean individual harvest weight of crayfish averaged 15.1 g and did not differ among treatments. Mean total yield of crayfish in ponds receiving supplemental feed was 32% higher than non-fed ponds (P≤ 0.05). Mean total yield and size of crayfish at harvest from reduced and non-reduced treatments did not differ. Density reduction and supplemental feeding implemented in early April did not increase individual crayfish weight to the commercially desirable size of 20 g.     

亲虾规格、隐蔽物、光照度及密度对克氏原螯虾繁殖效果的影响

按照正交试验设计原理,不考虑交互作用,选择L9(3～4)正交表,研究了亲虾规格、隐蔽物、光照度及放养密度4个因素对克氏原螯虾亲虾成活率、抱卵率、产卵量的影响,试验历时57d。研究结果表明,不同亲虾规格对抱卵量影响显著(P0.05),且规格为35～50g亲虾的平均抱卵量为489.8粒/尾,分别较25～30g、30～35g高20.8%、11.6%;不同隐蔽物种类对亲虾的成活率影响显著(P0.05),使用"水草+石棉瓦+砖块"作为隐蔽物,亲虾平均成活率为95.69%,分别较"水草+石棉瓦+PVC管"、"三角形栖息物"高9.6%、3.5%;光照度为50～500lx,亲虾的平均抱卵量为467.17粒/尾,高于其他两个光照度水平;放养密度为20尾/m2,亲虾的平均抱卵率为64.98%,高于其他两个密度水平。因此,亲虾规格为35～50g、隐蔽物种类为‘水草+石棉瓦+砖块’、光照度为50～500lx、放养密度为20尾/m2"组合有利于提高克氏原螯虾的繁殖效果。     

不同放养密度和水草覆盖率下克氏原螯虾池塘底泥中微生物群落特征

在底部埋有生物饵料培养基的克氏原螯虾池塘中,利用变性梯度凝胶电泳和基因测序技术,研究了2种放养密度(375 kg/hm2、600 kg/hm2,即A和B组)和2种水草覆盖率(占水域面积比20%、35%,即C和D组)条件下(每组设2个重复),底泥中微生物菌落结构特征。试验结果表明:4个试验组池塘底泥中微生物种类和数量存在一定差异。各试验组池塘底泥微生物的Shannon指数分别为2.72、2.94、2.82和2.96,说明水草覆盖率35%试验组池塘底泥微生物种类最丰富。聚类分析表明,不同月份不同处理组池塘底泥微生物群落结构相似度偏低,而放养密度600 kg/hm2试验组和水草覆盖率20%试验组在8月份相似度较高(70%以上),整体上,各样品在时间上的相似度比空间上的相似度高。对微生物组成多样性的分析表明,4组池塘底泥微生物克隆主要隶属于4个门:变形菌门(71%)、疣微菌门(9%)、放线菌门(8%)、绿弯菌门(11%)及其他门类未知的菌群,其中变形菌门的Ideonella属占主要优势,占总比例的24%。     

养殖密度对克氏原螯虾生长及消化酶、免疫酶活性的影响

水温(25±1)℃时,将体质量(3.11±0.10)g的克氏原螯虾幼虾饲养在120 cm×60 cm×20 cm的水族箱中,密度分别为14尾/m2(低密度组)、28尾/m2(中密度组)和42尾/m2(高密度组),研究室内养殖不同密度对生长、摄食、消化酶活性及非特异性免疫的影响.8周的养殖结果显示,克氏原螯虾的存活率随养...     

底泥对不同规格克氏原螯虾存活的影响

在大型(80cm×52cm×25cm)及小型水族箱(45cm×35cm×20cm)底部平摊1kg和8.5kg底泥(干质量),分别放养小规格[刚离开母体,(4.23±0.258)mg]、中规格(2.69±0.410)g、大规格(7.55±0.415)g 3个规格克氏原螯虾幼虾,密度分别为每箱30、18、6尾,以不加底泥为对照,每个处理5个重复。在水温18~25℃下常规投喂饲养5~6周,并测试了克氏原螯虾生长、存活、耐低氧和高温能力以及底泥对水体中溶氧量的影响。结果表明,底泥组小(7.82%/d)、中(0.90%/d)、大(0.92%/d)3个规格幼虾的特定生长率分别极显著(P0.01)以及显著(P0.05)高于对照组(5.56%/d,0.20%/d,0.59%/d)。底泥组小规格幼虾死亡率(12%)显著低于对照组(17.3%)(P0.05);耐高温时间极显著大于对照组(P0.01);其他组间差异不显著(P0.05)。3种规格幼虾底泥组窒息时间均极显著大于对照组(P0.01)。底泥使水中溶氧量显著降低。     

隐蔽所对不同生长阶段克氏原螯虾生长的影响

将体质量0.527 g(幼虾)和6.100 g(亚成体虾)的克氏原螯虾饲养在底面积为113 cm^2 、高为12 cm的圆形塑料盒中,一组放入内径为1.9 cm的PVC管作为隐蔽所为隐蔽组,以不放PVC管为对照组,其他条件同隐蔽组,定期测量各组克氏原螯虾的体长、体质量增长量、存活率和蜕壳率等指标,研究隐蔽所对不同规格克氏原螯虾生长的影响。2个月的饲养结果显示,试验第1个月隐蔽组幼虾组体长增长、体长相对增长率、体质量增长及蜕壳量均显著大于对照组( P <0.05),第2个月两组各数据无显著差异( P >0.05);隐蔽组亚成体螯虾摄食量、体质量及蜕壳量均小于对照组。研究结果表明,隐蔽所在螯虾的早期生长阶段对其生长有促进作用,但随着螯虾体格的增大,隐蔽所的促进作用随之减弱,甚至最终抑制螯虾的生长。本研究围绕克氏原螯虾穴居的习性以及趋触性等行为的特点,为生产提供了合理建议。     

Effects of Population Density and Feeding Rate on Growth and Feed Consumption of Red Swamp Crawfish Procambarns clarkii

Wire-mesh enclosures were used in production ponds to conduct growth trials in which population density and feeding rate were evaluated in a 2 × 2 factorial arrangement for their effects on crawfish growth. Juvenile Procambarus clarkii of uniform size (0.5 g) were stocked at 2 or 20 animals/m² in experiment 1 and weighed biweekly for 12 wk. Rice forage served as the detrital base, and supplemental feed (25% crude protein) was provided at either a low (26–52 kg/ha per week) or high (104–418 kg/ha per week) rate. In experiment 2, mixed sizes of crawfish were stocked at 10/m² or 20/m² and fed the formulated feed at either 52 or 312 kg/ha per week. Feed consumption was estimated for each treatment combination. Only population density significantly affected crawfish growth. Mean weight gain and final weights were inversely proportional to density but only when total crawfish biomass exceeded 1,235 kg/ha. Growth was not significantly influenced by feeding rate, but the high feeding rate resulted in a significantly greater ratio of hepatopancreas weight to body weight and tended to decrease hepatopancreas moisture levels, indicating improved condition. Population density, feeding rate, and their interaction had significant effects on estimated feed consumption. From the simple linear regression of mean feed consumption on crawfish standing crop, it was estimated that crawfish consume about 0.1 kg of dry feed per ha per week per kg of crawfish biomass on a 5 d per week feeding schedule at mean water temperatures, ranging from 14 to 30 C.     

亲缘关系对克氏原螯虾仔虾种内斗争的影响

将源于1、2、3、4尾雌虾的克氏原螯虾仔虾以4种方式混养,每个混养群体共有仔虾24尾,设3个重复。结果表明:亲缘关系对幼年螯虾种内斗争影响显著。随着仔虾来源的增多即亲缘关系复杂性的提高,螯虾的存活率总体呈下降趋势,而残虾率、体长变异系数、体长增长率总体上显著上升。     

克氏原螯虾领域占有现象的研究及其在养殖中的应用

在室内小型水体、户外中型水体及池塘大型水体3种环境下同步和异步养殖克氏原螯虾,对比了存活率、残肢率和质量变异系数等指标。小型、中型水体同步组的残肢率均显著低于异步组(P值分别为0.007、0.016);中型水体同步组的存活率显著高于异步组,P=0.006;中、大型水体同步组螯虾质量变异系数均小于异步组(P值分别为0.015、0.002)。结果显示,克氏原螯虾存在先期领域所有权现象,即"有产者原则"。人工养殖中异步放养虾苗违背该原则,易增加螯虾群体自相残杀而导致存活率下降;同步放养则符合"有产者原则",有利于降低螯虾种内格斗。试验结果为解决高密度水产养殖中克氏原螯虾自相残杀而导致的减产提供科学依据。