Digestive enzyme response to supplemental ingredients in practical diets for juvenile freshwater crayfish Cherax quadricarinatus

A feeding trial was conducted to determine digestive enzyme activity in Cherax quadricarinatus in response to diet composition. Eight experimental diets, each containing one of squid, red crab, sardine (600 and 650 g kg^?1 crude protein), sorghum, wheat meal, soy paste and the reference diet were evaluated over 30 days in terms of amylase, lipase, and protease activities in the hepatopancreas. The diet containing wheat meal produced the highest amylase activity. Lipase activity was not significantly different among treatments. Protease activity was higher in animals fed fish meal (60 g kg^?1 protein), soy paste and reference diet. Results suggest that C. quadricarinatus can modify hepatopancreatic enzyme levels in response to different compounds in the diet and can digest a broad variety of ingredients, particularly starch.     

Effect of dietary protein and lipid levels on gonadal development of female redclaw crayfish Cherax quadricarinatus

The effect of two crude dietary protein (26% and 32% P) and two lipid levels (4.7% and 12% L) on gonadal development of female redclaw crayfish Cherax quadricarinatus was determined. The gonadosomatic index (GSI), hepatosomatic index (HSI), biochemical composition of gonad and hepatopancreas, oocyte diameter and frequency of the developmental stage of oocytes were analysed. The GSI was significantly less using 26% P to 4.7% L. A significant interaction between P and L content was found for GSI. A significantly higher HSI value was obtained when L was 12%. P content in the hepatopancreas was significantly higher using 32% P and 4.7% L. The maximum L content in the hepatopancreas was obtained from the 32% P and 12% L diet. A significant interaction between P and L content was found for L content in the hepatopancreas. A higher frequency of post‐vitellogenic oocytes was obtained with diets containing 32% P. There was an interaction between dietary P and L level causing lipid accumulation in the hepatopancreas and changes in GSI. For an optimum 32% P, excess dietary lipid is bioaccumulated in the hepatopancreas, indicating that there is excess available energy. When the P and L levels are restricted, there is a limited gonad development, thus affecting overall reproduction in female C. quadricarinatus.     

Evaluation of practical diets containing various terrestrial protein sources on survival and growth parameters of redclaw crayfish Cherax quadricarinatus

Redclaw aquaculture has developed at a rapid pace during the past few years, yet no specialized diet for the species has been developed. The present study was designed to evaluate whether soybean‐based diets containing either fishmeal (FM), poultry by‐product meal (PBM), ground peameal (GPM) or distillers dried grains with solubles (DDGS) meal as a protein source are suitable for redclaw aquaculture. Juvenile redclaw crayfish Cherax quadricarinatus (0.125±0.025 g) were stocked into 20 rectangular tanks at a stocking density of 12.5 m^?2 for 8 weeks. Crayfish in four replicate tanks were maintained on one of five diets formulated to contain 35% crude protein and 7.1% lipids. Each 100 g of diet contained 25 g of protein from soybean meal (SBM) and 10 g of protein from the alternative protein sources mentioned above. A fifth treatment that did not receive feed was included to account for growth from natural productivity. There were no significant differences in survival (86–90%), growth (3.84–4.98 g animal^?1) or feed conversion ratio (2.10–2.79) of crayfish among the four treatments (P>0.05). Survival and growth of crayfish in the treatment that received no supplementary feed were significantly less than those in treatments offered experimental diets. Results of the present experiment suggest that SBM‐based diets with PBM, FM, DDGS or GPM have similar effects on growth performance and survival of juvenile redclaw, C. quadricarinatus.     

红螯螯虾胚胎发育过程中的生化成分变化

采用生物化学方法对红螯螯虾胚胎发育过程中主要生化成分(糖类、蛋白质及氨基酸、脂类及脂肪酸)进行了测定和分析,以期了解胚胎形态发生与营养需求的关系。结果显示：红螯螯虾胚胎发育过程中糖类总体含量很低。总蛋白与总氨基酸(TAA)的含量在胚胎发育过程中均呈下降趋势。在必需氨基酸(EAA)中亮氨酸（Leu）和精氨酸（Arg）的含量较高,而在非必需氨基酸中谷氨酸（Glu）和天冬氨酸（Asp）的含量较高。总脂在胚胎发育过程中的含量总体呈下降趋势,其中性脂和磷脂的主要脂肪酸均为C16:0、C18:0 、C18:1ω9和C18:3ω3。研究认为：在红螯螯虾胚胎发育过程中,糖类主要参与多种特异复合物的合成以及甲壳构建,这些特异复合物在细胞分化中起着重要的信号传递作用。蛋白质和脂类都是红螯螯虾胚胎发育过程中主要的结构和能源物质,蛋白质主要在早期被利用而脂类主要在晚期起作用。饱和脂肪酸（SFA）和单不饱和脂肪酸（MUFA）(C16:0,C18:0,C16:1ω7 和 C18:1ω9)主要作为能源物质被消耗而高不饱和脂肪酸（PUFA）(20:5ω3和22:6ω3)在胚胎发育过程中对于构建细胞膜以及调节中枢神经系统的发育起重要作用。     

红螯螯虾胚胎发育过程中的生化成分变化

采用生物化学方法对红螯螯虾胚胎发育过程中主要生化成分(糖类、蛋白质及氨基酸、脂类及脂肪酸)进行了测定和分析,以期了解胚胎形态发生与营养需求的关系.结果显示:红螯螯虾胚胎发育过程中糖类总体含量很低.总蛋白与总氨基酸(TAA)的含量在胚胎发育过程中均呈下降趋势.在必需氨基酸(EAA)中亮氨酸(Leu)和精氨酸(Arg)的含量较高,而在非必需氨基酸中谷氨酸(Glu)和天冬氨酸(Asp)的含量较高.总脂在胚胎发育过程中的含量总体呈下降趋势,其中性脂和磷脂的主要脂肪酸均为C16:0、C18:0 、C18:1ω9和C18:3ω3.研究认为:在红螯螯虾胚胎发育过程中,糖类主要参与多种特异复合物的合成以及甲壳构建,这些特异复合物在细胞分化中起着重要的信号传递作用.蛋白质和脂类都是红螯螯虾胚胎发育过程中主要的结构和能源物质,蛋白质主要在早期被利用而脂类主要在晚期起作用.饱和脂肪酸(SFA)和单不饱和脂肪酸(MUFA)(C16:0,C18:0,C16:1ω7 和 C18:1ω9)主要作为能源物质被消耗而高不饱和脂肪酸(PUFA)(20:5ω3和22:6ω3)在胚胎发育过程中对于构建细胞膜以及调节中枢神经系统的发育起重要作用.     

Effect of dietary protein‐to‐energy ratio on reproduction in female redclaw crayfish Cherax quadricarinatus

The effect of eight diets with different protein‐to‐energy ratios (P–E ratio=10, 11, 14, 16, 18, 20, 22, 24 mg kJ^?1) on reproduction of female redclaw crayfish Cherax quadricarinatus was tested under laboratory conditions. After 75 days, there was a significant effect of the P–E ratio on final weight, spawning females and the number of juveniles per female. Using the broken‐line and quadratic equations, optimal values for the P–E ratio were: 16.0, 17.1 and 16.0 mg kJ^?1. The P–E ratio significantly affected protein and carbohydrate content and energy in the hepatopancreas. The broken‐line model indicated that the respective recommended values of the P–E ratio for these parameters were: 21.8, 16.7 and 18.6 mg kJ^?1. The concentration of carbohydrates and energy in muscle tended to significantly diminish as the P–E ratio increased. From broken‐line regression analysis, the recommended P–E ratio was 16.6 and 20.2 mg kJ^?1 respectively. No significant differences were found in survival, fecundity, vitellin content in eggs, protein and lipid content in muscle and lipids in the hepatopancreas. We concluded that, overall, a P–E ratio of 18±2 mg kJ^?1 is optimal for reproductive activity of female redclaw crayfish.     

Effect of different dietary protein and lipid levels on growth and survival of juvenile Australian redclaw crayfish, Cherax quadricarinatus (von Martens)

This study determined the effect of different dietary protein and lipid levels on growth and survival of juvenile redclaw Cherax quadricarinatus. Nine practical test diets were formulated to contain three crude protein (CP) levels [260, 310 and 360 g kg^?1, equivalent to 225, 260 and 296 g kg^?1 digestible protein (DP) respectively] at three crude lipid (CL) levels (40, 80 and 120 g kg^?1, equivalent to 38, 67 and 103 digestible lipids respectively), with digestible protein : digestible energy (DP : DE) ranging from 14.6 to 22.6 mg protein kJ g^?1. Three replicate groups of 15 crayfish (initial weight mean ± SD, 0.71 ± 0.13 g) per diet treatment were stocked in 40 L tanks, at 28 °C for 60 days. The highest mean weight, specific growth rate and biomass, with values of 7.0 g, 3.67% day^?1, and 370.2 g m^?2, respectively, were achieved by feeding a diet with P : L = 310 : 80 (P < 0.05). The treatments resulted in a survival rate of 80–91%, feed conversion ratio of 1.08–1.61 and protein efficiency ratio of 2.24–3.08. Results indicated that a diet containing 270 g kg^?1 DP (equivalent to 320 g kg^?1 CP), 75 g kg^?1 digestible lipid (DL) with a DP/DE of 18.4 mg protein kJ^?1, and 0.031 g protein per animal per day was optimum for juvenile C. quadricarinatus under the tested experimental conditions.     

Effects of feeding practical diets containing various protein levels on growth, survival, body composition, and processing traits of Australian red claw crayfish (Cherax quadricarinatus) and on pond water quality

A 117‐day feeding trial was conducted in ponds with juvenile Australian red claw crayfish (Cherax quadricarinatus) to evaluate the effects on growth, survival, body composition, and processing traits when fed diets containing three different protein levels (22%, 32%, and 42%), and the effects of feeding these diets on pond water quality. Juvenile crayfish (mean weight of 4.6±2.2 g) were randomly stocked into nine 0.02‐ha ponds at a rate of 500 per pond (25 000 ha^?1), and each diet was fed to three ponds. There were two feedings per day, each consisting of one‐half of the total daily ration. At harvest, there were no significant differences (P>0.05) in the individual weight, percentage weight gain, or specific growth rate among treatments, which averaged 75.3 g, 1535%, and 2.38% day^?1 respectively. Red claw fed the 42% crude protein diet had significantly higher (P<0.05) feed conversion ratio (7.34) compared with crayfish fed diets containing 22% (5.18) or 32% (5.13) crude protein, and had significantly lower percentage survival (46.1%) compared with red claw fed diets with 22% (61.1%) or 32% (58.2%) protein. Total yield was significantly lower (P<0.05) in red claw fed the 42% protein diet (640 kg ha^?1) compared with red claw fed diets containing 22% (920 kg ha^?1) or 32% (904 kg ha^?1) protein. Mean total ammonia nitrogen (TAN) levels were significantly higher (P<0.05) in ponds with red claw fed the 42% protein diet (0.55 mg L^?1) compared with ponds with red claw fed diets containing 22% (0.32 mg L^?1) or 32% (0.38 mg L^?1) protein. Mean total nitrite concentrations in ponds with red claw fed the 42% protein diet was significantly higher (0.05 mg L^?1) compared with red claw fed diets containing 22% (0.01 mg L^?1) or 32% (0.02 mg L^?1) protein. These results indicate that a practical diet containing 22% (as fed basis) protein may be adequate for pond production of red claw when stocked at the density used in this study, and that a diet containing 42% protein adversely affected levels of TAN and nitrite, possibly reducing overall survival of red claw. Use of a diet with 22% protein may allow red claw producers to reduce diet costs and thereby increase profits.     

Effects of dietary soybean lecithin on gonadal development and vitellogenin mRNA expression in the female redclaw crayfish Cherax quadricarinatus (von Martens) at first maturation

The effect of increasing levels of dietary de‐oiled soybean lecithin (SL) on the ovarian development of female redclaw crayfish, Cherax quadricarinatus, was investigated. Five practical formulated diets were supplemented with 0% (Diet 1), 1% (Diet 2), 2% (Diet 3), 4% (Diet 4) and 6% (Diet 5) SL. Crayfish (initial weight: 25.64 ± 1.53 g) were fed each diet in four replicates for 8 weeks. Crayfish that were fed diets containing ≥2% SL had a significantly higher gonadosomatic index than those fed with Diets 1 and 2 (P < 0.05), while hepatosomatic index showed a decreasing trend (P > 0.05). The fatty acid composition of the hepatopancreas is largely due to the dietary composition. Higher dietary SL yielded a higher percentage of ovarian polyunsaturated and highly unsaturated fatty acids (P < 0.05). Furthermore, the higher content of linoleic acid and alpha linolenic acid in diets may be more important for ovarian development in C. quadricarinatus, as these originate from the hepatopancreas. The hepatopancreatic vitellogenin mRNA expression was the highest in crayfish that received Diet 3. Our results suggest that dietary SL has a positive effect on ovarian development in C. quadricarinatus broodstock, and at least 2% SL should be supplemented in broodstock diets to enhance ovarian maturation during aquaculture.     

Growth of redclaw crayfish Cherax quadricarinatus (Von Martens 1868) (Decapoda: Parastacidae) juveniles fed isoproteic diets with partial or total substitution of fish meal by soya bean meal: preliminary study

Growth of juvenile redclaw Cherax quadricarinatus fed 400 g kg^?1 crude protein isoproteic diets substituting fish meal with soya bean meal at various levels (250, 500, 750 and 1000 g kg^?1) was evaluated under laboratory conditions. Juvenile crayfish were reared individually in 1‐L plastic containers for 56 days. Total survival was recorded for all treatments at the end of the experiment. There were no significant differences (P > 0.05) for the specific growth rate among the treatments, although the animals fed with the control diet (100% fish meal) obtained the highest mean daily weight gain (0.055 g day^?1), individual final weight (4.12 g), molts per individual (0.04 molts day^?1) and molting frequency (23.57 days) values at the end of the experiment. Dietary inclusion of soya bean meal at the tested levels hampered the C. quadricarinatus juvenile growth.     

Carbohydrate and lipid digestibility of animal and vegetal ingredients and diets for juvenile Australian redclaw crayfish, Cherax quadricarinatus

Carbohydrate and lipid digestibility of three vegetal and four animal ingredients, and diets in which they were included, were evaluated for juvenile Australian redclaw crayfish, Cherax quadricarinatus. The ingredients were: soy paste, textured wheat, sorghum meal, sardine meals (67% and 58% crude protein), squid meal and red crab meal. A basal diet was formulated, and then seven experimental diets were created, including 150 g kg^?1 of each ingredient in the reference diet. Digestibility was measured in vivo, using chromic oxide as marker. A single‐factor, completely randomized experimental design with three replicates per treatment was performed. Mean carbohydrate digestibility of vegetal ingredients and the corresponding diets was better than carbohydrate digestibility of animal ingredients. Sorghum meal had a carbohydrate digestibility over 94%, and the diet in which it was included over 92%. Soy paste and wheat meals also presented excellent carbohydrate digestibility (around 88% for ingredients and over 90% for diets). Mean carbohydrate digestibility of animal ingredients and their corresponding diets were very poor (from 18% to 32%) and this affected the carbohydrate digestibility of diets in which they were included (87–89%). Lipid digestibility was also better for vegetal ingredients. Soy paste and wheat meal recorded values over 93% and their diets over 94%. Sorghum lipid presented slightly lower digestibility. Some of the animal ingredients, especially red crab, had an excellent lipid digestibility (92.1%).     

Carbohydrate and lipid digestibility of animal and vegetal ingredients and diets for the pre-adult redclaw crayfish, Cherax quadricarinatus (von Martens)

In vivo carbohydrate and lipid digestibility of four animal [sardine meals 67% and 58% crude protein (CP), squid meal and red crab meal] and three vegetal (soy paste, textured wheat and sorghum meal) ingredients and diets were evaluated in experimental diets for pre-adult redclaw crayfish, Cherax quadricarinatus . A reference and seven experimental diets were formulated, including 14.5% of each ingredient in the reference diet. A single factor, completely randomized experimental design with five replicates per treatment was done. Experimental organisms were pre-adult redclaw of 10±0.8 g. The best carbohydrate digestibilities were recorded for some vegetal ingredients such as sorghum and textured wheat (93.6% and 83.9%) and the corresponding diets (90.9% and 90.8%). For animal ingredients, carbohydrate digestibilities were very poor (from 12.3% to 41.1%), and the inclusion of these ingredients diminished the digestibility of the corresponding experimental diets as compared with the reference diet (86.3–89.2% vs. 89.9%). The highest lipid digestibility corresponded to red crab meal (97.5%). Textured wheat and soy paste meal also had excellent lipid digestibility (96.4% and 95.1%). The same tendency was found for the corresponding diets. The lowest percentages were obtained with 58% crude protein sardine meal (32.9%) and its diet (86.2%).     

Histopathological survey of diseases and pathogens present in redclaw crayfish, Cherax quadricarinatus (Von Martens), cultured in Ecuador

A histopathological survey of commercial farms in Ecuador culturing redclaw crayfish, Cherax quadricarinatus (Von Martens), revealed the presence of different viral, bacterial and non‐infectious pathologies. A total of 536 animals from 27 different farms were analysed during a 3‐year period; 25, 154 and 357 specimens in 1995, 1996 and 1997, respectively. From the total sampled, a virus referred to as Cherax quadricarinatus bacilliform virus (CqBV) had a prevalence of 44% in animals examined during 1996 and 33% in 1997. A rickettsia‐like organism (RLO) was detected in five specimens sampled from three different farms in 1995. This RLO was detected in 36 and 12% of samples analysed in 1996 and 1997, respectively, and was the infectious agent most frequently associated with mortalities above 60%. Co‐infection by CqBV and the RLO was observed in 18 and 3% of the crayfish examined in 1997 and 1998, respectively. Five specimens out of 25 examined presented no sign of an infectious agent during 1995. The proportion of specimens testing negative by histopathology to known or suspected infectious agents was 25 and 32% in 1996 and 1997, respectively. Although different infectious agents were present in cultured crayfish, farms in general had overall survivals higher than 50% in most ponds. Other conditions observed included an intracellular prokaryotic organism, iron granules in the R and F cells of the hepatopancreas, different species of epibionts on the surface of the gills and body, and two cases of haemocytic enteritis. Two cases of serious mortality in different farms were associated with the presence of Cowdry type A inclusions, pyknosis, karyorrhexis and haemocytic infiltration in the stomach hypodermis and the antennal gland.     

不同光周期下红螯螯虾幼虾摄食节律的研究

在不同光周期下对红螯螯虾(Cherax quadricarinatus)幼虾的摄食节律进行了研究。结果显示:红螯螯虾具有明显的日摄食节律,24 L(持续光照)、12 L∶12 D(12 h光照:12 h黑暗)和24 D(持续黑暗)光周期下,其摄食率、摄食量和摄食发生率均在19∶00-21∶00和5∶00-7∶00出现峰值,分别为:13.01%和15.58%、20.82%和14.75%、12.77%和16.89%,属晨昏型摄食。光周期和不同时段对红鳌幼虾摄食无显著的交互作用(P>0.05)。     

饲料中大豆磷脂对红螯光壳螯虾性腺发育期营养物质积累的影响

基础饲料中添加5种不同水平的大豆磷脂(SL):0%(Diet 1),1%(Diet 2),2%(Diet 3),4%(Diet 4)和6%(Diet 5)。饲喂初始体质量为(25.64±1.53)g的红螯光壳螯虾(Cherax quadricarinatus)雌虾8周,观察其卵巢发育期个体生长、性腺指数等参数的变化,分析卵巢和肝胰腺营养物质积累的快慢以及与营养物质积累相关基因脂肪酸结合蛋白(FABP)mRNA表达的差异。结果表明:饲料中不同水平的SL对卵巢发育期红螯光壳螯虾的成活率和相对增重率(WG)影响不显著(P>0.05),但饲喂≥2%(SL)饲料的雌虾性腺指数(GSI)显著升高(P<0.05),雌虾的肝胰腺指数(HSI)则随饲料中SL的增加而呈下降趋势(P>0.05);随着饲料中SL的增加,虾肝胰腺中脂滴的体积增大,数量增多,结构更加完整,质地更加均匀,卵巢中脂滴和卵黄颗粒的数量增多,体积增大;同时,饲料中SL的增加促进了FABP在肝胰腺和卵巢中的表达量。综上所述,饲料中的SL对红螯光壳螯虾雌虾卵巢发育具有促进作用,在培育红螯光壳螯虾雌虾亲体过程中,含6.5%鱼油的基础饲料至少补充2%的SL有利于雌虾卵巢的快速发育。本研究旨在为深入研究虾蟹生殖生理学和规模化红螯光壳螯虾早繁苗种生产等提供基础资料。     

Effect of dietary protein level on growth and survival of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda: Parastacidae)

Protein requirements of juvenile freshwater crayfish Cherax quadricarinatus, with initial mean weight of 1.08 ± 0.34 g, were studied. Juveniles were fed experimental diets containing seven levels of crude protein (CP) (20, 25, 31, 37, 43, 49, and 55%) and 18.73–21.45 kJ  g^?1 of gross energy. The highest mean weight and specific growth rate (SGR) (P < 0.05), with values of 9.6 g, and 3.64% day^?1, respectively, were achieved by feeding a diet of 31% CP. This diet resulted in a survival rate of 80% over 60 days of culture at 27 °C. The higher protein level tested (55% CP), yielded a significantly (P < 0.05) lower mean weight of 6.4 g. However, there were no significant differences in SGR among the 20, 25, and 49% CP diets. Feed Conversion Ratio (FCR) was close to 1 for all treatments except the lowest (20%) and highest (55%) CP. Optimum protein requirements were estimated by fitting mean weight gain data to a quadratic model (y = 1.142+0.484 ? 0.0071x², r² = 0.952, P < 0.05). Optimal growth occurred with 34.2% CP, but the results suggest that optimum protein level for 1‐g juvenile C. quadricarinatus is 31% in least‐cost diets. The information obtained will contribute to the formulation of diets that will enhance production of C. quadricarinatus.     

Lecithin requirements of juvenile Australian red claw crayfish Cherax quadricarinatus

Australian red claw crayfish Cherax quadricarinatus is considered a popular crustacean species in several countries around the world because of its large size potential and resemblance to high‐priced American lobsters. However, little is currently known of the nutrient requirements and practical diet formulations for red claw. Lecithin has been shown to be required in the diets of several crustacean species, but there are no reports of dietary lecithin requirements for red claw. A 10‐week feeding trial was conducted in an effort to evaluate lecithin requirements for juvenile red claw. Juvenile red claw (mean individual weight of 1.6 ± 0.91 g) were individually stocked in a recirculating system at random into 80 plastic‐mesh culture units, each containing its own individual water line. There were 20 red claw per treatment (diet). Water was recirculated through biological and mechanical filters. Four semi‐purified diets were formulated to contain increasing percentages of commercial soya bean lecithin (0, 0.5, 1.0 and 2.0%). Diet ingredients included solvent‐extracted menhaden fish meal (FM), casein, dextrin, wheat flour, pellet binder, vitamin and mineral mix, cod liver oil, and corn oil. Semi‐purified diets were formulated to contain 40% protein using casein, menhaden FM, and wheat flour as protein sources. After 10 weeks, no significant differences (P > 0.05) were found in final weight, percentage weight gain and specific growth rate with average values of 13.0 g, 934%, and 3.14% day^?1, respectively. Percentage survival was high during the 10‐week period (100, 95, 100 and 95%) as only two individuals died during the study; one of these, because of an escape from the culture unit. There was also no significant differences (P > 0.05) in percentage moisture, protein, fat and ash in whole‐body red claw carcasses (wet‐weight basis) among any treatment (diet) and averaged 77.1, 12.6, 1.3 and 6.2%, respectively. Based upon the present study, these results indicate that a diet containing 5% cod liver oil and 1% corn oil, and having no supplemental lecithin, may be sufficient for growth and survival of juvenile red claw crayfish.     

Estimating production costs of preadult redclaw crayfish,Cherax quadricarinatus,reared in a commercial nursery system: A stochastic bioeconomic approach

A stochastic bioeconomic model was used to estimate the production cost and risk factors affecting economic performance of juvenile redclaw crayfish, Cherax quadricarinatus, commercial nursery production, in a farm located in Baja California Sur, Mexico. At harvest, the biological submodel showed there is 95% confidence to obtain an average weight of 19.98 g, with 126,341/ha surviving organisms, representing 84% survival. Biomass was 2.5 t/ha, with a feed conversion ratio (FCR) of 0.98, reflecting the efficient adaptation of the species to culture conditions. The economic submodel showed that at Day 90, there is 95% confidence that the cost of producing a preadult will be US$0.090 or US$4.55/kg. With increasing demand and worldwide sale prices of US$9/kg, there is a potential market for 20–30 g redclaw reared in intensive lined ponds. Sensitivity analyses showed that the regression coefficients from a second‐order polynomial used for calculation of FCR associated with time (a₂ and a₁) were the most important parameters influencing the production cost. Mortality rate and parameters used to calculate individual weight also had considerable influence on production cost. The bioeconomic analysis contributes significantly to establishing the economic viability of the intensive three‐phase production system.     

Clove oil as an anaesthetic for Australian redclaw crayfish Cherax quadricarinatus

Crustaceans are aquacultured both for food and as ornamental organisms. Pain and distress are not entirely understood in crustaceans, but the industry is moving towards requiring protection for the welfare of these animals during handling. In the present study, we evaluated the efficacy of clove oil as an anaesthetic for redclaw crayfish (Cherax quadricarinatus) as a model for freshwater crustaceans. We also studied how factors such as body weight and sex of redclaw could affect this efficacy. The whole experiment was replicated in two consecutive years. Redclaw juveniles were sorted into three size classes: small (<5 g), medium (5–12 g) and large (12–37 g). At least 10 males and 10 females from each size class were placed individually in water containing clove oil concentrations of 375 and 500 μl/L. Both concentrations induced rapid induction and recovery times, with 500 μl/L being the more effective concentration of the two. Induction and recovery times increased with the increase in crayfish size. No significant differences were found in induction and recovery times between male and female crayfish. Results suggest that clove oil is an effective anaesthetic for redclaw.     

Effects of feeding practical diets containing different protein levels, with or without fish meal, on growth, survival, body composition and processing traits of male and female Australian red claw crayfish (Cherax quadricarinatus) grown in ponds

Four practical diets containing 2% of crude protein (CP) (180 and 280 g kg^?1), with or without menhaden fish meal (FM), were fed to Australian red claw Cherax quadricarinatus during a 97‐day feeding trial. Growth, survival, body composition and processing traits of pond‐cultured red claw were determined. Juvenile red claw (mean individual weight of 5.75 ± 3.3 g) were randomly stocked into twelve 0.04‐ha ponds at a rate of 1000 per pond (25 000 ha^?1), and each diet was fed to three ponds. At harvest, the final mean weight of red claw fed Diet 4 (0 g kg^?1 FM and 280 g kg^?1 CP) and Diet 3 (113 g kg^?1 FM and 280 g kg^?1 CP) was significantly (P < 0.05) higher (62.4 and 58.5 g, respectively) than red claw fed Diet 1 (73 g kg^?1 FM and 180 g kg^?1 CP; 51.7 g) and Diet 2 (0 g kg^?1 FM and 180 g kg^?1 CP; 53.0 g). Red claw fed diets containing 280 g kg^?1 CP, with or without FM, had significantly higher percent weight gain (894 and 959%, respectively) compared to red claw fed 180 g kg^?1 CP, with or without FM (778 and 799%, respectively). Feed conversion ratio, percent survival, and total yield among treatments, which averaged 3.55, 65.2%, and 724 kg ha^?1 overall, were not significantly different. Results from this study indicate that pond‐cultured red claw stocked at 25 000 ha^?1 can be fed a practical diet containing 280 g kg^?1 CP with 0 g kg^?1 FM if a combination of plant‐protein ingredients (soybean meal, distillers’ dried grains with solubles, and milo) is added; however, if the percentage of dietary protein level is 180 g kg^?1, growth is reduced even if FM is added at 73 g kg^?1 of the diet. Use of diets containing plant‐protein sources may help reduce diet costs to producers and thereby, increase profits.