Induced spawning, larval development and rearing of two indigenous Malaysian mahseer, Tor tambroides and T. douronensis

The Mahseers (Tor spp.) are highly valued freshwater fishes across the Himalayan and South‐east Asian regions. Over exploitation of natural stocks because of high demand and the deteriorating environmental conditions have resulted in marked decline of mahseers in the wild. Malaysian mahseers, T. tambroides (Bleeker) and T. douronensis (Valenciennes), locally known as empurau, kelah or belian and semah, respectively, have significant cultural and economic importance but both species are now threatened in the wild because of environmental degradation and over fishing. A captive breeding programme was instigated to attempt to propagate these two species artificially for conservation and aquaculture purposes. Both pond‐reared and tank‐held T. tambroides and T. douronensis reached sexual maturity in captivity and were successfully induced to spawn using hormone treatments. Ovaprim (0.5 mL kg^?1) was the most successful hormone treatment for both species. Pre‐treatment of fish with Ovaplant (28–68 μg kg^?1, 2–7 weeks before spawning induction) greatly improved the success rate of spawning induction. Repeat spawning (within 4 months of initial spawning) was induced in some captive fish. Use of formalin baths improved hatching by preventing fungal infections. Embryonic development and hatching are described. Juveniles were reared in static greenwater ponds. Tor tambroides reached 142–179 g (max 270 g) in 60 weeks. These results represent the first successful captive spawning and rearing of both species. Options for future research to improve production are discussed.     

长江水系野生和养殖中华绒螯蟹生殖性能、胚胎色泽和生化组成的比较

生殖性能是评价水生动物亲本质量的重要指标,本研究测定和比较了野生和养殖中华绒螯蟹亲本的生殖性能、胚胎质量、胚胎色泽、常规生化和脂肪酸组成。结果显示:①野生中华绒螯蟹亲本的生殖力、生殖指数和抱卵量略高于养殖亲本的,但2组间无显著性差异,野生和养殖中华绒螯蟹亲本的胚胎单卵湿重、单卵干重和卵径无显著性差异;②养殖组冻干胚胎的红度(a~*)、黄度(b~*)值和总类胡萝卜素含量显著高于野生组亲本,然而2组胚胎的亮度(L~*)和色差值(dE~*)无显著性差异;③2组亲本所产胚胎的水分、粗蛋白和粗脂肪含量均无显著性差异,但其脂肪酸组成差异显著,野生组胚胎的C18:1n9、C18:1n7、C20:4n6、C22:5n3和C22:6n3显著高于养殖组,但其C18:2n6和C18:3n3含量显著低于养殖组。研究表明,池塘养殖和野生亲本的生殖性能和胚胎中常规生化组成无显著差异,但2组胚胎的色泽、总类胡萝卜素含量和部分脂肪酸组成存在显著差异,该研究为中华绒螯蟹亲本选择、生殖性能评价和人工育苗提供了重要基础资料。     

饲料脂肪水平对克氏原螯虾亲虾生长性能、肌肉成分、繁殖性能以及血淋巴生化指标的影响

为研究克氏原螯虾亲虾对脂肪的需要量,本实验采用初始体质量为(15.46±0.20)g的克氏原螯虾亲虾324尾,分为6组(每组设置3个重复,每个重复18尾,雌雄比例为2:1),投喂粗蛋白质水平为30%,脂肪水平分别为1.98%(对照组)、4.12%、5.84%、7.89%、10.48%和11.89%的6组半精制饲料,饲养8周后,测定并分析亲虾的生长性能、肌肉成分、繁殖性能、肝胰腺消化酶活性以及血淋巴部分生化指标。结果发现:①随着饲料脂肪水平的升高,增重率和特定生长率先上升,在饲料脂肪水平达到7.89%后呈下降趋势;饲料系数和肝体比呈上升趋势,11.89%组最高。②饲料脂肪水平对亲虾肌肉水分和灰分含量无显著影响;随着饲料脂肪水平的升高,肌肉粗脂肪含量呈现先升高后降低最后趋于稳定的趋势,在饲料脂肪水平为5.84%时最高。③随着饲料脂肪水平的升高,性腺指数、抱卵率、抱卵量均呈现先上升后降低的变化规律,均在饲料脂肪水平为7.89%时达到最大。④血淋巴中总蛋白含量随饲料脂肪水平呈现先下降后上升趋势;谷草转氨酶、谷丙转氨酶活性均随饲料脂肪水平升高而升高,均在11.89%组最高;血淋巴中葡萄糖含量各组间无显著性差异。⑤饲料脂肪水平对实验虾肝胰腺蛋白酶和脂肪酶活性有显著影响,对淀粉酶活性无显著性影响。利用增重率与饲料脂肪水平进行折线回归分析,克氏原螯虾亲虾获得最佳增重率时对饲料的脂肪需要量为7.60%。对实验虾生长性能、肌肉成分、繁殖性能、肝胰腺消化酶活性、血淋巴生化指标进行综合分析,显示本实验条件下克氏原螯虾亲虾对脂肪需要量为7.60%～7.89%。     

Effects of different diets and seawater systems on egg production and quality of the broodstock Babylonia areolata L. under hatchery conditions

The broodstock of spotted Babylon snail, Babylonia areolata, were conditioned in indoor tanks under two seawater systems (static system and flow‐through system) and five types of foods (fish, shrimp, squid, green mussel and formulated diet). High survival and good feeding was found from broodstock conditioned in all treatments of seawater systems and diets. All broodstock showed active behaviour with no signs of stress as exhibited by active movement and feeding, protrusion of siphonal tube and constant egg laying throughout the experiment. Two‐way analysis of variance showed that there were no significant differences (P>0.05) in the total yield of egg capsules, size of egg capsules, size of newly hatched larvae and growth of larvae among broodstock B. areolata conditioned in the seawater system and diet treatments, but there were significant differences (P>0.05) in the frequency of egg capsule laying, number of fertilized eggs/embryos per capsule, total yield of fertilized eggs/embryos and final survival of larvae among broodstock B. areolata conditioned in the diet treatments. We present initial evidence that the seawater system had a stronger influence on the egg production and quality of broodstock B. areolata than conditioning diets.     

Biochemical composition of pond-reared and lake-stocked Chinese mitten crab Eriocheir sinensis (H. Milne-Edwards) broodstock

The morphological characteristics, tissue indices, proximate and fatty acid compositions of hepatopancreas, gonad and muscle of pond‐reared (PR) and lake‐stocked (LS) Eriocheir sinensis broodstock were compared. Lake‐stocked crabs are characterized by a blue carapace, white abdomen, golden legs and yellow setae while PR crabs have a brown carapace, grey abdomen, black legs and similar yellow setae. The carapace length and width of PR crabs were significantly less than those of LS crabs of the same wet weight (WW). The results showed that the hepatosomatic index (HSI) of PR males was significantly higher, but the gonadosomatic index (GSI) was significantly lower for PR females when compared with LS individuals of the same sex. Regardless of their origin, the muscular index (MI) of males was higher than that of females. The hepatopancreas of LS crabs had higher protein levels and lower lipid levels compared with PR crabs. The results of proximate analysis of male gonads from two different sources were similar, while the protein level in the ovary of LS females was higher than that of PR females. The tissues of males had higher water content but lower lipid and protein levels compared with females regardless of their source. The LS crabs had higher highly unsaturated fatty acid (HUFA) levels than PR crabs in their gonad and hepatopancreas. In conclusion, our results suggest that the nutritional quality of LS crabs is better than that of PR crabs, the nutritional quality of males is poorer than that of females. The reproductive performance and larval quality of crabs from these two rearing systems should be further verified.     

维生素C、E对中华绒螯蟹生殖性能的影响

通过对河蟹雌性亲体投喂不添加或添加VC、VE的4组实验饲料,并以新鲜河蚌为对照,进行198d饲养试验,以雌蟹性腺系数、产卵力、孵化率以及各组织中SOD活性、MDA含量等指标作为判据,研究了VC、VE对雌蟹生殖性能的影响。结果表明,1(投喂添加0.5mg·(100g)-1VC饲料组)、2(投喂添加0.022mg·(100g)-1VE饲料组)和3(投喂添加0.5mg·(100g)-1VC饲料和0.022mg·(100g)-1VE饲料组)3个组雌蟹的产卵力分别为3620个卵细胞·g-1体重、3540个卵细胞·g-1体重、3710个卵细胞·g-1体重,孵化率分别是83.03%、84.06%、86.27%,均极显著高于4组(投喂未添加维生素饲料组)雌蟹的产卵力(2490个卵细胞·g-1体重)和孵化率(29.28%)(P<0.01),也显著高于5组(饲喂河蚌)雌蟹的产卵力(3010个卵细胞·g-1体重)和孵化率(71.12%)(P<0.05)。雌蟹卵巢中SOD活性,1、2和3组则比4组和5组显著低(P<0.05),分别为56.35Nu·mL-1、53.61Nu·mL-1和39.87Nu·mL-1,相应地,MDA含量分别为6.03nmol·mL-1、5.65nmol·mL-1和5.57nmol·mL-1;4组雌蟹,虽然其卵巢中SOD活性较高,达79.25Nu·mL-1,但因饲料中缺乏抗氧化性的VC、VE,引发卵子脂质过氧化,MDA含量显著增加(P<0.05),为23.18nmol·mL-1,导致卵质低下,从而影响了卵子孵化。综上所述,雌蟹饲料中添加适量的VC     

亲本强化培育对中华绒螯蟹雌体生殖性能和Z1幼体质量的影响

系统比较了亲本强化培育和常规培育对池塘养殖中华绒螯蟹的生殖性能和Z_1幼体质量的影响,同时分析2组Z_1幼体的脂肪酸组成。结果表明,①两种培育方式对亲本的成活率和产卵率均无显著影响,强化组亲本的GSI、HSI、产卵量和生殖力显著高于常规组;②两种培育方式对卵的卵径、水分含量、单卵干重和湿重影响不显著,但强化组的受精率和孵化率略高于常规组;③强化组Z_1幼体的头胸甲长度、变态速度和抗逆境能力均高于常规组,这可能和幼体中高含量的HUFA有关;④生产性实验结果表明强化组的出苗率高于常规组,且幼体培育时间减少4～5 d。因此,亲本强化培育可以显著提高绒螯蟹中华的生殖性能和Z_1幼体质量。     

Reproductive performance and offspring quality of Chinese mitten crab Eriocheir sinensis (H. Milne-Edwards) females fed an optimized formulated diet and the razor clam Sinonovacula constricta

After feeding female Eriocheir sinensis on an optimized formulated diet or fresh razor clam Sinonovacula constricta for 7 months, their reproductive performance and offspring quality were compared. To evaluate diet nutrient contents, the proximate, fatty acid and amino acid compositions of the formulated diet and the razor clam were analysed. The nutritional value of the diets was determined by assessing survival, gonadosomatic index (GSI) and hepatosomatic index (HSI) of female crabs from both diet treatments, together with the percentage of females that spawned, total egg production per female and fecundity (number of eggs g^?1 female wet weight). Furthermore, the quality of eggs and newly hatched larvae from the two dietary treatments were determined using the following parameters: egg diameter, wet weight and dry weight, hatchability, proximate and fatty acid profile of eggs, larval carapace length, resistant to starvation and osmotic shock, larval survival and development to the zoea II stage. Higher protein, phospholipids (PL) and amino acids (AA) contents were found in the razor clam while the formulated diet contains higher levels of ash, total lipid (TL) and 18:1n‐9, 18:2n‐6 and 22:6n‐3 fatty acids. Although female crabs fed the two different diets showed similar reproductive performances, newly hatched zoea I larvae produced by the crabs fed the formulated diet had significantly longer mean carapace length and shorter development time to the zoea II stage under identical culture condition (P<0.05). Moreover, dietary fatty acid appeared to have more significant effects on the fatty acid composition of the hepatopancreas than it did on mature ovaries or eggs. This suggests that the fatty acid profile of mature ovaries is indicative of the specific fatty acid required for ovarian development in E. sinensis. In conclusion, our results show that the optimized formulated diet developed in this laboratory can totally replace the razor clam, a broodstock food widely used in E. sinensis hatcheries in China. This encouraging result should facilitate more reliable hatchery production of this important aquaculture species.     

Effects of varying dietary protein levels on growth, reproductive performance, body and egg composition of rohu, Labeo rohita (Hamilton)

A 360‐day feeding trial was conducted to observe the influence of varying levels of dietary protein on growth, reproductive performance, body and egg composition of rohu, Labeo rohita. Twenty fish (40.4 ± 0.24 cm; 852 ± 4.9 g), stocked in outdoor concrete tanks (200 m²), in duplicate, were fed diets with varying levels (200, 250, 300, 350 and 400 g kg^?1) of crude protein exchanged with carbohydrate to apparent satiation, twice daily, at 09:00 and 17:00 h. Higher (P < 0.05) weight increment was discernible in fish fed dietary protein ≥300 g kg^?1. Gonadosomatic index was comparable (P > 0.05) among fish of different dietary groups except those fed 200 g kg^?1 protein diet which produced least values. Egg diameter remained unaffected (P > 0.05) by variations in levels of dietary protein. Relative fecundity was maximum (P < 0.05) in fish fed 250 and 300 g kg^?1 protein diets. With the exception of fish fed 200 g kg^?1 protein diet, fertilizability (%) remained unaffected (P > 0.05) by variations in dietary protein level. Hatchability (%) followed the trend of variations almost similar to that of fertilizability. Proximate composition of muscle and eggs varied significantly (P < 0.05) with dietary protein levels. For broodstock L. rohita, a dietary protein level of 250 g kg^?1 was found optimum with regard to its reproductive performance, egg quality and composition.     

Marine yeast diet confers better protection than its cell wall component (1-3)-β-d-glucan as an immunostimulant in Fenneropenaeus indicus

A comparative study was performed to evaluate the immunostimulatory effect of yeast and yeast-derived glucan in white prawn Fenneropenaeus indicus (sub-adults of ∼20 gm). Feed with a whole cell biomass of marine yeast Candida sake S165 (CSY) at a concentration of 10% (w/w) and another feed with 0.2% glucan of C. sake S165 (CSG) were used in the study. Fenneropenaeus indicus were fed with these diets for 40 days and subsequently challenged with the white spot syndrome virus (WSSV). Haematological parameters such as the total haemocyte count, phenoloxidase activity, superoxide anion (O₂⁻) level, haemolymph peroxidase level and post-challenge survival against WSSV infection were determined to assess the immune status. In the present experiment, a higher immunity index and post-challenge survival were recorded in shrimps fed with the whole cell yeast diet. The better immunostimulatory performance of the whole cell yeast diet compared with the glucan diet could be attributed to the cellular constituents of yeast including the cell wall glucan, nucleotides, carotenoid pigments and vitamins. Here we observed that whole cell yeast performed better as an immunostimulant than the extracted cell wall glucans. Therefore, the use of yeast biomass in diets, rather than the yeast cell wall extract, glucan, would confer better protection against microbial infection besides reducing the cost of shrimp production.     

大蒜对印度明对虾黑鳃病原耐药菌株哈维氏弧菌抗菌活性的研究

本研究针对大蒜提取物对印度明对虾(Fenneropenaeus indicus)黑腮病病原多重耐药哈维氏弧菌(Vibrio harveyi)体外和体内的抗菌活性进行了评价。先利用市售的几种抗生素记录致病性哈维氏弧菌的抗菌谱。然后,利用琼脂扩散法来研究大蒜对哈维氏弧菌的抗菌活性。将哈维氏弧菌接种在琼脂平板上,对每种大蒜提取物(鲜榨大蒜提取物—FSGE,冻干大蒜提取物—FDGE以及用甲醇提取的大蒜提取物—MGE)设计三种不同的浓度。结果表明,鲜榨大蒜提取物对哈维氏弧菌的抑菌活性明显优于冻干大蒜提取物和用甲醇提取的大蒜提取物。本研究分别在对虾基础饲料中添加0%(对照)、0.5%和1%浓度梯度的大蒜来评价大蒜治疗感染哈维氏弧菌的对虾的效果。结果表明,综合大蒜提取物的短期和长期防治(1%含量)的效果分析,对虾累积死亡率降低了75%。本研究探讨了鲜榨大蒜提取物替代抗生素在印度明对虾饲养防病上的优点。     

Investigation of the temporal effects of spawning season and maternal and paternal differences on egg quality in Atlantic cod Gadus morhua L. broodstock

A better understanding of the parameters affecting egg quality and larval survival is of importance for continued development of cod broodstock and efficient husbandry practices. Decision tree analysis (DTA) was applied to analyse 3 years of egg quality data in an effort to extract the most important variables (i.e. predictors) in explaining differences in egg quality. The effect of three predictors (spawning time, maternal and paternal differences) has been studied on early cleavage pattern parameters, egg diameters, fertilization and hatching rates and has shown that females are the dominant variable and that time has a limited and inconsistent impact on the data. When using maternal, paternal differences and batch number (instead of spawning time) as predictors, the results confirm that no particular relationship is found between batch order (i.e. order in time) and egg quality. Moreover, batches with a higher egg quality show a consistency in the parameters assessed (i.e. batches with higher rates of normality in any parameter tend to be normal for other parameters). This is confirmed by the significant correlations found between cleavage parameters. Our results highlight that spawning time is of less importance than female parent contribution in ensuring high rates of fertilization and larval hatch, and maximizing general egg quality.     

Effects of dietary highly unsaturated fatty acids and astaxanthin on the fecundity and lipid content of pond-reared Penaeus monodon (Fabricius) broodstock

Five diets that contained fresh squid meat as the basic constituent and were supplemented with different amounts of highly unsaturated fatty acids (HUFA) and astaxanthin were fed to pond‐reared Penaeus monodon broodstock. Diet A was sole squid meat. Diets B and C were supplemented with astaxanthin 50 and 100 mg kg^?1 respectively. Diets D and E were supplemented with HUFA 5 and 10 g kg^?1 and astaxanthin 50 mg kg^?1 respectively. The result showed that the group fed diet E had the best reproductive performance in all experimental groups. It had a higher proportion of spawns (71.5%), spawning rate (0.047), a shorter latency period (7.7±0.3 d), higher absolute fecundity (× 10³) (361.6±5.5) and egg production/female (× 10³) (597.0±18.0) than all the other experimental groups. The fatty acid composition in broodstock diets strongly affected the tissue and fecundity of broodstock. Good correlations between the content of 20:4n‐6 in eggs and the fecundity (r²=0.6109) and egg production (r²=0.9876) of broodstock were found. On the other hand, 22:6n‐3 and DHA/EPA ratio was negatively correlated with the fecundity of broodstock (r²=0.5362, 0.8702 respectively). The result also showed that the balance between n‐3 and n‐6 fatty acid families, total polyunsaturated fatty acids and total saturated fatty acid and 20:5n‐3 (EPA) and 22:6n‐3 (DHA) may play vital roles in maturation and reproductive performance of P. monodon broodstock.     

Effects of Cooking Methods on Proximate Composition and Fatty Acids Profile of Indian White Prawn (Fenneropenaeus indicus)

The effects of baking, boiling, microwaving, and frying on the proximate composition and fatty acid content of the edible portion of Indian white prawns (Fenneropenaeus indicus) were determined. Mean moisture, lipid, protein, and ash contents of raw prawns were 72.1, 4.32, 21.5, and 1.31%, respectively. For all cooking methods, moisture decreased and protein increased, while fatty acid compositions changed uniquely for each method. In fried prawns, the n3/n6 ratio was the lowest and significantly differed from the other treatments. The heat treatment significantly changed the proximate composition and fatty acid content. Baking and microwaving are the best methods of the four for cooking prawn while preserving their nutritional value, especially on the basis of recommended dietary intake of DHA and EPA.