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1.
The effect of stocking density on the survival and growth of pikeperch, Sander lucioperca (L.), larvae was examined in two consecutive experiments. In experiment I, 4-day-old larvae [body wet weight (BW): 0.5 mg; total body length (TL): 5.6 mm] were reared in 200-l cylindro-conical tanks in a closed, recirculating system (20 ± 0.5°C) at three stocking densities (25, 50 and 100 larvae l−1) and fed a mixed feed (Artemia nauplii and Lansy A2 artificial feed) for 14 consecutive days. At densities of 25 and 100 larvae l−1, growth rate and survival ranged from 2.7 to 1.9 mg day−1 and from 79.2 to 72.3%, and fish biomass gain ranged from 0.6 to 2.0 g l−1, respectively. There were two periods of increased larval mortality: the first was at beginning of exogenous feeding and the second during swim bladder inflation. In experiment II, 18-day-old larvae (BW: 35 mg; TL: 15.6 mm) obtained from experiment I were reared under culture conditions similar to those of experiment I, but at lower stocking densities (6, 10 and 15 larvae l−1). The fish were fed exclusively with artificial feed (trout starter) for 21 consecutive days. At densities of 6 and 15 larvae l−1, the growth rate and fish biomass gain ranged from 28.8 to 23.1 mg day−1 and from 2.0 to 3.3 g l−1, respectively. The highest survival (56.5%) was achieved at a density of 6 larvae l−1. Mortality at all densities was mainly caused by cannibalism II type behaviour (27–35% of total). In both experiments, growth and survival were negatively correlated and fish biomass gain positively correlated with stocking densities. The present study suggests that the initial stocking density of pikeperch larvae reared in a recirculating system can be 100 individuals l−1 for the 4- to 18-day period post-hatch and 15 individuals l−1 for the post-19-day period.  相似文献   

2.
吴霓  江涛  江天久  吕颂辉  桓清柳 《水产学报》2013,37(9):1328-1333
为研究2009年10月下旬在广东珠海海域爆发的双胞旋沟藻赤潮对养殖鱼类及水体中其它生物的影响,实验以卤虫幼体、金鼓鱼苗和凡纳滨对虾苗作为受试生物,在赤潮现场测试双胞旋沟藻对卤虫幼体、鱼苗和虾苗的急性毒性效应。结果显示,24 h双胞旋沟藻对卤虫幼体的LC50(半致死浓度)为9.55×104/mL,藻密度为2.5×103/mL的双胞旋沟藻对卤虫幼体的LT50(半致死时间)为48.5 h。60 h内该赤潮水体对鱼苗和虾苗的存活无不利影响,卤虫幼体和金鼓鱼苗均可摄食双胞旋沟藻,卤虫幼体对双胞旋沟藻的摄食率低。研究表明,双胞旋沟藻赤潮水体对卤虫幼体有一定的毒性作用,但在低藻密度条件下,卤虫幼体能以该藻为食并维持其生命,双胞旋沟藻对金鼓鱼苗和凡纳滨对虾苗无急性毒性作用。  相似文献   

3.
Compensatory growth following stress is a strategy aquatic animals use to adjust themselves to a variable environment. Studies on the recovery growth of aquatic animals are not only of theoretical value in ecophysiology and evolution, but also important to applications in aquaculture and fisheries resource management. In this experiment, juvenile Fenneropenaeus chinensis with an initial average body weight of about 3.72 g were exposed to hypoxic water (about 2.08 and 3.11 mg/l of dissolved oxygen (DO) content) for 10 days and then switched to normoxic water (about 5.63 and 5.59 mg/l DO). Compared with juveniles in normoxia, juveniles in the hypoxia period allocated a greater proportion of energy to metabolism and exuviations but allocated less energy to daily metabolism per gram shrimp weight (J/g/day). This reduced feed conversion efficiency and feeding rate. Finally, F. chinensis suffered growth depression. The juveniles completely compensated for hypoxia-induced growth depression in 30 days after being switched into normoxic water and the compensation was achieved mainly by hyperphagia and slightly by improvement of feed conversion efficiency. During the recovery period the hypoxic-stressed shrimp showed higher daily metabolic energy (J/g/day) than controls (P < 0.05). Which means the stressed shrimp had more energy for feeding-related activities. So hyperphagia was observed. Energy analysis indicated that F. chinensis improved feed-conversion efficiency mainly by reducing the percentage of energy lost in feces and exuviations. The results showed that short-term non-lethal hypoxia would not affect the growth of juvenile F. chinensis if there were enough time for the stressed shrimp to recover. This suggested F. chinensis was capable of adapting to DO fluctuation to some extent and short-term non-lethal hypoxia would not have an obvious effect on natural, released, and cultured shrimp stock.  相似文献   

4.
The behavior of black mudfish (Neochanna diversus Stokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinis Baird & Girard, 1854: Poeciliidae) was investigated in laboratory tanks. Black mudfish are indigenous to northern New Zealand, and mosquitofish are introduced; both species are sympatric in wetlands in the Waikato region. By comparing position, feeding rates and aggressive behavior of both species, we found that black mudfish were increasingly able to compete with mosquitofish as they grew from fry to adults. Mosquitofish were more aggressive towards mudfish fry and juveniles than were these two life stages towards mosquitofish, but adult mudfish were aggressive towards mosquitofish. Both small (18–24 mm total length (TL)) and large mosquitofish (25–36 mm TL) showed high aggression towards mudfish fry (13–18 mm TL), and fry were eaten by large mosquitofish. However, 3 interspecific differences appear to allow coexistence of these two species. Firstly, mudfish reproduce in winter, whereas mosquitofish reproduce in summer, resulting in mudfish fry being present when mosquitofish are at their lowest abundance. Secondly, mudfish can survive in seasonally dry habitats by aestivation, while mosquitofish cannot. Thirdly, adult black mudfish are nocturnal, whereas mosquitofish are primarily diurnal.  相似文献   

5.
牙鲆室内人工养殖试验   总被引：7，自引：0，他引：7  
报道了室内养殖牙鲆的试验结果,１９９２年－１９９５年进行的小规模试验。将受精卵培育至鱼苗、成鱼直至成熟亲鱼。在水温为２－２５℃范围内,经过３６个月将全长为５．３ｃｍ鱼苗培育至全长为４６．８ｃｍ、体重为１７８０ｇ的商品鱼,成活率为５０．６％。１９９７年－１９９８年进行的生产性养殖试验,在水温为１０－３３℃范围内。经过１０个月将全长为５．４ｃｍ鱼苗养至全长为３３．４ｃｍ、体篝为３５６ｇ的商品鱼、成活率  相似文献   

6.
Three commercial starters (Carp Starter, Uni Starter and Perla Plus) and one non-commercial, with frozen Chironomidae larvae as a reference diet, were evaluated for the intensive rearing of juvenile lake minnow Eupallasella perenurus, a cyprinid fish that is critically endangered in Poland. The growth, condition, survival, body deformities, and chemical body composition were studied. The 90-day laboratory experiment was performed at 22 °C with fish that were initially 24.6 mm (mean total lenth (TL)) and 0.11 g (mean body weight (BW)). Satisfactory fish growth was attained with all of the diets; however, the largest (p ≤ 0.05) final size (48.5 mm TL, 1.55 g BW) and the lowest condition coefficient (K = 1.34) were noted in fish fed the non-commercial starter. The final survival rates were very high (97.5–100%). Skeletal deformities (in 74 to 92% fish) were recorded exclusively in fish fed commercial starters. All commercial starters resulted in considerably higher lipid content and lower ash content than did the non-commercial starter and the reference diet. This suggests that both these factors might be responsible for body deformities. The present results proved that only the non-commercial starter is suitable for juvenile E. perenurus rearing under controlled condition, and that none of the commercial starters can be recommended.  相似文献   

7.
为了解配合饲料和活饵料对刀鲚幼鱼生长、存活和几种酶活性的影响,对用配合饲料和活饵料喂养178 d的刀鲚幼鱼的生长、存活和消化酶、非特异性免疫酶、代谢酶以及抗氧化酶活性进行分析与比较。结果显示,配合饲料组的最终体长、体质量、成活率、鱼体肥满度和肝指数(分别为125.17 mm、6.27 g、65.73%、0.31 g/cm3和1.4%)显著低于活饵料组(分别为150.66 mm、12.39 g、85.59%、0.36 g/cm3和1.9%),两组鱼的肠长和体长比无显著差异(分别为25.3%和23.6%);两组鱼的肝脏中均未检测出蛋白酶,配合饲料组的幽门盲囊中碱性蛋白酶的活性(43.49 U/mg prot)显著低于活饵料组(86.37 U/mg prot),但两处理组鱼胃中酸性蛋白酶和肠道中碱性蛋白酶的活性均没有显著差异;配合饲料组肠道和幽门盲囊中的淀粉酶活性(分别为196.63和575.93 U/g prot)显著低于活饵料组(分别为928.91和1 755.90U/g prot),但两处理组鱼肝脏和胃中的淀粉酶活性没有显著差异;两处理组鱼的肝脏和胃中均未检测出脂肪酶,配合饲料组的肠道脂肪酶活性(23.55 U/g prot)显著高于活饵料组(14.39 U/g prot),但两处理组幽门盲囊中脂肪酶活性(分别为17.90和13.23 U/g prot)没有显著差异;配合饲料组的肝脏碱性磷酸酶(AKP)活性(103.44 U/g prot)显著高于活饵料组(58.20 U/g prot),而配合饲料组的肝脏谷草转氨酶(AST/GOT)活性(20.38 U/g prot)显著低于活饵料组(32.51 U/g prot);肝脏中其余被检测的5种酶活性(ACP、ALT/GPT、SOD、GSH-PX和CAT)和血清中被检测的代谢酶(ALT/GPT和AST/GOT)及抗氧化酶(SOD和GSH-PX)活性在两处理组之间均没有显著差异。研究表明,刀鲚能摄食配合饲料,配合饲料组和活饵料组的大多数消化酶、非特异性免疫酶、代谢酶及抗氧化酶活性,没有显著性差异,但配合饲料组的刀鲚生长和成活率远低于活饵料组,建议今后研发和改进刀鲚配合饲料,逐步替代活饵料。  相似文献   

8.
Four artificial, dry feeds and two diets consisting of natural, live food were evaluated for use as starter diets in the intensive rearing of European grayling (Thymallus thymallus). Long-term effects of the different diets were also studied. The investigation was divided into two parts: a 14 day starter period and the subsequent 115 days, during which the long-term effects were studied. Diets differed between the different treatment groups during the initial 2 weeks, whereafter all fish were offered a single diet. At the end of the starter period, significant differences in weight (p<0.001) were obtained between natural (control) feed groups and three of the artificial feed groups. The highest growth rate (9.6% day–1), and length increase (9 mm) as well as the lowest mortality rate (6.0%) were obtained with one of the artificial diets. Growth rate, length increase and mortality of grayling in the other diet groups varied from 3.6 to 7.7% day–1, 5 to 7 mm and 7.0 to 9.1%, respectively. The switchover to a different dry diet resulted in an increase in mean daily mortality for all groups previously fed a dry diet. For the fish previously fed live food the mortality rate remained about the same. Groups of fish growing slowly during one period seemed to compensate for their initially low growth by increasing their growth rates during the next period. The highest mean daily mortality for all groups during the experiment was observed during the period with the highest water temperature. It was concluded that European grayling can be intensively reared during the start-feeding phase on artificial as well as natural diets, and that artificial dry diets can be used exclusively throughout the first summer.  相似文献   

9.
Largemouth bass (LMB) Micropterus salmoides fry do not accept prepared diets at first feeding. Fry are initially reared in fertilized ponds on natural live foods until large enough to be feed trained. Unpredictable weather patterns and depletion of natural forages can affect nursery pond survival. A series of experiments was conducted to investigate the use of Artemia nauplii prepared diets and optimal feeding schedules to raise LMB fry from first feeding through habituation to a commercial dry diet. In Studies 1, 2, and 3, swim-up fry were transferred to a recirculating system and stocked into either 3-L (Studies 1 and 2) or 10-L (Study 3) acrylic aquaria. Study 1 screened candidate diets to evaluate whether LMB fry could be transitioned directly to prepared diets or if they required live foods. In Study 2 the optimum duration for feeding live Artemia (1, 2, or 3 weeks) and the appropriate size of commercial diets (<200 or 200–360 μm) were evaluated. Study 3 was designed to identify the best transitional feed. Results from Study 1 indicate that fry fed Otohime-A (<200 μm) and decapsulated Artemia cysts performed better than those fed other diets tested. However, survivals were low (6%–8%) indicating a need for live feed initially. In Trial 2, fry fed live Artemia nauplii for two weeks and then transitioned to a 200–360 μm diet (Otohime-B) performed better than other diet combinations tested. In Study 3, survival was significantly higher in treatments using decapsulated Artemia cysts or Otohime-B as transitional diets between initial live Artemia feeding and trout starter. These data indicate that LMB fry can be successfully raised from first feeding to fully habituated to a commercial trout starter by feeding live Artemia nauplii for two weeks, followed by a gradual transition to either decapsulated Artemia cysts or Otohime-B for one week, then gradually transitioning to trout starter. Surviving fish were easily transitioned to commercial floating feed (Study 4). This protocol yielded survival rates of approximately 70% and may improve the reliability of LMB fingerling production by eliminating the outdoor nursery pond phase.  相似文献   

10.
A 60-days feeding trial was conducted to delineate the effect of both gelatinized and non-gelatinized corn with or without supplementation with exogenous α-amylase at two dietary protein levels (35% and 28%) on dry matter digestibility, digestive enzymes and tissue glycogen content of Labeo rohita juveniles. Three hundred and sixty juveniles (average weight 10±0.15 g] were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets containing either 35% or 28% crude protein were prepared by including gelatinized (G) or non-gelatinized (NG) corn as carbohydrate source with different level of microbial α-amylase (0, 50, 100 and 150 mg kg−1). The dry matter digestibility of G corn fed groups was significantly higher (P < 0.05) than that of the NG corn fed groups. Hepatosomatic index (HSI), liver glycogen and intestinal amylase activity of G starch fed groups were significantly higher (P < 0.05) than those of the NG corn fed groups. However, the reverse trend was found for gastrosomatic index (GSI), muscle glycogen and intestinal protease activity. Addition of 50 mg α-amylase kg−1 feed improved the dry matter digestibility of NG starch fed groups, which was similar to that of the G corn fed groups or NG corn supplemented with 100/150 mg α-amylase kg−1 feed. HSI, liver glycogen and intestinal amylase activity were significantly increased (P < 0.05) at minimum level of α-amylase in the feed (50 mg kg−1) and did not increase due to further inclusion of amylase in the diet. Supplementation with α-amylase at 50 mg kg−1 increased the intestinal amylase activity beyond which no significant changes were observed. Protease activity of liver and intestine was highest (P < 0.05) in higher crude protein (CP) fed groups, but protease activity of the intestine was significantly higher in the α-amylase supplemented groups. Hence, it was concluded that feed with 28% CP containing either G corn without α-amylase or NG corn with 50 mg α-amylase kg−1 may be used as the alternative carbohydrate source for L. rohita juveniles.  相似文献   

11.
The suitability of the harpacticoid copepodTisbe holothuriae as a diet for larval and juvenile Dover sole (Solea solea) was assessed by rearing groups of sole for 42 days under a range of dietary regimes. Larval sole, approximately 1 week old, were reared onTisbe, Artemia, or a mixedTisbe-Artemia diet for 13 days. No significant differences in length between sole larvae from any diet were found after this time, but larvae offeredArtemia alone showed a significantly higher frequency of malpigmentation than those offered the other diets. After metamorphosis (day 16), survivors of this experiment were reared for a further 29 days on various diets to give the following dietary sequences:Tisbe-fed larvae, fed onArtemia as juveniles (Tis.-Art.);Artemia-fed larvae, fed onArtemia as juveniles (Art.-Art.);Artemia-fed larvae, fed onTisbe as juveniles (Art.-Tis.) and mixed diet fed larvae, fed on a mixed diet as juveniles (AT-AT). At the end of this period AT-AT and Tis.-Art.-fed juveniles were significantly larger than those on the Art.-Art. dietary regime. Juveniles from the Tis.-Art. dietary regime consumed more prey items than the Art.-Art group. AT-AT juveniles consumed similar amounts of food to Art.-Art. juveniles but were significantly larger after 29 days culture. This was attributed to the presence ofTisbe in their diet. Overall, the best larval and juvenile diet appeared to be a mixed diet throughout the culture period.  相似文献   

12.
Two bacterial strains, Lactobacillus fructivorans, isolated from sea bream (Sparus aurata) gut, and Lactobacillus plantarum, isolated from human faeces, were administered simultaneously, during sea bream development, using Brachionus plicatilis and/or Artemia salina as vectors. The probiotic treatment significantly affected gut colonization. To test the probiotic influence on stress responsiveness, sea bream fry, 47 days post-hatching (p.h.), were subjected to pH stress (from 8.6 to 6.3) and cumulative mortality, cortisol levels and HSP70 gene expression were analysed. Cortisol was selected, since under stress conditions its level increases. HSP70 was selected with consideration of its wide involvement in response to a great number of injuries, and because it protects cells probably by binding and refolding damaged proteins. The results obtained indicated that the administration of probiotic to sea bream fry induced higher HSP70 levels, indicating a greater potentiality to respond to the harmful conditions possibly present in fish farms. This hypothesis is supported by the fact that the levels of cortisol found were significantly lower (P < 0.05) in both groups under probiotic treatment. When pH was used as a stressor, it induced a higher cumulative mortality in the control; the mortality was found to be significantly lower in both treated groups. Interestingly, a significant increase (P < 0.05) in HSP70 gene expression was observed in all stressed groups. These results suggest an improvement in tolerance to acute stress of fry fed with probiotics.  相似文献   

13.
为探索高脂饲料中添加胆汁酸对齐口裂腹鱼幼鱼肠道组织结构及几种脂肪代谢酶活性的影响,以360尾初始体质量为(12.74±0.14)g的健康齐口裂腹鱼幼鱼为实验对象,随机分为4组,每组3个重复,每个重复30尾实验鱼,分别投喂添加了0、75、150和300mg/kg胆汁酸的4种实验饲料,养殖时间为70 d。结果显示,胆汁酸浓度从0增大到75 mg/kg时,齐口裂腹鱼前肠和中肠管壁厚度及肠绒毛高度显著升高,前肠皱襞宽度显著降低。而当胆汁酸浓度再进一步增大时,实验鱼前肠和中肠管壁厚度及肠绒毛高度则升高不明显,其皱襞宽度也降低不显著。未添加胆汁酸的实验组中齐口裂腹鱼前肠和中肠纹状缘畸形或脱落现象严重,随着胆汁酸添加量的增加,逐渐减少至消失。齐口裂腹鱼肠道中脂肪酶(LPS)及肝胰脏中脂蛋白酯酶(LPL)、肝酯酶(HL)和总酯酶(TL)活性均随胆汁酸添加量的增加而呈先升高后趋于稳定的变化趋势。且LPS、LPL活性均在胆汁酸添加量为300 mg/kg时最强(分别为2881.17 U/g和14.43 U/mg prot);HL、TL活性则在胆汁酸添加量为150 mg/kg时活性最强(分别为43.70和58.03 U/mg prot)。但LPS、LPL、HL和TL活性在150与300mg/kg组均无显著差异。研究表明,在饲料中添加75~150 mg/kg的外源胆汁酸能提高齐口裂腹鱼幼鱼脂肪代谢酶的活性,促进对饲料脂肪的代谢和利用,还能改善齐口裂腹鱼幼鱼肠道结构,保护肠道健康。  相似文献   

14.
The efficiencies of four feeding methods were compared in the transition period from live food to dry feed in pikeperch (Sander lucioperca). Pond-nursed fry were trained to artificial feed without a transition (Group P) and with a transition, using a combination of dry feed and different kinds of live food—Chironomus larvae (Group C), Tubifex (Group T) and Daphnia (Group D)—during a 12-day-long trial. The ratio of dry feed for the transition groups was increased from 0 to 100% in 3-day intervals. The highest specific growth rates and condition factors were detected for Group C (4.2%, 1.46 ± 0.5) and Group T (4.2%, 1.48 ± 0.6), respectively. The survival percentages of the groups were as follows: 86.7 ± 9% (Group C), 78 ± 4% (Group T), 52 ± 1.4% (Group D) and 41 ± 9% (Group P). The rate of cannibalism ranged between 6.3 and 13.7% during the transition period. Larger-sized fish seemed to learn more rapidly to accept dry feed than their smaller counterparts.  相似文献   

15.
Bacillus circulans PB7, isolated from the intestine of Catla catla, was evaluated for use as a probiotic supplement in the feeds for the fingerlings of Catla catla. The effect of supplement on the growth performance, feed utilization efficiency, and immune response was evaluated. Catla fingerlings (ave. wt. 6.48 ± 0.43 g) were fed diets supplemented with 2 × 104 (feed C1), 2 × 105 (feed C2), and 2 × 106 (feed C3) B. circulans PB 7 cells per 100 g feed for 60 days at 5% of the body weight per day in two equal instalments in triplicate treatments. The control feed (CC) was not supplemented with the B. circulans. All the feeds were isocaloric and isonitrogenous. Fish fed with feed C2 displayed better growth, significantly (P ≤ 0.05) highest RNA/DNA ratio, a lower feed conversion ratio (FCR), and a higher protein efficiency ratio (PER) than the other experimental diets. Highest carcass protein and lipid was also observed in the fish fed C2 feed compared to the others. Significantly (P ≤ 0.05), highest protease was recorded in fish fed feed C2 (47.9 ± 0.016) and lowest in fish fed feed C3 (32.10 ± 0.009), where α-amylase activity did not differ significantly (P ≤ 0.05) beyond the lowest inclusion level. ALP, ACP, GOT, and GPT in the liver of Catla catla were the highest (P ≤ 0.05) in fish fed C2 feed. The highest TSP, albumin, and globulin was observed in fish treated with C2 feed after 60 days feeding trial, but the lowest glucose level was observed in the same treatment. After the feeding trial, the non-specific immunity levels and disease resistance of fish were also studied. Phagocytic ratio, phagocytic index, and leucocrit value were the highest in fish fed feed C2. After the feeding trial, the fish were challenged for 10 days by bath exposure to Aeromonas hydrophila (AH1) (105c.f.u. ml−1 for 1 h, and, after 7 days, 107c.f.u. ml−1 for 1 h). Highest survival percentage was observed in fish fed with feed C2 compared with only 6.66% in the controls, which indicated the effectiveness of B. circulans PB 7 in reducing disease caused by A. hydrophila.  相似文献   

16.
An investigation was conducted to evaluate the annual variation in potential predation impact (PPI) on larval and juvenile Pseudopleuronectes yokohamae by Crangon uritai in Hakodate Bay using predator-prey size relationships. Laboratory experiments were designed to estimate the favorable prey size of C. uritai through back-calculation of body length (BL) of P. yokohamae from sagittal otolith diameter observed in the stomachs of C. uritai. The most favorable prey-predator size ratio (BL of P. yokohamae-total length (TL) of C. uritai) class was 0.15–0.19, and ranged from 0.12–0.31. There was a significant positive correlation between the BL increase of P. yokohamae and the bottom water temperature in the field, such that BLs stagnated during the cold year of 1999 from April to June, and increased during the warm year of 2002. In contrast, no significant correlation was found between the TL increase of C. uritai and the bottom water temperature. Moreover, there were no significant differences in the mean TL of C. uritai between months (April–June) or years (1998–2002). Variation of PPI depended on the relationships between the growth rates of P. yokohamae and bottom water temperature. Therefore, the warm year of 2002 resulted in higher potential predation impact (PPI≥20), and it was at least 20 days shorter than that of the cold year of 1999. These results suggest that increased bottom water temperature in the nursery area was one of the most important factors for cumulative predation loss.  相似文献   

17.
Experiments were conducted with larvae of theblack-lip pearl oyster, Pinctadamargaritifera fed on a regime of living algae(an equal mixture of Tahitian Isochrysisaff. galbana and Pavlova salina)either partially or completely substituted withheterotrophically grown spray-dried algae (Tetraselmis suecica). Two experiments wereconducted; in the first, 1-day old larvae werecultured for 13 days and, in the second, 13days old larvae were culture for 7 days. Inboth experiments larvae were fed the followingproportions of live algae (LA) and dried Tetraselmis (DT); (1) 100% LA, (2) 75% LA +25% DT, (3) 50% LA + 50% DT, (4) 25% LA +75% DT; and (5) 100% DT. The optimal dietsfor maximum larval growth were 100% LA and75% LA + 25% DT resulting in larvae with amean shell length (SL) of 132 ± 3.8 and 131± 2.7 µm, respectively, at day 13. Thisshowed that 25% substitution of livemicro-algae with DT is possible withoutaffecting growth of P. margaritiferalarvae of less than 150 µm SL. There was nosignificant difference in survival of P.margaritifera larvae fed 100% LA, 75% LA +25% DT and 50% LA + 50% DT over a period of13 days. Highest survival (43.7%) occurred inlarvae fed 100% DT while lowest (approximately18%) occurred in controls (50% livemicro-algae and unfed) during the firstexperiment. The result of the second experimentindicated that with increasing size, larvae arecapable of accepting a higher proportion ofdried Tetraselmis in their diet. Therewere no significant differences in larvalgrowth or survival, between treatments where LAwas partially and completely substituted dietswith DT.  相似文献   

18.
A 40 days feeding trial with Labeo rohita (rohu) fry was conducted in six outdoor cemented tanks (5m × 4m × 1 m; 6–8 cm soil base) to establish the relative impact of on‐farm grown live Wolffia globosa (a duckweed with crude protein of 28.57%) and a formulated iso‐nitrogenous feed (crude protein 28.37%) on growth performance, survival, health and overall quality of fingerlings. The experimental tanks were dried, limed at 250 kg/ha, filled with ground water and subsequently applied with cow dung (soaked overnight) and mustard oil cake at 1,000 kg/ha and 50 kg/ha respectively. The fry were stocked at 0.3 millions/ha in six prepared tanks, and fed live Wolffia (T1) and formulated feed (T2). Results of the study indicate better performance (p < 0.05) of fry in terms of final mean weight (7.83 g), length (8.82 cm), daily growth index (6.51 g %/day) and survival (89.5%) than those fed on formulated feed. Furthermore, significantly improved (p < 0.05) feed utilization parameters viz. apparent feed conversion ratio (AFCR), apparent protein conversion efficiency (APCE), apparent protein efficiency ratio (APER); haematological parameters viz. total erythrocyte count (TEC), total leucocyte count (TLC), packed cell volume (PCV), plasma glucose and protein of fry were also observed in T1 (live Wolffia). Overall findings from this study hints towards the possible utilization of on‐farm grown live Wolffia as a suitable nutrient source for fry rearing of L. rohita.  相似文献   

19.
Kutum Rutilus frisii kutum is known as a valuable commercial species in the southern part of Caspian Sea. Artificial rearing of fry has been introduced as an alternative to supply kutum fry in order to restock the kutum population in the Caspian Sea. The aim of this study was to find the suitable time to transfer kutum larvae from live food to artificial feed. The experiment began on day 3 post- hatching and lasted for 21 days. Mean initial weight of larvae was 4.5 mg. Five experimental groups including Group A (zooplankton alone for 21 days), Group B (12 days zooplankton + 9 days artificial feed), Group C (8 days zooplankton + 13 days artificial feed), Group D (4 days zooplankton + 17 days artificial feed) and Group E (artificial feed alone for 21 days) were considered for this experiment. According to the obtained results, the specific growth rate of kutum larvae varied from 8.01 to 13.58% day−1, and the highest and lowest specific growth rate were found in A and E treatments, respectively. The lowest mean body weight (24.6 mg) was found in larvae fed on artificial feed for 21 days. However, survival rates of kutum larvae fed mixed zooplankton for 8 and 12 days (85.83 and 89.33%, respectively) were comparable with those of larvae fed live food during the entire experiment (91.6%). The lowest survival rate (69.16%) was found in larvae fed artificial feed during the entire experiment.  相似文献   

20.
The oogenic cycle and biochemical composition of the ovary of raft-cultured great scallop (Pecten maximus) were studied during the period April 1990–July 1991. The ovary condition index (FGI) and stereological studies showed the existence of two principal spawning periods, winter and late spring-early summer. No sexual resting period was found. Oocyte lysis was high throughout the year. Ovarian lipid levels displayed a clear seasonal pattern linked to the gametogenic cycle. Total lipid (TL, 16–21% dry weight), acylglycerol (AG, 20–65% TL) and free sterol (FS, 2.8–6.4% TL) levels were, generally, higher in the ripe ovary and a decrease coincided with spawning. Protein (59–63% dry weight), glycogen (<3% dry weight) and phospholipid (PL, 26–35% TL) levels showed no clear seasonal trend. The TL and AG were a good index of ovarian sexual maturity. The TL % of dry weight) correlated well with the female gonad condition index (r s = 0.779, p < 0.001), and AG (% f TL) correlated well with the mean oocyte diameter (r s = 0.630, p < 0.01) and the female gonad condition index (r s = 0.443, p < 0.05).  相似文献   

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