Seasonal variation in the condition index of Pacific oyster postlarvae (Crassostrea gigas) in a land‐based nursery in Sonora,Mexico     

Ramón H Barraza‐Guardado  Jorge Chávez‐Villalba  Héctor Atilano‐Silva  Francisco Hoyos‐Chairez 《Aquaculture Research》2008,40(1):118-128

This study examined the seasonal variation in the condition index (CI) of Crassostrea gigas postlarvae (<5 mm) that were cultivated at a commercial hatchery. Oysters were sampled weekly at the nursery using seawater from a lagoon for the grow‐out that precedes commercialization. Temperature, salinity, seston, chlorophyll a, oxygen and pH were recorded at each sampling and water samples were taken to identify phytoplankton groups and their abundance. High levels of primary productivity, chlorophyll a and seston were detected during summer, but the highest CI occurred in winter. During winter, elevated phytoplankton biomass was composed by diatoms and phytoflagellates, which served as the main food source and promoted weight gain in this season. Variations in salinity, oxygen and pH were not related to differences in the CI. However, it appears that the wide temperature variation affected functions, such as feeding activity, apparently enhancing ingestion during winter (mean 16.5±1.4 °C) and reducing ingestion during summer (mean 31±1.5 °C). Winter production resulted in postlarvae with a homogeneous size range and a high CI, indicating that winter is more favourable to start cultivation. The CI represents a practical means to determine the physiological state of postlarvae before transfer to cultivation sites.  相似文献   

水稻籼粳杂种不育性的多基因遗传不平衡   总被引：1，自引：0，他引：1  

刘永胜  阴国大 《四川农业大学学报》1993,11(1):1-5

本文研究和讨论了水稻亚种间远缘杂种不育性的起源。就杂种不育性的遗传本质,作者提出了多基因遗传不平衡假说:远缘杂种不育性的遗传属于孢子体——配子体的互作,且存在一个多基因系统支配下的一种特殊的配子体选择方式对不育性起作用。具有r个遗传分歧的基因位点(无论连锁或独立)的远缘品种杂交F_1产生的配子中分为平衡配子和不平衡配子。平衡配子的r个基因位点为亲本基因组合类型,拥有亲本之一的整套基因系统而能正常发育;而不平衡配子含有双亲的部分基因系统,由于遗传分歧双亲的基因系统在单倍性细胞中不能很好地配合协调或互补,发育过程的障碍就可能产生败育。在平衡配子和极不平衡配子之间存在各种中间类型,配子体选择按S~(r+u)进行。我们的试验结果结合过去的研究,说明水稻亚种的分化是自然选择作用于遗传变异的结果,生殖隔离是籼亚种和粳亚种连续积累的遗传分歧的产物。  相似文献   

Critical limits of the degree of compactness and soil penetration resistance for the soybean crop in N Brazil   总被引：1，自引：0，他引：1       下载免费PDF全文

Pedro Daniel De Oliveira  Michel Keisuke Sato  Herdjania Veras de Lima  Sueli Rodrigues  Alvaro Pires da Silva 《植物养料与土壤学杂志》2016,179(1):78-87

In agricultural fields soil compaction is a major cause of physical degradation. Degree of compactness (DC) is a useful parameter for characterizing compaction and the response of crops for different soils. The objectives of this study were: (1) to identify the critical DC and PR values for soybean [Glycine max (L.) Merrill] using plant growth variables and (2) to verify the relationship between DC and PR, and assess which parameter is recommended for the evaluation of soil compaction. The study was conducted in a greenhouse in a completely randomized factorial design of 4 textures × 5 compaction levels for sandy loam and sandy clay loam soils, and 3 compaction levels for the clayey and very clayey soils. Soil samples were collected from the surface of a Xantic Kandiudox from the NE region of the State of Pará, Brazil. The DC was calculated from the maximum bulk density obtained by the Proctor test, and the PR curve was determined in undisturbed samples equilibrated in different matric potentials. The growth and development of the soybean was favored in the DC range of 80 to 85%, regardless of soil texture. The critical degree of compactness for the growth of soybean was around 98% regardless of soil texture, while the critical values for penetration resistance at field capacity varied according to soil texture and bulk density and were 28.2, 5.6, 3.5, and 5.2 MPa for the sandy loam, sand clay loam, clayey and very clayey soils, respectively. The root length was the plant growth variable most susceptible to soil compaction. Change in soil penetration resistance was poorly related with change in degree of compactness showing that one parameter cannot be replaced by the other. Because PR is quickly determined in field and have a direct relationship with plant growth, for the soils evaluated in this study we recommend the use of soil PR to assess the state of soil compaction.  相似文献   

Corrigendum to ‘Effect Of Suppressing The Synthesis Of Different Kafirin Sub-Classes On Grain Endosperm Texture,Protein Body Structure And Protein Nutritional Quality In Improved Sorghum Lines’ [Journal of Cereal Science 54/1 volume (2011) 160–167]     

Laura S. da Silva  Rudolf Jung  Zuo-yo Zhao  Kimberly Glassman  Andile W. Grootboom  Luke Mehlo  Maretha M. O'Kennedy  Janet Taylor  John R.N. Taylor 《Journal of Cereal Science》2012

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Biotechnology applied to fish reproduction: tools for conservation     

Diógenes Henrique de Siqueira-Silva  Taiju Saito  Amanda Pereira dos Santos-Silva  Raphael da Silva Costa  Martin Psenicka  George Shigueki Yasui 《Fish physiology and biochemistry》2018,44(6):1469-1485

This review discusses the new biotechnological tools that are arising and promising for conservation and enhancement of fish production, mainly regarding the endangered and the most economically important species. Two main techniques, in particular, are available to avoid extinction of endangered fish species and to improve the production of commercial species. Germ cell transplantation technology includes a number of approaches that have been studied, such as the transplantation of embryo-to-embryo blastomere, embryo-to-embryo differentiated PGC, larvae to larvae and embryo differentiated PGC, transplantation of spermatogonia from adult to larvae or between adults, and oogonia transplantation. However, the success of germ cell transplantation relies on the prior sterilization of fish, which can be performed at different stages of fish species development by means of several protocols that have been tested in order to achieve the best approach to produce a sterile fish. Among them, fish hybridization and triploidization, germline gene knockdown, hyperthermia, and chemical treatment deserve attention based on important results achieved thus far. This review currently used technologies and knowledge about surrogate technology and fish sterilization, discussing the stronger and the weaker points of each approach.  相似文献   

Fisheries or aquaculture? Unravelling key determinants of livelihoods in the Brazilian semi‐arid region          下载免费PDF全文

Priscila F M Lopes  Adriana R Carvalho  Sebastián Villasante  Gustavo Gonzaga Henry‐Silva 《Aquaculture Research》2018,49(1):232-242

In impoverished semi‐arid regions in the world, reservoirs serve multiple purposes, including food provision through fisheries and aquaculture. Yet, the socio‐economic benefits of promoting both activities remain unclear. We independently assessed the socio‐economic benefits generated from fisheries and aquaculture, in two reservoirs in the Brazilian semi‐arid region (June 2013 to June 2014). These reservoirs produced 27.75 ton of farmed tilapia over a year (USD Purchasing Power Parities [PPP] 88,778.73) and provided at least 16.5 ton of fish through fisheries (USD PPP 37,557.81), based on data from four farmer associations. Our input–output model revealed that the local economy depends on both activities, which, therefore, contribute similarly to providing goods and services to different branches. Aquaculture generated much higher revenues (seven times) than fisheries, but also much higher losses (the most successful farm yielded an average income of USD PPP 592.41 monthly). Still, there were no statistical differences in income among the compared associations. Fisheries provided very but guaranteed income (USD PPP 311.02 ± 82.94) and employed over three times as many people and contributed much more (>3 times) to food security than aquaculture. Encouraging aquaculture through specific policies while overlooking fisheries is not advisable because poor fishers would not be able to deal with unpredictable outcomes and it would put their food security at risk. However, if initial external support is provided to fishers in order to buffer large losses, aquaculture could represent a way out of poverty by generating an opportunity for larger gains, as long as potential negative ecological impacts of aquaculture are accounted for.  相似文献   

Arginine and phenylalanine requirement of juvenile silver perch Bidyanus bidyanus and validation of the use of body amino acid composition for estimating individual amino acid requirements   总被引：6，自引：0，他引：6  

Ngamsnae  De Silva  & Gunasekera 《Aquaculture Nutrition》1999,5(3):173-180

An experiment was conducted in a closed system to quantify the arginine requirement of juvenile silver perch Bidyanus bidyanus . Five experimental diets were formulated to contain 40% crude protein with five graded levels of arginine. The diets contained casein and gelatine as protein sources supplemented with crystalline L -amino acids to simulate the reference amino acid profile (except for arginine) of silver perch tissue protein. The experiment lasted 12 weeks and, based on growth data using broken-line analysis, the arginine requirement of juvenile silver perch was found to be 2.7 g 100 g⁻¹ dry diet (or 6.8% of protein).
Based on whole-body amino acid composition, A/E ratios (essential amino acid/total essential amino acids + (cystine + tyrosine) × 1000) were estimated. Using the experimentally determined requirement for arginine and A/E ratios, the phenylalanine requirement of silver perch was predicted to be 5.5 g 100 g⁻¹ protein. Another feeding trial was conducted to determine the phenylalanine require-ment of silver perch using a series of diets with various amounts of phenylalanine and a protocol similar to the previous one. It was found that the experimentally determined phenylalanine requirement of juvenile perch was similar to that predicted. The A/E ratios have been hitherto utilized for the estimation of essential amino acid requirements in three salmonids, common carp and channel catfish: the present findings extend the validity of the method to other fish species.  相似文献   

Finishing plant diet supplemented with microalgae meal increases the docosahexaenoic acid content in Colossoma macropomum flesh     

Carlos Andre Amaringo Cortegano  Aline Marculino de Alcntara  Allana Feitoza da Silva  Cludia Maiza Fernandes Epifnio  Sunique Po Cordeiro Bentes  Vanessa Jorge dos Santos  Jesuí Vergílio Visentainer  Ligia Uribe Gonalves 《Aquaculture Research》2019,50(4):1291-1299

The need for a sustainable aquaculture is increasing the use of plant ingredients in replacement to fishmeal and fish oil in diets for tambaqui Colossoma macropomum, which is leading to not detectable levels of docosahexaenoic acid (DHA) in its flesh. We evaluated the effect of a finishing plant diet supplemented with 5% of microalgae meal from Schizochytrium sp. (MD) on tambaqui growth, on proximal composition and fatty acid content of its flesh, comparing it to a non‐supplemented diet. One hundred and sixty‐two fish (489.67 g) were distributed into six tanks (2,000 L) and fed the experimental diets for a 90‐day period. Three fish per tank were euthanized for analyses every 15 days. The MD did not affect the growth and proximal composition of fish flesh. The MD increased the DHA content (from 14.81 to 38.60 mg/g of lipids) and the n‐3:n‐6 ratio (from 0.16 to 0.51) in the flesh of fish, beginning on the 15th day and reaching the highest DHA content on the 71st day (39.81 mg/g of lipids). We recommend C. macropomum to be fed with a finishing diet supplemented with microalgae meal for 71 days before slaughter to improve the DHA content and n‐3:n‐6 ratio in the flesh.  相似文献   

Effects of salinity on sexual maturity and reproduction of Poecilia velifera     

Luanna do Carmo Neves  Filipe Cipriano  Joo Paulo Silva Lorenzini  Kauana Santos de Lima Cipriano  Lucas Pedro Gonalves Junior  Cintia L. Nakayama  Ronald Kennedy Luz  Kleber Campos Miranda Filho 《Aquaculture Research》2019,50(10):2932-2937

Poecilia velifera is a popular fish in freshwater aquarism that naturally inhabits aquatic habitats with a wide range of salinities. Nonetheless, the effects of different salinities on the reproductive success and sex ratio of the species remain unknown. Male sex characters, sex ratio and reproductive success of P. velifera were evaluated by maintaining 160 juveniles (0.078 ± 0.011 g) in four different salinities (0; 12; 24; 36 g/L), with four replicates. The only modification observed in males was the formation of a copulatory organ from the anal fin, which was used to distinguish them from females. Timing of the formation of the male copulatory organ, and the weight and total length of males when it occurred, were recorded. Twenty‐eight fish from each treatment were euthanized after 150 day to examine the gonads and confirm sex. Eight females and four males from each treatment were then kept in their respective salinity treatments for 65 days to examine the effects of salinity on reproduction. Males were kept with females in the different treatments for 15 days, at which point they were removed. Salinity was negatively correlated with male weight and length. Salinity also affected the sex ratio, with the percentages of males and females being 32.5 and 67.5%, and 27.5 and 72.5% in the salinities of 24 and 36 g of salt/L, respectively. Fifty percent of the females kept in freshwater reproduced, while there was no reproduction in the other treatments. The maintenance of P. velifera in freshwater promoted greater reproductive success and precocity, as well as larger males.  相似文献   

Effect of photoperiod and tank colour on growth and survival of pelagic‐phase seahorse Hippocampus reidi          下载免费PDF全文

Maik dos Santos Cividanes da Hora  Jean‐Christophe Joyeux  Helder Coelho Guabiroba  Mônica Yumi Tsuzuki 《Aquaculture Research》2017,48(8):4300-4307

The effect of photoperiod and tank colour on the survival and growth of juvenile seahorse Hippocampus reidi was investigated in the first 15 days after release (DAR). In the first experiment, newly released seahorses were exposed to six photoperiods – 6 h of light (L):18 h of darkness (D), 10L:14D, 12L:12D, 14L:10D, 18L:6D and 24L:0D. In the second experiment, juveniles were kept in tanks of different background colours – blue, white, black, clear and red. No significant differences were observed in the growth and survival among seahorse subjected to 10–24 h of light (P > 0.05). At the end of 15 DAR, fish exposed to 6L:18D showed lower growth in height and weight compared to other treatments (13.8 mm vs. 20.0–22.2 mm and 13.4 mg vs. 37.2–43.2 mg respectively) and lower survival (80% vs. 88–95% respectively). Tank colour did not affect growth and survival of juveniles up to 15 DAR.  相似文献