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61.
Jonathan G. Lundgren Luis Augusto Becerra López-Lavalle Soroush Parsa Kris A. G. Wyckhuys 《Journal of pest science》2014,87(1):125-131
In South America, the whitefly Aleurotrachelus socialis is one of the principal pests of cassava (Manihot esculenta Crantz), reaching high population levels throughout the Andean region. Management of this species is primarily based upon the use of insecticides, while biological control has received limited attention. Till present, knowledge of A. socialis natural enemies is restricted to occasional records of predators and parasitoids. In this study, we developed PCR primer sets specific for the cassava whitefly, A. socialis, to identify their predator community in Colombian cassava. Eleven percent of 586 predator specimens (representing 131 taxa from 29 families) tested positive for cassava whitefly DNA. Of the 21 predator taxa that consumed cassava whiteflies, an unidentified netwing beetle (Lycidae), an unidentified spider species (Araneae), Harmonia axyridis (Coleoptera: Coccinellidae), a Cereaochrysa sp. (Neuroptera: Chrysopidae), and a Leucochrysa sp. (Chrysopidae) were the taxa that consumed cassava whiteflies most frequently under field conditions. Two abundant predators in the system, Delphastus sp. (Coccinellidae) and the long-legged fly, Condylostylus sp. (Diptera: Dolichopodidae), were both positive for whitefly DNA, but did not have the strongest trophic linkage to the pest relative to other predators. This study shows that a diverse predator community affects cassava whitefly in southern Colombia, and provides the groundwork for the design of cassava production systems with minimal pesticide inputs. 相似文献
62.
Reporting standards for biofilter performance studies 总被引:1,自引:0,他引:1
John Colt Jonathan Lamoureux Richard Patterson Gary Rogers 《Aquacultural Engineering》2006,34(3):377-388
The development of standardized rating and design procedures for biological filters will require that filter performance be evaluated and reported in a standardized manner. This article recommends draft reporting standards for biofilter performance studies. It is important that critical parameters are defined and reported in a standard manner, both in terms of definition, variable names, and units. Depending on the type and scale of an experiment, reporting of certain parameters will be either mandatory or optional. Basic principles of experimental design, statistical analysis, and randomization must be followed. Experimental protocols are recommended to ensure the accuracy of measured or computed parameters. The development of this reporting standard is being organized through the Standards and Reporting Committee of the Aquaculture Engineering Society (AES). It is anticipated that a revised version of these standards will be incorporated into the Guide to Authors for Aquacultural Engineering. 相似文献
63.
David M Liti Herwig Waidbacher Michael Straif Raphael K Mbaluka Jonathan M Munguti & Mark M Kyenze 《Aquaculture Research》2006,37(5):477-483
Despite the well‐documented herbivorous food habits, commercial feeds for production of Oreochromis niloticus usually contain between 7% and 15% animal protein. However, animal protein feedstuffs are expensive, hence the need to search for cost‐effective alternatives in plant‐protein sources. Such alternatives are probably more effective in semi‐intensive systems where natural pond food forms part of the diet. This study evaluated the performance of O. niloticus after feeding diets in which fresh shrimp meal (SM) was gradually replaced by a mixture of plant‐protein sources in fertilized ponds. Three isonitronegenous (24% crude protein) diets containing 12 (control), 6% and 0% SM were fed to three groups of O. niloticus in four replicates per group for 250 days. Fish were fed daily at 2% body weight and sampled monthly to monitor growth and make feed adjustments. Growth, yields, survival and feed conversion ratio were not significantly different (P>0.05) among treatments. Growth of males was double that of females, while the sex ratio was skewed towards females. Although complete substitution of SM by plant protein did not affect the growth of tilapia, production cost was reduced by 36%. In conclusion, animal protein is not required in diets for production of O. niloticus in fertilized ponds. 相似文献
64.
Gary S. Burr Peng Li Jonathan B. Goff Delbert M. Gatlin III Barbara Grisdale-Helland Ståle J. Helland 《Journal of the World Aquaculture Society》2006,37(4):421-430
To investigate potential use of increasing nutritional density of diets for rapid growth of warm‐water fishes, a feeding trial was conducted in which growth performance, body indexes, and whole‐body composition of juvenile hybrid striped bass fed diets comprising protein (49, 54, and 59%), lipid (16, 20, 23, and 28%), and energy (22.0–25.1 kJ/g) concentrations beyond established minimum levels were compared to those of fish fed a more typical commercial reference diet (37.5% crude protein, 10.5% crude lipid, and 19.6 kJ/g energy on a dry matter basis). A subset of the experimental diets and the commercial reference diet also were fed to juvenile red drum. After 6 wk of feeding, hybrid striped bass fed the high‐protein and high‐lipid diets showed much greater growth performance compared to fish fed the commercial diet. Increasing dietary protein level, but not lipid level, tended (P ≤ 0.1) to enhance weight gain and feed efficiency of hybrid striped bass. Hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and whole‐body protein were significantly (P < 0.01) influenced by dietary protein level. The dietary lipid and associated energy level had significant negative linear effects on daily feed intake. Linear regression analysis showed that dietary energy : protein ratio, largely influenced by dietary protein level, moderately but significantly influenced weight gain, HSI, IPF ratio, and whole‐body protein of hybrid striped bass and red drum. Red drum grew very similar to hybrid striped bass in response to the experimental diets. However, significant differences in HSI, IPF ratio, whole‐body protein, lipid, moisture, and ash between hybrid striped bass and red drum were observed, indicating species differences in protein and energy partitioning. In particular, the excessive lipid in the diet increased HSI and whole‐body lipid of red drum but not of hybrid striped bass. 相似文献
65.
Peter Davies Robert J. Britton Andrew D. Nunn Jamie R. Dodd Charles Crundwell Randolph Velterop Niall
Maoilidigh Ross O'Neill Emma V. Sheehan Thomas Stamp Jonathan D. Bolland 《水产资源保护:海洋与淡水生态系统》2020,30(7):1291-1298
- Most research on anadromous fishes has been invested in their freshwater life‐phases, resulting in a relatively sparse understanding of their spatial ecology during marine life‐phases. However, understanding the marine dispersal of anadromous fishes is essential to identify threats and to implement conservation measures that fully encompass their lifecycle.
- The twaite shad Alosa fallax is an anadromous fish increasingly imperilled across its range due to pollution, harvesting, and impediments to freshwater migration, but little is known about its distribution and movements during its marine life‐phase. Here, the application of acoustic telemetry provided novel insights into the coastal dispersal of twaite shad in the UK and Ireland during 2018–2019, and the freshwater entry of individuals during the 2019 spawning season.
- Of 73 twaite shad acoustic‐tagged during their upstream migration in the River Severn in May 2018, 58 emigrated from the river. Twelve were subsequently detected 200 km to the south‐west at the Taw–Torridge Estuary between July 2018 and April 2019, where estuarine movements up to 5.8 km inland occurred in summer, winter, and spring. One was subsequently detected in the Munster Blackwater Estuary (Ireland) and then in the River Severn, indicating a minimum movement distance of 950 km. Thirty‐four (59%) of the emigrating individuals from 2018 re‐entered fresh water in the rivers Severn (n = 33) and Wye (n = 2) in April and May 2019.
- These results suggest year‐round use of estuarine and nearshore habitats by at least a subset of the twaite shad population during their marine phase, providing evidence of potential range overlap between populations that spawn in different areas in the UK and Ireland, which may be facilitated by substantial dispersal. The results also highlight the potential of telemetry for estimating freshwater and marine mortality, and the benefits of sharing detection data across networks.
66.
David Teichert-Coddington Bruce Manning Jonathan Eya David Brock 《Journal of the World Aquaculture Society》2000,31(1):42-50
Feed treated with 17α-methyltestosterone (MT) is used to manipulate the gender of early tilapia fry. In the USA, hormone-treated feed is used by selected producers under an Investigational New Animal Drug (INAD) program. While monitoring the fabrication and on-farm use of this treated feed, concerns were raised about the high performance liquid chromatography (HPLC) analytical procedure for detecting MT in feeds, the incorporation of MT in feeds during fabrication, and effects of storage temperature on MT concentration. A series of experiments demonstrated that the analytical procedure for detecting MT in feeds lacked high precision, and, on average, biased results low. MT was uniformly mixed with feed by spraying an MT-alcohol solution on feed while it was blended in an industrial ribbon mixer. Alcohol volumes ranging from 15 mL/kg to 150 mL/kg were equally effective at dispersing MT in feed. The concentrations of MT in feeds consistently declined over time if the storage temperatures were 25 C or higher. Freezing preserved the MT in feed, and the refrigeration of feed fabricated to contain 60 mg MT/kg maintained acceptable MT concentrations during 6 mo of storage. 相似文献
67.
Jonathan Wadsworth 《Agricultural Systems》1985,16(2):85-107
The economic effect of increased stocking rate permitted by the introduction of dry season feedin is evaluated with reference to the growing/fatening system of beef production in the sub-humid tropics. A widely applicable model is derived which requires few input variables, all of which will be easily obtainable in a specific location. The economic break-even point in terms of feeding cost and dry season length can be determined in order to assess the value of local diets or attempt the formulation of new ones. Increae in profitability due to dry season feeding is assessed taking into account increase in stocking rate, seasonal de-stocking practices, length of dry season, growth rates, feed costs and beef price. The model is appropriate for use in developing countries and can be employed manually to determine rapidly those management options worthy of more detailed consideration. 相似文献
68.
69.
Cultivars of common bean (Phaseolus vulgaris L.) capable of yielding well at low levels of native or added phosphorus (P)
are highly desirable in many tropical production systems. The objective of the present study was to identify geographical
regions which might be sources of such genotypes. A total of 364 landraces, cultivars and wild genotypes, drawn from a broad
geographic range, were divided on the basis of growth habit into four field trials, each comprising two levels of P, stressed
and unstressed, on an infertile Andosol in Popayan, Colombia. The regression relationship between grain yield per plant in
the presence and in the absence of stress was determined, and each genotype's deviation from this relationship was used as
a measure of P-efficiency. There was highly significant variation in efficiency among genotypes in all growth habits, and
in climbing beans there were consistent regional differences, superior genotypes being identified with greater frequency among
those from Bolivia, West Mexico and South Mexico-West Guatemala. The latter region was promising for prostrate bush genotypes
also. Wild beans in general performed relatively poorly; it appears that P-efficiency traits in P. vulgaris have been acquired
during or after domestication. These results confirm that genetic differences in P-efficiency exist among common bean genotypes
and suggest that these are related to geographic origin. Furthermore, the use of a representative sample of germplasm can
help to identify segments of the gene bank that are especially promising as sources of desirable traits.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
70.