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961.
André L. Gandra Daniel R. Ituassú Manoel Pereira-Filho Rodrigo Roubach Roger Crescêncio Bruno A. S. Cavero 《Aquaculture International》2007,15(1):91-96
In order to assess the most suitable feeding schedule for pirarucu, Arapaima gigas, we placed groups of seven fish in 12 1-m3 cages and investigated various feeding variables in a 2 × 2 factorial design. The feeding variables analyzed were one feeding
(OC) or two feedings (TW), feeding daily (1D) or every other day (2D), and their interactions: one feeding once per day (OC/1D),
two feedings per day (TW/1D), one feeding every other day (OC/2D) and two feedings every other day (TW/2D). The experiment
lasted for 45 days, and the fish were maintained on a commercial extruded diet. The results showed similar final weights between
fish maintained on feedings OC and TW, but higher ones in fish fed 1D than 2D. Weight gain was higher when the fish were fed
TW and 1D. Apparent feed conversion was not affected in fish fed OC or TW and 1D or 2D. Daily feed consumption was also higher
for the feeding schedules of TW and 1D. The combination of feeding schedules produced higher final weights and weight gains
for fish fed OC/1D and TW/1D. The apparent feed conversion value was higher only in fish fed TW/1D. Daily feed consumption
values were significantly higher in fishes fed TW/1D. The lowest value was recorded for OC/2D. 相似文献
962.
Persistence of oxytetracycline in sediments from fish farms 总被引:7,自引:0,他引:7
The persistence of oxytetracycline, an antibacterial agent, in bottom deposits from fish farms was investigated. The drug was found in concentrations capable of causing antimicrobial effects up to 12 weeks after administration. A half-life of approximately 10 weeks was estimated through a pilot study. Possible effects on sulphide ion activity are suggested. 相似文献
963.
J. Máchová M. Prokeš Z. Svobodová V. Žlábek M. Peňáz V. Baruš 《Aquaculture International》2007,15(3-4):267-276
Diazinon 60 EC (chemical insecticide, organophosphate, active substance diazinon at a concentration of 600 g l−1) is used in fish-farming in well-founded cases as a biocide to suppress excessive propagation of coarse Daphnia zooplankton.
At the concentration of 10 μg l−1 (i.e., 100 g per 1 ha at a mean depth of the pond of 1 m), Diazinon 60 EC can highly selectively eliminate Daphnia zooplankton,
causes no harm to fish, and relatively quickly decomposes in the aquatic environment. This has been corroborated by results
of acute toxicity tests in fish: the 96 h LC50 is 3 mg l−1 for the guppy (Poecilia reticulata) and 10–25 mg l−1 for the common carp (Cyprinus carpio). As demonstrated by embryonic and larval tests of toxicity for the common carp (C. carpio), Diazinon 60 EC at the concentration of 10 μg l−1 causes no harm to the tested, individuals even in these sensitive (critical) stages of ontogeny. 相似文献
964.
Billy Nzau Matondo Michaël Ovidio Pascal Poncin Tampwo Alain Kakesa Lunkayilakio Soleil Wamuini Jean -Claude Philippart 《Fisheries Science》2007,73(5):1137-1146
ABSTRACT: Hybridization success at early developmental stages and larval resistance to osmotic, thermal and fasting tests in roach Rutilus rutilus , silver bream Blicca bjoerkna , common bream Abramis brama and their F1 hybrids were investigated. Results revealed that hybrid survival rates were similar to parents. At the eyed embryo stage, however, a maternal effect was observed as a general trend during hatchling and larval stages. After these stages, hybrids displayed a higher survival rate than their parents. Under stress tests, no survival was observed after 40 min for osmotic and thermal shocks and after 24 days for the prolonged fasting test in these species and their F1 hybrids. The median survivals of hybrids were intermediate between the two parents. For total mortality, hybrids were also affected by a maternal effect but to the advantage of the hybrids. 相似文献
965.
966.
No��mie Gaudio Philippe Balandier Gwena?l Philippe Yann Dumas Fr��d��ric Jean Christian Ginisty 《European Journal of Forest Research》2011,130(1):77-89
Depending on its developmental and morphological characteristics, shrubby or herbaceous understorey vegetation interacts differently with tree seedlings during the regeneration process. In acidic temperate forests, three common understorey plant species??Calluna vulgaris (L.) Hull, Pteridium aquilinum (L.) Kuhn in Kersten, Molinia caerulea (L.) Moench??are known to rapidly colonize forest gaps. Therefore, they often develop at the expense of light-demanding Scots pine (Pinus sylvestris L.) seedlings. An experiment was set up in a nursery in central France to mimic early competition occurring in a newly created gap between Scots pine seedlings and these three common understorey species (young forest-harvested individuals planted at 5 densities from 0 to 57 plants m?2). Pine seedling survival and growth (height, diameter, shoot and root biomass) and a functional trait (leaf mass on an area basis, LMA) were measured for 2 years, and cross-analysed against plant density, plant cover and available light. When understorey plant density increased, pine seedling diameter growth and biomass were negatively affected by all three plant species; height growth only slowed beneath Pteridium. These negative effects were closely linked to competition for light beneath Pteridium and Molinia. The application of the Beer?CLambert law gave an extinction coefficient k that was high for Pteridium, intermediate for Molinia and much lower for Calluna. LMA was confirmed as an effective foliar trait to reflect the degree of stress undergone by pine seedlings. 相似文献
967.
Jaume Gort-Oromi Lauri Mehtätalo Heli Peltola Ane Zubizarreta-Gerendiain Pertti Pulkkinen Ari Venäläinen 《Annals of Forest Science》2011,68(7):1233-1243
• Introduction
The objective of this work was to study how spacing and genetic entry and/or origin group affect radial growth (ring width and cumulative diameter development) and ring density from pith to bark in Scots pine (Pinus sylvestris L.) and in what sense their annual variability could be explained by the climatic variables. The spacing trial was located in central Finland, with current stand density range of 2,000–4,000 trees per hectare. All the six genetic entries had Kanerva pine (plus tree S1101) as a father tree, whereas the mother tree represented Finnish plus trees from southern, central and northern Finland. 相似文献968.
Jean Trap Fabrice Bureau Marthe Akpa-Vinceslas Thibaud Decaens Michaël Aubert 《Annals of Forest Science》2011,68(3):595-606
Introduction
We investigated changes in humus morphology and soil potential net N mineralization pathways along a pure beech even-aged forest chronosequence, composed of four stages (15, 65, 95, and 130 years old) on Luvisol. 相似文献969.
• Introduction
Size-density relationships define the maximum number of stems that even-aged stands of a given species can hold in relation to the mean size of trees. They are used to derive stand density measures and are useful tools used to control tree mortality. 相似文献970.