Interannual variability of Calanus helgolandicus in the English Channel     

Xabier Irigoien  Roger P. Harris 《Fisheries Oceanography》2003,12(4-5):317-326

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Effects of large woody debris removal on physical characteristics of a sand-bed river     

F. Douglas Shields  Roger H. Smith 《水产资源保护:海洋与淡水生态系统》1992,2(2):145-163

1. Removal of large woody debris (LWD) is one of the most widely practised stream alterations, particularly in sand-bed rivers of the south-eastern USA. Selective removal of LWD has been proposed as an alternative to orthodox non-selective clearing in order to conserve ecological resources, but methods for comparing hydraulic and environmental effects of selective and non-selective removal have not been developed. Conservation of stream habitats requires quantification of LWD removal impacts on physical habitat. 2. Physical characteristics of straightened, sand-bed reaches of the South Fork Obion River in western Tennessee, USA that were rich in LWD were compared with those in similar reaches where debris had recently been removed using selective removal guidelines. 3. The mean volume of LWD per unit water volume was 0.0545 in the uncleared reaches, but nearly 60% lower (0.0225) in the cleared reach. 4. A simple technique for predicting hydraulic roughness in channels with varying amounts of LWD was developed. Hydraulic roughness, as measured by the Darcy-Weisbach friction factor, was about 400% greater in uncleared reaches at base flow but declined to a level about 35% greater than for the cleared reaches at higher flows. Predicted friction factors were within 35% of measured friction factors at higher flows. 5. Physical habitat diversity in this channelized sand-bed stream was strongly related to the density of LWD. Flow conditions in the uncleared reaches were more heterogeneous than in the cleared reach, especially at low flow. At low flow, uncleared reaches tended to be shallower, have lower velocities, slightly finer bed material, and more heterogeneous conditions overall. Shannon indices based on depth and velocity were an average of 48% higher in uncleared reaches. 6. Bed sediments underneath and immediately adjacent to LWD formations were finer and contained more organic matter than sediments distant from LWD. However, when all bed samples were considered, organic content was positively correlated with median grain size.  相似文献   

Use of treated mine water for rainbow trout (Oncorhynchus mykiss) culture: a production scale assessment   总被引：1，自引：0，他引：1  

Roger C. Viadero  Jr.  Aislinn E. Tierney  Kenneth J. Semmens   《Aquacultural Engineering》2004,31(3-4):319-336

In previous proof-of-concept work, it was shown that the use of treated coal mine water for rainbow trout (Oncorhynchus mykiss) culture in a cage was technically feasible, though only a 50-fish bioassay was grown and no work on production-related issues was conducted. To further advance the use of treated mine water, an under-utilized water resource throughout Mid Appalachia, work was conducted to assess the effects of using treated coal mine water for the intensive production of rainbow trout in a flow-through system. During this study, comprehensive water quality data were collected to supplement fish weight and length data taken during routine monthly sampling events. The 8000 fish grew well in the raceway system over the 9 months of production, where a feed conversion ratio of 1.4 and a condition factor of 5.1 × 10⁻⁴ were measured with stocking and harvest densities of 26.4 and 50.2 kg/m³, respectively. Further, total net production was 3275 kg (7220 lb) with 98.6% survival. Throughout the study, dissolved ion concentrations (Fe, Al, Mg, Ca, and SO₄) often exceeded recommended tolerance limits. Further, elevated ammonia nitrogen concentrations generated from a component of the mine water-treatment process were identified as a potential limiting factor for aquaculture development. However, when the non-ideal effects of high ionic strength and the speciation of dissolved metal–ligand complexes were taken into account, the concentrations of free metal ions were within recommended tolerance limits.  相似文献   

“Indirect selection” for genetic change: A quantitative analysis illustrated with Macrobrachium rosenbergii     

Roger W. Doyle  Somsuk Singholka  Michael B. New 《Aquaculture (Amsterdam, Netherlands)》1983,30(1-4):237-247

“Indirect selection” is exerted on a trait indirectly, by means other than artificial selection for the trait itself. Expressions are derived for calculating the intensity of indirect selection in aquaculture environments. The calculations are illustrated with growth-rate data on M. rosenbergii from farm ponds in Thailand, and with computer-generated data which simulate measurements made during a multiple mark-recapture experiment. Indirect selection for growth is probably negligible in Thai prawn farms and hatcheries at present, but small changes in management practice could exert strong indirect selection on growth rate. One very effective change appears to be collecting broodstock as early in the production cycle as possible. Control of indirect selection may be useful for the genetic improvement of aquaculture stock, especially in developing countries and other situations where an intensive artificial selection program is not economically or biologically desirable. Like all selection programs, the probability of success is critically dependent on the genetics of the traits being selected.  相似文献   

Genetic improvement of farmed tilapias: Biochemical characterization of strain differences in Nile tilapia     

Julie M. Macaranas  Liza Q. Agustin  Ma. Carmen A. Ablan  Ma. Josefa R. Pante  Ambekar A. Eknath  Roger S. V. Pullin 《Aquaculture International》1995,3(1):43-54

Four African wild strains (Egypt, Ghana, Senegal and Kenya) and four established Asian farmed strains of Nile tilapia, Oreochromis niloticus (popularly known in the Philippines as Taiwan, Thailand, Singapore and Israel) were analysed electrophoretically at 30 protein loci to estimate genetic differences among the strains. All strains shared alleles at 14 monomorphic and 16 variable loci. Among the African strains, characteristic allele frequency differences were observed at AAT-1 ^* 46 for Ghana and Senegal, ADH ^* 83 for Kenya, ADH ^* 120 for Senegal, G3PDH-2 ^* 300 for Egypt, IDDH ^* 67 for Senegal, sMDH-1 ^* 120 for Kenya and SOD ^* 150 for Senegal. Genetic distance values among the strains revealed a clustering of the farmed strains with Egypt and Ghana O. niloticus, a slight separation of the Senegal strain and a larger separation of the Kenya strain. This profile may reflect the origins of the few founder populations of this species previously introduced to Asia. It also confirms the wider genetic divergence of the Kenya strain (O. niloticus vulcani) from the others studied here, which are all O. n. niloticus. Observed heterozygosities of the strains ranged from 0.026 to 0.071, with the African wild strains the lower values (mean Ho = 0.036) and the farmed strains the higher ones (mean Ho = 0.056). The implications of these results to the ongoing tilapia genetic improvement programme in the Philippines are discussed.  相似文献   

Effects of temperature change rate on nitrogen effluxes of Macrobrachium rosenbergii (DeMan)     

AndréS.C. Schmitt  Roger F. Uglow 《Aquaculture (Amsterdam, Netherlands)》1996,140(4):373-381

Ammonia-N (NH4⁺ + NH³) and total nitrogen (TN) efflux rates of Macrobrachium rosenbergii were measured during stepwise temperature changes (26 °C → 22 °C → 18 °C → 22 °C → 26 °C) at different rates. Sudden temperature reductions did not affect efflux rates, but sudden temperature rises evoked rapid and high increases in the efflux rates. A direct relationship between ammonia-N excretion and water temperature was observed when gradual temperature changes were effected over a 5 h period. When the animals were acclimated to a new temperature for 72 h, no clear effects of temperature on the efflux rates were found. Sudden temperature changes resulted in an increased proportion of ammonia-N in the total nitrogen excreted. It is suggested that temperature changes during the shipment of M. rosenbergii should be avoided or made gradually.  相似文献   

Validation of the otolith increment deposition ratio using alizarin marks in juveniles of the sparid fishes, Diplodus vulgaris and D. puntazzo     

Roger Villanueva  Balbina Molí 《Fisheries Research》1997,30(3):257-260

Deposition rate of otolith increments was validated by two immersions in alizarin complexone 10 days apart in juvenile Diplodus vulgaris and D. puntazzo. Alizarin complexone produced a well-defined scarlet band on the otoliths of all individuals. One increment:one day ratio was found for both species.  相似文献   

Resolvin D1, a Metabolite of Omega-3 Polyunsaturated Fatty Acid,Decreases Post-Myocardial Infarct Depression     

Kim Gilbert  Judith Bernier  Roger Godbout  Guy Rousseau 《Marine drugs》2014,12(11):5396-5407

We hypothesized that inflammation induced by myocardial ischemia plays a central role in depression-like behavior after myocardial infarction (MI). Several experimental approaches that reduce inflammation also result in attenuation of depressive symptoms. We have demonstrated that Resolvin D1 (RvD1), a metabolite of omega-3 polyunsaturated fatty acids (PUFA) derived from docosahexaenoic acid, diminishes infarct size and neutrophil accumulation in the ischemic myocardium. The aim of this study is to determine if a single RvD1 injection could alleviate depressive symptoms in a rat model of MI. MI was induced in rats by occlusion of the left anterior descending coronary artery for 40 min. Five minutes before ischemia or after reperfusion, 0.1 μg of RvD1 or vehicle was injected in the left ventricle cavity. Fourteen days after MI, behavioral tests (forced swim test and socialization) were conducted to evaluate depression-like symptoms. RvD1 reduced infarct size in the treated vs. the vehicle group. Animals receiving RvD1 also showed better performance in the forced swim and social interaction tests vs. vehicle controls. These results indicate that a single RvD1 dose, given 5 min before occlusion or 5 min after the onset of reperfusion, decreases infarct size and attenuates depression-like symptoms.  相似文献   

Flor Revisited(Again):eQTL and Mutational Analysis of NB-LRR Mediated Immunity to Powdery Mildew in Barley     

Roger Wise  Priyanka Surana  Greg Fuerst  Ruo Xu  Divya Mistry  Julie Dickerson  Dan Nettleton 《中国农业科学(英文版)》2014,(2):237-243

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COnfusion reigns — a reply     

Roger Marchant 《New Zealand veterinary journal》2013,61(5)

Extract

Madam:– Thank you for the opportunity to reply to the letter from Dr. Wiessing.  相似文献