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Average Growth Rate (average + growth_rate)
Selected AbstractsGrowth of juvenile tilapia, Oreochromis niloticus L. from Lakes Zwai, Langeno and Chamo (Ethiopian rift valley) based on otolith microincrement analysisECOLOGY OF FRESHWATER FISH, Issue 3 2000D. Admassu Abstract , Age and growth of juvenile tilapia, Oreochromis niloticus, from Lakes Zwai, Langeno and Chamo (Ethiopia) were studied from microincrements in otoliths. Growth in length was best described by the Gompertz model. Average growth rate of the fish was most rapid in Lake Chamo (0.39 mm,·,day,1, 1.14%,·,day,1), intermediate in Lake Zwai (0.20 mm,·,day,1, 0.72%,·,day,1) and slowest in Lake Langeno (0.16 mm,·,day,1, 0.62%,·,day,1). Similarly, back-calculation from otolith increment widths gave growth rates of 0.28 to 0.43 mm,·,day,1, 0.15 to 0.32 mm,·,day,1 and 0.11 to 0.28 mm,·,day,1 for Chamo, Zwai and Langeno fish, respectively. In addition, Fulton's condition factor was largest for Chamo tilapia and smallest for Langeno tilapia; the difference between fish from Langeno and Zwai was small. Rapid growth of juvenile O. niloticus in Lake Chamo was attributed to warm temperature and better food quality., [source] Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007F. Hakim Abstract Primary titania nanoparticles were coated with ultrathin alumina films using Atomic Layer Deposition (ALD). The deposited films were highly uniform and conformal with an average growth rate of 0.2,nm per coating cycle. The alumina films eliminated the surface photocatalytic activity of titania nanoparticles, while maintained their original extinction efficiency of ultraviolet light. Deposited films provided a physical barrier that effectively prevented the titania surface from oxidizing organic material whereas conserving its bulk optical properties. Parts fabricated from coated powders by pressureless sintering had a 13,% increase in surface hardness over parts similarly fabricated from uncoated particles. Owing to its homogeneous distribution, the secondary alumina phase suppressed excessive grain growth. Alumina films completely reacted during sintering to form aluminum titanate composites, as verified by XRD. Coated particles showed a pseudoplastic behavior at low shear rates due to modified colloidal forces. This behavior became similar to the Newtonian flow of uncoated nanoparticle slurries as the shear rate increased. Suspensions of coated particles also showed a decreased viscosity relative to the viscosity of uncoated particle suspensions. [source] Contrasting textural record of two distinct metamorphic events of similar P,T conditions and different durationsJOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2005O. LEXA Abstract A structural, metamorphic and geochronological study of the Staré M,sto belt implies the existence of two distinct metamorphic events of similar peak P,T conditions (700,800 °C, 8,10 kbar) during the Cambro-Ordovician and the Carboniferous tectonometamorphic events. The hypothesis of two distinct periods of metamorphism was suggested on the basis of structural discordance between an undoubtedly Carboniferous granodiorite sill intrusion and earlier Cambro-Ordovician fabrics of a banded amphibolite complex. The analysis of crystal size distribution (CSD) shows high nucleation density (N0) and low average growth rate (Gt) for Carboniferous mylonitic metagabbros and mylonitic granodiorites. The parameter N0 decreases whereas the quantity Gt increases towards higher temperatures progressively approaching the values obtained from the Cambro-Ordovician banded amphibolite complex. The spatial distribution of amphibole and plagioclase shows intense mechanical mixing for lower-temperature mylonitic metagabbros. In high-temperature mylonites a strong aggregate distribution is developed. Cambro-Ordovician amphibolites unaffected by Carboniferous deformation show a regular to anticlustered spatial distribution resulting from heterogeneous nucleation of individual phases. This pattern, together with CSD, was subsequently modified by the grain growth and textural equilibration controlled by diffusive mass transfer during Carboniferous metamorphism. The differences between the observed textures of the amphibolites are interpreted to be a consequence of the different durations of the Carboniferous and Cambro-Ordovician thermal events. [source] Application of Compensatory Growth to Enhance Production in Channel Catfish Ictalurus punctatusJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2001Nagaraj G. Chatakondi Four treatment groups that received repeating cycles of fixed feed deprivation for either 0, 1, 2, or 3 d (control, treatment 1, treatment 2, and treatment 3, respectively), followed by periods of refeeding with a 36% protein commercial catfish feed once daily as long as the active phase of compensatory growth (CG) persisted, were assessed in flow-through aquaria. No-feed periods elicited the CG state and were immediately followed by days of ad libatum refeeding. At the end of 10 wk, average growth rate (AGR) of fish was higher (P < 0.05) than the control by 40%, 180%, and 191% for treatment 1, treatment 2, and treatment 3, respectively. The average weight of fish in treatment 3 was heavier (P < 0.05) than the average control group at the end of the study period. Mean daily feed consumption was 3.91%, 5.03%, 5.36%, and 5.98% for control, treatment 1, treatment 2, and treatment 3, respectively. Mean feed consumption per fish per day was 24%, 71.3%, and 70.7% higher than the control in treatment 1, treatment 2, and treatment 3, respectively. Restricted feeding is one of the effective methods to contain ESC-related losses in commercial channel catfish fingerling operations. The mean cumulative survival of treatment groups registered higher (P < 0.05) survival to Edwardsiella ictaluri infection compared to the daily fed control fish. Results from this study show that compensatory growth response triggered by periodic non-feeding days can improve growth rate, feed consumption, and improved survival to ESC infections in channel catfish fingerlings. [source] Variation in pathogen aggressiveness within a metapopulation of the Cakile maritima,Alternaria brassicicola host,pathogen associationPLANT PATHOLOGY, Issue 3 2005P. H. Thrall Variation in aggressiveness and its consequences for disease epidemiology were studied in the Cakile maritima,Alternaria brassicicola host,pathogen association. Variability in pathogen growth rates and spore production in vitro, as well as disease severity and lesion growth rate on C. maritima in glasshouse inoculation trials, were investigated. Substantial variation was found in growth rates among individual A. brassicicola isolates, as well as among pathogen populations. A significant trade-off also existed between growth and spore production, such that faster-growing isolates produced fewer spores per unit area. While there was little evidence for a link between growth in vitro and either disease severity or lesion development among fast- vs slow-growth isolate classes at the individual isolate level, the results suggest that variation in pathogen fitness components associated with aggressiveness may influence disease dynamics in nature. An analysis using an independent data set of disease prevalence in the associated host populations found a significant positive relationship between the average growth rate of pathogen populations in vitro and disease progress over the growing season in wild host populations. Trade-offs such as those demonstrated between growth rate and spore production may contribute to the maintenance of variation in quantitatively based host,pathogen interactions. [source] A simple model for the determination of the relative utilization efficiency of protein by blacklip abalone (Haliotis rubra Leach)AQUACULTURE NUTRITION, Issue 1 2010G.A. DUNSTAN Abstract A 6-week growth rate trial of 6.7 mm ± 1.35 SD long blacklip abalone (Haliotis rubra) fed one of four graded protein feeds (26%, 32%, 37%, 45% crude protein, CP) resulted in a maximum average growth rate of 81 ,m day,1 (percentage daily weight gain of 5.2% day,1) with the 45% CP diet. Based on the results, a new, simple, non-destructive method to calculate the relative utilization efficiencies (RUE) of nutrients is presented to estimate the relative contributions of a nutrient to growth, body maintenance and the excess used for energy. Calculations of RUE of protein estimated that at the maximum growth rate, 59% of the CP was responsible for growth, while 31% was used for body maintenance and an excess of 10% was lost and presumably catabolized for energy and carbohydrate anabolism. At the %CP where the highest proportion of CP was used for growth, i.e. the maximum RUE of protein for growth (slightly higher at 62%), 35% was used for body maintenance and only 3% of the excess was lost to energy. [source] Using Population Count Data to Assess the Effects of Changing River Flow on an Endangered Riparian PlantCONSERVATION BIOLOGY, Issue 4 2006DIANE M. THOMSON análisis de viabilidad poblacional; gestión ribereña; método de difusión; presas; riesgo de extinción Abstract:,Methods for using simple population count data to project extinction risk have been the focus of much recent theoretical work, but few researchers have used these approaches to address management questions. We analyzed 15 years of census data on the federally endangered endemic riparian plant Pityopsis ruthii (Small) with the diffusion approximation (DA). Our goals were to evaluate relative extinction risk among populations in two different watersheds (in Tennessee, U.S.A.) and potential effects of variation in managed river flow on population dynamics. Populations in both watersheds had high projected risks of extinction within 50 years, but the causes of this risk differed. Populations of P. ruthii on the Hiwassee River had higher initial population sizes but significantly lower average growth rates than those on the Ocoee River. The only populations with low predicted short-term extinction risk were on the Ocoee. Growth rates for populations on both rivers were significantly reduced during periods of lower river flow. We found only marginal evidence of a quadratic relationship between population performance and flow. These patterns are consistent with the idea that low flows affect P. ruthii due to growth of competing vegetation, but the degree to which very high flows may reduce population growth is still unclear. Simulations indicated that populations were most sensitive to growth rates in low-flow years, but small changes in the frequency of these periods did not strongly increase risk for most populations. Consistent with results of other studies, DA estimates of extinction risk had wide confidence limits. Still, our results yielded several valuable insights, including the need for greater monitoring of populations on the Hiwassee and the importance of low-flow years to population growth. Our work illustrates the potential value of simple methods for analyzing count data despite the challenges posed by uncertainty in estimates of extinction risk. Resumen:,Los métodos que utilizan datos de conteos simples de la población para proyectar el riesgo de extinción han sido el foco reciente de mucho trabajo teórico, pero pocos investigadores han utilizado estos métodos para responder preguntas de gestión. Analizamos 15 años de datos de censos de la planta ribereña, endémica y federalmente en peligro Pityopsis ruthii (Small) mediante el método de difusión. Nuestras metas fueron evaluar el riesgo de extinción de poblaciones en dos cuencas hidrológicas distintas y con dos efectos potenciales de la variación del flujo de agua sobre la dinámica de la población. Las poblaciones en ambas cuencas tenían alto riesgo de extinción proyectado a 50 años, pero las causas de este riesgo difirieron. Las poblaciones de P. ruthii en el Río Hiwassee tuvieron poblaciones iniciales más grandes, pero tasas de crecimiento significativamente menores, que las poblaciones en el Río Ocoee. Las únicas poblaciones con bajo riesgo de extinción pronosticado estaban en el Ocoee. Las tasas de crecimiento de las poblaciones en ambos ríos se redujeron significativamente durante períodos de bajo flujo en el río. Sólo encontramos evidencia marginal de la relación cuadrática entre el funcionamiento de la población y el flujo. Estos patrones son consistentes con la idea de que los bajos flujos afectan a P. ruthii debido al crecimiento de vegetación competitiva, pero aun no es claro el grado en que flujos muy grandes pueden reducir el crecimiento poblacional. Las simulaciones indicaron que las poblaciones son más sensibles a las tasas de crecimiento en años con bajo flujo en los ríos, pero pequeños cambios en la frecuencia de esos períodos no aumentaron el riesgo en la mayoría de las poblaciones. Consistentemente con los resultados de otros estudios, las estimaciones del riesgo de extinción mediante el método de difusión tienen amplios límites de confianza. Aun así, nuestros resultados aportaron varios conocimientos valiosos, incluyendo la necesidad de mayor monitoreo de las poblaciones en el Hiwassee y la importancia para el crecimiento poblacional de los años con bajo flujo. Nuestro trabajo ilustra el valor potencial de métodos sencillos de análisis de datos de conteo a pesar de los retos impuestos por la incertidumbre en las estimaciones del riesgo de extinción. [source] Impact of a native predatory whelk on cultivated oysters (Crassostrea gigas) crops in San Quintin Bay, MexicoAQUACULTURE RESEARCH, Issue 4 2009Laura F Rodriguez Abstract San Quintin Bay (Baja, California, Mexico) is extensively utilized by artisanal farmers to cultivate Pacific oysters (Crassostrea gigas) using a rope/rack system. A large juvenile oyster mortality event was significantly correlated with the presence of native predatory whelks, Macron trochlea. Surveys, field and lab experiments were performed to identify the predatory behaviour of the whelk, determine factors affecting oyster mortality, and quantify the impact on oyster farmers. Macron trochlea was found to be a voracious, active predator, which can consume ,4 juvenile oysters day,1. Juvenile oysters suffer significantly higher mortality in the presence of whelks. Macron trochlea has the largest impact on small oysters. Once oysters grow to >30 mm they reach a size refuge above which there is much lower mortality. At average growth rates, an oyster can escape predation after ,3 months. But, in areas of highest whelk densities, at average predation rates, whelks could consume the standing crop of juvenile oysters in approximately 43 days. For the artisanal oyster farmers of San Quintin this represents a substantial economic loss, which was unaccounted for previously. Farmers can reduce loss to whelk predation by seeding juvenile oysters in low whelk density areas until oysters reach the size refuge. [source] Effects of stocking density and water exchange regimes on growth and survival of juvenile spotted babylon, Babylona areolata (Link), cultured in experimental earthen pondsAQUACULTURE RESEARCH, Issue 3 2009Sirusa Kritsanapuntu Abstract The growth and survival of juvenile spotted babylon, Babylonia areolata, were determined at five stocking densities (100, 200, 300, 400 and 500 snails m,2) and three water exchange regimes (7-, 15- and 21-day intervals) in experimental earthen ponds over a 6-month experimental period. The results showed that the growth of spotted babylons was not significantly different among any density treatments (P<0.05). At the end of the experiment, the average growth rates in body weights were 0.59, 0.59, 0.58, 0.42 and 0.41 g month,1 respectively. Growth was significantly different among the different water-exchange treatments (P<0.05). The higher body-weight gains were observed in snails held at water exchanges of 7- and 15-day intervals, when compared with those held at water exchange of 30-day intervals. At the end of the experiment, average body-weight gains were 4.22, 3.67 and 2.68 g for snails held in water-exchange treatments of 7-, 15- and 30-day intervals respectively. This study recommended that stocking densities ,300 snails m,2 and water exchange of 7,15-day intervals are suitable for cultured B. areolata juveniles in earthen pond. [source] Growth and production of hatchery-reared juvenile spotted babylon Babylonia areolata Link 1807 cultured to marketable size in intensive flowthrough and semi-closed recirculating water systemsAQUACULTURE RESEARCH, Issue 5 2000N Chaitanawisuti Hatchery-reared juvenile spotted babylon Babylonia areolata (mean initial shell length 12.8 mm) were cultured intensively to marketable size in three 3.0 × 2.5 × 0.7 m indoor canvas rectangular tanks. The duplicate treatments of flowthrough and semi-closed recirculating sea-water systems were compared at an initial stocking density of 300 individuals m,2 (2250 juveniles per tank). The animals were fed ad libitum with fresh carangid fish Selaroides leptolepis once daily. During 240 culture days, average growth rates in shell length and body weight were 3.86 mm month,1 and 1.47 g month,1 for the flowthrough system and 3.21 mm month,1 and 1.10 g month,1 for those in the semi-closed recirculating system. Survival in the flowthrough system (95.77%) was significantly higher than that in the semi-closed recirculating system (79.28%). Feed conversion ratios were 1.68 and 1.96 for flowthrough and semi-closed recirculating systems respectively. [source] | |||||||||||||