High Survival (high + survival)

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Terms modified by High Survival

  • high survival rate

  • Selected Abstracts

    An individual-based model of the early life history of mackerel (Scomber scombrus) in the eastern North Atlantic, simulating transport, growth and mortality

    J. Bartsch
    Abstract The main purpose of this paper is to provide the core description of the modelling exercise within the Shelf Edge Advection Mortality And Recruitment (SEAMAR) programme. An individual-based model (IBM) was developed for the prediction of year-to-year survival of the early life-history stages of mackerel (Scomber scombrus) in the eastern North Atlantic. The IBM is one of two components of the model system. The first component is a circulation model to provide physical input data for the IBM. The circulation model is a geographical variant of the HAMburg Shelf Ocean Model (HAMSOM). The second component is the IBM, which is an i-space configuration model in which large numbers of individuals are followed as discrete entities to simulate the transport, growth and mortality of mackerel eggs, larvae and post-larvae. Larval and post-larval growth is modelled as a function of length, temperature and food distribution; mortality is modelled as a function of length and absolute growth rate. Each particle is considered as a super-individual representing 106 eggs at the outset of the simulation, and then declining according to the mortality function. Simulations were carried out for the years 1998,2000. Results showed concentrations of particles at Porcupine Bank and the adjacent Irish shelf, along the Celtic Sea shelf-edge, and in the southern Bay of Biscay. High survival was observed only at Porcupine and the adjacent shelf areas, and, more patchily, around the coastal margin of Biscay. The low survival along the shelf-edge of the Celtic Sea was due to the consistently low estimates of food availability in that area. [source]

    Growth and survival of first-feeding spotted wolffish (Anarhichas minor Olafsen) at various temperature regimes

    Tove K Hansen
    Abstract In order to define temperature regimes that could benefit successful production of spotted wolffish (Anarhichas minor) juveniles, experiments with offspring from two different females were carried out. The larvae were fed a new formulated feed or a commercial start-feed for marine fish, both of which have given high survival rates. In the first experiment newly hatched larvae were fed at constant 6 C, 8 C, 10 C and 12 C as well as at ambient seawater temperature (2.9,4.5 C) during 63 days. High survival, 90% to 96%, was registered at ambient and most constant temperature regimes, whereas in the 12 C groups survival was reduced to 80%. Growth rate (SGR) was very low, 1.8% day,1, at the low ambient temperatures. Growth rate was positively correlated with temperature and varied between 3.1% day,1 to 4.7% day,1, from 6 C to 12 C. In the second experiment, set up to include potential detrimental temperatures and study beneficial effects of a more restricted, elevated first-feeding temperature regime, the larvae were fed at constant 8 C, 10 C, 12 C, 14 C and 16 C until 30 days post hatch, followed by constant 8 C for the next 33 days. In this experiment, low survival, 25% and 2.0%, was registered at 63 days post hatch when larvae were reared initially at 14 C and 16 C respectively. The survival of the larvae at the other temperature regimes varied from 47% to 64%, highest survival rate (64%) was found at 8 C. The lowest specific growth rate, 2.6% day,1, was noted in the 16 C group. At constant 8 C to 14 C (regulated to 8 C), the SGR varied from 4.45% day,1 to 5.13% day,1. The larvae grew faster in the experiment when initially comparable temperatures (8 C, 10 C and 12 C) were regulated to constant 8 C after 30 days compared with the first experiment where feeding was carried out at the same constant temperatures (8 C, 10 C and 12 C) during the whole experimental period. [source]

    Use of a novel nonantibiotic triple marker gene cassette to monitor high survival of Pseudomonas fluorescens SBW25 on winter wheat in the field

    Lotta Jderlund
    Abstract Pseudomonas fluorescens SBW25 was tagged with a triple marker gene cassette containing gfp, encoding green fluorescent protein; luxAB, encoding luciferase; and telABkilA, encoding tellurite resistance, and the tagged strain was monitored in the first Swedish field release of a genetically modified microorganism (GMM). The cells were inoculated onto winter wheat seeds and the GMM cells (SBW25,tgl) were monitored in the field from September 2005 to May 2006 using plating, luminometry and microscopic analyses. Cell numbers were high on all sampling occasions and metabolically active cells were detected on all plant parts. Field results were similar to those obtained in a parallel phytotron study, although the amount of SBW25,tgl detected on shoots was significantly higher in the phytotron than in the field. After winter, cell counts were 100-fold higher on the roots and root-associated soil compared with prewinter measurements, although the cells had a lower relative metabolic activity. The wheat seeds were naturally infested with Microdochium nivale, but no treatment resulted in reduction of disease symptoms. No SWB25,tgl cells were ever found in bulk soil or uninoculated plants. The Swedish field trial results complement and contrast with prior field studies performed with the same parent organism in the United Kingdom under different soil, plant and climatic conditions. [source]

    Evidence for density-dependent survival in adult cormorants from a combined analysis of recoveries and resightings

    Morten Frederiksen
    Summary 1.,The increasing population of cormorants (Phalacrocorax carbo sinensis) in Europe since 1970 has led to conflicts with fishery interests. Control of cormorant populations is a management issue in many countries and a predictive population model is needed. However, reliable estimates of survival are lacking as input for such a model 2.,Capture,recapture estimates of survival of dispersive species like cormorants suffer from an unknown bias due to permanent emigration from the study area. However, a combined analysis of resightings and recovery of dead birds allows unbiased estimates of survival and emigration. 3.,We use data on 11 000 cormorants colour-ringed as chicks in the Danish colony Vors 1977,97 to estimate adult survival and colony fidelity. Recent statistical models allowing simultaneous use of recovery and resighting data are employed. We compensate for variation in colour-ring quality, and study the effect of population size and winter severity on survival, as well as of breeding success on fidelity by including these factors as covariates in statistical models. 4.,Annual adult survival fluctuated from year to year (074,095), with a mean of 088. A combination of population size in Europe and winter temperatures explained 52,64% of the year-to-year variation in survival. Differences in survival between sexes was less than 1%. Cormorants older than ,,12 years experienced lower survival, whereas second-year birds had survival similar to adults. Colony fidelity declined after 1990 from nearly 1 to ,,090, implying 10% permanent emigration per year. This change coincided with a decline in food availability. 5.,Apparently, survival was more severely affected by winter severity when population size was high. This could be caused by saturation of high-quality wintering habitat, forcing some birds to winter in less good habitat where they would be more vulnerable to cold winters. There was thus evidence for density dependence in adult survival, at least in cold winters. 6.,The high population growth rate sustained by European Ph. c. sinensis in the 1970s and 1980s can partly be accounted for by unusually high survival of immature and adult birds, probably caused by absence of hunting, low population density and high food availability. [source]

    Lichen acclimatization on retention trees: a conservation physiology lesson

    Kadi Jairus
    Summary 1.,Green-tree retention (GTR) has been suggested as a means to effectively support epiphytic lichen species in managed forests, given the low lichen mortality on retention trees in the short term. However, a long-term perspective requires a physiological understanding of lichen responses to logging. This study compares anatomical, morphological and physiological traits of lichens on retention trees and on intact forest trees. 2.,Thalli of nine taxa (Buellia griseovirens, Cladonia digitata, Hypogymnia physodes, Lecanora allophana, Lecanora pulicaris, Lepraria spp., Peltigera praetextata, Pertusaria amara and Phlyctis argena) were sampled from birch Betula spp. and aspen Populus tremula in GTR cuts, where they had previously been reported to survive well, and in adjacent managed forests. In the laboratory, chlorophyll fluorescence parameter Fv/Fm, thickness of the upper cortex, photobiont to mycobiont ratio and (in Lecanora species) the relative area of the apothecia were measured. 3.,All the lichen samples collected from GTR cuts appeared alive, but their Fv/Fm was significantly lower, relative areas of the apothecia were larger and the upper cortices of thalli were thicker compared with the samples from adjacent forests. No difference in photobiont to mycobiont ratio was found. These patterns were broadly consistent among species, indicating a common mechanism: while suffering from photoinhibition, the lichens had acclimatized to the open conditions and increased their investment to sexual reproduction in a few years. 4.,Synthesis and applications. The study highlights the value of a morpho-physiological framework for conservation management by pointing out that, in GTR areas, lichen survival is high-irradiation limited and heavily dependent on phenotypic plasticity. A thin upper cortex may be a common feature of the most sensitive species. To sustain epiphyte populations in managed forests, precautionary harvesting strategies (gradual felling; group-retention; extended rotations) should be preferred and large-enough populations should be preserved, even though short-term studies suggest a high survival of lichens in cut areas. [source]

    Growth, fat content and fatty acid profile of South American catfish, surubim (Pseudoplatystoma fasciatum) juveniles fed live, commercial and formulated diets

    M. Arslan
    Summary South American catfish, barred surubim (Pseudoplatystoma fasciatum) juveniles (117.6 11.8 mg individual weight; 28.3 2.5 mm total length) were fed various diets: one live (Tubifex worms), two commercial (Aglo Norse and Bio Kyowa), and one semi-purified formulated diet (75% peptide based protein) over a 2-week period. Fish fed the Aglo Norse diet showed the highest growth performance, but cannibalism also was very high (42%). Fish fed peptide based formulated diet demonstrated the lowest growth rate, with no cannibalism. The highest survival was achieved with fish fed Tubifex worms (100%). Lipid level in the whole body of the fish fed four different experimental diets did not differ significantly, averaging 3.6 0.7%. Fatty acid composition of neutral and phospholipid fractions of whole body lipids of fish reflected the fatty acid composition of the diets. The high level of 20:4n -6 in Tubifex worms resulted in a high level of this fatty acid in the tissue of fish fed this diet. It remains uncertain how high survival and no cannibalism is related to dietary lipids/fatty acids. In all cases, the increasing ratio of n -3 HUFA (highly unsaturated fatty acids)/n -6 HUFA in phospholipid fractions suggested the elongation and desaturation of 18:3n -3 to 22:6n -3 via 20:5n -3. Moreover, in respect to the 20:4n -6 levels in the diets, an increase in the concentration of this fatty acid in phospholipid fraction suggests that South American catfish can transform linoleate into arachidonate. [source]

    Population dynamics and stage structure in a haploid-diploid red seaweed, Gracilaria gracilis

    JOURNAL OF ECOLOGY, Issue 3 2001
    Carolyn Engel
    Summary 1,Many red seaweeds are characterized by a haploid-diploid life cycle in which populations consist of dioecious haploid (gametophyte) and diploid (tetrasporophyte) individuals as well as an additional diploid zygote-derived sporangium (carposporophyte) stage. A demographic analysis of Gracilaria gracilis populations was carried out to explore and evaluate the population dynamics and stage structure of a typical haploid-diploid red seaweed. 2,Four G. gracilis populations were studied at two sites on the French coast of the Strait of Dover. Survival, reproduction and recruitment rates were measured in each population for up to 4 years. Eight two-sex stage-based population projection matrices were built to describe their demography. 3,All four populations were characterized by high survival and low recruitment rates. Population growth rates (,) were similar between populations and between years and ranged from 1.03 to 1.17. In addition, generation times were found to be as long as 42 years. 4,Sex and ploidy ratios were variable across populations and over time. Female frequencies ranged from 0.31 to 0.59 and tetrasporophyte frequencies from 0.44 to 0.63. However, in most cases, the observed population structures were not significantly different from the calculated stage distributions. 5,Eigenvalue elasticity analysis showed that , was most sensitive to changes in matrix transitions that corresponded to survival of the gametophyte and tetrasporophyte stages. In contrast, the contribution of the fertility elements to , was small. Eigenvector elasticity analysis also showed that survival elements had the greatest impact on sex and ploidy ratios. [source]

    Animal decisions and conservation: the recolonization of a severely polluted river by the Eurasian otter

    M. Delibes
    Abstract Animals make decisions relying on environmental cues associated to high survival or breeding success along their evolutionary history. However, because of rapid anthropogenic changes in the environment, they may lack useful cues, making bad decisions with potential consequences for individuals and populations. Contaminants are difficult or impossible to detect for animals, so polluted habitats could be used in spite of their dangerous effects. The Eurasian otter Lutra lutra reoccupied the Guadiamar River (SW Spain) <1 year after a toxic spill that killed the fauna living in it. The levels of heavy metals and arsenic (As) in the river trophic web at that moment were probably harmful for otters. To investigate this, we determined the amount of several heavy metals including copper, cadmium, zinc (Zn) and lead (Pb) and metalloids such as As in otter faeces and estimated the exposure of otters to these elements as average ingestion. Concentrations of Zn, Pb and As were statistically higher in faeces collected along the Guadiamar River than in those collected along the Guadalete River (reference area). An ,average otter' in the Guadiamar River would consume 3,4 mg of Pb and more than 5 mg of As daily. Such doses must be hazardous for the species and challenge the usual assertion that otter presence is a good indicator of river quality. [source]

    Quantitative l -lysine requirement of juvenile black sea bream (Sparus macrocephalus)

    F. ZHOU
    Abstract An 8-week feeding experiment was conducted to determine the quantitative l -lysine requirement of juvenile black sea bream Sparus macrocephalus (initial mean weight: 9.13 0.09 g, SD) in eighteen 300-L indoors flow-through circular fibreglass tanks provided with sand-filtered aerated seawater. The experimental diets contained six levels of l -lysine ranging from 20.8 to 40.5 g kg,1 dry diet at about 4 g kg,1 increments. All the experiment diets were formulated to be isoenergetic and isonitrogenous. Each diet was assigned to triplicate groups of 20 fish in a completely randomized design. Weight gain and specific growth rate (SGR) increased with increasing levels of dietary lysine up to 32.5 g kg,1 (P < 0.05) and both showed a declining tendency thereafter. Feed efficiency ratio and protein efficiency ratio was poorer for fish fed the lower lysine level diets (P < 0.05) and showed no significant differences among other treatments (P > 0.05). All groups showed high survival (above 90%) and no significant differences were observed. The whole body crude protein and crude lipid contents were significantly affected (P < 0.05) by dietary lysine level, while moisture and ash showed no significant differences. The composition of muscle and liver also presented similar change tendency. Total essential amino acid and lysine contents in muscle both obtained the highest value when fish fed 32.5 g kg,1 lysine diet (P < 0.05). Serum protein, cholesterol and free lysine concentration were affected by different dietary treatments (P < 0.05), triacylglyceride and glucose contents were more variable and could not be related to dietary lysine levels. Dietary lysine level significantly affected condition factor and intraperitoneal fat ratio of juvenile black sea bream (P < 0.05) except for hepatosomatic index. There were no significant differences in white blood cell count and red blood cell count (P > 0.05), however, haemoglobin level was significantly influenced by different diets (P < 0.05). Analysis of dose (lysine level)-response (SGR) with second order polynomial regression suggested the dietary lysine requirement of juvenile black sea bream to be 33.2 g kg,1 dry diet or 86.4 g lysine kg,1 protein. [source]

    Strategies for the capture and transport of bonefish, Albula vulpes, from tidal creeks to a marine research laboratory for long-term holding

    Karen J Murchie
    Abstract Throughout their circumtropical distribution, bonefish (Albula spp.) play a vital role in local economies as a highly prized sport fish. Recent interest in stock enhancement to sustain bonefish fisheries has led to the recognition that there currently are no data on how to live capture large numbers of adults (potential broodstock), transport them to captive facilities and how to handle them to ensure high survival. The objective of this study was to develop strategies for the capture and relocation of wild bonefish to a marine research holding facility to enable basic research and explore the potential for culturing bonefish for stock enhancement. Bonefish Albula vulpes (Linnaeus, 1758) were captured as they entered or left tidal creeks on Eleuthera, The Bahamas using seine nets and then transported by boat or truck to the laboratory. The relocation process evoked secondary stress responses at the metabolic, osmoregulatory and haematological levels as indicated by changes in blood glucose, lactate, haematocrit and ion values, relative to control fish. Physical and behavioural disturbances were also observed in bonefish that were unable to acclimate to laboratory conditions. Successful laboratory acclimation and long-term holding of wild bonefish was achieved through an adaptive learning process, whereby we identified a series of strategies and handling techniques to facilitate the acclimation of wild adult bonefish to captivity. This knowledge will enable future laboratory research on bonefish and is a prerequisite to the culture of this highly prized sport fish, and other sub-tropical and tropical marine species. [source]

    Population ecology of the velvet gecko, Oedura lesueurii in south eastern Australia: Implications for the persistence of an endangered snake

    AUSTRAL ECOLOGY, Issue 7 2008
    Abstract Ecological specialization, such as major dependence upon a single-prey species, can render a predator taxon vulnerable to extinction. In such cases, understanding the population dynamics of that prey type is important for conserving the predator that relies upon it. In eastern Australia, the endangered broad-headed snake Hoplocephalus bungaroides feeds largely on velvet geckos (Oedura lesueurii). We studied growth, longevity and reproduction in a population of velvet geckos in Morton National Park in south-eastern Australia. We marked 458 individual geckos over a 3-year period (1992,1995) and made yearly visits to field sites from 1995,2006 to recapture marked individuals. Female geckos grew larger than males, and produced their first clutch at age 4 years. Males can mature at 2 years, but male,male combat for females probably forces males to delay reproduction until age 3 years. Females lay a single clutch of two eggs in communal nests in November, and up to 22 females deposited eggs in a single nest. Egg hatching success was high (100%), and juveniles had high survival (76%) during their first 6 months of life. Velvet geckos are long-lived, and the mean age of marked animals recaptured after 1995 was 6.1 years (males) and 8.4 years (females). Older females (7.5,9.5 years) were all gravid when last recaptured. Like other temperate-climate gekkonids, O. lesueurii has a ,slow' life history, and population viability could be threatened by any factors that increase egg or adult mortality. Two such factors , the removal of ,bush rocks' for urban gardens, and the overgrowth of rock outcrops by vegetation , could render small gecko populations vulnerable to extinction. In turn, the reliance of predatory broad-headed snakes on this slow-growing lizard species may increase its vulnerability to extinction. [source]

    Performance Trade-offs Driven by Morphological Plasticity Contribute to Habitat Specialization of Bornean Tree Species

    BIOTROPICA, Issue 4 2009
    Daisy H. Dent
    ABSTRACT Growth-survival trade-offs play an important role in niche differentiation of tropical tree species in relation to light-gradient partitioning. However, the mechanisms that determine differential species performance in response to light and soil resource availability are poorly understood. To examine responses to light and soil nutrient availability, we grew seedlings of five tropical tree species for 12 mo at < 2 and 18 percent full sunlight and in two soil types representing natural contrasts in nutrient availability within a lowland dipterocarp forest in North Borneo. We chose two specialists of nutrient-rich and nutrient-poor soils, respectively, and one habitat generalist. Across all species, growth was higher in high than low light and on more nutrient rich soil. Although species differed in growth rates, the ranking of species, in terms of growth, was consistent across the four treatments. Nutrient-rich soils improved seedling survival and increased growth of three species even under low light. Slower-growing species increased root allocation and reduced specific leaf area (SLA) and leaf area ratio (LAR) in response to decreased nutrient supply. All species increased LAR in response to low light. Maximum growth rates were negatively correlated with survival in the most resource-limited environment. Nutrient-poor soil specialists had low maximum growth rates but high survival at low resource availability. Specialists of nutrient-rich soils, plus the habitat generalist, had the opposite suite of traits. Fitness component trade-offs may be driven by both light and belowground resource availability. These trade-offs contribute to differentiation of tropical tree species among habitats defined by edaphic variation. [source]