Linking laboratory and field responses of fish populations to acidification     

Webster Van Winkle  Sigurd W. Christensen  James E. Breck 《Water, air, and soil pollution》1986,30(3-4):639-648

To increase understanding of mechanisms by which fish populations respond to water chemistry changes resulting from acidification, it is necessary to link the results of laboratory studies of the effects of pH, Al, and Ca on the survival, growth, and reproduction of individual fish to responses of fish populations in the field. Our framework for achieving this goal is based on the types of data commonly available from both laboratory and field studies. One of the models (PHALCA) in this framework estimates the number of fish surviving as a function of time, given pH, Al, and Ca levels. A second model (FISHEGGS) evaluates the reduction in reproductive potential of a fish population attributable to the effects of pH, Al, and Ca on the survival of young-of-the-year and older fish and on fecundity. Preliminary results from these two models are presented, and the entire framework will be applied and tested over the next year using data for brook trout and lakes in the Adirondacks. The framework and models are a complementary alternative to the statistical analysis of survey data on water chemistry and on presence or absence of a fish species.  相似文献   

Crystal growth of silicon and germanium in metal films     

Ottaviani G  Sigurd D  Marrello V  McCaldin JO  Mayer JW 《Science (New York, N.Y.)》1973,180(4089):948-949

Amorphous silicon in contact with silver films and amorphous germanium in contact with aluminum films form crystalline precipitates when heated to temperatures well below those at which any liquid phase is present. Crystallization occurs by an initial dissolution of the semiconductor into the metal filmsolvent followed by the growth of crystals out of the solvent.  相似文献   

Does malpigmentation improve growth in juvenile turbot (Scophthalmus maximus Rafinesque) and halibut (Hippoglossus hippoglossus L.)?     

Albert K Imsland  Trond Wergeland  Thor M Jonassen  & Sigurd O Stefansson 《Aquaculture Research》2006,37(3):306-312

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Effect on Carcass Traits of Selection for Increased Lean Tissue Growth Rate in Swine on Low or High Dietary Protein Levels     

Sigurd Johansen  Jan Håkansson  Kjell Andersson 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(4):207-213

Pigs were selected for lean tissue growth rate (LTGR) in two lines, fed low (LP line) or high (HP line) protein levels. This investigation comprised 92 and 95 pigs, respectively, from generation 3 of the two lines, tested on low, medium and high protein diets between 25 and 105 kg body weight. HP compared to LP line pigs had higher ham percentage (P=0.02), thinner backfat (P=0.003) and lower intramuscular fat content (P = 0.01). A positive correlated response (P=0.02) in osteochondrosis score of femur (OCDf) was found in the HP line. There were unfavourable correlations (P<0.05) between OCDf and performance in the LP line. There were numerically negative correlations between length of the small intestines (LSI) and feed conversion ratio in both lines, and a numerically positive correlation between LSI and daily weight gain in the HP line. There were no interactions between selection lines and test diets. The present results indicate that selection for LTGR ought to be performed on a high protein feeding regime.  相似文献   

Prevalence and subtypes of Influenza A Viruses in Wild Waterfowl in Norway 2006-2007     

Anna Germundsson  Knut I Madslien  Monika Jankowska Hjortaas  Kjell Handeland  Christine Monceyron Jonassen 《Acta veterinaria Scandinavica》2010,52(1):28

The prevalence of influenza A virus infection, and the distribution of different subtypes of the virus, were studied in 1529 ducks and 1213 gulls shot during ordinary hunting from August to December in two consecutive years, 2006 and 2007, in Norway. The study was based on molecular screening of cloacal and tracheal swabs, using a pan-influenza A RT-PCR. Samples found to be positive for influenza A virus were screened for the H5 subtype, using a H5 specific RT-PCR, and, if negative, further subtyped by a RT-PCR for the 3''-part of the hemagglutinin (HA) gene, encompassing almost the entire HA2, and the full-length of the neuraminidase (NA) gene, followed by sequencing and characterization. The highest prevalence (12.8%) of infection was found in dabbling ducks (Eurasian Wigeon, Common Teal and Mallard). Diving ducks (Common Goldeneye, Common Merganser, Red-breasted Merganser, Common Scoter, Common Eider and Tufted Duck) showed a lower prevalence (4.1%). In gulls (Common Gull, Herring Gull, Black-headed Gull, Lesser Black-headed Gull, Great Black-backed Gull and Kittiwake) the prevalence of influenza A virus was 6.1%. The infection prevalence peaked during October for ducks, and October/November for gulls. From the 16 hemagglutinin subtypes known to infect wild birds, 13 were detected in this study. Low pathogenic H5 was found in 17 dabbling ducks and one gull.  相似文献   

Lethal cerebrospinal elaphostrongylosis in a reindeer calf.     

K Handeland  H S Norberg 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1992,39(9):668-671

Lethal elaphostrongylosis in a reindeer calf is described. The calf showed signs of abnormal behaviour, mental confusion and reduced vision due to lesions in the brain parenchyma caused by migrating mature Elaphostrongylus rangiferi. Traumatically caused malacia and secondary axon degeneration were observed in all brain areas. Nematodes were found in the skeletal muscles, epidural space of the spinal cord, and in the subdural spaces and leptomeninges of the cord and brain. Developing nematode ova were sectioned along migratory tracks in the brain, in the subdural space of the cord, epidural adipose tissue, perineurium of the spinal nerve roots and in the lungs.  相似文献   

Enzootic ataxia in a Norwegian red deer herd     

Handeland K  Flåøyen A 《Acta veterinaria Scandinavica》2000,41(3):329-331

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The germination of freshly harvested seed of ripe and unripe barley and oats     

Sigurd Andersen 《Euphytica》1965,14(1):91-96

Barley and oats were grown in a greenhouse and outside in the field to different stages of ripeness. After harvest the plants were threshed as soon as possible. The seeds were treated in different ways and sown immediately in a sand-bed. The kernels which germinated were counted.Seeds from plants which were grown in the greenhouse, on average germinated better than seeds from plants grown outside. Seeds from ripe plants germinated better than green seeds, but in some trials germination of green seeds was exceptionally good. The percentage of germination was increased by several treatments. Drying at 50°C was found to be the most efficient method.The result from such experiments may be different when the plants are grown in another environment. Under our conditions drying at a temperature of about 50°C was an efficient way to increase the germination of freshly cut seeds of barley and oats.  相似文献   

Seawater adaptation and growth of post-smolt Atlantic salmon (Salmo salar) of wild and farmed strains     

S. O. Handeland  Bjrnsson  A. M. Arnesen  S. O. Stefansson 《Aquaculture (Amsterdam, Netherlands)》2003,220(1-4):367-384

Atlantic salmon smolts (Salmo salar L.) of wild (Namsen) and farmed (AquaGen) strains were transferred to full-strength seawater (33‰) for 0 (initial control group), 0.5, 1, 2, 4, 8, 14, 30, 42 and 60 days at three different temperatures (4.3, 9.4 and 14.3 °C). Freshwater temperature in each tank was adjusted to test conditions 10 days prior to transfer. Physiological adaptation was monitored as changes in plasma growth hormone levels, gill Na⁺,K⁺-ATPase activity, plasma chloride levels and survival in seawater. Overall, smolts from the wild strain were better able to tolerate transfer to seawater than smolts from the hatchery strain. A delay in the osmotic disturbance and a prolonged period of osmotic stress were observed at the low temperature. Circulating GH levels increased transiently in all groups during the first 12–48 h in seawater and long-term GH levels were positively correlated with seawater temperature. Growth rates were influenced by temperature and strain, with the farmed smolts showing a higher growth than the wild smolts. Food Conversion Efficiency (FCE) was higher in smolts from the farmed strain, whereas no differences in daily food consumption were observed. Optimum temperature for FCE was calculated to be 10.5 °C, whereas the optimal temperature for growth in seawater was calculated to be 13.0 °C. We suggest that the observed differences in seawater tolerance, growth and food conversion probably are genetic and may reflect the fact that the hatchery fish have been bred for rapid growth for several generations.  相似文献   

Establishment of Tabulated Values for Standardized Ileal Digestibility of Crude Protein and Essential Amino Acids in Common Feedstuffs for Pigs     

Carsten Pedersen  Sigurd Boisen 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(3):121-140

Literature data on apparent ileal digestibility of crude protein (CP) and amino acids in pigs from 79 references (203 observations) including 13 different common feedstuffs, and other data on basal endogenous ileal loss of CP and amino acids from 32 references (36 observations) were analysed statistically. The analyses revealed that the cannulation method as well as the method for determining endogenous ileal losses of CP and amino acids affected the results. After correction for these effects a new set of tabulated values for apparent and standardized ileal digestibility of crude protein and essential amino acids was generated. The results were in most cases in good agreement with three recently published tables for standardized ileal digestibility of amino acids in feedstuffs. Therefore, it was concluded that the data obtained in the present work, together with those given in the recently published tables, would be a suitable basis for a general table for standardized ileal digestibility of CP and amino acids in common feedstuffs for pigs.  相似文献