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91.
Tore S. Kristiansen Lars H. Stien Jan Erik Fosseidengen Espen Strand Jon-Erik Juell 《Aquaculture International》2011,19(4):625-636
Atlantic cod and other teleosts with closed swimbladders have slow gas resorption rates and are therefore vulnerable to sudden pressure reductions that lead to swimbladder expansion and possible loss of behavioural control. This problem is of particular relevance to fish farmers, who require safe protocols for lifting of cages containing cod that account for swimbladder expansion. To recommend a limit for pressure reduction, we experimentally determined the maximum pressure reduction, relative to neutral buoyancy pressure, free-swimming farmed cod would expose themselves to. Classical reward conditioning was used to motivate cod that were neutrally buoyant at 2?C3.3 ATM (10?C23 m depth) to respond to a sound signal by swimming rapidly upwards to a feeding station positioned at 1.5 ATM (5 m depth). Sixteen cod were implanted with data storage tags (DSTs) that registered their ambient pressure throughout the experiment. The DST data showed that cod voluntarily stopped rapid ascents before they reached the feeding station at an average maximum pressure reduction of about 41% relative to their neutral buoyancy pressure. This was equivalent to a 70% swimbladder expansion relative to neutral volume. During the experiment, cod seldom remained above their neutral buoyancy depths, except when feeding, indicating a behavioural aversion to positive buoyancy. To avoid the loss of buoyancy control in cod, we conclude that single lifting events of sea-cages, which forces swimbladder expansion, should never exceed a 70% expansion of the swimbladder above the pre-existing neutral buoyancy volume. 相似文献
92.
Gustav Hellström Tore Prestegaard Johan Dannewitz K. Håkan Olsén 《Fish physiology and biochemistry》2013,39(3):471-478
Male goldfish (Carassius auratus) exposed to female hormonal pheromones express increased milt volumes and their sperm fertilize more eggs than sperm from unprimed males. Ovulated salmonid females also release odours that increase volumes of strippable milt in males. It is, however, not known if the priming pheromones affect the ability of sperm to fertilize eggs in salmonids. In this study, we compare the proportion of larvae produced from in vitro fertilization tests between primed brown trout (Salmo trutta) males exposed to a mix of female urine and ovarian fluids, and control males exposed only to 0.9 % sodium chloride. We also investigate priming effects on milt yield and sperm motility. Fertilization tests with sperm from single males, as well as sperm from two males (i.e., sperm competition), were performed. Primed males generated more larvae in both the single male and competition fertilization tests. No differences between treatments in milt yield and sperm motility could be established. 相似文献
93.
Ulf Erikson Elin Kjørsvik Tora Bardal Hanne Digre Marte Schei Tore S. Søreide 《Journal Of Aquatic Food Product Technology》2013,22(7):1001-1020
ABSTRACTGutted Atlantic cod, packed in cartons, were frozen immediately after killing in a magnetic field (cell alive system). The results were compared with traditional air-blast freezing or by putting the cartons directly in a cold storage room (without forced convection of air). After frozen storage, external and fillet properties were compared. In spite of differences in freezing rates, only minor differences were found among treatments. The mechanism for the freezing of fish in the magnetic field, under the current conditions, appeared to be similar to that of traditional freezing methods. 相似文献
94.
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96.
Growth and nutrition of birch seedlings (Betula pendula Roth) with and without 0.5 mM Al3+ were studied. The seedlings were cultivated at growth-limiting Mg- or Ca-conditions by adding one of these elements at relative addition rates (RMg, RCa) of 0.15 day?1. The concentration of Ca2+ in the Mg-limited treatments was 0.01.0.1 or 1 mM and Mg2+ was given in equal molarities in the Ca-limited treatments. The relative growth rates, RG, of the plants and plant parts attained values close to RMg or RCa and were not affected by the concentration of Ca2+, Mg2+ or Al3+ in the culture solution. Uptake of Ca, at Ca-limitation, increased significantly in the roots after addition of Al, and decreased in all plant parts when the Mg concentration of the culture solution was raised. Less clear effects were found on Mg uptake at Mg-limitation. The inhibitory effect of Al on Mg uptake decreased with time as a result of the growth technique. The root mass fraction was significantly larger in plants limited in Ca (24%) than in plants limited in Mg (20%). The usefulness in using the balance between Ca and Al or ratios between Ca, Mg, K and Al as diagnostic tools for assessing the nutritional status of trees is discussed. 相似文献
97.
Wiebke Neumann Göran Ericsson Holger Dettki Nils Bunnefeld Nicholas S. Keuler David P. Helmers Volker C. Radeloff 《Biological conservation》2012,145(1):70-78
Human–wildlife conflicts like wildlife–vehicle collisions pose major challenges for the management and conservation of mobile wildlife in human-dominated landscapes, particularly when large species are involved. Mitigation measures to reduce risk of collisions may be based on information given by wildlife movement and collision data. To test whether movement and collision data indicate different spatiotemporal risk zones, we predicted year-around probabilities of road-crossings of GPS-marked female moose (Alces alces) (n = 102), and compared them with spatiotemporal patterns of police recorded moose-vehicle collisions (n = 1158). Probability of moose road-crossings peaked in May, June, and between mid November and the beginning of January, i.e. during moose migration. Moose-vehicle collisions were more likely during autumn and winter. Comparing environmental attributes of crossing and collision sites showed significant differences. The likelihood of collisions increased with the abundance of human-modified areas and higher allowed speed, and was lower on forest roads. We found that animal movement data alone are insufficient to predict collision risk zones, while analyses of collision data alone overestimate the collision risk in certain habitats. Our findings suggest that higher collision risk is largely due to low light and poor road surface conditions rather than to more animal road-crossings. This suggests that efforts to reduce wildlife collisions should focus on driver attitudes and road conditions rather than animal movement, and any efforts to model the collision risk will require actual collision data, and not just movement data. 相似文献
98.
Tore Schweder Dinara Sadykova David Rugh William Koski 《Journal of Agricultural, Biological & Environmental Statistics》2010,15(1):1-19
Abundance, mortality, and population growth of bowhead whales (Balaena
mysticetus) are estimated from captures of 4,894 putatively different individuals obtained from 10 years of systematic photographic
surveys conducted during the spring migration when most of the Bering–Chukchi–Beaufort population of bowheads migrates past
Point Barrow, Alaska. A stringent matching protocol designed to prevent false positive matches of the naturally, but variably
marked individuals, led to 42 resightings between years. The flip side of this stringency is a presence of false negatives,
i.e., some true recaptures are not recognized as such. The problem of false negatives is addressed by modeling the capture
process and the matching process. The captures of an individual are assumed to follow a Poisson process with intensity depending
stochastically on the individual whale and on the year. The probability of successfully matching a capture to a previous capture
is estimated by logistic regression on the degree of marking and image quality. Individuals are recruited by the Pella–Tomlinson
population model, and their mortality rate is assumed to be constant. The point estimate of yearly growth rate is 3.2%, and
bowhead abundance in 2001 is estimated to be 8,250, similar to previous estimates. 相似文献
99.
Suzanne Higgins Saskia D. Keesstra Žydrė Kadziuliene Lionel Jordan-Meille David Wall Alessandra Trinchera Heide Spiegel Taru Sandén Andreas Baumgarten Johannes L. Jensen Juliane Hirte Frank Liebisch Susanne Klages Philipp Löw Katrin Kuka Maarten De Boever Karoline D'Haene Sevinc Madenoglu Hesna Özcan Wieke Vervuurt Janjo de Haan Willem van Geel Bo Stenberg Pascal Denoroy Rok Mihelič Alar Astover Raquel Mano Cristina Sempiterno Fatima Calouro Giuseppe Valboa Helena Aronsson Tore Krogstad Stanislav Torma Jose Gabriel Peter Laszlo Nils Borchard Bartosz Adamczyk Anna Jacobs Beata Jurga Bożena Smreczak Bruno Huyghebaert Morgan Abras Raimonds Kasparinskis Eloise Mason Claire Chenu 《European Journal of Soil Science》2023,74(5):e13422
The European Commission has set targets for a reduction in nutrient losses by at least 50% and a reduction in fertiliser use by at least 20% by 2030 while ensuring no deterioration in soil fertility. Within the mandate of the European Joint Programme EJP Soil ‘Towards climate-smart sustainable management of agricultural soils’, the objective of this study was to assess current fertilisation practices across Europe and discuss the potential for harmonisation of fertilisation methodologies as a strategy to reduce nutrient loss and overall fertiliser use. A stocktake study of current methods of delivering fertilisation advice took place across 23 European countries. The stocktake was in the form of a questionnaire, comprising 46 questions. Information was gathered on a large range of factors, including soil analysis methods, along with soil, crop and climatic factors taken into consideration within fertilisation calculations. The questionnaire was completed by experts, who are involved in compiling fertilisation recommendations within their country. Substantial differences exist in the content, format and delivery of fertilisation guidelines across Europe. The barriers, constraints and potential benefits of a harmonised approach to fertilisation across Europe are discussed. The general consensus from all participating countries was that harmonisation of fertilisation guidelines should be increased, but it was unclear in what format this could be achieved. Shared learning in the delivery and format of fertilisation guidelines and mechanisms to adhere to environmental legislation were viewed as being beneficial. However, it would be very difficult, if not impossible, to harmonise all soil test data and fertilisation methodologies at EU level due to diverse soil types and agro-ecosystem influences. Nevertheless, increased future collaboration, especially between neighbouring countries within the same environmental zone, was seen as potentially very beneficial. This study is unique in providing current detail on fertilisation practices across European countries in a side-by-side comparison. The gathered data can provide a baseline for the development of scientifically based EU policy targets for nutrient loss and soil fertility evaluation. 相似文献
100.
Marianne Bechmann Tore Krogstad Andrew Sharpley 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):205-213
Abstract The phosphorus (P) Index, a risk assessment tool, is a simple approach used to rank the potential for P loss from agricultural fields. The P Index identifies areas where sources of P coincide with high risk of P transfer. Factors included in the P Index, developed for Pennsylvania, USA were justified in relation to Norwegian conditions and relevant changes were made. Phosphorus application rate was modified by crop P removal. Additional factors for: 1) P release by freezing of plant residues, 2) flooding frequency, 3) risk of leaching, and 4) annual precipitation were included. Management practices in the Index were adjusted to reflect the effect of time and method of P application on P loss, as well as erosion control measures relevant to agricultural management in Norway rather than Pennsylvania. Testing of the suggested P Index showed that it ranks the potential for P loss from several agricultural catchments in the south-eastern part of Norway relatively well (R 2=0.79). Continuous development of the Index to include new knowledge about processes for P loss as well as regional differences is of great importance for future use of the P Index. 相似文献