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Rainbow trout (Oncorhynchus mykiss) (mean initial weight 0.84 g) were fed diets containing graded levels of magnesium (Mg) (78 to 725µg/g) while being exposed to one of several levels in the rearing water (1.4 to 1000 mg/l). Uptake of Mg from the water, in Mg-deficient fish, was linearly related to the water Mg concentrated. It appears that the fish's Mg requirement can be met from either or both the diet or water. Under the experimental conditions, a water-borne concentration of 46 mg/l was calculated to be sufficient to meet the Mg requirement of the fish fed a Mg-free diet. 相似文献
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Eva B. Thorstad Torbjørn Forseth Ingar Aasestad Finn ØKland Bjørn Ove Johnsen 《Water, air, and soil pollution》2005,165(1-4):187-194
An accidental release of non-toxic waste from decommissioned wood pulp industry in the River Numedalslågen, Southern Norway, occurred in the upper part of the accessible stretches for anadromous fish during a study of migration behaviour of radio tagged Atlantic salmon (Salmo salar, n=32, body length 51–99 cm). The fish had completed the migration phase and initiated the resident phase characterised by little movement until spawning. When the wooden fibres and pulp were released, 16 of 32 (50%) salmon showed an immediate avoidance response. Six (19%) salmon moved upstream and 10 (31%) salmon moved downstream. Of the salmon moving downstream, eight (25%) moved all the way to sea (average 14.8 km). Four re-entered the River Numedalslågen, two entered a neighbouring river and two were not recorded later. Fish moving downstream but without moving to the sea, moved on average 5.3 km during the episode, whereas those moving upstream moved on average 6.7 km. All fish recorded after the episode (n=30) survived until the spawning season. The study demonstrates that fish in nature may show an evident avoidance response, even to non-toxic contaminants. For Atlantic salmon, the size of the spawning population may be reduced by fish leaving the river (13% left the river and never came back). Moreover, the dispersal of salmon to other rivers may increase, and the distribution of the spawning population within the contaminated river may shift. 相似文献
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David Huyben Aleksandar Vidakovic Andreas Nyman Markus Langeland Torbjörn Lundh Anders Kiessling 《Fish physiology and biochemistry》2017,43(2):421-434
Yeast is a potential alternative to fish meal in diets for farmed fish, yet replacing more than 50 % of fish meal results in reduced fish growth. In a 4-week experiment, 15 rainbow trout (Oncorhynchus mykiss) were cannulated and fed three diets each week: 30 % fish meal as a control (FM); 60 % replacement of fish meal protein, on a digestible basis, with Saccharomyces cerevisiae (SC); and 60 % replacement with Wickerhamomyces anomalus and S. cerevisiae mix (WA). Blood was collected at 0, 3, 6, 12 and 24 h after feeding. In the final week, fish were exposed to a 1-min netting stressor to evaluate possible diet–stress interactions. Significant increases in pH, TCO2, HCO3 and base excess were found after fish were fed the SC and WA diets compared with FM, which elevated blood alkaline tides. Yeast ingredients had lower buffering capacity and ash content than fish meal, which explained the increase in alkaline tides. In addition, fish fed the WA diet had significantly reduced erythrocyte area and fish fed SC and WA diets had increased mean corpuscular haemoglobin levels, indicating haemolytic anaemia. Higher levels of nucleic acid in yeast-based diets and potentially higher production of reactive oxygen species were suspected of damaging haemoglobin, which require replacement by smaller immature erythrocytes. Acute stress caused the expected rise in cortisol and glucose levels, but no interaction with diet was found. These results show that replacing 60 % of fish meal protein with yeasts can induce haemolytic anaemia in rainbow trout, which may limit yeast inclusion in diets for farmed fish. 相似文献
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Ana T. Silva Martyn C. Lucas Theodore Castro‐Santos Christos Katopodis Lee J. Baumgartner Jason D. Thiem Kim Aarestrup Paulo S. Pompeu Gordon C. O'Brien Douglas C. Braun Nicholas J. Burnett David Z. Zhu Hans‐Petter Fjeldstad Torbjørn Forseth Nallamuthu Rajaratnam John G. Williams Steven J. Cooke 《Fish and Fisheries》2018,19(2):340-362
Much effort has been devoted to developing, constructing and refining fish passage facilities to enable target species to pass barriers on fluvial systems, and yet, fishway science, engineering and practice remain imperfect. In this review, 17 experts from different fish passage research fields (i.e., biology, ecology, physiology, ecohydraulics, engineering) and from different continents (i.e., North and South America, Europe, Africa, Australia) identified knowledge gaps and provided a roadmap for research priorities and technical developments. Once dominated by an engineering‐focused approach, fishway science today involves a wide range of disciplines from fish behaviour to socioeconomics to complex modelling of passage prioritization options in river networks. River barrier impacts on fish migration and dispersal are currently better understood than historically, but basic ecological knowledge underpinning the need for effective fish passage in many regions of the world, including in biodiversity hotspots (e.g., equatorial Africa, South‐East Asia), remains largely unknown. Designing efficient fishways, with minimal passage delay and post‐passage impacts, requires adaptive management and continued innovation. While the use of fishways in river restoration demands a transition towards fish passage at the community scale, advances in selective fishways are also needed to manage invasive fish colonization. Because of the erroneous view in some literature and communities of practice that fish passage is largely a proven technology, improved international collaboration, information sharing, method standardization and multidisciplinary training are needed. Further development of regional expertise is needed in South America, Asia and Africa where hydropower dams are currently being planned and constructed. 相似文献
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Equine dentistry should no longer be thought of as art over science. To be an effective equine dental clinician requires considerable investment in knowledge beyond the basic veterinary degree. It requires current scientific dental knowledge and adherence to the fundamental principles of medicine, dentistry, and surgery. Knowledge and principles will provide clinicians with the necessary information to make more evidence-based decisions as the scientific literature continues to evolve. Diagnosis and therapy should be seen as journeys with a destination, keeping in mind the values of the Hippocratic oath. Equine dentistry no longer needs to be seen as hard physical work with considerable risk to all involved. There is a demand for providers of equine dental care to be appropriately trained veterinarians and for veterinarians to further develop the science of equine dentistry. The rewards to the horse, client, and clinician are likely to be evident to those who make the investment. 相似文献
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Chau T Da Le T Hung Håkan Berg Jan E Lindberg Torbjörn Lundh 《Aquaculture Research》2013,44(3):427-438
A technical and socio‐economic survey was conducted in Dong Thap, Can Tho and An Giang, provinces of Vietnam in 2009. The results showed that most of the small scale farmers of striped catfish (Pangasius hypothalamus) carry out fish pond culture, developed and operated by self‐learned experience and from neighbours knowledge. The mean pond depth varied from 3.5 to 4.0 m, ranging from 2 to 6 m. Most of the fish farms have extremely high stocking density, with an average of about 40 fish m?2, in some cases up to 70 fish per m2. The average yields and net income of small‐scales pond farming is about 21–27 kg per m2 crop?1 and US$ 0.184–0.329 kg?1 crop?1 respectively. These figures are not significantly different compared with large‐scale pond farming. About 75%, 86% and 80% of fish farmers in Dong Thap, Can Tho and An Giang province, respectively, received positive net returns. Farm‐made feed is still playing an important role because of higher net profit compared with commercial pellet feeds. Rice bran and trash fish are the main feed ingredients for farm‐made feed formulations. Striped catfish farmers are now actively searching for locally produced plant protein sources as alternatives to marine trash fish or fish meal. 相似文献
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Hanna Lundmark Torbjörn Josefsson Lars Östlund 《European Journal of Forest Research》2017,136(2):269-285
The effects of clear-cutting and potential alternatives continue to be hot topics during discussions of forestry and nature conservation. This study presents forest data from Ridön, an island in Lake Mälaren in central Sweden, where forest management and clear-cutting have been applied for almost 200 years. The main objective of the study was to identify changes in forest management and forest conditions over time. The forest transition in Sweden during the 1800s is also covered, and the importance of early forest experiments is discussed, exemplified by Ridön. This study is based on eight forest management plans and maps, from 1832 to 2014. Our results show a transformation from large, continuous areas of heterogeneous forest to small homogeneous stands. Clear-cutting has been the main logging method applied to Ridön for almost 200 years, which is in contrast with the general historical trend of selective cutting preceding clear-cutting in the Nordic countries. Our analysis shows that forestry has changed from the exploitation of resources to sustainable management. Currently, forest management at Ridön aims to create a nature reserve characterized by uneven-aged forest with an increased deciduous component. Hence, the intention is to obtain a forest similar to as it was in 1832. By analyzing spatially precise data on forest stands over long periods and in relation to contemporary silvicultural methods, it is possible to discern the impact of forest management, to understand the drivers of the long-term changes in managed forest, and it also allows for a more educated discussion on today’s forest management. 相似文献
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Failure of predator conditioning: an experimental study of predator avoidance in brown trout (Salmo trutta) 
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下载免费PDF全文 Many studies have documented that hatchery‐reared salmonids generally have inferior survival after being stocked compared with wild conspecifics, hatchery and wild salmonids have been observed to differ in their antipredator responses. The response of brown trout (Salmo trutta) juveniles (0+) of differing backgrounds to a live predator was compared in two experiments. First, the antipredator behaviour of predator‐naïve hatchery‐reared brown trout and wild‐exposed brown trout were assessed in behavioural trials which lasted for eight days. Second, predator‐naïve and predator‐conditioned hatchery‐reared brown trout were assessed in identical behavioural trials. Brown trout were ‘predator‐conditioned’ by being held in a stream‐water aquarium with adult Atlantic salmon (Salmo salar) and adult brown trout for two days prior to behavioural trials. Predator‐conditioned hatchery‐reared brown trout spent more time in shelters in the trial aquaria than predator‐naïve hatchery‐reared fish, but did not differ in time spent in the predator‐free area. Predator conditioning may account for the increased time spent in the shelter, but does not appear to have affected time spent in the predator‐free area. However, even if significant alteration in behaviour can be noted in the laboratory, the response might not be appropriate in the wild. 相似文献