Low Success Rate in Re-Establishing European Perch in Some Highly Acidified Lakes in Southernmost Norway     

Trygve Hesthagen  Hans M. Berger  Ann Kristin Lien Schartau  Terje Nøst  Randi Saksgård  Leidulf Fløystad 《Water, air, and soil pollution》2001,130(1-4):1361-1366

In order to test whether major reductions in acid inputs had improved water quality sufficiently for fish populations to recover, we stocked wild European perch (Perca fluviatilis) in three highly acidified lakes that had previously supported this species, and in one limed lake. The fish, which were introduced from a local lake (donor lake), generally ranged from 12 to 16 cm in total length, and were stocked at densities of 117–177 fish ha^?1. The untreated lakes were highly acid, with minimum pH values and maximum inorganic aluminium concentrations (Al_i) during the spring of 4.6–4.7 and 118–151 µg L^?1 respectively. In the limed lake, the corresponding values for pH and Al_i ranged between 5.8 and 6.6 and 5 and 19 µg L^?1 respectively. Gill-netting in two subsequent years after the introduction yielded only a few recruits (0+) and one adult in one of the three acidified lakes in one year only. However, stocked perch reproduced successfully in both years in the limed lake. There was a significant linear relationship between the catches (CPUE) of juvenile perch (age 0+) in the different lakes in the autumn and the water quality in May (time of hatching), both in terms of Al_i (r ²=0.934, P<0.05) and pH (r ²=0.939, P<0.05). Our data suggest unsuccessful recruitment in waters of pH <5.1 and Al_i>60 µg L^?1.  相似文献   

Landraces and folk varieties: a conceptual reappraisal of terminology   总被引：1，自引：0，他引：1  

Trygve Berg 《Euphytica》2009,166(3):423-430

Farmers’ seeds are most often lumped together in one broad category called ‘landraces’. But such a category covers variety types that reflect different levels of farmer involvement. Those differences matters when we discuss such issues as genetic erosion, on-farm conservation and seed related policies. The term landrace can be traced to the time when ‘modern’ varieties of cereals were introduced to European farmers in the late nineteenth century. The farmers’ varieties of the time were called ‘landraces’ and understood as seeds adapted to local growing conditions through natural adaptation usually with no intentional selection. But the term was quickly adopted as generic for all farmers’ varieties including those that are bred and maintained by active seed selection on-farm. Such farmer-bred varieties are better termed ‘folk varieties’. The article discusses how interaction of crop characteristics and developing technologies resulted in the evolution of crop varieties as either landraces or folk varieties. It is argued that vulnerability to different agents of genetic erosion and feasibility of on-farm conservation are clearly different for the two categories of farmers’ varieties. Likewise seed policies, particularly the issue of Farmers’ Rights would benefit from clarity of type of farmers’ varieties.  相似文献   

Dynamics of low-temperature acclimation in temperate and boreal conifer foliage in a mild winter climate     

Strimbeck GR  Kjellsen TD  Schaberg PG  Murakami PF 《Tree physiology》2008,28(9):1365-1374

To provide baseline data for physiological studies of extreme low-temperature (LT) tolerance in boreal conifers, we profiled LT stress responses, liquid nitrogen (LN(2))-quench tolerance, and sugar concentrations in foliage of boreal-temperate species pairs in the genera Abies, Picea and Pinus, growing in an arboretum in a temperate oceanic climate from August 2006 through April 2007. The boreal species acclimated more rapidly and deeply than the temperate species, acquiring LN(2)-quench tolerance by late November, despite unusually warm conditions throughout the autumn and early winter. Maximum LT tolerance in the temperate species was in the -25 to -35 degrees C range, and was reached only after a period of freezing temperatures in late January and February. During LT acclimation in the temperate species, sigmoid temperature-relative electrolyte leakage (REL) curves shifted toward lower temperatures, whereas in boreal species there was both a temperature shift and a lowering of the maximum REL until it fell below a threshold associated with irreversible injury. These differences may reflect differences in mechanisms of LT acclimation and LT tolerance. The concentrations of total and individual sugars did not show a clear pattern that could differentiate the boreal and temperate groups. Raffinose and, in three of the six species, stachyose showed the closest association with LT tolerance. Sugar concentrations, principally sucrose, decreased during mild weather, perhaps because of respiratory losses or phloem export, and increased after periods of freezing temperatures. Low-temperature acclimation in boreal species appears to follow a rigid program that may affect their ability to avoid excessive respiratory losses in the event of continued climate warming in boreal regions.  相似文献   

Selection experiments with salmon: I. Differences in resistance to vibrio disease of salmon parr (Salmo salar)     

Trygve Gjedrem  Dag Aulstad 《Aquaculture (Amsterdam, Netherlands)》1974,3(1):51-59

The research facilities at the fish experimental station at Sunndalsöra are described. The design of a selection experiment with salmon and sea trout is presented. The station is also used for other purposes, such as investigations into nutrition, pathology and environmental factors.In this paper analyses of observed differences to vibrio disease (Vibrio anguillarum) are reported. Significant differences in resistance between river strains of salmon parr were found. The difference between localities are supposed to be partly heritable.The data were also used to estimate the heritability on an intra-river basis. The estimates were 0.12 and 0.07 based on the sire and dam component, respectively. It is concluded that selection against vibrio disease will result in genetic change.  相似文献   

Possibilities for genetic gain in salmonids     

Trygve Gjedrem 《Aquaculture (Amsterdam, Netherlands)》1975,6(1):23-29

A review of the literature concerning phenotypic and genetic parameters for economic production traits in salmonids show that very few estimates are available. However, based on the present knowledge the possibilities for genetic gain in, for example, growth rate are extremely good even if conservative estimates are considered. The high genetic gain may be obtained primarily because of high fertility, a large phenotypic variance and a moderate length of the generation interval. There is a great need to start selection in order to get a more productive animal which is better adapted to captivity.  相似文献   

Survival of Arctic char in the sea during fall and winter     

Trygve Gjedrem 《Aquaculture (Amsterdam, Netherlands)》1975,6(2):189-190

Arctic char which were kept in floating nets in the sea during summer showed a very high death rate in early fall.  相似文献   

DIAGNOSTIC ULTRASOUND EXAMINATION AND ECHOCARDIOGRAPHY IN ATLANTIC SALMON (Salmo salar)     

Ronald D.  Sande  DVM  PhD  Trygve T.  Poppe  DVM  Dr. Scient 《Veterinary radiology & ultrasound》1995,36(6):551-558

Diagnostic ultrasound examination was performed on 53 mature, tranquillized, Atlantic salmon. Wild fish and farmed fish were equally represented. The purpose was to find a rapid method of examination that could be used to identify and separate fish with cardiomyopathy syndrome while fish are tranquillized for other procedures. Three methods of examination were studied. The non-elastic pericardium and absence of lungs results in cardiac function which is clearly different from that in mammals. M-mode echocardiography was complex, technical and time consuming and calculated fractional shortening was not reliable. Subjective evaluation of the heart and liver was valuable and easy to perform. Measurement of the transverse dimension of the atrium and ventricle on a ventro-dorsal axis through the cranial limit of the A-V valve gave acceptable objective data for comparison of the ventricular and atrial size. Diagnostic ultrasound is both practical and valuable for the clinical study of disease in fish.  相似文献   

Increased abundance of European eel (Anguilla anguilla) in acidified Norwegian rivers after liming          下载免费PDF全文

Bjørn M. Larsen  Trygve Hesthagen  Eva B. Thorstad  Ola H. Diserud 《Ecology of Freshwater Fish》2015,24(4):575-583

The prevalence and abundance (density 100 m^?2) of European eel (Anguilla anguilla) were studied by means of electrofishing in 13 acidified rivers in Norway that had been limed to restore acceptable water quality for Atlantic salmon (Salmo salar). Status of Atlantic salmon in these rivers varied prior to liming, from being entirely lost in six highly acidified rivers and in different stages of decline in seven less acidified rivers. Four of the rivers are heavily affected by hydropower development. The abundance and prevalence of European eel increased significantly during the study period. The best model for predicting eel abundance was that with four explanatory variables: time after liming, time after liming squared, status of salmon stocks and hydropower regulation. The eel density was expected to increase by a factor of almost 5 after 10 years of liming. The model also predicts that a river with a formerly reduced Atlantic salmon stock has a 2.8 times higher density of eel than rivers with formerly lost salmon stocks. Before liming, European eel were on average recorded at 15 and 41% of the sampling stations in rivers with formerly lost and reduced Atlantic salmon populations, respectively, increasing to 49 and 68% in individual rivers, respectively, after 10 years of liming. The recovery of European eel in these formerly acidified rivers by means of liming took place during the same period as their abundance declined in other parts of their distribution area in Norway and elsewhere in Europe.  相似文献   

Methyl jasmonate treatment of mature Norway spruce (Picea abies) trees increases the accumulation of terpenoid resin components and protects against infection by Ceratocystis polonica, a bark beetle-associated fungus     

Zeneli G  Krokene P  Christiansen E  Krekling T  Gershenzon J 《Tree physiology》2006,26(8):977-988

When conifers such as Picea abies Karst. (Norway spruce) are attacked by insects or pathogens, they often respond by producing increased quantities of terpenoid oleoresin. This response can be mimicked in young P. abies seedlings by treatment with methyl jasmonate (MJ). In this study, we determined the effects of MJ on terpenoids and other chemical defenses of mature P. abies, and investigated whether this treatment protected trees against attack by the blue-stain fungus Ceratocystis polonica (Siem.) C. Moreau, the most important fungal associate of the spruce bark beetle Ips typographus L. Methyl jasmonate treatment induced the formation of traumatic resin ducts in the developing xylem, enhanced resin flow and stimulated increased accumulation of monoterpenes, sesquiterpenes and diterpene resin acids. However, only minor changes were detected in terpene composition in response to MJ treatment and no changes in soluble phenolic concentration were measured. There was much variability in the timing and degree of response to MJ among clones. The observed chemical and anatomical changes in response to MJ treatment were correlated with increased resistance to C. polonica, suggesting that terpenoid oleoresin may function in defense against this pathogen.  相似文献   

Recovery of Young Brown Trout in Some Acidified Streams in Southwestern and Western Norway     

Trygve Hesthagen  Torbjørn Forseth  Randi Saksgård  Hans M. Berger  Bjørn M. Larsen 《Water, air, and soil pollution》2001,130(1-4):1355-1360

Temporal changes in densities of young brown trout (Salmo trutta), mainly of age 0+, and in water quality (pH and alkalinity) were assessed by means of electrofishing in lake tributaries in three acidic, software watercourses in western and southwestern Norway; Gaular and Vikedal (1987–1999) and Bjerkreim (1988–1999). Approximately 74 sites were sampled each year. Most of the streams were acidic with mean annual pH levels between 5.1–5.9. Alkalinity and pH increased significantly in all three areas during the study period. Brown trout fry densities increased significantly during the period in Vikedal and Bjerkreim. Also in Gaular, the density of young brown trout has exhibited a positive trend in recent years. We suggest that the increase in the density of young brown trout is because the study areas have became less acidified during recent years due to reduction in sulphate deposition.  相似文献