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1.
T. Hesthagen H. M. Berger B. M. Larsen R. Saksgård 《Water, air, and soil pollution》1995,85(2):641-646
The Norwegian Monitoring Programme for Long-Range Transported Air Pollutants started in 1980. The biological part of this programme includes besides invertebrate studies in streams, (i) fish community status in lakes by means of interviews, test-fishing in lakes by using standard gill-net series, recruitment studies of brown trout in inland streams, and juvenile stock assess and monitoring of fish kills in salmon rivers. Damaged fish stocks are recognized within a land area of 51,500 km2 in southern Norway and 30 km2 in northern Norway. At least 6,000 lake-dwelling fish stocks have either been lost or are at various stages of reduction. Brown trout (Salmo trutta) is the most widespread and abundant species of fish in Norwegian watersheds, and is also most severe affected by acidification. More recently, there are some indications of an increase in the abundance of brown trout in some areas. However, analysis of age structure in lakes, and fry densities in streams in such areas revealed large annual variations in recruitment rate, which indicates unstable water chemical conditions. Atlantic salmon (Salmo salar) is virtually extinct in 25 rivers in southernmost, southwestern and western Norway. 相似文献
2.
T. Hesthagen & L. Flòystad O. Hegge M. Staurnes J. Skurdal 《Fisheries Management and Ecology》1999,6(1):47-61
Wild and non-native hatchery-reared brown trout, Salmo trutta L., released when 2 summers old, were caught in the littoral habitat of Vinstervatna Reservoir, southern Norway. Hatchery-reared brown trout grew more slowly and had a smaller asymptotic length (293 ± 71 mm CL) than native fish (391 ± 56 mm CL). Hatchery-reared brown trout also exhibited significantly shorter life spans than native fish. This category consisted mainly of individuals aged 2+ and 3+ years, and only 1.5% of the specimens were aged ≥5 years. The ages of the native fish in the sample were between 2 and 8 years, and the most abundant age groups of trout were 4+ and 5+ years. It is suggested that the differences in life-history characteristics are related to adaptations by the native trout to the local environmental conditions. In this reservoir, which has a limited food supply as a result of water level fluctuations and a high level of inter- and intraspecific competition, environmental effects might be significant. 相似文献
3.
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 (Ali) 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 Ali 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 Ali (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 Ali>60 µg L?1. 相似文献
4.
Increased abundance of European eel (Anguilla anguilla) in acidified Norwegian rivers after liming 
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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
5.
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
6.
Trygve Hesthagen 《Water, air, and soil pollution》1986,30(3-4):619-628
This paper documents population responses of Atlantic salmon and brown trout to fish kills in River Vikedal, an acidified river in SW Norway. The angling statistics show that the adult population of Atlantic salmon in the river has decreased to low numbers during recent years, whereas catches of migrant brown trout have increased in the same period. A total of 659 dead salmon and trout were either collected or observed during spring snowmelt in the years 1982–1985. Parr suffered the highest mortality, and most large specimens. Only a few dead kelts were registered. In the springs of most unfavourable water quality and most severe episods of fish kills (1983 and 1984), salmon parr mortality were significantly higher than that of brown trout. Episodic death of parr in the spring is thought to be an important cause of the reduction in the adult stock of Atlantic salmon in the river during recent years. 相似文献
7.
The Lake Fjorda water system in southern Norway consists of several lakes which exhibit a gradient in acidification. The system is inhabited by populations of brown trout, Arctic char, whitefish, perch, European minnows and Crucian carp. Populations of Arctic char, whitefish and brown trout were nearly wiped out in some of the locations, as a result of acidification, In 1985, Lake Fjorda was limed in order to improve water quality so the fish community would be recovered. Fish stock assessment by means of gill-net fishing in the epibenthic and pelagic zones was carried out before (1983) and three years after liming (1991–1993). Populations of Arctic char and whitefish have not recovered after eight years of liming. Brown trout are almost extinct and do not seem to be recovering. Perch were less affected by acidification, exhibiting good recruitment also before liming. 相似文献
8.
Bjørn Walseng Roy M. Langåker Tor E. Brandrud Pål Brettum Arne Fjellheim Trygve Hesthagen Øyvind Kaste Bjørn M. Larsen Eli-A. Lindstrøm 《Water, air, and soil pollution》2001,130(1-4):1331-1336
On a large scale, the acidified River Bjerkreim, southwestern Norway, has been treated with lime since the autumn 1996. During the Atlantic salmon (Salmon salar) smolting period pH has been above 6.2 and LAl concentrations below 10 µg L-l. Before 1996, only the western part of the watercourse harboured acid-sensitive species, such as the Atlantic salmon, snails, mayflies, daphnids and Gammarus lacustris. Prior to liming in 1996, Atlantic salmon fry (0+) and parr (≥1+) were found in 4 of 20 sampling sites, contrary to 17 (fry) and 12 (parr) in 1999. Atlantic salmon catches have increased from about 0.8 tons in 1994 to about 10 tons in 1998 and 1999. Acid-sensitive invertebrates have invaded the limed parts of the river. 相似文献
9.
Magnus Appelberg Hans -Mack Berger Trygve Hesthagen Einar Kleiven Mika Kurkilahti Jari Raitaniemi Martti Rask 《Water, air, and soil pollution》1995,85(2):401-406
The awareness of the effects of transboundary pollution has increased the necessity to use comparable methods and to initiate joint studies between countries in environmental monitoring. In freshwater fish monitoring a number of different methods have been used, strongly reducing the possibilities to comparative assessments between countries. In 1990, a workshop on freshwater fish sampling was initiated in order to develop and intercalibrate methods used in freshwater fish studies in the Nordic countries. During a three year period, a new type of multi-mesh gillnet to be used for fish monitoring in Norway, Finland and Sweden have been developed. Comparative studies and gillnet-selectivity assessments show that these new multi-mesh gillnets better describe the actual population structure of European perch (Perca fluviatilis), roach (Rutilus rutilus) and Arctic char (Salvelinus alpinus) than do the traditional gillnet series used in the Nordic countries. Ageing of fish is central in most environmental studies, however, the comparability of analyses performed at different laboratories may be low. Comparative age analyses between the three countries have been performed for a number of fish species. The results of ageing E. perch, whitefish (Coregonus sp.) and roach indicate that differences between laboratories can be reduced by intercalibration. In the future, the workgroup will be focused on a further development of joint methods within studies of freshwater fish and on joint intemordic assessments on species distribution, abundance and life history characteristics in relation to airborne pollutants and liming. 相似文献
10.
Recovery and re-establishment of Atlantic salmon, Salmo salar, in limed Norwegian rivers 总被引：1，自引：0，他引：1
A total of 21 acidified Norwegian rivers are now being limed to re‐establish or restore Atlantic salmon, Salmo salar L., stocks. Natural reproduction of Atlantic salmon was evident 1 year after the first year of liming in all rivers that had lost their native stocks (n = 9) except for one river. The density of fry (age 0+) developed significantly more rapidly in rivers that supported remnant stocks than in rivers that had lost their stocks, based on data 5 years after treatment. Nine of the study rivers were supplied with hatchery‐reared salmon, mainly unfed fry. Of the rivers with lost stocks, those which were supplied with fish had significantly higher densities than those that were not enhanced. On the other hand, rivers with remnant stocks that were supplied with fish had significantly lower densities of salmon fry than those that did not undergo such mitigation measures. In 2001, all limed rivers yielded 41.9 t of salmon. 相似文献