The distribution of the amphipod Gammarus lacustris on the Hardangervidda mountain plateau was ma... more The distribution of the amphipod Gammarus lacustris on the Hardangervidda mountain plateau was mapped by screening published data from 245 lakes in 11 and 16 catchments in western and central/eastern areas, respectively. These data are primarily based on stomach analyses of brown trout Salmo trutta. In central/eastern areas, G. lacustris was recorded in 79% of all the lakes examined, while there are only two former records (4%) in the western area. The distribution pattern of G. lacustris on Hardangervidda appears to be related to environmental conditions. The apparent absence of G. lacustris in the western area may be explained by a combined effect of cold water due to higher deposits of snow and water with low ionic strength as a consequence of its bedrock of Precambrian gneisses and granites with little or no moraine cover. However, lakes in central/eastern areas sustain G. lacustris in spite of dilute water, as G. lacustris has been recorded in 89 lakes of which 28% had calcium ...
Fish community feeding and production rates may differ between lakes despite similar fish biomass... more Fish community feeding and production rates may differ between lakes despite similar fish biomass levels because of differences in size structure and local temperature. Therefore, across‐lake comparisons of the strength and direction of top‐down and bottom‐up fish–phytoplankton relationships should consider these factors. We used the metabolic theory of ecology to calculate size‐ and temperature‐corrected community energy demand (CEDom) and community production (CP) of omnivorous fishes in 227 European lakes from major habitat types (MHTs) of polar freshwaters, temperate floodplain rivers and wetlands, and temperate coastal rivers. We related CEDom with total phosphorus (TP)‐corrected chlorophyll a (Chl a) concentrations to evaluate a potential top‐down directed trophic cascade from fish to phytoplankton. Furthermore, we related Chl a with CP to demonstrate potential bottom‐up effects of phytoplankton on fish. For both analyses, we added the CED of piscivorous fishes (CEDpi) as a predictor to account for potential predation effects on the omnivorous fish community. CEDom was weakly positively related with TP‐corrected Chl a, but the strength of the relationship differed between MHTs. In contrast, CP was consistently positively related with Chl a in the entire dataset. CEDpi did not contribute to top‐down or bottom‐up relationships. The application of metabolic variables characterizing fish community feeding and production rates makes these results robust because the approach accounted for the usually neglected effects of fish size and temperature in across‐lake comparisons. Our results suggest that bottom‐up effects from phytoplankton on fish secondary production in lakes are substantially stronger than top‐down effects from fish on phytoplankton biomass.
Non-native brook trout (Salvelinus fontinalis MITCHILL, 1815) was introduced into Norway in 1883.... more Non-native brook trout (Salvelinus fontinalis MITCHILL, 1815) was introduced into Norway in 1883. However, it was not until the late 1970s that this acid-tolerant salmonid species was stocked into many acidified lakes that many populations became established. In 2004, all brook trout stocking in Norway ceased. In this study, we surveyed the distribution of brook trout in Norwegian water bodies. A totally of 202 self-sustaining populations were identified, mostly in unregulated lakes (n=101), streams (n=71) and also to some extent in reservoirs (n=25). Only four populations were found in inland rivers, and one population in a river with Atlantic salmon (Salmo salar L.). Localities with brook trout covered a wide range of altitudes and sizes. Analyses of time-series catches in sympatric populations of brown trout (Salmo trutta L.) and brook trout from 12 lakes (1997-2012) revealed a strong decline in brook trout stocks. A similar development in abundance has also emerged from other st...
The Arctic tadpole shrimp Lepidurus arcticus has a circumpolar distribution where the Hardangervi... more The Arctic tadpole shrimp Lepidurus arcticus has a circumpolar distribution where the Hardangervidda mountain plateau in Norway marks its southernmost limit. Within this area, we searched for L. arcticus in 238 lakes in 27 catchments. On Hardangervidda, the distribution pattern of L. arcticus is highly skewed. In the 16 catchments located in the central and eastern parts, L. arcticus was recorded in 70% of all the lakes studied (n=191). The remaining 11 catchments located in western areas, are almost free of lakes with L. arcticus (n=47). The most striking difference between these two areas is the significantly higher level of snow deposition in the western areas. This delays the ice break-up, which results in lower water temperatures and a shorter growing season. The water of lakes in western areas (N=36) is also more dilute than those in the central and eastern areas (N=201), with mean calcium concentrations of 0.81±0.48 and 1.62±1.12 mg L-1, respectively. In the lakes in the cent...
Rapporten presenterer resultater fra 2004 og trender gjennom tid for overvåking av luft, vann, og... more Rapporten presenterer resultater fra 2004 og trender gjennom tid for overvåking av luft, vann, og akvatisk biologi (krepsdyr, bunndyr og fisk) under overvåkingsprogrammet “Overvåking av langtransportert forurenset luft og nedbør”. The report presents results for 2004 from the national monitoring programmes on long-range transboundary air pollution
In this paper we document the effects of acidification on fish populations in lakes in Sør-Varang... more In this paper we document the effects of acidification on fish populations in lakes in Sør-Varanger near the Russian border in northern Norway. We used questionnaires in order to assess the current status and distribution of different fish species, and conducted test-fishing to determine relative abundance (CPUE-T) and age structure. Acidification of surface waters in this area is due to
Det var knyttet spenning til seminaret om fortidens fjellfiske som ble holdt ved Fjellmuseet i Lo... more Det var knyttet spenning til seminaret om fortidens fjellfiske som ble holdt ved Fjellmuseet i Lom 3.–4. juni 2015. Aldri før hadde et bredt utvalg av kultur- og naturhistorikere møttes for å diskutere dette temaet. Hva ville det komme ut av et slikt møte mellom fagfolk med helt ulike tilnærminger og utgangspunkt? Tanken om et seminar hadde dukket opp to år tidligere i forbindelse med arkeologiske undersøkelser i fjellvannet Tesse i Jotunheimen. Denne innsjøen er rik på arkeologiske funn, men også velstudert av biologer. I tillegg er det sjeldne historiske kilder knyttet til vannet. Samlet var det altså mye kunn-skap om fortidens fiske i vannet, men kunnskapen var spredt på ulike fag og flere fagmiljøer. Gjennom seminaret og denne boken har målet vært å samle kunnskap og stimulere til ny forskning. Det har også vært et mål å skape økt oppmerksomhet om fjellfiske og tilgjengeliggjøre kunnskapen for forskere og et bredere publikum. Seminaret og bokutgivelsen hadde ikke vært mulig uten velvilje fra Riksantikvaren, samarbeid med og økonomisk støtte fra Oppland fylkes kommune og midler fra Norsk arkeologisk selskap. Prosjektet hadde heller ikke latt seg gjennomføre uten bidrag fra Norsk Maritimt Museum og Kulturhistorisk museum. Det må også rettes en spesiell takk til Norsk Fjellmuseum i Lom, som var vertskap for seminaret, og som har vært en betydningsfull administrativ støttespiller. Til slutt må også foredragsholdere og artikkelforfattere takkes. Uten deres innsats ville det ha eksistert mindre kunnskap om fjellfiske i fortiden. Oslo, 1. juni 2016 Axel Mjærum og Elling Utvik Wamme
The distribution of the amphipod Gammarus lacustris on the Hardangervidda mountain plateau was ma... more The distribution of the amphipod Gammarus lacustris on the Hardangervidda mountain plateau was mapped by screening published data from 245 lakes in 11 and 16 catchments in western and central/eastern areas, respectively. These data are primarily based on stomach analyses of brown trout Salmo trutta. In central/eastern areas, G. lacustris was recorded in 79% of all the lakes examined, while there are only two former records (4%) in the western area. The distribution pattern of G. lacustris on Hardangervidda appears to be related to environmental conditions. The apparent absence of G. lacustris in the western area may be explained by a combined effect of cold water due to higher deposits of snow and water with low ionic strength as a consequence of its bedrock of Precambrian gneisses and granites with little or no moraine cover. However, lakes in central/eastern areas sustain G. lacustris in spite of dilute water, as G. lacustris has been recorded in 89 lakes of which 28% had calcium ...
Fish community feeding and production rates may differ between lakes despite similar fish biomass... more Fish community feeding and production rates may differ between lakes despite similar fish biomass levels because of differences in size structure and local temperature. Therefore, across‐lake comparisons of the strength and direction of top‐down and bottom‐up fish–phytoplankton relationships should consider these factors. We used the metabolic theory of ecology to calculate size‐ and temperature‐corrected community energy demand (CEDom) and community production (CP) of omnivorous fishes in 227 European lakes from major habitat types (MHTs) of polar freshwaters, temperate floodplain rivers and wetlands, and temperate coastal rivers. We related CEDom with total phosphorus (TP)‐corrected chlorophyll a (Chl a) concentrations to evaluate a potential top‐down directed trophic cascade from fish to phytoplankton. Furthermore, we related Chl a with CP to demonstrate potential bottom‐up effects of phytoplankton on fish. For both analyses, we added the CED of piscivorous fishes (CEDpi) as a predictor to account for potential predation effects on the omnivorous fish community. CEDom was weakly positively related with TP‐corrected Chl a, but the strength of the relationship differed between MHTs. In contrast, CP was consistently positively related with Chl a in the entire dataset. CEDpi did not contribute to top‐down or bottom‐up relationships. The application of metabolic variables characterizing fish community feeding and production rates makes these results robust because the approach accounted for the usually neglected effects of fish size and temperature in across‐lake comparisons. Our results suggest that bottom‐up effects from phytoplankton on fish secondary production in lakes are substantially stronger than top‐down effects from fish on phytoplankton biomass.
Non-native brook trout (Salvelinus fontinalis MITCHILL, 1815) was introduced into Norway in 1883.... more Non-native brook trout (Salvelinus fontinalis MITCHILL, 1815) was introduced into Norway in 1883. However, it was not until the late 1970s that this acid-tolerant salmonid species was stocked into many acidified lakes that many populations became established. In 2004, all brook trout stocking in Norway ceased. In this study, we surveyed the distribution of brook trout in Norwegian water bodies. A totally of 202 self-sustaining populations were identified, mostly in unregulated lakes (n=101), streams (n=71) and also to some extent in reservoirs (n=25). Only four populations were found in inland rivers, and one population in a river with Atlantic salmon (Salmo salar L.). Localities with brook trout covered a wide range of altitudes and sizes. Analyses of time-series catches in sympatric populations of brown trout (Salmo trutta L.) and brook trout from 12 lakes (1997-2012) revealed a strong decline in brook trout stocks. A similar development in abundance has also emerged from other st...
The Arctic tadpole shrimp Lepidurus arcticus has a circumpolar distribution where the Hardangervi... more The Arctic tadpole shrimp Lepidurus arcticus has a circumpolar distribution where the Hardangervidda mountain plateau in Norway marks its southernmost limit. Within this area, we searched for L. arcticus in 238 lakes in 27 catchments. On Hardangervidda, the distribution pattern of L. arcticus is highly skewed. In the 16 catchments located in the central and eastern parts, L. arcticus was recorded in 70% of all the lakes studied (n=191). The remaining 11 catchments located in western areas, are almost free of lakes with L. arcticus (n=47). The most striking difference between these two areas is the significantly higher level of snow deposition in the western areas. This delays the ice break-up, which results in lower water temperatures and a shorter growing season. The water of lakes in western areas (N=36) is also more dilute than those in the central and eastern areas (N=201), with mean calcium concentrations of 0.81±0.48 and 1.62±1.12 mg L-1, respectively. In the lakes in the cent...
Rapporten presenterer resultater fra 2004 og trender gjennom tid for overvåking av luft, vann, og... more Rapporten presenterer resultater fra 2004 og trender gjennom tid for overvåking av luft, vann, og akvatisk biologi (krepsdyr, bunndyr og fisk) under overvåkingsprogrammet “Overvåking av langtransportert forurenset luft og nedbør”. The report presents results for 2004 from the national monitoring programmes on long-range transboundary air pollution
In this paper we document the effects of acidification on fish populations in lakes in Sør-Varang... more In this paper we document the effects of acidification on fish populations in lakes in Sør-Varanger near the Russian border in northern Norway. We used questionnaires in order to assess the current status and distribution of different fish species, and conducted test-fishing to determine relative abundance (CPUE-T) and age structure. Acidification of surface waters in this area is due to
Det var knyttet spenning til seminaret om fortidens fjellfiske som ble holdt ved Fjellmuseet i Lo... more Det var knyttet spenning til seminaret om fortidens fjellfiske som ble holdt ved Fjellmuseet i Lom 3.–4. juni 2015. Aldri før hadde et bredt utvalg av kultur- og naturhistorikere møttes for å diskutere dette temaet. Hva ville det komme ut av et slikt møte mellom fagfolk med helt ulike tilnærminger og utgangspunkt? Tanken om et seminar hadde dukket opp to år tidligere i forbindelse med arkeologiske undersøkelser i fjellvannet Tesse i Jotunheimen. Denne innsjøen er rik på arkeologiske funn, men også velstudert av biologer. I tillegg er det sjeldne historiske kilder knyttet til vannet. Samlet var det altså mye kunn-skap om fortidens fiske i vannet, men kunnskapen var spredt på ulike fag og flere fagmiljøer. Gjennom seminaret og denne boken har målet vært å samle kunnskap og stimulere til ny forskning. Det har også vært et mål å skape økt oppmerksomhet om fjellfiske og tilgjengeliggjøre kunnskapen for forskere og et bredere publikum. Seminaret og bokutgivelsen hadde ikke vært mulig uten velvilje fra Riksantikvaren, samarbeid med og økonomisk støtte fra Oppland fylkes kommune og midler fra Norsk arkeologisk selskap. Prosjektet hadde heller ikke latt seg gjennomføre uten bidrag fra Norsk Maritimt Museum og Kulturhistorisk museum. Det må også rettes en spesiell takk til Norsk Fjellmuseum i Lom, som var vertskap for seminaret, og som har vært en betydningsfull administrativ støttespiller. Til slutt må også foredragsholdere og artikkelforfattere takkes. Uten deres innsats ville det ha eksistert mindre kunnskap om fjellfiske i fortiden. Oslo, 1. juni 2016 Axel Mjærum og Elling Utvik Wamme
(Foreløpig bare innledning, innhold, litteraturliste m.m. lagt ut her.)
Fjellfisket i Sør-Norge ... more (Foreløpig bare innledning, innhold, litteraturliste m.m. lagt ut her.)
Fjellfisket i Sør-Norge har vaert omfattende og mangfoldig i flere tusen år. I Fjellfisket i fortiden samles ny kunnskap om dette fisket i én bok, og for første gang har fagfolk fra ulike natur-og kulturhistoriske disipliner gått sammen for å belyse temaet. I elleve artikler formidles ny innsikt i fangst av ørret og andre arter i fjellet fra steinalderen til nyere tid.
Artiklene retter seg både til forskere og til et bredere publikum med interesse for fjellets kulturhistorie og for fjellfiske. I boken kan du blant annet lese om de mange fisketomme fjellvannene etter siste istid og om når, hvorfor og hvordan mennesker bar fisk til fjellheimen. Artiklene presenterer også kunnskap om gamle fiskemetoder, dem som utnyttet ressursene i vannene, og den betydning fiskefangsten hadde i fortiden.
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Papers by Trygve Hesthagen
Fjellfisket i Sør-Norge har vaert omfattende og mangfoldig i flere tusen år. I Fjellfisket i fortiden samles ny kunnskap om dette fisket i én bok, og for første gang har fagfolk fra ulike natur-og kulturhistoriske disipliner gått sammen for å belyse temaet. I elleve artikler formidles ny innsikt i fangst av ørret og andre arter i fjellet fra steinalderen til nyere tid.
Artiklene retter seg både til forskere og til et bredere publikum med interesse for fjellets kulturhistorie og for fjellfiske. I boken kan du blant annet lese om de mange fisketomme fjellvannene etter siste istid og om når, hvorfor og hvordan mennesker bar fisk til fjellheimen. Artiklene presenterer også kunnskap om gamle fiskemetoder, dem som utnyttet ressursene i vannene, og den betydning fiskefangsten hadde i fortiden.
isbn 978-82-8314-078-1