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140 results on '"Arnekleiv, Jo Vegar"'

115. Efforts to aid downstream migrating brown trout (Salmo trutta L.) kelts and smolts passing a hydroelectric dam and a spillway.

Author

Martens, K., Almeida, Pedro R., Quintella, Bernardo R., Costa, Maria J., Moore, Andrew, Arnekleiv, Jo Vegar, Kraabøl, Morten, and Museth, Jon

Abstract

The autumn and spring descent of 41 brown trout kelts (spent trout) (average total length Lt 75.9 cm) and the spring descent of 27 hatchery-reared smolts (average Lt 26.2 cm) were studied by radiotelemetry in 1993/1994 (kelts) and 1997/1998 (kelts and smolts) at the Hunderfossen dam and power plant, south-east Norway. In 1999 we studied spring descent of 48 untagged kelts by visual observations and video-monitoring at one spillway. In autumn 1993 and 1997, 62.4% and 44.0% of the tagged kelts migrated downstream to the dam at water temperatures between 0.1 and 0.8°C. During release of spillwater, the kelts gathered along the dam with limited movements. Neither smolts nor kelts used the 2 m submerged turbine shafts as a pathway to migrate downstream Hunderfossen dam. Nor did release of large amounts of deep water through spillways provide downstream migration possibilities for kelts and possibly for smolts. The majority of both smolts and kelts migrated downstream at short periods of surface water release through the spillways, indicating high importance of surface water release. The threshold value of descend of kelts at surface release was between 1 and 4 m3 s−1 which correspond to a water column between 12 and 36 cm. These findings are highly relevant regarding hydroelectric development in river systems containing iteroparous salmonid species. [ABSTRACT FROM AUTHOR]

Published
2007
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120. Does ice matter? Site fidelity and movements by Atlantic salmon (Salmo salarL.) parr during winter in a substrate enhanced river reach

Author

Linnansaari, Tommi, Alfredsen, Knut, Stickler, Morten, Arnekleiv, Jo Vegar, Harby, Atle, and Cunjak, Richard A.

Abstract

In‐stream habitat enhancement is a common remedial action in rivers where degradation/lack of suitable fish habitat can be diagnosed. However, post‐project monitoring to assess the response of the biota to modification is rare particularly during winter. We conducted in situmonitoring during the winters of 2004–2006 in the regulated Dalåa River, central Norway, in order to determine if winter habitat requirements of Atlantic salmon (Salmo salarL.) parr were realized in an enhanced (substrate and mesohabitat modification) reach. In total, 140 parr were marked with passive integrated transponder (PIT) tags and the fish were followed by carrying out active tracking surveys under variable ice conditions throughout the winter. Highest emigration (44%) occurred before ice formation started. Emigration was reduced after ice formed and was largely offset by parr re‐entering the enhanced area. Dispersal into the non‐enhanced, small substrate control area was observed only when the study reach was ice covered, and no parr were subsequently encountered in the control section after ice had melted. In the enhanced area, declining water temperature and surface ice conditions did not affect the spatial distribution of the resident salmon parr at the studied scale. Areas with ‘solid’ anchor ice precluded access for salmon parr whilst areas with ‘patchy’ anchor were used throughout the winter. Our results indicate that surface ice creates conditions that allow salmon parr to use stream habitats that otherwise provide only a limited amount of in‐stream cover. Ice processes should be taken into consideration when habitat enhancement projects are carried out and subsequently assessed for effectiveness. Copyright © 2008 John Wiley & Sons, Ltd.

Published
2009
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138. Hydropeaking Effects on Riverine Benthic Invertebrate Fauna Composition and Drift

Author

Sollien, Vegard Pedersen, Arnekleiv, Jo Vegar, and Berg, Ole Kristian

Subjects
Biologi, Økologi, atferd, evolusjon og biosystematikk, sense organs
Abstract

In earlier studies, changes have been detected in the composition of the lotic benthic macroinvertebrate fauna as a consequence of hydropeaking. Rapid fluctuations in discharge lead to sudden dewatering of river bed area when discharge drops. Stranding of organisms is a well known consequence of dewatering. But also in the water column, hydropeaking leads to frequent changes in the habitats. In rivers, where stranding in greater or lesser extent always occurs with rapid discharge fluctuations, it may be difficult to distinguish whether the observed changes in invertebrate fauna is caused by the stranding, or if other factors play a role as well. An experiment was therefore performed with rapid discharge fluctuations in a setup with semi-natural stream channels in Paltamo, Finland, where dewatering of the river bed was eliminated. The stream channels were kept under two different discharge regimes in both a winter and a summer experimental period. Abiotic factors and total water flow throughout the experimental periods was identical for each of the stream channels. Hence, we could test if rapid discharge fluctuations without dewatering changed the benthic macroinvertebrate density, diversity and drift. The study revealed no significant changes in the total density of benthic macroinvertebrates or for the density within the taxonomic groups. Small indications of changes within individual groups could be observed, though. Drift samples show the same indication of changes in some lower taxonomic levels, but mostly no changes were detectable. This is consistent with earlier studies in which it have been shown that drift densities of macroinvertebrates are higher immediate after a peaking operation. The results from this study imply along with the earlier findings that the major challenges for the lotic fauna under a hydropeaking discharge regime are dewatering and stranding.

Published
2015

139. The effect of hydropeaking on density, diversity and species richness of mayflies (Ephemeroptera) and stoneflies (Plecoptera) in two river systems

Author

Herland, Anne Karine, Arnekleiv, Jo Vegar, and Norges teknisk-naturvitenskapelige universitet, Fakultet for naturvitenskap og teknologi, Institutt for biologi

Subjects
Økologi, ntnudaim:6810, MBI Biologi, 6810 [ntnudaim]
Abstract

Hydropeaking corresponds to the management of hydropower resources where electricity is produced in accordance with prices and demand. Although fully justified economically, hydropeaking may have adverse consequences for the aquatic ecosystem. Due to frequent and rapid fluctuations in water discharge hydropeaking could generate negative effects on the ecosystem downstream the outlet of the hydropower station. Frequent fluctuations in water discharge, altered temperature regime, substrate composition and vegetation cover can result in reduced macroinvertebrate density and variety downstream the outlet of hydropower stations. Furthermore, macroinvertebrates inhabiting the shallow zone could be exposed to stranding as a consequence of frequent dewatering of the river-margin.In order to provide environmental guidelines for the hydropower industry, it is essential to understand how changes brought upon hydropeaked rivers affect the aquatic ecosystem.We studied the effect of hydropeaking on the total macroinvertebrate density and on the density, diversity and species richness of the orders Ephemeroptera and Plecoptera in two hydropeaked rivers, the Bævra River and the Lundesokna River, in central Norway. Findings from the given study demonstrated negative effects on the macroinvertebrates, likely caused by hydropeaking. The results showed a lowered total density and a lowered density, diversity and species richness of Ephemeroptera and Plecoptera in the locations exposed to frequent dewatering. In the permanently water covered location, however, there was less indication of a hydropeaking effect. These findings suggest that hydropeaking prevent establishment of normal benthic macroinvertebrate communities in the exposed shallow location, while the macroinvertebrate fauna in the permanently water covered location are less affected.

Published
2012

140. Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar).

Author

Otero J, L'Abée-Lund JH, Castro-Santos T, Leonardsson K, Storvik GO, Jonsson B, Dempson B, Russell IC, Jensen AJ, Baglinière JL, Dionne M, Armstrong JD, Romakkaniemi A, Letcher BH, Kocik JF, Erkinaro J, Poole R, Rogan G, Lundqvist H, Maclean JC, Jokikokko E, Arnekleiv JV, Kennedy RJ, Niemelä E, Caballero P, Music PA, Antonsson T, Gudjonsson S, Veselov AE, Lamberg A, Groom S, Taylor BH, Taberner M, Dillane M, Arnason F, Horton G, Hvidsten NA, Jonsson IR, Jonsson N, McKelvey S, Naesje TF, Skaala O, Smith GW, Saegrov H, Stenseth NC, and Vøllestad LA

Subjects
Animals, Chlorophyll analysis, Chlorophyll A, Oceans and Seas, Rivers, Temperature, Time Factors, Animal Migration, Climate Change, Salmo salar physiology
Abstract

Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater ('parr') stage to the migratory stage where they descend streams and enter salt water ('smolt') is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes., (© 2013 John Wiley & Sons Ltd.)

Published
2014
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