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Enefalk, Å. & Bergman, E. (2016). Effect of fine wood on juvenile brown trout behaviour in experimental stream channels. Ecology of Freshwater Fish, 25(4), 664-673.
Open this publication in new window or tab >>Effect of fine wood on juvenile brown trout behaviour in experimental stream channels
2016 (English)In: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 25, no 4, p. 664-673Article in journal (Refereed) Published
Abstract [en]

In-stream wood can increase shelter availability and prey abundance for stream-living fish such as brown trout, Salmo trutta, but the input of wood to streams has decreased in recent years due to harvesting of riparian vegetation. During the last decades, fine wood (FW) has been increasingly used for biofuel, and the input of FW to streams may therefore decrease. Although effects of in-stream FW have not been studied as extensively as those of large wood (LW), it is probably important as shelter for small-sized trout. In a laboratory stream experiment, we tested the behavioural response of young-of-the-year wild brown trout to three densities of FW, with trout tested alone and in groups of four. Video recordings were used to measure the proportion of time allocated to sheltering, cruising and foraging, as well as the number of aggressive interactions and prey attacks. Cruising activity increased with decreasing FW density and was higher in the four-fish groups than when fish were alone. Foraging decreased and time spent sheltering in FW increased with increasing FW density. Our study shows that juvenile trout activity is higher in higher fish densities and that trout response to FW is related to FW density and differs from the response to LW as reported by others. © 2015 John Wiley & Sons A/S.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keyword
salmonid; YOY; streams; wood; small woody debris
National Category
Ecology Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-42488 (URN)10.1111/eff.12244 (DOI)000388307300015 ()2-s2.0-84938718603 (Scopus ID)
Available from: 2016-05-27 Created: 2016-05-23 Last updated: 2017-12-06Bibliographically approved
Enefalk, Å. & Bergman, E. (2016). Effects of fine wood on macroinvertebrate drift in four boreal forest streams. Hydrobiologia, 765(1), 317-327.
Open this publication in new window or tab >>Effects of fine wood on macroinvertebrate drift in four boreal forest streams
2016 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 765, no 1, p. 317-327Article in journal (Refereed) Published
Abstract [en]

Most studies of stream wood have focused on pieces a parts per thousand yen0.1 m diameter. However, this approach may overlook an important feature of small streams, where wood < 0.1 m can constitute the majority of wood pieces. We examined the effect of fine wood (FW) on local drift of stream macroinvertebrates. The study was carried out at seven sites in four boreal forest streams, from early June to mid-August 2011. This was done by anchoring bundles of FW at each site and measuring drift upstream and downstream of each bundle. We hypothesized that FW would increase drift density, biomass and diversity of aquatic invertebrates. Ten weeks after FW addition, aquatic drift density was higher downstream than upstream of FW bundles, while drift biomass and drift diversity did not differ significantly downstream and upstream of FW.

Keyword
Invertebrates, Colonization, FWD, In-stream wood, Small woody debris
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-40971 (URN)10.1007/s10750-015-2423-x (DOI)000366641200022 ()
Available from: 2016-03-03 Created: 2016-03-03 Last updated: 2017-12-06Bibliographically approved
Watz, J., Bergman, E., Piccolo, J. & Greenberg, L. (2016). Ice cover affects the growth of a stream-dwelling fish. Oecologia, 181(1), 299-311.
Open this publication in new window or tab >>Ice cover affects the growth of a stream-dwelling fish
2016 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 181, no 1, p. 299-311Article in journal (Refereed) Published
Abstract [en]

Protection provided by shelter is important for survival and affects the time and energy budgets of animals. It has been suggested that in fresh waters at high latitudes and altitudes, surface ice during winter functions as overhead cover for fish, reducing the predation risk from terrestrial piscivores. We simulated ice cover by suspending plastic sheeting over five 30-m-long stream sections in a boreal forest stream and examined its effects on the growth and habitat use of brown trout (Salmo trutta) during winter. Trout that spent the winter under the artificial ice cover grew more than those in the control (uncovered) sections. Moreover, tracking of trout tagged with passive integrated transponders showed that in the absence of the artificial ice cover, habitat use during the day was restricted to the stream edges, often under undercut banks, whereas under the simulated ice cover condition, trout used the entire width of the stream. These results indicate that the presence of surface ice cover may improve the energetic status and broaden habitat use of stream fish during winter. It is therefore likely that reductions in the duration and extent of ice cover due to climate change will alter time and energy budgets, with potentially negative effects on fish production.

Place, publisher, year, edition, pages
Berlin Heidelberg: Springer Berlin/Heidelberg, 2016
Keyword
Climate change, Energy budget, Global warming, Salmonid, Winter
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-39125 (URN)10.1007/s00442-016-3555-z (DOI)000374564000026 ()26787075 (PubMedID)
Available from: 2016-01-25 Created: 2016-01-25 Last updated: 2017-12-06Bibliographically approved
Nyqvist, D., Calles, O., Bergman, E., Hagelin, A. & Greenberg, L. (2016). Post-Spawning Survival and Downstream Passage of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: Is There Potential for Repeat Spawning?. Rivers Research and Applications: an international journal devoted to river research and management, 32(5), 1008-1017.
Open this publication in new window or tab >>Post-Spawning Survival and Downstream Passage of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: Is There Potential for Repeat Spawning?
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2016 (English)In: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 32, no 5, p. 1008-1017Article in journal (Refereed) Published
Abstract [en]

Repeat salmonid spawners may make large contributions to total recruitment and long term population stability. Despite their potential importance, relatively little is known about this phase of the life history for anadromous populations, and nothing has been reported for landlocked populations. Here, we studied post-spawning behaviour and survival of landlocked Atlantic salmon in relation to downstream dam passage in the River KlarÀlven, Sweden. Eight hydropower stations separate the feeding grounds in Lake VÀnern from the spawning grounds in the River KlarÀlven, and no measures to facilitate downstream migration are present in the river. Forty-nine percent of the salmon survived spawning and initiated downstream migration. Females and small fish had higher post-spawning survival than males and large fish. The post-spawners migrated downstream in autumn and spring and remained relatively inactive in the river during winter. Downstream migration speed in the free flowing part of the river was highly variable with a median of 9.30km/day. Most fish passed the first hydropower station via upward-opening spill gates after a median residence time in the forebay of 25min. However, no tagged fish survived passage of all eight hydropower stations to reach Lake VÀnern. This result underscores the need for remedial measures to increase the survival of downstream migrating kelts.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keyword
migration; kelt; multiple dam passage; telemetry; hydropower; gender difference
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-42458 (URN)10.1002/rra.2926 (DOI)000378715500018 ()2-s2.0-84931843504 (Scopus ID)
Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2017-11-02Bibliographically approved
Hagelin, A., Calles, O., Greenberg, L., Piccolo, J. J. & Bergman, E. (2016). Spawning migration of wild and supplementary stocked landlocked atlantic salmon (Salmo Salar). Rivers Research and Applications: an international journal devoted to river research and management, 32(3), 383-389.
Open this publication in new window or tab >>Spawning migration of wild and supplementary stocked landlocked atlantic salmon (Salmo Salar)
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2016 (English)In: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 32, no 3, p. 383-389Article in journal (Refereed) Published
Abstract [en]

Upstream migration by adult salmonids is impeded by dams in many regulated rivers, as is the case for landlocked Atlantic salmon, Salmo salar, in the River Klarälven, Sweden. There, the salmon cannot reach the spawning grounds due to the presence of eight dams. Hence, hatchery-reared smolts are released downstream of the dams, and upstream migrating spawners are caught in a trap at the lowermost dam before transported by truck to the spawning grounds past the dams. To identify the spawning grounds and compare the behavior of wild and hatchery-reared Atlantic salmon during upstream migration and spawning, 34 wild and 28 hatchery-reared, radio-tagged Atlantic salmon were followed during their spawning migration from August to October 2011. Half (50%) of the hatchery fish, but only 11,8% of the wild fish ended up as fallbacks, i.e. they migrated past the first downstream power station, and did not spawn. A significantly higher proportion (21.4%) of hatchery- reared salmon moved in an erratic way, with several up and down stream movements, when compared to the wild salmon (5.9%). When looking at the salmon that stayed in the river (exc. fallbacks), wild individuals exhibited a holding behavior (little or no movements before presumed spawning) more often (86.7%) than the reared ones (50%). The wild salmon also held position (and presumably spawned) for longer time (25.4 days) than the reared salmon (16.1 days). Reared salmon held position, on average, 10 km further upstream than wild salmon, passing the presumed best-quality spawning habitat. The migration speed (average 17.4 km/day) between two logger stations did not differ between wild and reared fish or between sexes. Our results suggest that the reproductive success of hatchery-reared Atlantic salmon is relatively low and their capacity as supplementary spawners to the wild population in the Klarälven, is probably small.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keyword
Salmo salar, supplementary stocking, spawning, migratory behaviour, landlocked, telemetry
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-35930 (URN)10.1002/rra.2870 (DOI)000372354700014 ()
Available from: 2015-04-29 Created: 2015-04-29 Last updated: 2017-12-06Bibliographically approved
Hagelin, A., Calles, O., Greenberg, L., Nyqvist, D. & Bergman, E. (2016). The Migratory Behaviour and Fallback Rate of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: does Timing Matter?. Rivers Research and Applications: an international journal devoted to river research and management, 32(6), 1402-1409.
Open this publication in new window or tab >>The Migratory Behaviour and Fallback Rate of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: does Timing Matter?
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2016 (English)In: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 32, no 6, p. 1402-1409Article in journal (Refereed) Published
Abstract [en]

The behavior of early (June-July) and late (August-September) migrating, adult Atlantic salmon, in The River Klaralven, Sweden, was analyzed using radio telemetry. River Klaralven is a regulated river without functioning fishways, instead upstream migrating salmon are trapped and trucked past eight hydropower plants before released back to the river. We distinguished two parts of the spawning migration, that is, one part being the migration from the place where the fish was released to the spawning grounds. The other part was a holding phase on the spawning grounds with little or no movements before spawning. The late salmon spent less of their total time on holding, 36.2%, and more on migration, 63.8%, compared with early migrating salmon, which distributed their time rather evenly between migration, 47.5%, and holding, 52.5%. In total, early salmon used 30% more time migrating and 156% more time holding than late salmon. Some Atlantic salmon (Salmo salar) fell back over the hydropower plant after release and got excluded from spawning. The fallback rates of transported, tagged spawners were higher in the early than in the late group in both years. The fallback rate in 2012 was 42.8% of the early group and 15.1% in the late. In 2013, there were 51.7 % fallbacks in the early group and 3.4% in the late. The salmon fell back on average 9days after being released in 2012 and 16days in 2013. A high mean daily discharge on the day of release increased the probability of becoming a fallback. Copyright (c) 2016 John Wiley & Sons, Ltd.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keyword
Atlantic Salmon, upstream migration, fallback, spawning, behaviour, timing
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-44678 (URN)10.1002/rra.3007 (DOI)000379952900023 ()
Available from: 2016-08-12 Created: 2016-08-12 Last updated: 2017-12-06Bibliographically approved
Jones, D. A., Bergman, E. & Greenberg, L. (2015). Food availability in spring affects smolting in brown trout (Salmo trutta). Canadian Journal of Fisheries and Aquatic Sciences, 72(11), 1694-1699.
Open this publication in new window or tab >>Food availability in spring affects smolting in brown trout (Salmo trutta)
2015 (English)In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 72, no 11, p. 1694-1699Article in journal (Refereed) Published
Abstract [en]

Prior to out-migration, salmonid fish typically undergo physiological and morphological changes-a process known as smolting. This study indicates that smolting in brown trout (Salmo trutta) is affected by feeding conditions in spring immediately prior to out-migration. This conclusion was reached after experimentally testing the effect of seasonal variation in food availability on smolt status in the spring. A migratory strain of trout was administered either high or low food rations in the autumn, winter, or spring prior to release in the spring. While fish growth or condition could be affected in any season, it was spring rationing that reduced growth and growth-related variables and that caused increased smolting. Our result supports the idea that smoltification and the decision to migrate is affected by spring food availability regardless of conditions in the previous autumn or winter.

Keyword
JUVENILE ATLANTIC SALMON; PROBABILISTIC REACTION NORMS; LIFE-HISTORY PATTERNS; POPULATION-DENSITY; MIGRATORY BEHAVIOR; EARLY MATURATION; STEELHEAD TROUT; ARCTIC CHARR; SALAR SMOLTS; GROWTH
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-40686 (URN)10.1139/cjfas-2015-0106 (DOI)000364104300009 ()
Available from: 2016-02-24 Created: 2016-02-24 Last updated: 2017-11-30Bibliographically approved
Watz, J., Bergman, E., Calles, O., Enefalk, Å., Gustafsson, S., Hagelin, A., . . . Bror, J. (2015). Ice cover alters the behavior and stress level of brown trout Salmo trutta. Behavioral Ecology, 26(3), 820-827.
Open this publication in new window or tab >>Ice cover alters the behavior and stress level of brown trout Salmo trutta
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2015 (English)In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 26, no 3, p. 820-827Article in journal (Refereed) Published
Abstract [en]

Surface ice in rivers and lakes buffers the thermal environment and provides overhead cover, protecting aquatic animals from terrestrial predators. We tested if surface ice influenced the behavior (swimming activity, aggressive encounters, and number of food items eaten) and stress level (coloration of eyes and body) of stream-living brown trout Salmo trutta at temperatures of 3–4 °C in indoor experimental flumes. We hypothesized that an individual’s resting metabolic rate (RMR, as measured by resting ventilation rate) would affect winter behavior. Therefore, groups of 4 trout, consisting of individuals with high, low, or mixed (2 individuals each) RMR, were exposed to experimental conditions with or without ice cover. Ice cover reduced stress responses, as evaluated by body coloration. Also, trout in low RMR groups had a paler body color than those in both mixed and high RMR groups. Trout increased their swimming activity under ice cover, with the highest activity found in high RMR groups. Ice cover increased the number of aggressive encounters but did not influence the number of drifting food items taken by each group. In mixed RMR groups, however, single individuals were better able to monopolize food than in the other groups. As the presence of surface ice increases the activity level and reduces stress in stream-living trout, ice cover should influence their energy budgets and production. The results should be viewed in light of ongoing global warming that reduces the duration of ice cover, especially at high latitudes and altitudes.

Place, publisher, year, edition, pages
Oxford: Oxford University Press, 2015
Keyword
aggression, climate change, energy budget, metabolic rate, winter
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-35931 (URN)10.1093/beheco/arv019 (DOI)000356585100024 ()
Available from: 2015-04-29 Created: 2015-04-29 Last updated: 2017-12-06Bibliographically approved
Watz, J., Bergman, E., Piccolo, J. J. & Greenberg, L. (2015). Winter Behavior of Brown Trout: The Presence of Ice Cover Influences Activity, Stress and Growth. In: : . Paper presented at 145th Annual Meeting of the American Fisheries Society. Portland August 16-20, 2015.. American Fishery Society.
Open this publication in new window or tab >>Winter Behavior of Brown Trout: The Presence of Ice Cover Influences Activity, Stress and Growth
2015 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Predation on fish by mammals and birds may be high during winter in boreal streams, and juvenile salmonids respond by reducing their daytime activity to minimize exposure. Surface ice may offer protection from terrestrial predators, and salmonids under ice cover should spend less time on anti-predator behaviors and increase their activity. Using brown trout as a test species, these predictions were tested in laboratory and field experiments.

In an artificial laboratory stream, the presence of ice cover reduced stress and increased swimming activity, foraging and aggression. The effect of ice cover on activity was greatest for trout with high resting metabolic rates, suggesting that individual intraspecific differences in metabolism may influence the strategies used to cope with different winter conditions. In a boreal forest stream, we simulated ice by suspending plastic sheeting over five 30-m-long stretches, and trout that spent winter under this simulated ice cover grew better than trout in control stretches. These results may explain why salmonid production is high in rivers with long periods of stable ice cover and should be viewed in light of ongoing global warming.

Place, publisher, year, edition, pages
American Fishery Society, 2015
National Category
Behavioral Sciences Biology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-38056 (URN)
Conference
145th Annual Meeting of the American Fisheries Society. Portland August 16-20, 2015.
Available from: 2015-09-28 Created: 2015-09-28 Last updated: 2017-12-06Bibliographically approved
Bergman, E., Norrgård, J., Piccolo, J., Gustafsson, P., Nilsson, F. & Hart, P. (2014). Atlantic salmon and brown trout in Lake Vänern: A proposal for a co-management system. Aquatic Ecosystem Health & Management, 17(4), 365-373.
Open this publication in new window or tab >>Atlantic salmon and brown trout in Lake Vänern: A proposal for a co-management system
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2014 (English)In: Aquatic Ecosystem Health & Management, ISSN 1463-4988, E-ISSN 1539-4077, Vol. 17, no 4, p. 365-373Article in journal (Refereed) Published
Abstract [en]

Co-management is of increasing interest for fisheries management. We explore possibilities for, and barriers to, developing a co-management system, using threatened populations of landlocked Atlantic Salmon and Brown Trout as examples. Good management of natural resources requires not only knowledge about the resource but also suitable tools to collect information and make decisions. In large ecosystems this can be difficult because many actors are involved, and various societal borders and traditions become barriers. Vänern is the largest lake in the EU and it holds several distinct populations of large-bodied landlocked Atlantic Salmon and Brown Trout. The lake is used for commercial, subsistence, and sport fishing as well as for other recreational activities, and in Klarälven, the largest river entering Vänern, sport fishing is popular. These salmonid populations were at critically low levels during the 1960s, but a stocking program since then has maintained the fishery, and at least one wild stock appears to be recovering since being protected in 1993. Ecosystem users all have different needs: in the lake, sport fishermen say that catches of hatchery fish have declined, and commercial fishermen have focused on other species. In the river, wild salmon may be recovering: sport fishing is popular and an ongoing project investigates the possibilities for salmon to be able to circumvent hydro-electrical plants and reach historical Norwegian spawning areas. Not only do we lack information about the salmonids’ different life stages, we also lack a suitable socio-political organization to find sustainable solutions to the different needs of diverse user groups. We argue that a co-management system that enfranchises user groups in the Vänern-Klarälven ecosystem will improve sustainable management of wild and hatchery fish.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2014
Keyword
fishery, barriers, bi-national-ecosystems, scientists, managing authorities, stakeholder
National Category
Biological Sciences Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-34008 (URN)10.1080/14634988.2014.965119 (DOI)000346423200008 ()
Available from: 2014-10-04 Created: 2014-10-04 Last updated: 2017-08-08Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2220-1615

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