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Nyqvist, D., Zagars, M., Calles, O. & Comoglio, C. (2019). Behavior of trap-and-transported Atlantic salmon spawners of hatchery origin in the Daugava River system (Latvia). Journal of limnology, 78(2), 210-219
Open this publication in new window or tab >>Behavior of trap-and-transported Atlantic salmon spawners of hatchery origin in the Daugava River system (Latvia)
2019 (English)In: Journal of limnology, ISSN 1129-5767, E-ISSN 1723-8633, Vol. 78, no 2, p. 210-219Article in journal (Refereed) Published
Abstract [en]

Where migrating fish have to pass multiple dams, very high passage performance is required at the series of obstacles to avoid accumulated negative effects of multiple dam passage. In some rivers, migrating fish are trapped, transported past several obstacles, and released to continue their migration. Such trap-and-transport solutions, however, have seldom been evaluated. In the Daugava River, Latvia, several dams with no functional fishways block the river for migrating fish. A remnant Atlantic salmon population is being sustained by a sea ranching regime, where returning spawners are caught and artificially spawned, the juveniles raised in hatcheries, and smolts released in to the river in time for their seaward migration. Hatchery released fish, however, differ substantially from wild conspecifics, and in Latvia, as elsewhere throughout the range of salmon, reduced dependency on hatchery production and the re-establishment of wild salmon populations are being discussed. In the Daugava River system, suitable spawning and rearing habitat remains upstream two dams and an associated large reservoir in a mainstem tributary, the Ogre River, offering the potential to restore a wild salmon population.  To explore the potential of a trap-and-transport solution to bring Atlantic salmon spawners in contact with remaining spawning grounds in the Daugava River system, spawners were caught, radio tagged, transported upstream of the two dams and the reservoir, and released to pursue their spawning migration in the tributary. Despite being unfamiliar with the river, some of the tagged spawners moved upstream, reaching areas up to 12 km from the release sites. Males were observed higher upstream in the river compared to females, and some males were tracked relatively close to potential salmon spawning habitat. Females, although displaying some movements in the lower parts of the river, were not observed close to any suitable spawning areas, highlighting potentially important sex differences in post trap-and-transport behaviour. Perhaps due to different responses to handling stress, such low post-transportation spawning success among females has the potential to negatively impact restoration efforts in the Daugava River system and elsewhere. The present study represents a first step towards the restoration of wild Daugava salmon, one of several unique Baltic Atlantic salmon populations, and a potential model for future restoration efforts.

Place, publisher, year, edition, pages
PAGEPress, 2019
Keywords
Baltic salmon, reintroduction, fish passage, salmon migration, sex differences
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-74810 (URN)10.4081/jlimnol.2019.1871 (DOI)
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-10-14
Watz, J. (2019). Climbing the ladder: an evaluation of three different anguillid eel climbing substrata and placement of upstream passage solutions at migration barriers. Animal Conservation, 1-11
Open this publication in new window or tab >>Climbing the ladder: an evaluation of three different anguillid eel climbing substrata and placement of upstream passage solutions at migration barriers
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2019 (English)In: Animal Conservation, ISSN 1367-9430, E-ISSN 1469-1795, p. 1-11Article in journal (Refereed) Published
Abstract [en]

Conservation programmes for endangered, long-lived and migratory species often have to target multiple life stages. The bottlenecks associated with the survival of juvenile anguillid eels migrating into inland waters, the survival and growth of the freshwater life stage, as well as the recruitment and survival of silver eels, migrating back to the ocean to spawn, must be resolved. In this study, we focus on the efficiency of passage solutions for upstream migrating juveniles. Such solutions can consist of inclined ramps lined with wetted climbing substrata. We evaluated different commonly used substrata in a controlled experiment, recorded eel behaviour at the entrance of the ramp with infrared videography and validated the experimental results at a hydropower dam, where we also investigated the effects of ramp placement on performance. In the experiment on eel substratum selection, 40 % of the eels passed in lanes with studded substratum, whereas only 21 and 5 % passed using open weave and bristle substrata, respectively. Video analysis revealed that the studded substratum attracted more approaches and initiated climbs than the other substrata, but once a climb had been initiated, passage success rates did not differ between substrata. Eels using the studded substratum climbed 26 % faster than those using the bristle substratum and almost four times as fast as those climbing in the open weave. The superior performance of the studded substratum was supported by data from the field validation. Moreover, ramps positioned by the bank with low water velocities caught the most eels, but proximity to the dam had no effect on performance. To strengthen the European eel population, more juveniles need to reach their freshwater feeding grounds. A critical step to achieve this increase is to equip upstream passage solutions with suitable substrata and to optimize ramp placement at migration obstacles.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
anguillid, fishway, hydropower, migration, recruitment, passage solutions, migration obstacles
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-71418 (URN)10.1111/acv.12485 (DOI)
Funder
Swedish Research Council Formas, 2015-824
Available from: 2019-03-04 Created: 2019-03-04 Last updated: 2019-09-12Bibliographically approved
Tamario, C., Calles, O., Watz, J., Nilsson, P. A. & Degerman, E. (2019). Coastal river connectivity and the distribution of ascending juvenile European eel (Anguilla anguilla L.): Implications for conservation strategies regarding fish-passage solutions. Aquatic conservation, 29(4), 612-622
Open this publication in new window or tab >>Coastal river connectivity and the distribution of ascending juvenile European eel (Anguilla anguilla L.): Implications for conservation strategies regarding fish-passage solutions
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2019 (English)In: Aquatic conservation, ISSN 1052-7613, E-ISSN 1099-0755, Vol. 29, no 4, p. 612-622Article in journal (Refereed) Published
Abstract [en]

Many diadromous fish populations are declining and at risk of collapse. Lack of river connectivity is a major contributor to these declines, as free migration routes between marine and freshwater habitats are crucial for life-history completion. For the conservation and ultimately recovery of such species, it is imperative that remedial measures aimed at increasing connectivity are effective. This study investigated the distribution patterns of ascending juvenile European eel (Anguilla anguilla L.) in rivers in south-western Sweden, with a focus on the effects of barriers and measures that aim to reduce the impact of barriers, i.e. fish-passage solutions (FPSs). Eel occurrence data were spatially and temporally integrated with the national databases of dams and FPSs in a Geographic Information System (GIS) environment to evaluate their effect on ascending eel distribution. The types of barriers assessed were: (i) dams with nature-like fishways; (ii) dams with eel ramps; (iii) dams with technical fishways; and (iv) dams without FPSs. Dams fitted with eel ramps or technical fishways, as well as dams without FPSs, produced a significant negative effect on the probability of eel occurrence upstream. This negative effect was not found for dams fitted with nature-like fishways, indicating that these solutions may function better than the other FPS types in this study. The probability of eel occurrence decreased with distance from the sea and increased with area sampled, number of electrofishing runs, water temperature, and with the size of the bottom substrate. We suggest that future conservation strategies for improving the natural immigration of juvenile eels should include optimizing FPS function (e.g. placement and design), the continued maintenance of FPSs, the construction of nature-like fishways, and preferably the removal of dams, which will also benefit the downstream migration of maturing eels as well as restoring other ecosystem services.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2019
Keywords
Barriers, dams, dispersal, eel ladders, eel management, electrofishing, fish passage, fishways, ramps
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-72118 (URN)10.1002/aqc.3064 (DOI)000465962300010 ()
Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-06-13Bibliographically approved
Degerman, E., Tamario, C., Watz, J., Nilsson, P. A. & Calles, O. (2019). Occurrence and habitat use of European eel (Anguilla anguilla) in running waters: lessons for improved monitoring, habitat restoration and stocking. Aquatic Ecology, 1-12
Open this publication in new window or tab >>Occurrence and habitat use of European eel (Anguilla anguilla) in running waters: lessons for improved monitoring, habitat restoration and stocking
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2019 (English)In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, p. 1-12Article in journal (Refereed) Epub ahead of print
Abstract [en]

To improve the management of the Europeaneel (Anguilla anguilla) in freshwater, it isessential to define important lotic habitats. Electrofishingdata from 289 wadeable, hard-bottom sites in 69Swedish coastal rivers and streams, originally surveyedfor salmonid monitoring, were used to evaluatethe effects of sampling- and habitat-related factors oneel occurrence. Probability of eel occurrence, asinfluenced by sampling procedure (sampled area,number of consecutive runs and ambient watertemperature) and habitat characteristics (size ofcatchment, dominating bottom substrate, shade, watervelocity, mean depth), was evaluated for small (totallength B 150 mm) and large ([150 mm) yelloweels. Data were analysed in a mixed presence/absencegeneralized linear model with dispersal (distance tomouth from sampled site), habitat and samplingrelatedvariables as covariates. The two modelsexplained variation in occurrence to 81.5% for smalleel and 76.2% for large eel. Probability of eeloccurrence decreased with distance from the rivermouth, and increased with sampled area, number ofruns, water temperature, coarser substrate and size ofriver. We suggest that future eel habitat restorationshould focus on lower reaches of larger rivers withsuitable coarse bottom habitats. Stocking of young eelshould be carried out in comparable accessible habitatsin the upper reaches where eel densities are low.The results also strongly indicate that eel may besampled together with young salmonids with DCelectrofishing in wadeable habitats.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Eel management, electrofishing, river, temperature, restoration, sampling, stocking
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-74806 (URN)10.1007/s10452-019-09714-3 (DOI)
Projects
Ålyngel 2016-2018 Formas
Funder
Swedish Research Council Formas, 2015-824
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-10-14
Nyqvist, D., Elghagen, J., Heiss, M. & Calles, O. (2018). An angled rack with a bypass and a nature-like fishway pass Atlantic salmon smolts downstream at a hydropower dam. Marine and Freshwater Research, 69(12), 1894-1904
Open this publication in new window or tab >>An angled rack with a bypass and a nature-like fishway pass Atlantic salmon smolts downstream at a hydropower dam
2018 (English)In: Marine and Freshwater Research, ISSN 1323-1650, E-ISSN 1448-6059, Vol. 69, no 12, p. 1894-1904Article in journal (Refereed) Published
Abstract [en]

Hydropower dams disrupt longitudinal connectivity and cause fragmentation of river systems, which has led to declines in migratory fish species. Atlantic salmon smolts rely on intact longitudinal connectivity to move downstream from rearing habitats in freshwater to feeding grounds at sea. Smolts often suffer increased mortality and delays when they encounter hydropower plants during their downstream migration. Currently, there are few examples of downstream passage solutions that allow safe and timely passage. We assessed the performance of two passage solutions at a hydropower dam, namely, an angled 15-mm rack with a bypass and a large nature-like fishway. The performance of these new fish passage solutions was evaluated by tracking radio-tagged Atlantic salmon smolts as they encountered the facilities. The radio-tagged smolts passed the dam 9.5 h after release (median) and exhibited a dam-passage efficiency of 84%, with passage rates increasing with body length. Fish passage occurred through both the rack bypass and the nature-like fishway. The passage efficiencies were 70-95% for the rack bypass and 47% for the nature-like fisway. The new fish passage facilities resulted in improved passage conditions at the site, confirming that angled racks with bypasses as best-practise solutions for downstream passage, but also that large nature-like fishways may act as downstream passage routes for salmon.

Place, publisher, year, edition, pages
CSIRO, 2018
Keywords
downstream passage, fish passage solution, migration, passage efficiency.
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-70349 (URN)10.1071/MF18065 (DOI)000451437700011 ()2-s2.0-85055562911 (Scopus ID)
Available from: 2018-11-29 Created: 2018-11-29 Last updated: 2018-12-20Bibliographically approved
Watz, J., Nilsson, P. A., Degerman, E., Tamario, C. & Calles, O. (2018). Enhancing upstream passage solutions for juvenile eels: Effects of climbing substrate and ramp placement. In: : . Paper presented at International Conference on River Connectivity (Fish Passage 2018), 10-14 december 2018, Albury, Australia.
Open this publication in new window or tab >>Enhancing upstream passage solutions for juvenile eels: Effects of climbing substrate and ramp placement
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2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Juvenile anguillid eels migrating into inland waters often face migration barriers. Upstream passage solutions normally consist of inclined ramps lined with a wetted climbing substrate. In this study, we compared the performance of three commonly used substrate types in a controlled experiment, using European eel as the test species. We also analyzed climbing behavior with videography and validated the experimental results under natural conditions at a hydropower plant. In addition, we investigated the effects of ramp placement. Studded substrate attracted more approaches and climbs and passed more eels at a higher climbing velocity than open weave and bristle substrates, results that were confirmed by the field validation. Moreover, ramps placed in the tailrace caught more eels in low than in high water velocities. To conserve anguillid eels, both safe routes for downstream-migrating adult silver eels and improved recruitment at the freshwater feeding life stage must be achieved. Optimizing ramp position and equipping upstream passage solutions with functioning climbing substrate are key factors to enhance the performance of eel ramps.

National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-70694 (URN)
Conference
International Conference on River Connectivity (Fish Passage 2018), 10-14 december 2018, Albury, Australia
Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-31Bibliographically approved
Szabo-Meszaros, M., Navaratnam, C. U., Aberle, J., Silva, A. T., Forseth, T., Calles, O., . . . Alfredsen, K. (2018). Experimental hydraulics on fish-friendly trash-racks: an ecological approach. Ecological Engineering: The Journal of Ecotechnology, 113, 11-20
Open this publication in new window or tab >>Experimental hydraulics on fish-friendly trash-racks: an ecological approach
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2018 (English)In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 113, p. 11-20Article in journal (Refereed) Published
Abstract [en]

The obstruction of fish migratory routes by hydroelectric facilities is worldwide one of the major threats to freshwater fishes. During downstream migration, fish may be injured or killed on the trash-racks or in the hydropower turbines. Fish-friendly trash-racks that combine both ecological and technical requirements are a solution to mitigate fish mortality at a low operational cost. This study presents results from an experimental investigation of head-losses and the hydrodynamic performance of six angled trash-rack types with 15 mm bar spacing, varying bar-setup (vertical-streamwise, vertical-angled and horizontal bars) and bar profiles (rectangular and drop shape) under steady flow conditions. The trash-racks were positioned at 30 degrees to the wall of the flume and combined with a bypass at their downstream end. The impact of the different trash-rack types on the upstream flow field was characterized using Image based Volumetric 3-component Velocimetry (V3V) and at the bypass-entrance using an Acoustic Doppler Velocimeter (ADV). The results show that trash-racks with vertical-streamwise and horizontal oriented bars with drop-shape profiles have similar head-losses (13% difference), while trash-racks with vertical-angled bars provide 3-8 times larger head-losses compared to the remaining configurations. The velocity measurements showed that the highest flow velocities occurred for configurations with vertical-angled bars (0.67 m s(-1) and 0.81 m s(-1) on average, respectively). Turbulence related parameters (e.g. Reynolds shear stresses and Turbulent kinetic energy) were also investigated to evaluate the performance of the alternative trash-racks from both, engineering and ecological perspectives.

National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-66708 (URN)10.1016/j.ecoleng.2017.12.032 (DOI)000426093400002 ()
Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2018-05-24Bibliographically approved
Watz, J., Calles, O., Carlsson, N., Teemu, C., Huusko, A., Jörgen, J., . . . Nyqvist, D. (2018). Wood addition in the hatchery and river environments affectspost-releaseperformance of overwintering brown trout. Freshwater Biology, 64(1), 71-80
Open this publication in new window or tab >>Wood addition in the hatchery and river environments affectspost-releaseperformance of overwintering brown trout
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2018 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 64, no 1, p. 71-80Article in journal (Refereed) Published
Abstract [en]

1. Habitat structural complexity affects the behaviour and physiology of individuals,and responses to the environment can be immediate or influence performancelater in life through delayed effects.

2. Here, we investigated how structural enrichment, both pre-release in the hatcheryrearing environment and post-release in the wild, influenced winter growthand site fidelity of brown trout stocked into side channels of a regulated river.

3. Experiencing structural enrichment in the rearing environment during 3 months inautumn had no pre-release effect on growth, but a delayed positive effect afterrelease during the subsequent winter. Moreover, trout recaptured in wood-treatedsections of the side channels had grown more than trout recaptured in controlsections. Wood enrichment in the side channels also increased overwinter sitefidelity.

4. These results show that adding structure during a relatively short period may altergrowth trajectories, and adding wood to side channels is a cost-effective methodto enhance winter habitat carrying capacity for juvenile salmonids in regulatedrivers.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
growth, habitat complexity, restoration, site fidelity, stream wood
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-69976 (URN)10.1111/fwb.13195 (DOI)000453853500006 ()
Funder
Knowledge Foundation, ProSpekt 15-20160021
Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2019-03-07Bibliographically approved
Nyqvist, D., McCormick, S. D., Greenberg, L., Ardren, W. R., Bergman, E., Calles, O. & Castro-Santos, T. (2017). Downstream migration and multiple dam passage by Atlantic salmon smolts. North American Journal of Fisheries Management, 4(37), 816-828
Open this publication in new window or tab >>Downstream migration and multiple dam passage by Atlantic salmon smolts
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2017 (English)In: North American Journal of Fisheries Management, ISSN 0275-5947, E-ISSN 1548-8675, Vol. 4, no 37, p. 816-828Article in journal (Refereed) Published
Abstract [en]

The purpose of this study was to investigate behavior and survival of radio-tagged wild and hatchery-reared landlocked Atlantic Salmon Salmo salar smolts as they migrated past three hydropower dams equipped with fish bypass solutions in the Winooski River, Vermont. Among hatchery-reared smolts, those released early were more likely to initiate migration and did so after less delay than those released late. Once migration was initiated, however, the late-released hatchery smolts migrated at greater speeds. Throughout the river system, hatchery-reared fish performed similarly to wild fish. Dam passage rates varied between the three dams and was highest at the dam where unusually high spill levels occurred throughout the study period. Of the 50 fish that did migrate downstream, only 10% managed to reach the lake. Migration success was low despite the presence of bypass solutions, underscoring the need for evaluations of remedial measures; simply constructing a fishway is not synonymous with providing fish passage.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
Keywords
SALAR SMOLTS; CHINOOK SALMON; FISH PASSAGE; JUVENILE SALMONIDS; DELAYED MORTALITY; COLUMBIA RIVER; SNAKE RIVER; HYDROPOWER SYSTEM; TRUTTA SMOLTS; K+ ATPASE
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-46900 (URN)10.1080/02755947.2017.1327900 (DOI)000407192600012 ()
Available from: 2016-10-19 Created: 2016-10-19 Last updated: 2018-09-10Bibliographically approved
Watz, J., Elghagen, J., Nilsson, P. A. & Calles, O. (2017). Evaluation of a novel mobile floating trap for collecting migrating juvenile eels, Anguilla anguilla, in rivers. Fisheries Management and Ecology, 24(6), 512-514
Open this publication in new window or tab >>Evaluation of a novel mobile floating trap for collecting migrating juvenile eels, Anguilla anguilla, in rivers
2017 (English)In: Fisheries Management and Ecology, ISSN 0969-997X, E-ISSN 1365-2400, Vol. 24, no 6, p. 512-514Article in journal (Refereed) Published
Abstract [en]

To improve the situation for the threatened European eel in regulated rivers, better methods need to be developed that more efficiently collect and transport juvenile eels past dams. In this study, a novel mobile, floating eel trap is described, and the results from an evaluation of the trap in two Swedish regulated rivers are presented. The mobile trap was designed to reduce the length of the climbing distance while maximizing the width of the entrance. The mobile trap caught more juvenile eels than a stationary eel ladder, serving as control. Furthermore, the mobility of the floating trap enables adaptive placement and thus offers managers the possibility to search for the spatial optimum for trapping efficiency.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
eel ladder, elver, trap-and-transport
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-65233 (URN)10.1111/fme.12248 (DOI)000419209500010 ()
Available from: 2017-11-16 Created: 2017-11-16 Last updated: 2018-05-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8738-8815

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