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Publications (10 of 31) Show all publications
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
Filipsson, K., Bergman, E., Österling, M., Erlandsson, A., Greenberg, L. & Watz, J. (2019). Effects of temperature and a piscivorous fish on diel winter behaviour of juvenile brown trout (Salmo trutta). Freshwater Biology, 1-9
Open this publication in new window or tab >>Effects of temperature and a piscivorous fish on diel winter behaviour of juvenile brown trout (Salmo trutta)
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2019 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, p. 1-9Article in journal (Refereed) Epub ahead of print
Abstract [en]

Low winter temperatures constrain predator-detection and escape capabilities, making poikilotherms vulnerable to predation. Investigations of temperature effects on predator-prey interactions can therefore be of special importance in light of ongoing climate change, where winter temperatures are predicted to increase substantially at northern latitudes. Behavioral responses of stream fishes to terrestrial predators in winter are well recognised, whereas responses to predatory fish have received little attention. Using stream flumes, we examined the anti-predator behaviour of one-summer-old brown trout (Salmo trutta) at 3 and 8 degrees C in the presence and absence of burbot (Lota lota) under night, dawn, and daylight conditions. Burbot was placed upstream of the trout, separated by net screens. Lower temperature and the presence of burbot reduced trout activity. Light increased trout shelter use, and trout sheltered more in the presence of burbot. An interaction between the presence of burbot and light conditions affected trout position in the flumes: at night and dawn, trout positioned themselves further downstream when burbot were present than when absent, whereas during the day, trout maintained the same position in the presence or absence of the predator. Our results suggest that piscivorous fish, in addition to terrestrial predators, shape the behaviour of prey fishes in streams during winter. We show how predator avoidance results in altered diel patterns of juvenile brown trout under winter conditions, and that temperature has additional effects on trout behaviour.

Keywords
anti-predator, burbot, climate change, light, predator avoidance
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-74573 (URN)10.1111/fwb.13371 (DOI)000480404400001 ()
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29Bibliographically 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
Watz, J. (2019). Structural complexity in the hatchery rearing environment affects activity, resting metabolic rate and post‐release behaviour in brown trout Salmo trutta. Journal of Fish Biology, 95(2), 638-641
Open this publication in new window or tab >>Structural complexity in the hatchery rearing environment affects activity, resting metabolic rate and post‐release behaviour in brown trout Salmo trutta
2019 (English)In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 95, no 2, p. 638-641Article in journal (Refereed) Published
Abstract [en]

The effects of structural enrichment in the hatchery rearing environment of brown trout Salmo trutta was linked to post‐release performance. Enrichment resulted in reduced swimming activity scored in an open field test and reduced movement in a natural river after release. Also, enrichment increased resting metabolic rates, which correlated positively with overwinter growth.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
movement, phenotypic plasticity, reintroduction, Salmo trutta, winter
National Category
Zoology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-72374 (URN)10.1111/jfb.14049 (DOI)000480645900028 ()
Funder
Knowledge Foundation, 20160021
Available from: 2019-06-10 Created: 2019-06-10 Last updated: 2019-09-16Bibliographically approved
Watz, J., Otsuki, Y., Nagatsuka, K., Hasegawa, K. & Koizumi, I. (2019). Temperature-dependent competition between juvenile salmonids in small streams. Freshwater Biology, 1534-1541
Open this publication in new window or tab >>Temperature-dependent competition between juvenile salmonids in small streams
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2019 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, p. 1534-1541Article in journal (Refereed) Published
Abstract [en]

Biotic interactions affect species distributions, and environmental factors that influence these interactions can play a key role when range shifts in response to environmental change are modelled. In a field experiment using enclosures, we studied the effects of the thermal habitat on intra- versus inter-specific competition of juvenile Dolly Varden Salvelinus malma and white-spotted charr Salvelinus leucomaenis, as measured by differences in specific growth rates during summer in allopatric and sympatric treatments. Previous laboratory experiments have shown mixed results regarding the importance of temperature-dependent competitive abilities as a main driver for spatial segregation in stream fishes, and no study so far has confirmed its existence in natural streams. Under natural conditions in areas where the two species occur in sympatry, Dolly Varden dominate spring-fed tributaries (cold, stable thermal regime), whereas both species often coexist in non-spring-fed tributaries (warm, unstable thermal regime). Enclosures (charr density = 6 per m2) were placed in non-spring-fed (10–14°C) and spring-fed (7–8°C) tributaries. In enclosures placed in non-spring-fed tributaries, Dolly Varden grew 0.81% per day in allopatry and had negative growth (−0.33% per day) in sympatry, whereas growth rates were similar in allopatry and sympatry in spring-fed tributaries (0.68 and 0.58% per day). White-spotted charr grew better in sympatry than in allopatry in both thermal habitats. In non-spring-fed tributaries, they grew 0.17 and 0.79% per day and in spring-fed tributaries 0.46 and 0.75% per day in allopatry and sympatry, respectively. The negative effect of inter-specific competition from white-spotted charr on Dolly Varden thus depended on the thermal habitat. However, there was no strong evidence of a temperature-dependent effect of intra- and inter-specific competition on white-spotted charr growth. Multiple factors may shape species distribution patterns, and we show that temperature may mediate competitive outcomes and thus coexistence in stream fish. These effects of temperature will be important to incorporate into mechanistic and dynamic species distribution models.

Place, publisher, year, edition, pages
Blackwell Publishing, 2019
Keywords
biotic interactions, climate change, global warming, growth, species distribution
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-73363 (URN)10.1111/fwb.13325 (DOI)000474661800014 ()2-s2.0-85067379707 (Scopus ID)
Available from: 2019-07-02 Created: 2019-07-02 Last updated: 2019-08-15Bibliographically approved
Watz, J. (2018). Brown trout in ice-covered streams: effects of surface ice on anti-predator behavior and habitat use. In: : . Paper presented at The 65th Annual Meeting of the Ecological Society of Japan (ESJ65), Sapporo, Japan, March 14-18, 2018.
Open this publication in new window or tab >>Brown trout in ice-covered streams: effects of surface ice on anti-predator behavior and habitat use
2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-66871 (URN)
Conference
The 65th Annual Meeting of the Ecological Society of Japan (ESJ65), Sapporo, Japan, March 14-18, 2018
Available from: 2018-03-28 Created: 2018-03-28 Last updated: 2018-04-05Bibliographically 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
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
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/0000-0002-4417-6636

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