Daniel Nyqvist, Jonas Elghagen, Marius Heiss and Olle Calles recently published the article “An angled rack with a bypass and a nature-like fishway pass Atlantic salmon smolts downstream at a hydropower dam” in the journal Marine and Freshwater Research.

In the abstract, the authors write:

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 naturelike fishway. The passage efficiencies were 70–95% for the rack bypass and 47% for the nature-like fishway. 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.

Access the paper here, or contact any of the authors.

Stina Gustafsson presenting her thesis.

Last Friday, Stina Gustafsson successfully defended her PhD-thesis Habitat compensation in nature-like fishways – effects on benthos and fish”. Paul Giller (Cork University, Ireland) was the opponent, and Frauke Ecke (SLU, Sweden), Brendan McKie (SLU, Sweden) and Jouni Taskinen (University of Juväskylä, Finland) constituted the grading committee.

Stina Gustafssons supervisors during her PhD were Martin Österling and Olle Calles.

The thesis is available online here. Contact Stina Gustafsson for questions and additional information.

On Friday, 15 December, from 13:00, Stina Gustafsson will defend her PhD-thesis “Habitat compensation in nature-like fishways – effects on benthos and fish”. Paul Giller (Cork University, Ireland) will be the opponent, and Frauke Ecke (SLU, Sweden), Brendan McKie (SLU, Sweden) and Jouni Taskinen (University of Juväskylä, Finland) constitute the grading committee. The defense will take place in 1B306 (Fryxellsalen) at Karlstad University. Everyone is welcome to attend!

In the abstract to the thesis, Stina Gustafsson writes: “The construction of nature-like fishways has become an increasingly common measure to restore longitudinal connectivity in streams and rivers affected by hydroelectric development. These fishways also have the potential to function as habitat compensation measures when running waters have been degraded or lost. The habitat potential has however often been overlooked, and therefore the aim of this thesis was to examine the potential of nature-like fishways for habitat compensation, with special focus on the effect of added habitat heterogeneity. 

This thesis examines the effects of habitat diversity on the macroinvertebrate family composition and functional organization in a nature-like, biocanal-type fishway. The biocanal contained four habitat types; riffle, pool, braided channel and floodplain. The effects of habitat diversity and large woody debris on brown trout habitat choice was also investigated in the biocanal. In addition, and prior to introduction of the threatened freshwater pearl mussel into the biocanal, the suitability of different brown trout strains as hosts for the mussel was examined. 

The results show that the habitat heterogeneity in the biocanal contributed to an increased macroinvertebrate family diversity. The functional organization of the macroinvertebrate community suggests that it was a heterotrophic system and more functionally similar to the main river than to the small streams that it was created to resemble. Brown trout habitat choice studies showed that high densities of large woody debris increase the probability of fish remaining at the site of release. Testing of different brown trout strains as host for the freshwater pearl mussel revealed that both wild and hatchery-reared brown trout strains were suitable hosts. In summary, the results indicate that it is possible to create a fish passage with added value through its high habitat function and that nature-like fishways can be designed to reach multiple species restoration goals.”

The thesis is available online here.

On Thursday, 14 December 14:00, Brendan McKie, one of the members of the grading committee, will give a presentation titled:  “River restoration and biodiversity and ecosystem functioning in tributaries of the Vindel River: The importance of restoration intensity and time”. The seminar will be given in room 5F416, at Karlstad University. Everyone is welcome to attend also the seminar.

Last Friday, I, Daniel Nyqvist, successfully defended my PhD-thesis “Atlantic salmon in regulated rivers – Migration, dam passage, and fish behavior” at Karlstad University. Scott Hinch (University of British Columbia, Canada) was opponent and Eva Thorstad (NINA, Norway), Kim Aarestrup (DTU AQUA, Denmark) and Hans Lundqvist (Swedish University of Agriculture) constituted the grading committee (betygskommitté). The short abstract of the thesis reads:

“Hydropower dams block migration routes, thereby posing a threat to migratory fish species. Fishways and other fish passage solutions may aid fish to pass hydropower dams. A functional fish passage solution, however, must ensure safe and timely passage for a substantial portion of the migrating fish. In this thesis, I focus on downstream passage and evaluate the behavior and survival of migrating Atlantic salmon in relation to dams in systems with (1) no fish passage solutions (2) simple passage solutions (3) best available passage solutions. In addition, I studied the survival and behavior of post-spawners and hatchery-released smolts.

A large portion of the spawners survived spawning and initiated downstream migration. For hatchery-reared smolts, early release was associated with faster initiation of migration and higher survival compared to late release. Multiple dam passage resulted in high mortality, and high spill levels were linked to high survival and short delay for downstream migrating salmon. For smolts, dam passage, even with simple passage solutions, was associated with substantial delay and mortality. Rapid passage of a large portion of the migrating adult salmon was achieved using best available passage solutions.”

The frame of the thesis is available here. Already published papers included in the thesis are Post-Spawning Survival and Downstream Passage of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: Is There Potential for Repeat Spawning? (in River Research and Applications) and Migratory delay leads to reduced passage success of Atlantic salmon smolts at a hydroelectric dam (in Ecology of Freshwater Fish). For full access to the thesis, contact daniel.nyqvist@kau.se.