Johan Watz, Assistant Professor at Karlstad University, recently published two papers on juvenile salmonid ecology:

 

Temperature‐dependent competition between juvenile salmonids in small streams

By Johan Watz, Yasuhiko Otsuki, Kenta Nagatsuka, Koh Hasegawa & Itsuro Koizumi, published in the journal Freshwater Biology.

In the abstract, the authors write:

Johan Watz, doing field work during his PostDoc in Japan.

1) 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.

2) 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.

3) 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.

A forest stream on Hokkaido, northern Japan.

4) 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.

5) 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.

6) 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.

 

Read more about the Koizumi lab at Hokkaido University (where Johan did his PostDoc) on their website!

 

Structural complexity in the hatchery rearing environment affects activity, resting metabolic rate and post‐release behaviour in brown trout Salmo trutta

By Johan Watz, published in the Journal of Fish Biology

In the abstract, Johan writes:

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.

 

Contact the author to access the papers.

 

The left photographs show Dolly Varden (a) and white‐spotted charr (b). The right photographs show enclosures in a non‐spring‐fed (c) and a spring‐fed (d) tributary.

 

The structurally enriched (left) and barren (right) tanks used in the study on how structural complexity in the hatchery environment affects juvenile brown trout.

 

River Rottnan in winter.

A Dolly Varden trout (Salvelinus malma).

On Tuesday 16 October, Johan Watz from Karlstad University will give a seminar titled: “Report from a postdoctoral research stay in Sapporo and results from a field experiment: Condition-specific competition between two Japanese charr species”. The seminar will start at 13:15 in room 5F416 at Karlstad University. Everyone who wants to are welcome to attend the seminar.

Dennis Lafage relatively recently started a postdoc within the NRRV-research group at Karlstad University. Here he briefly presents his background and what he plans to do during his postdoc:

My name is Denis Lafage. I recently started a post-doc in the NRRV group to work on aquatic/terrestrial exchanges. I started research after working 10 years in Nature Reserves and Conservation Agencies where I was specialized in terrestrial fauna monitoring and conservation (mainly birds, invertebrates, and bats), statistics, GIS and database management.

I completed my doctorate in 2014 from the Muséum National d’Histoire Naturelle de Paris (France). My PhD thesis was dealing with the impact of management practices and natural perturbations (mainly flooding) on arthropods (spiders and carabid beetles) and plants in meadows. It also included a study using remote sensing technics to map vegetation associations using satellite imagery.

I consider myself as a community ecologist with a particular focus on arthropods. In the NRRV group, I will particularly work on a meta-analysis on the landscape drivers of aquatic/terrestrial fluxes. I will mainly focus on studies using stable isotopes for diet partitioning. As I have a particular interest in what we could call ‘perturbation ecology’ I will also work on food webs after spring floods. I have also the chance to be the co-advisor of a PhD based in Norway aiming at forecasting the impact of climate change on fishing spiders repartition in Scandinavia. Finally, I will also be involved in various projects where my skills in terrestrial arthropod ecology are required.”

Read more about Denis Lafage on his blog denislafage.wordpress.com.

Denis Lafage, sampling spiders in Sweden.

Denis Lafage, in back, and a collegue, sampling vegetation in Nantes, France.

In Denis Lafage precious work, he has been counting birds (Flamingo) in Caramargue, France.

And capturing and counting bats in roosts (France).

Andrew Harbicht recently started a postdoc within the NRRV-research group at Karlstad University. Here he briefly presents his background and what he plans to do during his postdoc:

“Hello, my name is Andrew Harbicht and I’m one of the new Post-Docs to have joined the NRRV. My research experience has primarily been focused on salmonids (rainbow trout, brook charr, and Atlantic salmon) and extends from fisheries modeling to population genetics and radio telemetry. I moved to Karlstad from Montreal, Canada, where I conducted my Ph.D. at Concordia University, working together with the US Fish and Wildlife Service on Atlantic salmon restoration in Lake Champlain. During that time we investigated the impacts of hatchery rearing and release techniques on the lifetime survival and dispersal rates of landlocked salmon and investigated the impact of a thiamine deficiency on the migratory capabilities of returning spawners.

My work with this group will focus on the implications of migratory barriers for longitudinal connectivity among Atlantic salmon populations in the Baltic Sea. With the ever-increasing efficiency of new hydroelectric turbines and the costs associated with maintaining outdated installations, more and more energy producers are opting to remove older facilities to focus their efforts on newer structures. The removal of such aging dams and other barriers to migration within rivers is undoubtedly a positive step for river connectivity, though exactly what changes will occur as a result of such actions is simply unknown in many situations. In fact, over the short term, the removal of barriers can cause as many changes as initial installation. In other situations, maintaining instream infrastructure may be the best option available to energy producer. In which case, including structures that permit fish passage is important, but which type of structure is best suited to the job isn’t always clear. Where several options exist, managers need access to accurate information to assist in their decision-making process.

With my project, I’ll be looking at the impact of removing a partial barrier to migration on the movement patterns of Atlantic salmon, as well as the river ecosystem itself in the Mörrumsån river in southern Sweden. Our holistic approach will monitor all levels of the ecosystem, from the mechanisms that shape river terrain (sedimentation) to the smallest bacteria (decomposition) and the largest predators (fish), as well as all things in between (food-webs). I will also be investigating the genetic consequences of changes in movement patterns that result from the removal of a hydroelectric plant. In another river, the river Emån, we’ll be assessing the performance of a new type of fish lift, and Archimedes screw, which permits upstream and downstream passage, all the while producing its own energy. If found to be effective, such devices could greatly improve connectivity in fragmented river landscapes.”

Andrew Harbicht (left) and William Ardren (right) releasing tagged fish in the Boquet River, a  tributary to Lake Champlain.

Andrew Harbicht tracking radio tagged Atlantic salmon.

A postdoc position in the ecology of river restoration is open for applications at Karlstad University: “The main duty of the position is to conduct research on the effects of dam removal and the installation of fish-friendly turbines on river connectivity and ecology. Intact river connectivity is essential for many organisms in running water, and especially so for organisms that move between different habitats to complete their life cycle, such as many migratory fish species. Many rivers are modified by dams such as hydroelectric power plants. Dams disconnect river stretches and habitats, thereby reducing dispersal and migration possibilities for fish, benthos, and plants, with negative effects on individuals, populations, and communities. The post-doctoral candidate will be expected to evaluate the effects of complete dam removal and installation of fish-friendly turbines as measures to improve connectivity in rivers.“. The deadline for applying is February 28. Read the full announcement here:

Post-doctoral Research Fellow in Ecology of River Restoration: Dam Removal and fish-friendly Turbine

As advertised previously, NRRV at Karlstad University, also has two additional openings for full-time post-doctoral research fellows and one opening for a PhD-student (deadline February 10). Read full announcements for these positions here:

Post-doctoral Research Fellow in Aquatic-Terrestrial Linkages

Post-doctoral Research Fellow in Ecology of River Connectivity.

PhD position in Global climate change and winter ecology

removalThere are currently two openings for full-time post-doctoral research fellows with the River Ecology and Management (NRRV) group at the Department of Environmental and Life Sciences, Karlstad University  One position is in the field of stream-riparian ecology with focus on the reciprocal interactions and linkages between aquatic and terrestrial habitats. The other position is on river connectivity with focus on rehabilitation, management and development strategies. Read full position announcements here:

Post-doctoral Research Fellow in Aquatic-Terrestrial Linkages

Post-doctoral Research Fellow in Ecology of River Connectivity

Last application date is February 10.