Louis Addo (a Ph.D. student in Biology at Karlstad University) will be giving a talk about the interaction of salmonids fry with changing flows. The talk will be a presentation of a recently published article entitled “Growth and mortality of sympatric Atlantic salmon and brown trout fry in fluctuating and stable flows” by Louis and others from the River Ecology and Management Research group working with salmonids ecology and IBM’s.

You are invited to join this seminar live on zoom and at the biology department at Karlstad University (5F416) at 13:15 CET on 6th December 2022. To join in via zoom use the link: https://kau-se.zoom.us/my/kaubiology

Post Doctoral Researcher Mahboobeh Hajiesmaeili and others from Karlstad University’s biology department and the River Ecology and Management (RivEM) group have recently published an article (open access) entitled Individual-based modelling of hydropeaking effects on brown trout and Atlantic salmon in a regulated river where they parameterized and used inSTREAM version 7.2-SD (an individual based model with the capability of considering important fish ecological behavior) as a soft river management tool to analyze the effect of hydropeaking on juvenile fish in Lilla Åråsforsen (located downstream of the Gullspång dam along the Gullspång River in Sweden). Different scenarios of flows with and without hydropeaking were tested to access the impact of hydropeaking on growth, survival and distribution of age 0+ to 1+ juvenile brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). Perhaps the most interesting finding was that hydropeaking had a modest negative effect on the survival and growth of both species but survival was more negatively affected than growth, especially in smaller juveniles. Most importantly, the study has demonstrated the potential use of IBMs for testing different research questions and assessing and prioritizing alternative management strategies in regulated rivers.

The paper is open access and can be found at https://onlinelibrary.wiley.com/doi/full/10.1002/rra.4037

Åsa Enefalk, Ari Huusko, Pauliina Louhi and Eva Bergman recently published the paper “Fine stream wood decreases growth of juvenile brown trout (Salmo trutta L.)” in the journal Environmental Biology of Fishes. In the abstract, the authors write:

A juvenile brown trout (Salmo trutta) hiding in fine stream wood.

“In this study, the growth rate, gut fullness, diet composition and spatial distribution of brown trout was compared between artificial channels with and without fine wood (FW). Access to FW resulted in significantly lower brown trout growth rates over the study period from late summer to early winter as water temperatures declined from 17 °C to 1 °C. Access to FW resulted in minor differences in occurrence of the most common taxa found in brown trout diets, except for chironomid larvae which were found in c. 60% of the brown trout guts from control treatments but in only 30% of the guts from FW treatments in early winter. Diet consisted primarily of case-bearing and free-living Trichoptera larvae, Asellus, chironomid and Ephemeroptera larvae. Brown trout gut fullness was not significantly affected by access to FW bundles. Brown trout aggregated among FW but were more evenly distributed in channels lacking it. Our results suggest that juvenile brown trout use FW as a shelter at a wide range of water temperatures, and that this behaviour may result in reduced growth rates during their first fall and the onset of their first winter. We also show that prey availability and the composition of brown trout diet changes from late summer to early winter and that FW has a small but significant effect on brown trout diet composition.”

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

Salmonid (Atlantic salmon) eggs (photoscienceimage)

Larry Greenberg is currently working on a research project on potential effects of increased winter temperature on brown trout growth and behavior. The research is funded by Karlstad University’s Lecturers and Professors Research Award. Larry describes the project:

“The predicted climate change over the next 65 years will have a major impact on the Earth’s plants and animals. Climate scenarios for Sweden predict that mean annual temperature will increase by 3-5 ° C, with a greater increase in winter than in summer. Because incubation of eggs laid by brown trout and related fishes occurs during winter, the predicted increased winter temperatures may have a major impact on egg development, with far-reaching consequences for fish after they have hatched. The fact that environmental conditions during the egg stage can affect later life stages (juveniles and adults) may seem unlikely, but recent studies have already shown that temperature conditions during egg development can affect growth of juveniles and even reproductive output of adults. As embryonic temperature conditions have been shown to affect growth, one would also expect such conditions to even affect behavior, as behavior and growth are often linked.

For this project, I plan to investigate how an increase in winter temperature conditions during egg development affects the behavior and growth of juvenile brown trout. I will raise fertilized brown trout eggs over the winter at ambient temperature and at 5° C warmer water, and test for subsequent effects on the feeding behavior and personality of juveniles as well as on their growth and metabolic rates.  The research is novel by being the first to investigate whether or not thermal conditions during egg development can affect both the behavior and growth of juveniles.”

The eggs are presently developing under different temperature regimes at Gammelkroppa fish hatchery.