Behavior of immature sea trout in a river system impacted by hydropower
1 Formål
Blenkje is a small form of the juvenile migrants of sea trout. Blenkje are small and inexperienced and are believed to be highly vulnerable to disturbances at sea and in freshwater. In Aurland, blenkje have been found to be increasingly rare in the river and there is concern that losses of blenkje are affecting the overall recruitment in the river. However, it is not well known where the blenkje are most likely disappearing. There are two major stressors in the river: the hydropower outlet in the vangen powerstation and the marine area where sea lice are prolific. This project will track the migrations of blenkje using acoustic transmitters in an array established in Aurland for monitoring the native sea trout population.
In addition, hatchery production is one consequence of the river regulation, which involves collection of broodstock salmon to reproduce. These fish are released back to the river and may be important to the population if they survive and thrive, but this is unknown and flagged as a priority question by industry. We will therefore, in to tagging blenkje, tag and track 15 hatchery reared salmon in Aurland.
2 Skadevirkninger
This is a moderately stressful procedure involving the capture by electrofishing, netting, or angling and tagging of blenkje. This procedure is standard for telemetry studies and widely used with great success and limited mortality. We believe that we can capture 100 blenkje per year in the river to track them within our acoustic array to give representative results about where and when these fish move and what stressors are most salient during their migrations.
3 Forventet nytteverdi
This research aims to provide new data about the blenkje that will be useful to both industry and management. Eco Energi is in need of data on the movement of blenkje in Aurland and the information revealed in this study will be applied to operations.
4 Antall dyr og art
The project will require 200 brown trout in the life stage “blenkje”, which is a small silver coloured individual larger than a smolt that is not yet reproductive. These individuals measure 20-35 cm and about 120-250 g typically. We will tag 40 in 2022, 30 in 2023 and 30 in 2024 . We will use smaller tags (7 mm Thelma tag measuring 28 mm long and 3 g in air with a battery life of 9 months) for smaller individuals and have slightly larger tags (9 mm diameter, 32 mm long, 6 g in air) for larger individuals. The tags will have depth, acceleration, and temperature sensors on board to better understand the movements and activity of these fish in the river, lake, and ocean. In addition, we will also tag 15 hatchery salmon in 2023 with internal LP13 tags with several years of battery life.
5 Hvordan etterleve 3R
We intend to reduce the number of animals used in this study by using acoustic tags, which provide much higher resolution detail about movement and behaviour than PIT or other monitoring methods that provide such poor resolution data that many fish must be tagged to make good observations.
Blenkje is a small form of the juvenile migrants of sea trout. Blenkje are small and inexperienced and are believed to be highly vulnerable to disturbances at sea and in freshwater. In Aurland, blenkje have been found to be increasingly rare in the river and there is concern that losses of blenkje are affecting the overall recruitment in the river. However, it is not well known where the blenkje are most likely disappearing. There are two major stressors in the river: the hydropower outlet in the vangen powerstation and the marine area where sea lice are prolific. This project will track the migrations of blenkje using acoustic transmitters in an array established in Aurland for monitoring the native sea trout population.
In addition, hatchery production is one consequence of the river regulation, which involves collection of broodstock salmon to reproduce. These fish are released back to the river and may be important to the population if they survive and thrive, but this is unknown and flagged as a priority question by industry. We will therefore, in to tagging blenkje, tag and track 15 hatchery reared salmon in Aurland.
2 Skadevirkninger
This is a moderately stressful procedure involving the capture by electrofishing, netting, or angling and tagging of blenkje. This procedure is standard for telemetry studies and widely used with great success and limited mortality. We believe that we can capture 100 blenkje per year in the river to track them within our acoustic array to give representative results about where and when these fish move and what stressors are most salient during their migrations.
3 Forventet nytteverdi
This research aims to provide new data about the blenkje that will be useful to both industry and management. Eco Energi is in need of data on the movement of blenkje in Aurland and the information revealed in this study will be applied to operations.
4 Antall dyr og art
The project will require 200 brown trout in the life stage “blenkje”, which is a small silver coloured individual larger than a smolt that is not yet reproductive. These individuals measure 20-35 cm and about 120-250 g typically. We will tag 40 in 2022, 30 in 2023 and 30 in 2024 . We will use smaller tags (7 mm Thelma tag measuring 28 mm long and 3 g in air with a battery life of 9 months) for smaller individuals and have slightly larger tags (9 mm diameter, 32 mm long, 6 g in air) for larger individuals. The tags will have depth, acceleration, and temperature sensors on board to better understand the movements and activity of these fish in the river, lake, and ocean. In addition, we will also tag 15 hatchery salmon in 2023 with internal LP13 tags with several years of battery life.
5 Hvordan etterleve 3R
We intend to reduce the number of animals used in this study by using acoustic tags, which provide much higher resolution detail about movement and behaviour than PIT or other monitoring methods that provide such poor resolution data that many fish must be tagged to make good observations.