Studying the cumulative effect of hydropower and aquaculture on salmon smolt survival
1 Purpose:
Hydropower is a major stressor for Atlantic salmon smolts when barriers in rivers result in entrainment through turbines or result in other physical damage to the animals. There is conflict between aquaculture and hydropower about the fate of smolts migrating through rivers and fjords. Release groups of hatchery salmon smolts have demonstrated an increasing survival as fish are transported and released in the fjord compared to being released in freshwater (Vollset et al. 2016), while simultaneously showing that impacts of salmon lice from fish farms are reducing their survival as they migrate through the fjords. A tagging experiment will advance understanding of these conflicts to identify the fate of smolts and the timing and location of death for those that perished during their migration.
We will use the three study sites Modalen, Tysse and Dale to tag Atlantic salmon smolts. Dale will be used as a site for a study on anaethetic effects to help refine our experimental protocols and compare the migration timing and success of smolts tagged under anaesthesia with Aqui-S and MS-222. Modalen and Tysse rivers are impacted by hydropower and will be used to study the freshwater migration and survival of smolts through hydropower generating plants and fish passage structures. Understanding the risk for smolts at these critical migration points is an urgent need for industries and management to ensure sustainability of the salmon populations. Individual tagging is necessary to calculate the migration path of the fish in the river and the potential for adverse impacts due to entrainment.
2 Distress:
Smolts will be captured, sedated and tagged with acoustic tags using standard operating procedures for tagging smolt with acoustic tags (SOP 12.E).
3 Expected benefit:
It is plausible that a large proportion of salmon smolts is currently being impacted by the concessions to produce hydropower in these rivers. Meanwhile, it is expected that there may be high impacts in the fjords that affect the survival of smolts as they move towards the open ocean. Studies that can illuminate ways to reveal the impacts of these industry operations and identify suitable mitigations will have large animal welfare implications in the long term.m.
4 Number of animals, and what kind:
Total acoustic tag: 600 salmon smolts
Total PIT tag for anaesthetic effect study: 600 salmon smolts
5 How to adhere to 3R:
Non-invasive methods are not feasible in these systems because of the size of the study systems (e.g. not possible to observe fish using a camera setup). Alternative methods include tagging with smaller tags (e.g. PIT), but because of low detection levels this necessitates a much larger sample size to get accurate predictions and will often also render the conclusions uncertain. For the tagging procedure study, PIT tags are sufficient to observe the effects and provide an opportunity for refinement.
Hydropower is a major stressor for Atlantic salmon smolts when barriers in rivers result in entrainment through turbines or result in other physical damage to the animals. There is conflict between aquaculture and hydropower about the fate of smolts migrating through rivers and fjords. Release groups of hatchery salmon smolts have demonstrated an increasing survival as fish are transported and released in the fjord compared to being released in freshwater (Vollset et al. 2016), while simultaneously showing that impacts of salmon lice from fish farms are reducing their survival as they migrate through the fjords. A tagging experiment will advance understanding of these conflicts to identify the fate of smolts and the timing and location of death for those that perished during their migration.
We will use the three study sites Modalen, Tysse and Dale to tag Atlantic salmon smolts. Dale will be used as a site for a study on anaethetic effects to help refine our experimental protocols and compare the migration timing and success of smolts tagged under anaesthesia with Aqui-S and MS-222. Modalen and Tysse rivers are impacted by hydropower and will be used to study the freshwater migration and survival of smolts through hydropower generating plants and fish passage structures. Understanding the risk for smolts at these critical migration points is an urgent need for industries and management to ensure sustainability of the salmon populations. Individual tagging is necessary to calculate the migration path of the fish in the river and the potential for adverse impacts due to entrainment.
2 Distress:
Smolts will be captured, sedated and tagged with acoustic tags using standard operating procedures for tagging smolt with acoustic tags (SOP 12.E).
3 Expected benefit:
It is plausible that a large proportion of salmon smolts is currently being impacted by the concessions to produce hydropower in these rivers. Meanwhile, it is expected that there may be high impacts in the fjords that affect the survival of smolts as they move towards the open ocean. Studies that can illuminate ways to reveal the impacts of these industry operations and identify suitable mitigations will have large animal welfare implications in the long term.m.
4 Number of animals, and what kind:
Total acoustic tag: 600 salmon smolts
Total PIT tag for anaesthetic effect study: 600 salmon smolts
5 How to adhere to 3R:
Non-invasive methods are not feasible in these systems because of the size of the study systems (e.g. not possible to observe fish using a camera setup). Alternative methods include tagging with smaller tags (e.g. PIT), but because of low detection levels this necessitates a much larger sample size to get accurate predictions and will often also render the conclusions uncertain. For the tagging procedure study, PIT tags are sufficient to observe the effects and provide an opportunity for refinement.