Tracking salmon in otter habitat
1 Purpose
The purpose is to track the upriver migration of Atlantic salmon moving through habitat in a river occupied by carnivorous otters, to which locals are ascribing high impacts of predation.
2 Distress
Internal implantation of telemetry transmitters under anesthesia is not expected to result in lasting distress. There will be placed particular caution on inflicting as little stress as possible on the animals during capture. Animals should recover within minutes and resume migration within a few days.
3 Expected benefit
Determining how otters affect this population is crucial to both local and national management and to mitigate conflicts between humans and otters. Data are needed for evidence-based management of the local salmon population to replace narratives about otter predation based on anecdotes.
4 Number of animals, and what kind
We will tag 150 Atlantic salmon in 2020-2022 with radio transmitting tags
5 How to adhere to 3R
By replicating the study in multiple years we will reduce the total number needed for a representative sample (by having temporal replication). We cannot replace wild salmon with alternative species or simulations because we do not have any underlying data with which to simulate. A key refinement is to implant the tags internally under anesthesia rather than externally attach tags. External attachment is faster but can have longer-lasting impacts on the fish.
The purpose is to track the upriver migration of Atlantic salmon moving through habitat in a river occupied by carnivorous otters, to which locals are ascribing high impacts of predation.
2 Distress
Internal implantation of telemetry transmitters under anesthesia is not expected to result in lasting distress. There will be placed particular caution on inflicting as little stress as possible on the animals during capture. Animals should recover within minutes and resume migration within a few days.
3 Expected benefit
Determining how otters affect this population is crucial to both local and national management and to mitigate conflicts between humans and otters. Data are needed for evidence-based management of the local salmon population to replace narratives about otter predation based on anecdotes.
4 Number of animals, and what kind
We will tag 150 Atlantic salmon in 2020-2022 with radio transmitting tags
5 How to adhere to 3R
By replicating the study in multiple years we will reduce the total number needed for a representative sample (by having temporal replication). We cannot replace wild salmon with alternative species or simulations because we do not have any underlying data with which to simulate. A key refinement is to implant the tags internally under anesthesia rather than externally attach tags. External attachment is faster but can have longer-lasting impacts on the fish.
Etterevaluering
I hht §13 om instruks om forvaltning av forsøksyrforskriften kan Mattilsynet etterevaluere alle forsøk med dyr. I dette tilfellet ble det ført tilsyn med forsøket som resulterte i vedtak om etterevaluering.
Begrunnelse for etterevalueringen
The aims of the experiment were achieved as salmon were successfully tagged and tracked through the spawning period and into the winter in 2020 and 2021. The tagging protocol underwent refinement between 2020 and 2021, and the overall outcome was positive.
The experiment revealed important information about the ecology of salmon in these small streams where they are vulnerable to predation by otters. In partnership with the local stakeholder groups, the researchers learned more about the behaviour of otters and the risk faced by small rivers with small salmon populations to otter predation.
The experiment revealed that predation is a significant cause of mortality among Atlantic salmon in the small streams that we studied and may be impacting the biomass of salmon spawning. The data helped address concerns from local stakeholders about the status of the salmon populations in these rivers. The data were used in a Master's thesis that has been submitted to the journal Freshwater Biology. The findings of the project have also led to a new Norwegian Research Council funded project "Return of the Otter" to further study the biology of otters and the impacts on salmon.
Totally 85 of the 150 approved animals were used in the project, all classified as moderately harmed. The researchers caught fewer animals than planned due to a lower catching rate than expected. They were still able to achieve the project objectives. It would, however, have strengthened the statistical power if more salmon had been tagged.
The findings were novel and somewhat unexpected in the timing and rate of otter predation. The developing knowledge on this topic makes it challenging to envision replacing the field trials with simulations in the near future.
Welfare protocols were used throughout the process and helped the researchers to identify a few fish in the first year that were not in good condition to be released after tagging. These ongoing evaluation mechanisms help keep track of any deviations and provide the field leader with immediate feedback if there are any problems. Our protocol is to stop tagging whenever we flag an issue revealed by the scoring schemes and welfare protocols.
The researchers state that they constantly work to refine the experimental protocols during their research. The findings of the experiment reflect ongoing efforts to maximize welfare and improve protocols.
The experiment revealed important information about the ecology of salmon in these small streams where they are vulnerable to predation by otters. In partnership with the local stakeholder groups, the researchers learned more about the behaviour of otters and the risk faced by small rivers with small salmon populations to otter predation.
The experiment revealed that predation is a significant cause of mortality among Atlantic salmon in the small streams that we studied and may be impacting the biomass of salmon spawning. The data helped address concerns from local stakeholders about the status of the salmon populations in these rivers. The data were used in a Master's thesis that has been submitted to the journal Freshwater Biology. The findings of the project have also led to a new Norwegian Research Council funded project "Return of the Otter" to further study the biology of otters and the impacts on salmon.
Totally 85 of the 150 approved animals were used in the project, all classified as moderately harmed. The researchers caught fewer animals than planned due to a lower catching rate than expected. They were still able to achieve the project objectives. It would, however, have strengthened the statistical power if more salmon had been tagged.
The findings were novel and somewhat unexpected in the timing and rate of otter predation. The developing knowledge on this topic makes it challenging to envision replacing the field trials with simulations in the near future.
Welfare protocols were used throughout the process and helped the researchers to identify a few fish in the first year that were not in good condition to be released after tagging. These ongoing evaluation mechanisms help keep track of any deviations and provide the field leader with immediate feedback if there are any problems. Our protocol is to stop tagging whenever we flag an issue revealed by the scoring schemes and welfare protocols.
The researchers state that they constantly work to refine the experimental protocols during their research. The findings of the experiment reflect ongoing efforts to maximize welfare and improve protocols.