How often are Atlantic salmon smolts eaten by predators during their migration?
We propose to advance the understanding of tagged Atlantic salmon smolt survival through lake environments using biotelemetry enhanced by predation sensors. The expected relevance to society is to improve the status of the Vosso River salmon, a culturally important stock of wild fish that provides ecosystem services to the local river. Twenty-five Atlantic salmon smolts will be collected from the Vosso River, anaesthetized with Finquel (MS-222), and tagged with small, lightweight electronic tags that have predation sensors (Vemco, Halifax, Canada). The expected impact of these tags on the smolts is expected to be minimal but tagging and handling can be stressful, which is why we tag under anaesthesia and provide post-operative care. These tags transmit signals on 180 kHz and we will therefore place acoustic listening stations at key checkpoints within the lake. Smolts recorded at the checkpoints will be known to have survived that phase of the lake migration, those detected with the predation sensor triggered will be known to have been eaten and to have not survived. Checkpoints will be placed at the inlet of the river into Lake Evanger, at the first chokepoint following the initial basin, and at the outlet. Ten receivers will be required to cover these areas and ensure complete coverage to be certain that fish migrating to these areas will be detected to ascertain their fate. At the end of the summer we will conduct a manual tracking of Lake Evanger using a VR-100 mobile receiver, which can detect and georeference tags that remain in the lake, presumed to be mortalities, at the conclusion of the study. This will give a highly accurate description of the fate of fish released in this study to improve our ability to model the fates of fish released and determine the relative balance between predation and non-predation mortality during the lake migration.
In parallel, a small study will be conducted to study the evacuation times of tags ingested by brown trout, in which trout of two size classes (small and large) will be fed deceased smolts with dummy transmitters simulating the predation tags. Sixteen brown trout will be held in tanks and will be monitored throughout the day to calculate the time to evacuate the tag. This will be critical to inform our study and will yield a new publication on its own as such data are not presently available. These animals may experience some confinement stress but handling will be minimal and no invasive procedures are anticipated. If they do not eat the dead smolts they may be force fed but this is not expected to adversely affect their welfare.
This project proposes a smaller number of smolts as a pilot study under the principles of reduction. We also propose to use a new, smaller tag, another refinement to our study that will improve animal welfare. The parallel study on brown trout tag evacuation is a refinement that will maximize the value of the tagging results to ensure we can interpret the findings.
In parallel, a small study will be conducted to study the evacuation times of tags ingested by brown trout, in which trout of two size classes (small and large) will be fed deceased smolts with dummy transmitters simulating the predation tags. Sixteen brown trout will be held in tanks and will be monitored throughout the day to calculate the time to evacuate the tag. This will be critical to inform our study and will yield a new publication on its own as such data are not presently available. These animals may experience some confinement stress but handling will be minimal and no invasive procedures are anticipated. If they do not eat the dead smolts they may be force fed but this is not expected to adversely affect their welfare.
This project proposes a smaller number of smolts as a pilot study under the principles of reduction. We also propose to use a new, smaller tag, another refinement to our study that will improve animal welfare. The parallel study on brown trout tag evacuation is a refinement that will maximize the value of the tagging results to ensure we can interpret the findings.