Using light for sea lice sterilization (copy)
The objective of this project is to extend some recent work on a new preventative method against lice in sea cage salmon farming. With this new technique, we are able to sterilize fertilized lice eggs by disrupting their DNA while they are still attached to female lice on host fish. Our aim is to reduce hatching success and make any copepodids that hatch unviable with a technique that requires no handling of fish. The concept is to deploy sterilizing lights in sea cages attached to standard light arrays that deliver multiple micro-doses of sterilizing light to the egg strings on female lice passing by on fish.
In a recent project (ID 14862) we demonstrated that multiple short exposures to short wavelength light (UVC) are highly effective at reducing production of copepodid stages from exposed egg strings. A pilot study testing the impact of a similar dose on salmon post-smolts found no evidence for negative effects on fish welfare, but a higher daily dose applied during a larger-scale experiment (targeting egg strings on lice attached to salmon) led to some negative welfare effects on host fish, at which point the experiment was terminated early. We now plan to investigate the maximum UVC dose that can be applied without short-term negative effects on fish welfare. This ‘welfare threshold’ will likely lie between the cumulative doses received by fish in the pilot and larger-scale tank trials.
The aims are to:
(1) determine the welfare threshold at which sterilizing light has detectable negative welfare impacts on fish under a realistic exposure regime
(2) compare this threshold to the dose-response curve obtained from earlier experiments to estimate the reduction in copepodid production can be achieved without detectable short-term negative effects on host fish
The experiment will require exposing a total of 40 fish to numerous small doses per day. We will subsample 4 fish on each of 10 occasions corresponding to 10 cumulative doses or exposure levels (spanning the 0-90 % effective doses estimated by our earlier work). Fish welfare will be assessed according to the SWIM model at this time, before fish are tagged and placed in a common recovery tank for an additional 4 days of monitoring. At the end of the monitoring period an additional SWIM assessment will be conducted and skin and eye tissue samples taken for expert analysis. If at any point fish show symptoms of UVC exposure (e.g. skin irritation, lesions, cataract development or excessive rubbing or jumping behaviours), all fish assigned to that exposure level or higher will be euthanised immediately. Fish in lower exposure level groups will continue to be monitored for delayed development of symptoms. Small numbers of fish, regular monitoring and swift euthanasia will limit the amount of distress caused if any exposure level exceeds the welfare threshold dose, while still achieving the aims of the study. Replacement is not possible as welfare impacts must be assessed on the study animal, however the proposed setup has been refined through experience from the previous linked experiment.
In a recent project (ID 14862) we demonstrated that multiple short exposures to short wavelength light (UVC) are highly effective at reducing production of copepodid stages from exposed egg strings. A pilot study testing the impact of a similar dose on salmon post-smolts found no evidence for negative effects on fish welfare, but a higher daily dose applied during a larger-scale experiment (targeting egg strings on lice attached to salmon) led to some negative welfare effects on host fish, at which point the experiment was terminated early. We now plan to investigate the maximum UVC dose that can be applied without short-term negative effects on fish welfare. This ‘welfare threshold’ will likely lie between the cumulative doses received by fish in the pilot and larger-scale tank trials.
The aims are to:
(1) determine the welfare threshold at which sterilizing light has detectable negative welfare impacts on fish under a realistic exposure regime
(2) compare this threshold to the dose-response curve obtained from earlier experiments to estimate the reduction in copepodid production can be achieved without detectable short-term negative effects on host fish
The experiment will require exposing a total of 40 fish to numerous small doses per day. We will subsample 4 fish on each of 10 occasions corresponding to 10 cumulative doses or exposure levels (spanning the 0-90 % effective doses estimated by our earlier work). Fish welfare will be assessed according to the SWIM model at this time, before fish are tagged and placed in a common recovery tank for an additional 4 days of monitoring. At the end of the monitoring period an additional SWIM assessment will be conducted and skin and eye tissue samples taken for expert analysis. If at any point fish show symptoms of UVC exposure (e.g. skin irritation, lesions, cataract development or excessive rubbing or jumping behaviours), all fish assigned to that exposure level or higher will be euthanised immediately. Fish in lower exposure level groups will continue to be monitored for delayed development of symptoms. Small numbers of fish, regular monitoring and swift euthanasia will limit the amount of distress caused if any exposure level exceeds the welfare threshold dose, while still achieving the aims of the study. Replacement is not possible as welfare impacts must be assessed on the study animal, however the proposed setup has been refined through experience from the previous linked experiment.