Facilitating behavioural adaptation of cleaner wrasse to improve lice reduction via video playback and social learning
Ballan wrasse are stocked with farmed Atlantic salmon in sea cages to eat and reduce loads of the problematic parasite, the salmon louse, on farmed salmon. Yet lice removal efficacy of wrasse is estimated to be low and variable. It is important to improve wrasse capacity to eat lice to ensure the cleaner fish industry is sustainable and safeguard wrasse welfare in sea cages.
We plan to investigate whether (1) lice removal efficacy of wrasse can be improved by exposing wrasse to a video playback of wrasse eating lice on salmon, and (2) whether salmon-and-lice experienced wrasse can ‘teach' to salmon-and-lice naïve wrasse to eat lice via social learning. We propose to use a total of 330 salmon and 180 wrasse in a two-part study to explore whether behavioural adaptation via video playback and social learning is a commercially viable tool to improve wrasse lice removal efficacy.
Study 1 will investigate the lice-removal performance of video ‘taught’ wrasse to control wrasse. For part 1 of the experiment, a total of 330 salmon are required to be infested with lice (30 lice/salmon) that will be stock for the remaining experiment. 1 large tank will hold 30 salmon and 10 wrasse for 1-2 weeks to film wrasse eating lice behaviour. Then, 5 replicate aquaria will be stocked with 10 wrasse/aquaria (50 x treatment wrasse) that will be exposed to the video footage of wrasse eating lice filmed previously. 5 replicate control aquaria will be stocked with 10 wrasse/aquaria (50 x control wrasse) that will have no video exposure. To compare the effect of video playback on capacity of wrasse to learn lice removal, after 1 week of being in aquaria, wrasse will be transferred to medium-small tanks with 30 lice infested salmon. Here, interactions between wrasse and salmon will be filmed for 1 week, and lice removal efficacy of video-exposed and control wrasse will be compared. Lice counts on salmon before and after wrasse transfer (10 salmon per tank) will be conducted.
Study 2 will compare the lice-removal performance of groups of wrasse with different ratios of salmon-and-lice experienced: naïve wrasse in tanks with salmon infested with lice to explore what size of pioneer group is required for social transfer of lice-feeding skills to occur in the naïve population. Study 2 will use 180 lice-infested salmon from Study 1 and split them amongst six experimental tanks (30/tank). 50 wrasse will be reused from Study 1 as teacher fish. 70 new wrasse that are salmon-and-lice naïve will be sourced from a stock tank nearby and come from the same cohort as experimental wrasse. All 70 of the new wrasse will be externally tagged prior to the trial. Interactions between wrasse and salmon will be filmed for 1 week, and lice removal efficacy of video-exposed and control wrasse will be compared. Lice counts will be conducted on salmon before and after wrasse transfer (10 salmon per tank).
We expect mild distress in salmon during infestation and moderate distress in wrasse during tagging.
We plan to investigate whether (1) lice removal efficacy of wrasse can be improved by exposing wrasse to a video playback of wrasse eating lice on salmon, and (2) whether salmon-and-lice experienced wrasse can ‘teach' to salmon-and-lice naïve wrasse to eat lice via social learning. We propose to use a total of 330 salmon and 180 wrasse in a two-part study to explore whether behavioural adaptation via video playback and social learning is a commercially viable tool to improve wrasse lice removal efficacy.
Study 1 will investigate the lice-removal performance of video ‘taught’ wrasse to control wrasse. For part 1 of the experiment, a total of 330 salmon are required to be infested with lice (30 lice/salmon) that will be stock for the remaining experiment. 1 large tank will hold 30 salmon and 10 wrasse for 1-2 weeks to film wrasse eating lice behaviour. Then, 5 replicate aquaria will be stocked with 10 wrasse/aquaria (50 x treatment wrasse) that will be exposed to the video footage of wrasse eating lice filmed previously. 5 replicate control aquaria will be stocked with 10 wrasse/aquaria (50 x control wrasse) that will have no video exposure. To compare the effect of video playback on capacity of wrasse to learn lice removal, after 1 week of being in aquaria, wrasse will be transferred to medium-small tanks with 30 lice infested salmon. Here, interactions between wrasse and salmon will be filmed for 1 week, and lice removal efficacy of video-exposed and control wrasse will be compared. Lice counts on salmon before and after wrasse transfer (10 salmon per tank) will be conducted.
Study 2 will compare the lice-removal performance of groups of wrasse with different ratios of salmon-and-lice experienced: naïve wrasse in tanks with salmon infested with lice to explore what size of pioneer group is required for social transfer of lice-feeding skills to occur in the naïve population. Study 2 will use 180 lice-infested salmon from Study 1 and split them amongst six experimental tanks (30/tank). 50 wrasse will be reused from Study 1 as teacher fish. 70 new wrasse that are salmon-and-lice naïve will be sourced from a stock tank nearby and come from the same cohort as experimental wrasse. All 70 of the new wrasse will be externally tagged prior to the trial. Interactions between wrasse and salmon will be filmed for 1 week, and lice removal efficacy of video-exposed and control wrasse will be compared. Lice counts will be conducted on salmon before and after wrasse transfer (10 salmon per tank).
We expect mild distress in salmon during infestation and moderate distress in wrasse during tagging.