Understanding and optimizing the lice eating behaviour of Cyclopterus lumpus
The objective of the trial is understand the food preferences of farmed lumpfish by determining if individual fish are specialists or generalists, and to optimize the lice-eating behaviour of the lumpfish with different forms of training such as being fed live-feed prior to sea transfer or through cohabitation with known lice-eating “teachers”.
Millions of cleaner fish are deployed to act as biological controls for salmon lice annually. However, little is known about their feeding behaviour (Barrett et al. 2020) and to optimize cleaner fish as a management strategy better understanding of this is needed. Here, we propose three research-scale experiments which aim to increase the proportion of individuals which eat lice; (a) tank trial where lumpfish are fed live feed, (b) sea-cage trial examining feeding preference of lumpfish without any prior training as well as fish fed live feed prior to transfer and (c) sea-cage trial examining lice-eating efficiency between lumpfish which have cohabitated with known lice-eating “teachers” and naïve fish.
The experiments will be run at Austevoll Research Station operated by Havforskningsinstituttet. There will be six 5x5x5m sea cages, each stocked with 600 salmon (Nsalmon = 3,600). Lumpfish will be stocked at densities around 10%. Trial A and B use the same lumpfish while in trial C only a portion of the lumpfish that are known lice-eaters are being reused and the remaining cleaner fish need to be replaced. This sums up to a total of 540 lumpfish for trial A and B and between 180–210 lumpfish for trial C, ending up in a total sum of 720–750 lumpfish.
The trials are being conducted in 5x5x5m sea cages which mimic conditions that fish are exposed to in commercial sea cages but greatly minimize the number of animals required to achieve reasonable stocking densities. To give cleaner fish and salmon sufficient densities to interact, 600 salmon will be stocked in each sea cage to give an initial stocking density of around 0.7 kg/m3, which is the lowest stocking density will be on farms. The same salmon can be used for all the trials, thereby minimizing the total number of animals required. To obtain enough lice-eating teachers for trial C, a stocking density of 10% will be used for trial A and B, while in trial C cleaner fish are stocked at 8%. These are both stocking densities normally used in commercial sea cages.
The level of distress for fish is expected to be intermediate. The main stressor for the fish would be intraperitoneally PIT tagging and gastric lavage which is needed to investigate individual food preference in lumpfish over time. Sampling will be performed a total of eight times throughout both sea cage trials and there will be three weeks between each sampling event for cleaner fish to recover. Anaesthesia will be used for all handling events. All fish will be maintained using best known husbandry practices. Environmental conditions will be monitored daily throughout the trial and behaviour and physical condition of salmon and cleaner fish will also be monitored.
Millions of cleaner fish are deployed to act as biological controls for salmon lice annually. However, little is known about their feeding behaviour (Barrett et al. 2020) and to optimize cleaner fish as a management strategy better understanding of this is needed. Here, we propose three research-scale experiments which aim to increase the proportion of individuals which eat lice; (a) tank trial where lumpfish are fed live feed, (b) sea-cage trial examining feeding preference of lumpfish without any prior training as well as fish fed live feed prior to transfer and (c) sea-cage trial examining lice-eating efficiency between lumpfish which have cohabitated with known lice-eating “teachers” and naïve fish.
The experiments will be run at Austevoll Research Station operated by Havforskningsinstituttet. There will be six 5x5x5m sea cages, each stocked with 600 salmon (Nsalmon = 3,600). Lumpfish will be stocked at densities around 10%. Trial A and B use the same lumpfish while in trial C only a portion of the lumpfish that are known lice-eaters are being reused and the remaining cleaner fish need to be replaced. This sums up to a total of 540 lumpfish for trial A and B and between 180–210 lumpfish for trial C, ending up in a total sum of 720–750 lumpfish.
The trials are being conducted in 5x5x5m sea cages which mimic conditions that fish are exposed to in commercial sea cages but greatly minimize the number of animals required to achieve reasonable stocking densities. To give cleaner fish and salmon sufficient densities to interact, 600 salmon will be stocked in each sea cage to give an initial stocking density of around 0.7 kg/m3, which is the lowest stocking density will be on farms. The same salmon can be used for all the trials, thereby minimizing the total number of animals required. To obtain enough lice-eating teachers for trial C, a stocking density of 10% will be used for trial A and B, while in trial C cleaner fish are stocked at 8%. These are both stocking densities normally used in commercial sea cages.
The level of distress for fish is expected to be intermediate. The main stressor for the fish would be intraperitoneally PIT tagging and gastric lavage which is needed to investigate individual food preference in lumpfish over time. Sampling will be performed a total of eight times throughout both sea cage trials and there will be three weeks between each sampling event for cleaner fish to recover. Anaesthesia will be used for all handling events. All fish will be maintained using best known husbandry practices. Environmental conditions will be monitored daily throughout the trial and behaviour and physical condition of salmon and cleaner fish will also be monitored.