Dietary effects on growth, physiology, morphology, and behavioural responses
1 Purpose
There is an increasing demand for cleaner fish by the salmon industry to combat the sea lice problem, and there is an ongoing effort to produce lumpfish in captivity. To date there are no standard procedures, and growth rates and juvenile quality vary from hatchery to hatchery and also between years. Lumpfish larvae are larger and more developed than e.g. ballan wrasse larvae when they hatch. Their first feed can be formulated diets, although as the larvae of this species do not grow well on pelleted feeds. The current 'industry standard' used to rear lumpfish larvae are either formulated diets or Artemia nauplii, before the fish can be weaned on larger pellets. Artemia are known to be feeds of inferior food quality for marine, pelagic fish larvae, and can result in high mortality rates, low growth rates and low disease resistance of larval fish (Hamre et al., 2013; Øie et al., 2017), and the use of these feed items is solely owed to the ease of accessibility and application. For lumpfish larvae, our recent experiments have shown much better growth from Artemia than for formulated diets as start feed (Kjørsvik, unpublished). To improve growth, survival, and juvenile quality in larval rearing of lumpfish we aim at developing feeding regimes using natural plankton (larval stages of copepods and barnacles), which are known to be superior compared to rotifers and Artemia. These have only recently become commercially available and are hence underutilized at present. The experiments will be conducted in flow-through systems in 100 L tanks in triplicates. We will test 3 novel, size adaptive feeding regimes against a 'state of the art' industrial feeding regime. Larvae will be analysed for growth, prey selectivity, biochemical composition, as well as gene expression.
2 Distress
The fish larvae will not suffer more than under normal hatchery production conditions.
3 Expected benefit
Expected benefit is improved nutritional quality and rearing regimes for lumpfish larvae, with better understanding of larval requirements and improved juvenile quality.
4 Number of animals, and what kind
We will start with 150 000 newly hatched larvae, with expected 90-99 % survival by the end of experiment. However, a relatively high larval density is necessary in order to have a good turn-over of the live feed organisms (and thus good nutritional quality and less debris), and we plan for 100 larvae per litre (10.000 larvae/tank), similar to commercial rearing. About 1000 larvae will be sampled during the experiment to perform analysis (growth, morphology, gene expression, development etc). We will have 5 dietary treatments in triplicates.
5 How to adhere to 3R
The objective of the study is to improve culture conditions for larval lumpfish, hence replacing them by e.g. mathematical models or tissue cultures is not feasible. The number of animals for sampling is calculated to the least possible, having the inherent optimal larval density and tank size for lumpfish larval fish in mind. Greatest care will be taken to reduce handling stress to a minimum.
There is an increasing demand for cleaner fish by the salmon industry to combat the sea lice problem, and there is an ongoing effort to produce lumpfish in captivity. To date there are no standard procedures, and growth rates and juvenile quality vary from hatchery to hatchery and also between years. Lumpfish larvae are larger and more developed than e.g. ballan wrasse larvae when they hatch. Their first feed can be formulated diets, although as the larvae of this species do not grow well on pelleted feeds. The current 'industry standard' used to rear lumpfish larvae are either formulated diets or Artemia nauplii, before the fish can be weaned on larger pellets. Artemia are known to be feeds of inferior food quality for marine, pelagic fish larvae, and can result in high mortality rates, low growth rates and low disease resistance of larval fish (Hamre et al., 2013; Øie et al., 2017), and the use of these feed items is solely owed to the ease of accessibility and application. For lumpfish larvae, our recent experiments have shown much better growth from Artemia than for formulated diets as start feed (Kjørsvik, unpublished). To improve growth, survival, and juvenile quality in larval rearing of lumpfish we aim at developing feeding regimes using natural plankton (larval stages of copepods and barnacles), which are known to be superior compared to rotifers and Artemia. These have only recently become commercially available and are hence underutilized at present. The experiments will be conducted in flow-through systems in 100 L tanks in triplicates. We will test 3 novel, size adaptive feeding regimes against a 'state of the art' industrial feeding regime. Larvae will be analysed for growth, prey selectivity, biochemical composition, as well as gene expression.
2 Distress
The fish larvae will not suffer more than under normal hatchery production conditions.
3 Expected benefit
Expected benefit is improved nutritional quality and rearing regimes for lumpfish larvae, with better understanding of larval requirements and improved juvenile quality.
4 Number of animals, and what kind
We will start with 150 000 newly hatched larvae, with expected 90-99 % survival by the end of experiment. However, a relatively high larval density is necessary in order to have a good turn-over of the live feed organisms (and thus good nutritional quality and less debris), and we plan for 100 larvae per litre (10.000 larvae/tank), similar to commercial rearing. About 1000 larvae will be sampled during the experiment to perform analysis (growth, morphology, gene expression, development etc). We will have 5 dietary treatments in triplicates.
5 How to adhere to 3R
The objective of the study is to improve culture conditions for larval lumpfish, hence replacing them by e.g. mathematical models or tissue cultures is not feasible. The number of animals for sampling is calculated to the least possible, having the inherent optimal larval density and tank size for lumpfish larval fish in mind. Greatest care will be taken to reduce handling stress to a minimum.