Participating organizations (WP leader in bold): P3. IRTA, P9. UL, P21. DTU and P29. ASIALOR
Task 16.1 Optimal combinations of factors to improve larval rearing. Using a pilot scale larval rearing system (RAS, ten 700 L tanks) and based on existing protocols used by the SME, successive experiments will be conducted over four years (from larval stage to 5 g mean weight, 4 months per experiment) using factorial designs (4 factors tested with 8 experimental units) (UL). Multifactorial designs such as fractional or complete factorial designs are efficient methods to successfully optimize larval protocols. Such methodology allows (i) to integrate the effects of each simple factor tested and interactions between them, (ii) to rank and evaluate the effects induced by factors or interactions, (iii) to identify rapidly an optimal combination of factors that increase larval survival, and (iv) to establish a first modeling of the complex multifactorial determinism of output variables. This method has been applied successfully by UL in aquaculture.
Experimentally, the effects of the environmental parameters such as photoperiod, light intensity, temperature and water current; nutritional parameters such as feeding frequency, meal timing and food composition; and population parameters such as larval density, strain and domestication level will be studied successively. Specific experiments will be carried out for the weaning step. Cannibalism in pikeperch larvae being the major reason for mortality observed in larval rearing especially from 18 to 39 dph, a specific care will concern this target. Finally, selected combinations of factors will be applied on farm conditions at an SME. That will concern protocols for larval rearing and weaning.
How the combination of different environmental factors affects cannibalistic behavior and larval morphogenesis will be also assessed by the description of different organ systems that are involved in prey location and capture (sensory and digestive systems), locomotion and predator avoidance (sensory and musculoskeletal systems) and maturation of the digestive capabilities. This approach is based on the hypothesis that fish displaying cannibalistic behavior may be more morphologically developed and fit that their conespecifics, which may enhance their chances of displayin such behavioral pattern. In particular, larvae will be sampled to describe the ontogeny of the skeleton and skeletal deformities. Sampled larvae will be fixed in buffered formaldehyde and stained with standard alizarine red (bones) and alcian blue (cartilage) for radiographic analysis. In addition samples for histology will be examined to study the ontogeny and functionality of the digestive system and evaluate the level of maturation of the digestive function by enzyme quantification and spectrophotometric procedures including analyses of the development of the sensory system like eye. These analyses will be combined to complementary approaches including real time RT-PCR in order to quantify and locate gene expression of transcription factors, signaling molecules and protein of extracellular matrix, involved in the skeletal system, and molecular tools to study some digestive hormones. Concerning cannibalism, based on small scale rearing and on the tagging of some individuals (microsatellites) or sub-populations (otoliths), the onset of cannibalism will be analyzed by video-recording.
Task 16.2 Development of an industrial protocol. From the results obtained in Tasks 16.1 (especially over the year 4), an industrial protocol (larval rearing + weaning) will be proposed and tested by an SME during year 5 to improve pikeperch larval growth and to reduce significantly cannibalism and larval mortality. This final protocol will integrate SME constraints.
Task 16.1 Optimal combinations of factors to improve larval rearing. Using a pilot scale larval rearing system (RAS, ten 700 L tanks) and based on existing protocols used by the SME, successive experiments will be conducted over four years (from larval stage to 5 g mean weight, 4 months per experiment) using factorial designs (4 factors tested with 8 experimental units) (UL). Multifactorial designs such as fractional or complete factorial designs are efficient methods to successfully optimize larval protocols. Such methodology allows (i) to integrate the effects of each simple factor tested and interactions between them, (ii) to rank and evaluate the effects induced by factors or interactions, (iii) to identify rapidly an optimal combination of factors that increase larval survival, and (iv) to establish a first modeling of the complex multifactorial determinism of output variables. This method has been applied successfully by UL in aquaculture.
Experimentally, the effects of the environmental parameters such as photoperiod, light intensity, temperature and water current; nutritional parameters such as feeding frequency, meal timing and food composition; and population parameters such as larval density, strain and domestication level will be studied successively. Specific experiments will be carried out for the weaning step. Cannibalism in pikeperch larvae being the major reason for mortality observed in larval rearing especially from 18 to 39 dph, a specific care will concern this target. Finally, selected combinations of factors will be applied on farm conditions at an SME. That will concern protocols for larval rearing and weaning.
How the combination of different environmental factors affects cannibalistic behavior and larval morphogenesis will be also assessed by the description of different organ systems that are involved in prey location and capture (sensory and digestive systems), locomotion and predator avoidance (sensory and musculoskeletal systems) and maturation of the digestive capabilities. This approach is based on the hypothesis that fish displaying cannibalistic behavior may be more morphologically developed and fit that their conespecifics, which may enhance their chances of displayin such behavioral pattern. In particular, larvae will be sampled to describe the ontogeny of the skeleton and skeletal deformities. Sampled larvae will be fixed in buffered formaldehyde and stained with standard alizarine red (bones) and alcian blue (cartilage) for radiographic analysis. In addition samples for histology will be examined to study the ontogeny and functionality of the digestive system and evaluate the level of maturation of the digestive function by enzyme quantification and spectrophotometric procedures including analyses of the development of the sensory system like eye. These analyses will be combined to complementary approaches including real time RT-PCR in order to quantify and locate gene expression of transcription factors, signaling molecules and protein of extracellular matrix, involved in the skeletal system, and molecular tools to study some digestive hormones. Concerning cannibalism, based on small scale rearing and on the tagging of some individuals (microsatellites) or sub-populations (otoliths), the onset of cannibalism will be analyzed by video-recording.
Task 16.2 Development of an industrial protocol. From the results obtained in Tasks 16.1 (especially over the year 4), an industrial protocol (larval rearing + weaning) will be proposed and tested by an SME during year 5 to improve pikeperch larval growth and to reduce significantly cannibalism and larval mortality. This final protocol will integrate SME constraints.