how does the larvae of fish gets its nutrition
Answers
Despite considerable progress in recent years, many questions regarding fish larval nutrition remain largely unanswered, and several research avenues remain open. A holistic understanding of the supply line of nutrients is important for developing diets for use in larval culture and for the adaptation of rearing conditions that meet the larval requirements for the optimal presentation of food organisms and/or microdiets. The aim of the present review is to revise the state of the art and to pinpoint the gaps in knowledge regarding larval nutritional requirements, the nutritional value of live feeds and challenges and opportunities in the development of formulated larval diets.
The major objectives of this review are (i) to analyse the current knowledge, research trends and efforts; and based on this analysis (ii) to identify the gaps and bottlenecks that need to be tackled in future research for the advanced and more efficient production of fish larvae.
Marine fish larvae are very vulnerable during the first stages of development and have strict requirements for biotic and abiotic conditions to survive, develop and grow properly. There are several recent reviews that cover different aspects of larval nutrition and show the advances in knowledge from different perspectives (see reviews in Holt 2011). In spite of the variety of conditions that a developing larva may face in nature, the current knowledge of nutrition in early stages has been based mainly on laboratory studies carried out following reductionist approaches under artificial conditions based on limited prey types and under relatively constant abiotic and biotic conditions. Another aspect to take into account is the variety in ontogeny, feeding physiology and nutritional requirements among species, even within the same family. Consequently, many specific processes cannot directly be extrapolated from findings obtained in model species and require specific studies.
Obviously, a good knowledge of the larval nutritional requirements throughout development would contribute to optimize diets and feeding protocols, and thereby improve larval and juvenile quality. Nevertheless, considering the vulnerability of fish larvae, it is always difficult to identify and meet nutritional requirements when several physiological and metabolic constraints are linked and each of them may prevent growth or an appropriate development. An integrated understanding of the different factors and events interacting in the food acquisition and processing is necessary for designing larval diets that meet the larval requirements for optimal ingestion, digestion and absorption of these diets. This review, which covers the gaps in knowledge on fish larval nutritional requirements, should therefore be read together with the review by Rønnestad et al. (in press) that covers the aspects of appetite, feed acquisition and digestive physiology.
Considering all these limitations and based on the analysis of the current information available in marine fish nutrition, the present review attempts to identify the most burning gaps to be addressed in future research to achieve a more efficient production of high quality fish larvae.
Larval nutrition
What are the larval nutrient requirements?
We know very little about the nutritional requirements of marine fish larvae (Holt 2011). Both qualitatively and quantitatively they may differ from those of juveniles or adult fish, since fish undergo dramatic morphological and physiological changes, including metamorphosis, during ontogenesis. Moreover, fish larvae grow extremely rapidly, feed continuously and, therefore, the total ingestion of nutrients must be high. In cod larvae, for example, growth rates of up to 30% per day have been measured while some species such as African catfish may grow up to 100% per day...
The requirement for a particular nutrient can be defined from a physiological point of view as the nutrient intake needed to fulfil a physiological role (Izquierdo & Lall 2004). However, the design and formulation of diets requires translation of the nutritional requirements into the nutrient content in the diet....Micronutrient requirements, but also requirements for protein/amino acids, fatty acids and so forth, are often given as dietary concentrations/fractions, and, expressed in this way requirements do not always increase under demanding conditions, such as high growth rates and metamorphosis. However, if food intake increases, the absolute intake of each single nutrient will also increase under constant dietary composition. The reason for stressing this argument is to differentiate between requirements for a certain volume of feed and the requirement for a balanced diet, where the different nutrients may be required in different ratios to each other, dependent on the developmental stage and the growth rate of the animal.
Answer:
Despite considerable progress in recent years, many questions regarding fish larval nutrition remain largely unanswered, and several research avenues remain open. A holistic understanding of the supply line of nutrients is important for developing diets for use in larval culture and for the adaptation of rearing conditions that meet the larval requirements for the optimal presentation of food organisms and/or microdiets. The aim of the present review is to revise the state of the art and to pinpoint the gaps in knowledge regarding larval nutritional requirements, the nutritional value of live feeds and challenges and opportunities in the development of formulated larval diets.
The major objectives of this review are (i) to analyse the current knowledge, research trends and efforts; and based on this analysis (ii) to identify the gaps and bottlenecks that need to be tackled in future research for the advanced and more efficient production of fish larvae.
Marine fish larvae are very vulnerable during the first stages of development and have strict requirements for biotic and abiotic conditions to survive, develop and grow properly. There are several recent reviews that cover different aspects of larval nutrition and show the advances in knowledge from different perspectives (see reviews in Holt 2011). In spite of the variety of conditions that a developing larva may face in nature, the current knowledge of nutrition in early stages has been based mainly on laboratory studies carried out following reductionist approaches under artificial conditions based on limited prey types and under relatively constant abiotic and biotic conditions. Another aspect to take into account is the variety in ontogeny, feeding physiology and nutritional requirements among species, even within the same family. Consequently, many specific processes cannot directly be extrapolated from findings obtained in model species and require specific studies.
Obviously, a good knowledge of the larval nutritional requirements throughout development would contribute to optimize diets and feeding protocols, and thereby improve larval and juvenile quality. Nevertheless, considering the vulnerability of fish larvae, it is always difficult to identify and meet nutritional requirements when several physiological and metabolic constraints are linked and each of them may prevent growth or an appropriate development. An integrated understanding of the different factors and events interacting in the food acquisition and processing is necessary for designing larval diets that meet the larval requirements for optimal ingestion, digestion and absorption of these diets. This review, which covers the gaps in knowledge on fish larval nutritional requirements, should therefore be read together with the review by Rønnestad et al. (in press) that covers the aspects of appetite, feed acquisition and digestive physiology.
Considering all these limitations and based on the analysis of the current information available in marine fish nutrition, the present review attempts to identify the most burning gaps to be addressed in future research to achieve a more efficient production of high quality fish larvae.
Larval nutrition
What are the larval nutrient requirements?
We know very little about the nutritional requirements of marine fish larvae (Holt 2011). Both qualitatively and quantitatively they may differ from those of juveniles or adult fish, since fish undergo dramatic morphological and physiological changes, including metamorphosis, during ontogenesis. Moreover, fish larvae grow extremely rapidly, feed continuously and, therefore, the total ingestion of nutrients must be high. In cod larvae, for example, growth rates of up to 30% per day have been measured while some species such as African catfish may grow up to 100% per day...
The requirement for a particular nutrient can be defined from a physiological point of view as the nutrient intake needed to fulfil a physiological role (Izquierdo & Lall 2004). However, the design and formulation of diets requires translation of the nutritional requirements into the nutrient content in the diet....Micronutrient requirements, but also requirements for protein/amino acids, fatty acids and so forth, are often given as dietary concentrations/fractions, and, expressed in this way requirements do not always increase under demanding conditions, such as high growth rates and metamorphosis. However, if food intake increases, the absolute intake of each single nutrient will also increase under constant dietary composition. The reason for stressing this argument is to differentiate between requirements for a certain volume of feed and the requirement for a balanced diet, where the different nutrients may be required in different ratios to each other, dependent on the developmental stage and the growth rate of the animal.