Feeding behaviour and digestion physiology in larval fish: current knowledge and gaps and bottlenecks in research

The principal objectives of this chapter are (i) to analyse current knowledge, research trends and efforts in basic and applied aspects of the feeding behaviour and digestive physiology of fish larvae focusing primarily on marine species, and (ii) to identify the gaps and bottlenecks that need to be tackled in future research on advanced and more efficient production of fish larvae. Several reviews have covered various aspects of larval development, with emphasis on feed acquisition and digestive processes (i.e. Morais et al. 2007; Rønnestad et al. 2007b; Yufera & Darias 2007a; R.nnestad & Morais 2008; Finn & Kapoor 2008; Gisbert et al. 2008; Zambonino-Infante et al. 2008; Holt 2011). These reviews illustrate the advances made in knowledge from different perspectives, highlighting the essential role of feeding and digestive organs, as well as behaviour and the digestive machinery that enables rapid growth (larvae multiply their body mass to adult size by a factor of 105–107; Finn et al. 2002), in addition to the anatomical status and transformations exhibited by fish during the first weeks of life. Although there is a substantial literature regarding the direct effect of some abiotic factors such as temperature on exogenous feeding activity, less attention has been paid to the impact of temperature, illumination and feeding protocol in a rhythmic or circadian perspective (Yoseda et al. 2008; Villamizar et al. 2009).The potential importance of environmental and endogenous rhythms and transient conditions on food uptake and feeding physiology is recognized but not well understood, as are even less so their implications for nutritional composition, growth rates and survival. Another important aspect that should be taken into account is the variety in ontogeny, feeding physiology and behaviour even within the same family. Thus, species-specific findings for a process or function in a model species cannot be extrapolated directly to other teleosts and specific validation studies are essential.