As fish are efficient protein producers, in fact the most efficient farmed animal, aquaculture has been recognized as a key activity in terms of food security worldwide. Europe imports a substantial fraction of its fish consumption. Currently, the European aquaculture industry produces about 2.3 million tonnes of finfish per annum (FAO 2016), equal to one-third of the EU fishery market value, while representing only 20% of its volume! The Food and Agriculture Organization (FAO 2016) estimates that in order to achieve the per capita contribution of fisheries to the 2030 per capita consumption, the yearly global aquaculture production needs to grow by 27 million tonnes.

In order to meet the challenge of a steadily growing global aquaculture sector, there is a need to assure a steady supply of high numbers of high-quality fish larvae. Furthermore, in terms of future feed conversion efficiency, reduced malformation rates and the efficient conversion of feed to high-quality fish, quality fingerlings are of paramount importance for environmentally and economically sustainable aquaculture growth. However, aquaculture currently suffers from poor-quality fingerlings in terms of their future efficiency in converting food to fish meat, which affects aquaculture economics and its impact on the environment. Despite considerable progress in European aquaculture in the past 20 years, for example with production of over 1 billion seabass and seabream fry in 2012, high mortality during larval production and variable fry quality still plague the industry. This is exacerbated by an increasing need for diversification into new species, where these problems are even more acute. Therefore, there is still a significant amount of research to do to make the industry more cost-effective and sustainable.

The lack of a predictable supply of high-quality fish juveniles is largely attributed to uncontrolled environmental and nutritional factors during the larval rearing phase as well as the lack of tools for early prediction of larval quality in terms of phenotype and performance. There is thus a clear need for improvement of the scientific knowledge base that will support sustainable development of aquaculture. In addition, the well-documented environmental impact of factors such as climate change on fish production will place even greater demands on the application of an integrated multidisciplinary approach to improve larval performance and juvenile quality in the European aquaculture industry. This refers essentially to all non-salmonid fish species, as salmon and trout do not have a true larval stage, and most of the problems described for these species throughout this book are already solved or have a lower impact.

Maximizing fish production requires in-depth knowledge of biological, ecological and abiotic mechanisms, which affect the developing organism prior to reaching the grow-out farms. This is further exacerbated by the fact that the aquaculture industry is based on a multitude of species. So for instance, first feeding diets given to larvae have been identified as a determining factor for the quality of the juvenile phenotype in a number of species. This stems from the fact that various nutrients act on gene regulation of major physiological functions and thus should be an important feature of stage- and species-specific diet formulation but this has been largely ignored so far. While waterborne components such as endocrine disruptors have been well investigated for their effects on fish reproduction, there is almost no research on their effects on the larval to juvenile transition, despite the well-documented important role of hormones, and the endocrine system in general, in this process. The integration of molecular, nutritional and morphophysiological results is of paramount importance, as the influences on juvenile fish quality are multifactorial. Epigenetic research, for example how early environmental and nutritional impact can affect the phenotype later in life and even in the next generation(s), is relatively ‘new’ within research on farmed animals, including fish, although basic research in this area has been ongoing for several decades. The new tools which become available within this field will probably revolutionize the possibilities for juvenile quality prediction. Thus, in order to achieve a quality and sustainable aquaculture in Europe, there is a clear need for investment in fish larval research, to improve its scientific knowledge basis.

In order to tackle the aforementioned challenges, LARVANET, a network of researchers and producers working with fish larvae, was started in 2008. LARVANET was supported by a COST Action (FA0801). As a forum for constructive dialogue between stakeholders and researchers, LARVANET aimed to directly co-ordinate and build the know-how necessary to promote sustainable development and competitiveness at a basic level, and contribute to the cost-effective production of quality juveniles. It intended to integrate knowledge obtained in national and European research projects, and practical experience, in order to look for knowledge gaps on the way to improve quality of fish larvae used in aquaculture. It facilitated international co-operation, exchange of scientists and students, and efficient use of resources at all levels, and intended to exercise a lobby to influence long-term policy in the area of edible species larval research as a means to dramatically influence the resulting EU aquaculture efficiency, product quality and environmental and societal impact.