Success Factors for Fish Larval Production

Luis Conceicao, Amos Tandler, Luis Conceicao, Amos Tandler

• Publisher: Wiley-Blackwell
• Year: 2018
• ISBN:
  9781119072133
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Pêche et aquaculture

A comprehensive and authoritative synthesis on the successful production of fish larvae

Success Factors for Fish Larval Production is a vital resource that includes the most current understanding of larval biology, in the context of larval production. The text covers topics such as how external (environmental and nutritional) and internal (molecular/ developmental/ physiological/ behavioral/ genetic) factors interact in defining the phenotype and quality of fish larvae and juveniles. The expert contributors review broodstock genetics and husbandry, water quality, larval nutrition and feeding, growth physiology, health, metamorphosis, underlying molecular mechanisms, including epigenetics, for development, larval behavior and environmental conditions. Compiled by members of a European Union-funded consortium of top researchers, Success Factors for Fish Larval Production provides a wide-range of authoritative information for the aquaculture industry and academia.

In addition to a wealth of information, the authors review research and commercially applicable larval quality indicators and predictors. The successful production of good-quality fish larvae is of vital importance for fish farming and stock enhancement of wild fisheries:

• Includes contributions from a consortium of noted researchers and experts in the field
• Deals with on how to improve egg quality and larval production via broodstock management and nutrition
• Suggests ways to control the phenotype of juveniles and table-size fish via manipulations of the conditions of larval rearing (e.g., epigenetics)
• Includes ideas for optimizing diet composition, formulation, and technology
• Integrates knowledge and practical experience in order to help advancing excellence in aquaculture

Success Factors for Fish Larval Production offers fish biologists, developmental biologists, physiologists and zoologists the most current and reliable information on the topic. All those working in fish aquaculture facilities and hatcheries in particular will find great interest to their commercial operations within this book.

Chapter 1
Introduction

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.

Reference

1. FAO (2016) The State of World Fisheries and Aquaculture 2016. Contributing to Food Security and Nutrition for All. Food and Agriculture Organization, Rome.

Chapter 2
Gamete Quality and Broodstock Management in Temperate Fish

Herve Migaud¹, Gordon Bell¹, Elsa Cabrita², Brendan McAndrew¹, Andrew Davie¹, Julien Bobe³, Maria Paz Herráez⁴ and Manuel Carrillo⁵

¹Institute of Aquaculture, University of Stirling, Stirling, Scotland

²CCMAR, Centre of Marine Sciences, University of the Algarve, Campus de Gambelas, Faro, Portugal

³INRA, UR1037 Fish Physiology and Genomics, Rennes, France

⁴Department of Molecular Biology, Faculty of Biology, University of Leon, Leon, Spain

⁵Institute of Aquaculture of Torre de la Sal, Castellon, Spain

Executive Summary

Background

The ability to fully control sexual maturation and spawning and produce large numbers of high-quality seeds ‘on demand’ (i.e. all year long) is a primary requirement for the successful development of aquaculture. This relies on optimal broodstock management practices based on extensive knowledge of the nutritional and environmental requirements of fish in captivity. However, for many established, emerging and new farmed fish species, such knowledge is limited or not available yet. The level of domestication also plays an essential role as stocks with improved traits in farming conditions are selected. Importantly, reliable indicators of egg quality are still lacking as in many farmed fish species hatcheries still rely on wild harvested broodstocks. These key challenges must be addressed urgently to ensure the sustainable development of the European fish farming sector.

Principal Findings

The growth of the aquaculture industry depends to a large extent on the ability of hatcheries to supply good-quality eggs with selected traits, as required by the grow-out farmers. However, this remains problematic in many species, especially emerging new species selected for domestication for the diversification of the aquaculture industry. These often suffer from high variability in egg quality among stocks and parents. Therefore, more basic and applied research is required on all aspects of broodstock management including, inter alia, nutrition, environmental effects, genetics, gamete quality and preservation. This includes the definition of optimal egg quality at the genomic, proteomic and physiological levels in fish and the translation of this basic knowledge into a set of robust, reliable markers/analytical tools that can provide early confirmation of quality parameters for commercial hatcheries. A better understanding of the process of postovulatory ageing in fish broodstock is also required. The nutritional requirements of fish broodstock for optimal gametogenesis and egg/larvae quality and development (such as reduced deformity, etc.) must be defined, and sustainable, species-specific feed formulations developed.

The development of domestication/selective breeding programmes for emerging and new aquaculture species is critical to select the best strains, stocks and families for a range of traits of interest. Knowledge-based breeding programmes should be developed to minimize the effects of inbreeding on fertility, fecundity and egg/larvae quality traits (survival, growth, malformation). Research should also focus on gaining a better understanding of the environmental conditions that promote spontaneous, out-of-season spawning and good egg quality in established and new candidate species. Finally, the roles of maternally transferred mRNA, proteins and any other biomolecules on egg and larvae quality/performance should be studied and how broodstock conditioning/management can influence such epigenetic processes.

Scientific Significance

This review gives an overview of methods to assess egg/sperm quality and many of the most important factors impacting on gamete production and quality, including broodstock nutrition, environmental and spawning induction protocols, and genetic factors for broodstock management, gamete prese...