|FAO FISHERIES TECHNICAL PAPER|
Selective breeding programmes or medium-sized fish farms
Douglas Tave .
Coos Bay, Oregon
Food and Agriculture Organization of the United Nations
TABLE OF CONTENTS
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© FAO 1995
Selective breeding programmes for medium-sized fish farms.
FAO Fisheries Technical Paper. No. 352. Rome, FAO. 1995. 122 p.
|This manual, written for extension workers and aquaculturists, deals with methods for selective breeding programmes to improve cultured populations of food fish on medium-sized fish farms. The manual contains chapters on general principles, basic genetics, selection for qualitative phenotypes, selection for quantitative phenotypes, and how to conduct simple selective breeding programmes; a glossary and selected reading list are also included. The principles of quantitative and qualitative genetics are explained through examples of tilapia and carp breeding studies. The resources that are necessary for aquaculturists to possess in order to successfully implement selective breeding programmes are discussed and serve to help evaluate the prospects of success before starting a genetic improvement programme.|
PREPARATION OF THIS DOCUMENT
This document has been prepared within the framework of the Regular Programme activities of the Inland Water Resources and Aquaculture Service of the Fishery Resources and Environment Division. The primary objective of this document is to outline selective breeding programmes that can be used to improve cultured populations of food fish on medium-sized farms. The document is directed to extension personnel and aquaculturists.
The original manuscript was prepared by Douglas Tave of Urania Unlimited, Oregon, USA. It was reviewed by Charles (Bo) Collins, Katherine Bruner Tave, and Devin M. Bartley. The figures were prepared by Sally Rader under the supervision of Douglas Tave.
FAO Fisheries Department
Inland Waters - General
FAO Regional Fisheries Officers
The purpose of this manual is to outline selective breeding programmes that can be used to improve cultured populations of food fish on medium-sized farms. This manual is not a complete genetics text book; it is designed to explain one topic-selective breeding as it relates to aquaculture on medium-sized fish farms.
There is no good definition of what a medium-sized fish farm is, but it was assumed to be a farm with about 2 ha of ponds. The same principles and ideas that are discussed in this manual also apply to selective breeding programmes that could be conducted on larger fish farms, although some breeding programmes that could be conducted on larger farms are not included in this manual. Some of the selective breeding programmes discussed in the manual could be conducted on smaller fish farms.
There is no magic farm size that allows or prohibits a selective breeding programme. The number of ponds on the farm is more important than the overall size of the fish farm. The selective breeding programmes outlined in this manual can be conducted in one to 150 ponds, depending on the type of breeding programme that is used and the culture system that is typically used to produce the fish. Additional ponds would be needed to hold and/or spawn brood fish. Holding tanks and other facilities might also be needed.
Most of the selective breeding programmes outlined in this manual are simple and inexpensive, although there is no such thing as a free breeding programme. Several of the breeding programmes that are presented can be conducted in only one to five ponds. Breeding programmes that require a large number of ponds are included to illustrate a particular type of selection and to contrast them with the simpler ones.
Even though selective breeding is a tried-and-true method of increasing yields, most farmers should not be encouraged to conduct one. The most important criteria that determine whether a farmer should conduct a selective breeding programme are his ability to conduct a breeding programme and his desire to conduct one. The farmer who conducts a selective breeding programme:
- Must be a good manager.
- Must be able to record data and to manage information. If he cannot do this, the
- extension agent must be willing to do it for him.
- Must be willing to allocate ponds and other facilities for the breeding programme.
- Must be willing and able to allocate money to conduct the breeding programme.
- Must be willing to allocate the labour needed to conduct the breeding programme.
- Must accept the fact that the benefits are long-term benefits. Often, genetic gain is not transferred to the production ponds which are used to grow fish for market for one generation (the replacement of brood fish with their progeny). Annual gains made as a result of selective breeding are usually small, but they are cumulative, and over time they can significantly improve growth rate and yield.
The manual is divided into five chapters, a glossary, and a suggested reading list. Chapter 1 is a brief introduction that explains what the manual is about and discusses selection in relation to other types of breeding programmes. Chapter 2 is a brief discussion about some aspects of basic genetics and presents background information that helps explain how selection works. Chapter 3 discusses selective breeding programmes that are needed to create true-breeding populations when working with qualitative phenotypes (phenotypes such as colour). Chapter 4 discusses selective breeding programmes that can be used to improve quantitative phenotypes (phenotypes such as length). Chapter 5 outlines simple selective breeding programmes that can be conducted to improve growth rate and other quantitative phenotypes, and provides examples of the types of data that must be recorded and data tables that can be used to record these data when conducting selective breeding programmes.
This manual was written to help educate extension specialists or university-trained aquaculturists understand the basic ideas and the basic work plans that are needed to conduct selective breeding programmes to improve growth rate and other phenotypes. As such, the manual contains information that does not need to be discussed in workshops that might be held for interested farmers. The information in Chapter 2 was presented only to provide some background information that helps explain the breeding programmes that are outlined in Chapters 3,4, and 5. Those who have a good background in genetics can skip this chapter. When conducting a workshop for farmers, extension personnel should omit most of the material in Chapter 2. Nothing will destroy a farmer's interest in selective breeding faster than a long, boring technical lecture on genetics. Few farmers really need to know the basic genetics that was discussed in Chapter 2.
Some of the material discussed in Chapters 3, 4, and 5 should also be omitted when conducting a workshop for farmers. For example, some of the selective breeding programmes that were mentioned in Chapter 4 were discussed only for the sake of completeness, and especially because I wanted to discourage their use.
Chapter 3, which outlines selective breeding programmes that can be used to fix desirable qualitative phenotypes, such as body colour or scale pattern, was included in the manual because I wanted to make the mechanics of selective breeding more understandable. The selective breeding programmes outlined in Chapter 3 are simple and easy to understand. A reader who studies the breeding programmes that are outlined in Chapter 3 and who understands the processes that allow a farmer to fix qualitative phenotypes will find the information in Chapters 4 and 5 easier to understand.
Chapters 4 and 5 are the heart and soul of the manual. Chapter 4 outlines the basic types of selective breeding programmes that can be used to improve a quantitative phenotype, such as growth rate: individual selection, between-family selection, and within-family selection. It explains the type of information that must be gathered before a farmer conducts a breeding programme; it outlines how the different breeding programmes are conducted; it discusses how a farmer measures fish and decides which fish should be saved; and it shows how a farmer can evaluate the results of the breeding programme.
Chapter 5 outlines of how simple selective breeding programmes can be conducted to improve growth rate by individual selection, within-family selection, and between-family selection. Included are examples of selective breeding programmes that can be conducted using only one or two ponds. Techniques that can be used to transfer gain made from selection to the production ponds are also discussed.
The manual was written for extension personnel and for aquaculturists; it is not a genetics text book. It is written in a simple straightforward manner. I tried to use as little jargon as possible, but some had to be used. Scientific terms are defined in the text when they are first used, and there is an extensive glossary that defines the terms used in the book.
Finally, citations were not included in the text or tables. The omission of citations is not intended to slight the contributions made by others. I simply wanted to produce an uncluttered readable manual. A list of suggested references is provided at the end of the manual for those who want to pursue the subject of selective breeding in fish in greater detail.
I thank Charles (Bo) Collins and Katherine Bruner Tave for critical review of the manuscript. I also thank Sally Rader for turning my preliminary figures into works of art.
This book is for Katherine and Kai, because they never stopped believing in me.
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Chapter 1: Introduction
Chapter 2: Genetics
Phenotype and genotype
Genetics of qualitative phenotypes
Qualitative phenotypes produced b y single autosomal genes
Qualitative phenotypes controlled by two autosomal genes
Genetics of quantitative phenotypes
Role of environment in phenotypic expression
Chapter 3: Selection for qualitative phenotypes
Factors that must be considered before conducting selective breeding programmes
Selective breeding programmes to produce true-breeding populations
Selection for homozygous phenotypes
Selection for phenotypes controlled by more than one genotype
Selection for phenotypes controlled by heterozygous genotypes
Chapter 4: Selection for quantitative phenotypes
Factors that must be considered before conducting selective breeding programmes
Environmental effects that must be controlled
Selection for more than one phenotype
Combining between and within family selection
Spawning select brood fish
Assessing results of selection with a control population
Chapter 5: Simple selective breeding programmes to improve growth rate and other quantitative phenotypes
Selection for growth rate
Selection for growth rate and another phenotype