Preface. The scope of applied fish genetics. Introduction. Fish cultivation. Ornamental fish breeding. Fishing. Habitat destruction. Sexuality and reproduction. Gonochorism. Primary sexual characteristics. Secondary sexual characteristics. Modes of reproduction. Egg production. Production of spermatozoa. Fertilization. Cryopreservation. Mendelian inheritance: I. Colour. The beginning. Simple gene effects. Complex effects of alleles. Interaction of genes. Summary of colour genetics. Mendelian inheritance: II. Characters other than colour. Introduction. Scale patterns of carp. Scale patterns in sticklebacks. Body shape. Fin shape. Electrophoretic variations. Miscellaneous characteristics. Quantitative genetics: I. Metrical characteristics. Introduction. Polygenic inheritance. Heritability. Growth rate. Stocks and strains. Spawning time. Food conversion efficiency. Disease resistance. Selective improvement in fancy fish. Quantitative genetics: II. Population studies. Introduction. Blood groups. Electrophoresis of soluble proteins. Inferences from population data. Molecular studies. Inbreeding. Application of electrophoresis. Summary. Chromosomes of fish. Introduction. Methods in cytology. Chromosome numbers and gross morphology. Linkage and chromosome mapping. Sex determination. Introduction. Sex ratio. Sex linkage. Sex chromosome maps. Sex reversal and sex determination. Hybridization and sex determination. Gynogenesis and sex determination. Cytology of sex chromosomes. An oddity, the H-Y antigen. Hybridization. Introduction. Hybridization in nature. Artificial hybridization. Summary of applied use of hybrids. Hybridization and introgression. Atypical modes of sexuality. Introduction. Normal hermaphroditism. Abnormal hermaphroditism. Female-only species. Control of sex ratio. Introduction. Methods of sex ratio control. Commercial application. Chromosome engineering. Introduction. Meiotic diploid gynogenesis. Mitotic diploid gynogenesis. Androgenesis. Induced triploidy. Induced tetraploidy. Gene manipulation. Introduction. Choosing the gene. Inserting the gene. Asssessing the success of gene transfer. Expression of the transferred genes. Future developments in molecular genetics. Featured fish: I. Ornamental species. Introduction. The goldfish. Koi - ornamental common carp. The toothcarps. Other species. Featured fish: II. Cultivated species. Introduction. Common carp. Salmon and trouts. Tilapias. Author index. Species index. Subject index.