Abstract

Within fish research and production, the term biotechnology includes broodstock management, induction of oocytes and spermatozoa maturation, in vitro gamete manipulation, DNA manipulation, controlling the sex of the populations bred, and embryo development. Broadly speaking, many of these technologies focus on the early stages of the life cycle of the species of commercial interest, through gamete and chromosome manipulation, cryopreservation, transgenesis, production of chimeras, cloning and controlling the phenotypic expression of sex [1]. The present chapter offers a conceptual analysis of the principal biotechnologies used in the production of fish of commercial interest, particularly Atlantic salmon (Salmo salar), silver or coho salmon (Oncorhynchus kisutch), and rainbow trout (Oncorhynchus mykiss). It also describes biotechnologies applied to the production of other freshwater species such as tilapia, catfish, and carp, and marine fish such as cobia, bass, and sea bream. These biotechnologies focus on a number of areas: artificial manipulation of the photoperiod to obtain out-of-season spawning (advanced or delayed), use of hormone treatments with extracts of carp or salmon hypophysis [human chorionic gonadotropin (hCG), luteinizing hormone-releasing hormone analogue (LH-RHa), and gonadotropin-releasing hormone analogue (GnRHa)] to synchronize final maturation of the oocyte, acceleration of sexual maturity and/or increasing the volume of semen produced by males, and cold storage of semen (up to several weeks) using different media enriched with antioxidants, antibiotics, and salts. The cryopreservation of semen in liquid nitrogen, where sperm cells have an almost indefinite lifetime, is used on a massive scale in some species like salmonids and marine species. Oocytes can be stored for up to 48 hours, and experimentally for up to 4 days. In slow-growing cold-water species such as salmonids, the number of days of embryo development is regularly reduced or prolonged, by increasing or reducing the water temperature during incubation. Monosex populations are frequently produced in species where one sex is preferred for its productive yield (e.g., females in salmonids or males in tilapias). The survival of polyploid specimens allows commercial production of triploid (3n) or tetraploid (4n) specimens by temperature shock close to 28C or pressure shock around 10,000 psi. In 3n groups, females do not reach sexual maturity or express secondary sexual characteristics, resulting in better yield per carcass and greater growth. On the other hand, 4n groups are used for the production of interploid (3n) populations by crossing a 2n female with a 4n male. A wide variety of polyploid groups can be produced experimentally. The present review will discuss only those which are most developed in fish farming worldwide or which offer the best prospects for future application.