Practical Hatchery Management of Warmwater Fishes
Chapter 1: Introduction
To produce an agricultural crop, you need seed that can be planted, grown to a larger size, and then harvested. To culture fish you also need seed to begin the production. A role of a fish hatchery is to produce the seed. How the final product is used may vary. The fish may be produced as a food for human consumption, as a sportfish for recreation, as a means for restoring natural populations, or in the case of ornamental fishes, as a companion animal. In each case the fish are cultured under controlled conditions (aquaculture) and seed is needed to begin production.
Finfish aquaculture had its beginnings in the method of collecting seed from the wild and culturing them under controlled conditions. However, this had numerous disadvantages, including seasonal changes in availability as well as year-to-year variability in supply, the lack of genetic control, and the potential for overfishing of the natural seed supply. A more controlled supply of seed was needed before the culture of a given species could become widespread. As appropriate hatchery techniques were developed adult fish could be brought into maturation, stimulated to spawn, eggs and larvae managed under suitable conditions for growth and survival, and then reared to a suitable size to provide the seed needed to begin the production phase.
Often under hatchery conditions, solving a few critical steps in the life history of a fish has resulted in major changes in the quantities of fish being produced. In the case of the Chinese carps, they were cultured for thousands of years but the extent of their culture was limited geographically by how far wild-caught larvae could be safely transported from the collection site to the culture site. Chinese carp such as Bighead (Hypophthalmichthys nobilis), Silver (Hypophthalmichthys molitrix) and Grass Carp (Ctenopharyngodon idella) are riverine spawners that will mature in ponds but will not spawn in static water. In the 1950s and 1960s, hormone induced spawning methods were developed that allowed static water raised brood fish to be artificially spawned. This allowed Chinese carp larvae and fingerlings to be shipped to other parts of the world where they could come to maturity in static water ponds, successfully be induced to spawn, and produce fingerlings.