Chapter 3: Production Alternatives and Brood Management
The mode of reproduction and feeding habits of a given species of fish needs to be understood before they can be effectively produced in a hatchery setting. This includes knowing the basic biology of the species as to: under what environmental conditions the species mature and reproduce, what are the natural food habits at the different life stages, what factors stimulate reproduction, what are the characteristics of the eggs and larvae, and what type of care is given by the parents to the eggs and larvae? Based on that, an appropriate set of hatchery techniques can be selected to produce a given species. What techniques are applied also depends on:
1. Difficulty of spawning and rearing the species to a distributable size
2. Number of seed required
3. Delivery schedules
4. Distribution requirements such as size of seed, distance of shipment, hardiness of the species, etc.
5. Labor available and their knowledge and skills
6. Facilities available
7. Disease problems
There are a number of techniques and combinations of techniques that can be used to meet production goals, varying in the level of intervention required by the hatchery staff, the input requirements, and the consistency in yields. The most basic approach is a Spawning-Rearing approach where much of the operation takes place in the same production setting with little management intervention. Broodfish are stocked into a spawning pond, allowed to spawn naturally, and the progeny and brooders are harvested at a later date. This can be an acceptable approach when working with species that will spawn naturally in a static water pond setting as little human intervention is needed. The disadvantages include the uncontrolled spawning results in an unknown number of fish being produced, and because the fish may be spawning over an extended period of time there will be variation in sizes of fish produced. This size variation will contribute to competition for food and possible cannibalism, resulting in poor yields from the later spawns. However, because of the simplicity of the method it is still used with some species such as Bluegill Lepomis macrochirus.