Chapter 2: Hatchery Facilities
There are several aspects of hatchery facilities that are unique to a fish hatchery often not considered in standard construction practices. A hatchery biologist does not have to be an architect or an engineer but needs to be able to explain to an architect or an engineer what is needed for a fish hatchery to function effectively and why.
A good water supply is an essential requirement for consistent production of high-quality fish seed. Each species of fish has an acceptable range of physical and chemical characteristics of water conducive to growth and reproduction. The water quality requirements for successful fish reproduction are more demanding than those for growth. Often the first indication of poor environmental conditions at a hatchery is a depression in fish reproduction. Acceptable water quality conditions for freshwater fish spawning are shown in Table 2.1. The chemical profile of the water supply will impact pond fertilization success, efficacy of chemical weed control, levels of photosynthesis, organic matter decay rates, and other processes. Physical characteristics such as temperature and suspended materials are also highly important in culturing some species.
The quantity of water available should be ample enough to fill all the ponds on a hatchery within 5 to 10 days. After the ponds are filled, a similar volume of water may be required to replace seepage and evaporation losses during the culture period. When the fish crop is being harvested some new water may be needed for trapping or draining operations. Additional volumes of water may be needed to flush ponds in the event of low oxygen levels, or dilute the pond water following weed or disease treatments. A substantial amount of water is also needed for hatching, holding, processing, and shipping. At a minimum, a flow of 0.4 m3/min/ ha will be needed for all these purposes. The yearly quality of water needed for holding facilities is often equal or greater than that needed for filling ponds.
In intensive culture units the quantity of water available should permit 1 or 2 water changes or more per hour, depending upon the type unit and species involved. Supply and drain lines should be of a size to quickly admit and remove the quantity of water required. Generally, the younger the fish, the greater the requirement for high quality water with a minimum fluctuation in any parameter.
Sources of water for a fish hatchery include springs, wells, lakes, reservoirs and streams, each with advantages and disadvantages. Two or more sources may be used to supply a given hatchery. The best quality water should be reserved for the hatchery buildings where fish are to be reproduced and eggs or larvae are to be held. The source providing the largest volume should be available for the ponds.