Driftwood State Fish Hatchery

Driftwood is an extensive culture facility. Most fish species are raised on the food items that occur naturally in ponds, such as zooplankton (i.e., minute animals), aquatic insects, frogs, snails, etc. The number of fish that can be raised is limited by the amount of forage the pond can produce, which is known as its carrying capacity. Fish production can be increased above the natural carrying capacity of a pond by using formulated feeds. Some species take readily to artificial diets.

To be as efficient as possible, ponds are multi-cropped. For instance, fathead minnows are usually raised in ponds previously used for bass short fingerling rearing, channel catfish are raised in ponds previously used for bass spawning, and so on.

Maintaining adequate water quality is an important task in the operation of the hatchery. Oxygen must be maintained above 5 parts per million or growth and survival will be reduced. Other gases (e.g., carbon dioxide, nitrogen, etc.) must remain below critical lethal concentration. Oxygen concentration is typically monitored at first light, when the level is theoretically at its lowest, and is monitored more closely during the summer months in spring and fall, usually daily. This is because warm water holds less oxygen than cold water. In addition, higher temperatures result in increased metabolic and respiration rate in fish and increased decomposition of organic matter, which causes increased oxygen use.

Mechanical aeration/circulation is used to improve the water quality of the pond. A centrally located 150 CFM blower system supplies aeration to the nine rearing ponds. Atmospheric air is injected near the bottom in the deep end. As the air rises, the upper water is pushed away, and the bottom water moves in to fill the void (note the boil). This action causes the pond to continuously “turn over”, which in turn mixes oxygen throughout the water column. It also keeps nutrients suspended in the water and available for plankton use.

During the growing season, aquatic vegetation is monitored and controlled as needed. “Summer kills” occur when oxygen depletion results from a die-off of a large algal bloom or extensive weed growth. Pond harvest is also affected as the fingerlings become trapped under the vegetation. Also, excessive algae plugs screens, slowing harvest and subjecting the fingerlings to longer periods of stress.

Fish production accounts for only part of the day-to-day operation of an extensive culture operation. Mowing and trimming of grounds to maintain a pleasant appearance; mowing levees to aid in the detection of muskrat dens and limit fish predators and disease vectors; maintaining buildings and structures; maintenance, repair and fabrication of equipment; and administrative duties are all equally important to the operation of the hatchery.

The months of October and November are generally when the fall fingerling ponds are harvested in preparation for stocking public waters. The fingerlings are moved to the culture room, graded, counted, weighed, and measured, and then loaded at the prescribed pounds of fish per gallon of water into insulated transport tanks for the trip to their new home. While in transit, water conditioners, bottled oxygen, and agitation are applied to the transport water to minimize stress and ensure a healthy product. At the lake, the fingerlings are acclimated to the temperature and chemistry of the receiving water before being unloaded.