Effects of Freshwater Crayfish Aquaponics System on Growth and Yield of Leafy Vegetables.

Aquaponics is an agricultural production system in which the waste produced by aquatic animals, such as fish, provides nutrients for plants. Bacteria in the water convert ammonium from the animal waste into nitrites and then nitrates that plants can use for nourishment. An aquaponics study was conducted at a climate controlled greenhouse at Georgia Southern University, Statesboro, GA, where romaine and green leaf lettuce were used as agricultural crops. Red crayfishes and white river crayfishes were used as the aquatic species. The objectives of the study were to understand and compare the effects of a crayfish aquaponics system and hydroponic (no crayfish) on the growth, vigor and yield of leafy vegetable crops. Six tanks were used to create 12 floating plots of green leaf and romaine combinations. Five of each variety of lettuce were placed on each plot. Randomized complete block design was used to layout the plots.

The seedlings were planted in coconut coir and vermiculite and placed in the holes of floating polystyrene sheets, allowing the roots to remain submerged in the water. Each tank housed twelve crayfishes. Crayfish are territorial, so hiding places were provided in the tank to lower the risk of injury and/or mortality in the tanks. The crayfishes were observed throughout the experiment to determine if they can maintain relatively stable populations that will provide enough nutrients for the vegetables. FloraNova Grow (7-4-10) Hydroponic Nutrient Solution was applied to all tanks (355 mL per tank) as a basic nutrient source. The tanks were monitored for water quality to ensure there was a balance between waste production and water/nutrient filtration. The vigor of the vegetable crops was measured periodically and the final yield of both the crop and the crayfishes were measured at the end of the experiment.