Survival and growth of fish in water reclaimed from cattle feedlots
Today there is a growing realization that we must reuse and conserve our natural resources to minimize pollution and environmental degradation. This concern has brought about an interest in integrated systems, which reuse water and produce marketable products in the process. With this in mind, several departments from Texas Tech University have collaborated to construct an integrated system to treat the effluent from a 1000-head cattle feedlot at the Texas Tech Animal Science Farm. This integrated system includes an integrated facultative pond (IFP), which produces and captures methane for energy production, a constructed wetland for filtration and plant production, and a aquaculture system.
The goal of this research was: (1) to assess the feasibility of growing and maintaining stocks of bait fish, sport fish, and tropical fish within an integrated system designed to remediate effluents from confined animal feeding operations; and (2) to determine environmental tolerance ranges for each of the fish species tested.
This research was conducted at the Texas Tech University 4th Street greenhouse location in Lubbock, Texas. Anaerobically digested cattle manure was diluted with freshwater to prepare seven concentrations, which were loaded into six pilot-scale wetland systems. Effluents exiting each wetland then passed through a four-tank raceway system constructed after each wetland. Fish were evaluated in reclaimed water containing a target COD concentrations of 0, 20, 100, 300, 500, 650, and 900 mg/L. The survival and growth of eight species: koi (Cyprinus carpio). bluegill (Lepomis macrochirus), channel catfish (Ictalurus punctatus), fathead minnow (Pimephales promelas), redfin shiner (Notropis umbratilis). tilapia (Tilapia aurea), sailfin molly Poecilia latipinna), and platies (Xiphophorus maculatas) were evaluated in 2-week trials (10 fish/ trial).
It was concluded that it is feasible for all of the species tested to be utilized in an integrated waste management system. Koi, platy, bluegill, molly, fathead minnow, redfin shiner were tolerant of COD concentrations up to 366 mg/L. Channel catfish and tilapia were the most tolerant of the species tested and had survival rates as high as 73% in COD concentrations of 810 mg/L.
Optimal ranges for each of the species were based on the highest survival, growth rates and condition. Platty, fathead minnow, and tilapia preformed optimally at COD concentrations between 79-145 mg/L. The optimal range for molly, bluegill, and channel catfish was at COD concentrations of approximately 366 mg/L. Koi and redfin shiner survival and growth rates were optimal at COD concentrations between 145-366 mg/L.